Response of vitamin K status to different intakes and sources of phylloquinone-rich foods: comparison of younger and older adults

Role of vitamin K2 in bone-vascular crosstalk

Vitamin K (VK) is a fat-soluble vitamin that is indispensable for the activation of vitamin K-dependent proteins (VKDPs). It has been shown to play an important role in the proper calcium deposit at the bone level, hindering that on the vascular walls. The deficiency of this vitamin in European populations is frequent and unknown. It is related to several factors, poor dietary intake, altered intestinal absorption or altered production by bacteria, indicating possible dysbiosis. For Vitamin K2 (VK2), there is currently no official reference daily intake (RDI). However, the effects of VK2 on the improvement of health in cardiovascular diseases, on bone metabolism, on chronic kidney diseases have been the subject of research in recent decades. The microbiota in the gastrointestinal tract plays an important role: Bacteroides are primarily capable of synthetizing very long chain forms of menaquinones and, in addition to the bacteria present in the intestinal flora, VK2 is also produced by bacteria used in food fermentation processes. This review provides an update on the current literature regarding the origin of VK2 and its implications in what is called the "calcium paradox", namely the lack of calcium in the bone and its storage in the wall of the vessel.

Novel QuEChERS-ultra-performance liquid chromatography-atmospheric-pressure chemical ionization tandem mass spectrometry method for the simultaneous determination of vitamin D and vitamin K in vitamin-fortified nanoemulsions

Nanoemulsion is a new vehicle for food fortification. In this study, a simple and reliable method for the simultaneous analysis of vitamins D₂, D₃, K₁, and K₂ in vitamin-fortified nanoemulsions was developed using QuEChERS (quick, easy, cheap, effective, rugged, and safe) extraction and ultra-high performance liquid chromatography-atmospheric-pressure chemical ionization tandem mass spectrometry techniques. Response surface methodology was employed to optimize the extraction parameters. The method was validated for the vitamins in terms of LOD (0.03-0.25 μg/L), LOQ (0.10-0.77 μg/L), intra-day (≤4.50%), inter-day precisions (≤6.43%), and accuracy (98.5%-108.0%). The recoveries of the vitamin-fortified nanoemulsion and yogurt were in the ranges of 104.0%-109.2% and 73.3%-85.2%, respectively. The solvent consumption and analysis time were reduced by 5.6 and 3.3 folds, respectively, rendering it superior to the traditional extraction methods established by the Association of Official Analytical Chemists and the Ministry of Food and Drug Safety.

Dietary Vitamin K1 intake is associated with lower long-term fracture-related hospitalization risk: the Perth longitudinal study of ageing women

This study examined the association between dietary Vitamin K1 intake with fracture-related hospitalizations over 14.5 years in community-dwelling older Australian women (n = 1373, ≥70 years). Dietary Vitamin K1 intake at baseline (1998) was estimated using a validated food frequency questionnaire and a new Australian Vitamin K nutrient database, which was supplemented with published data. Over 14.5 years, any fracture (n = 404, 28.3%) and hip fracture (n = 153, 10.7%) related hospitalizations were captured using linked health data. Plasma Vitamin D status (25OHD) and the ratio of undercarboxylated osteocalcin (ucOC) to total osteocalcin (tOC) from serum was assessed at baseline. Estimates of dietary Vitamin K1 intake were supported by a significant inverse association with ucOC : tOC; a marker of Vitamin K status (r = -0.12, p < 0.001). Compared to women with the lowest Vitamin K1 intake (Quartile 1, <61 μg d^-1), women with the highest Vitamin K1 intake (Quartile 4, ≥99 μg d^-1) had lower hazards for any fracture- (HR 0.69 95%CI 0.52-0.91, p < 0.001) and hip fracture-related hospitalization (HR 0.51 95%CI 0.32-0.79, p < 0.001), independent of 25OHD levels, as part of multivariable-adjusted analysis. Spline analysis suggested a nadir in the relative hazard for any fracture-related hospitalizations at a Vitamin K1 intake of approximately 100 μg day^-1. For hip fractures, a similar relationship was apparent. Higher dietary Vitamin K1 is associated with lower long-term risk for any fracture- and hip fracture-related hospitalizations in community-dwelling older women.

The effects of vitamin K-rich green leafy vegetables on bone metabolism: A 4-week randomised controlled trial in middle-aged and older individuals

Background

High vegetable intake is associated with beneficial effects on bone. However, the mechanisms remain uncertain. Green leafy vegetables are a rich source of vitamin K1, which is known to have large effects on osteoblasts and osteocalcin (OC) metabolism.

Objective

To examine the effects of consumption of two to three extra serves of green leafy vegetables daily on bone metabolism.

Methods

Thirty individuals (mean age 61.8 ± 9.9 years, 67% male) completed three experimental phases in a randomised controlled crossover design, each lasting four weeks, with a washout period of four weeks between phases (clinical trial registration: ACTRN12615000194561). The three experimental phases were: (i) increased dietary vitamin K1 by consuming green leafy vegetables (H-K; ~200 g/d containing 164.3 [99.5-384.7] μg/d of vitamin K1); (ii) low vitamin K1 by consuming vitamin K1-poor vegetables (L-K; ~200 g/d containing 9.4 [7.7-11.6] μg/d of vitamin K1); and (iii) control (CON) where participants consumed an energy-matched non-vegetable control. OC forms, total OC (tOC), carboxylated OC (cOC) and undercarboxylated OC (ucOC), were measured in serum pre- and post-intervention for each experimental phase using a sandwich-electrochemiluminescence immunoassay.

Results

Pre-intervention tOC, ucOC and ucOC:tOC levels were similar between phases (P > .05). Following H-K, but not L-K, tOC, ucOC and ucOC:tOC levels were significantly lower compared to pre-intervention levels (P ≤ .001) and compared to CON (~14%, 31% and 19%, respectively, all P < .05), while cOC remained unchanged.

Conclusions

In middle-aged healthy men and women, an easily achieved increase in dietary intake of vitamin K1-rich green leafy vegetables substantially reduces serum tOC and ucOC suggesting increased entry of OC into bone matrix, where it may improve the material property of bone. In conjunction with previous epidemiological and randomised controlled trial data, these findings suggest that interventions to increase vegetable intake over extended periods should include bone end points including fracture risk.

Laboratory assessment of vitamin K status

Vitamin K is required for the ɣ-carboxylation of specific glutamic acid residues within the Gla domain of the 17 vitamin K-dependent proteins (VKDPs). The timely detection and correction of vitamin K deficiency can protect against bleeding. Vitamin K also plays a role in bone metabolism and vascular calcification. Patients at increased risk of vitamin K deficiency include those with a restricted diet or malnutrition, lipid malabsorption, cancer, renal disease, neonates and the elderly. Coagulation assays such as the prothrombin time have been used erroneously as indicators of vitamin K status, lacking sufficient sensitivity and specificity for this application. The measurement of phylloquinone (K1) in serum is the most commonly used marker of vitamin K status and reflects abundance of the vitamin. Concentrations <0.15 µg/L are indicative of deficiency. Disadvantages of this approach include exclusion of the other vitamin K homologues and interference from recent dietary intake. The cellular utilisation of vitamin K is determined through measurement of the prevalence of undercarboxylated VKDPs. Most commonly, undercarboxylated prothrombin (Protein Induced by Vitamin K Absence/antagonism, PIVKA-II) is used (reference range 17.4–50.9 mAU/mL (Abbott Architect), providing a retrospective indicator of hepatic vitamin K status. Current clinical applications of PIVKA-II include supporting the diagnosis of vitamin K deficiency bleeding of the newborn, monitoring exposure to vitamin K antagonists, and when used in combination with α-fetoprotein, as a diagnostic marker of hepatocellular carcinoma. Using K1 and PIVKA-II in tandem is an approach that can be used successfully for many patient cohorts, providing insight into both abundance and utilisation of the vitamin.

The Contribution of Lipids to the Interindividual Response of Vitamin K Biomarkers to Vitamin K Supplementation

SCOPE

A better understanding of factors contributing to interindividual variability in biomarkers of vitamin K can enhance the understanding of the equivocal role of vitamin K in cardiovascular disease. Based on the known biology of phylloquinone, the major form of vitamin K, it is hypothesized that plasma lipids contribute to the variable response of biomarkers of vitamin K metabolism to phylloquinone supplementation.

METHODS AND RESULTS

The association of plasma lipids and 27 lipid-related genetic variants with the response of biomarkers of vitamin K metabolism is examined in a secondary analysis of data from a 3-year phylloquinone supplementation trial in men (n = 66) and women (n = 85). Year 3 plasma triglycerides (TG), but not total cholesterol, LDL-cholesterol, or HDL-cholesterol, are associated with the plasma phylloquinone response (men: β = 1.01, p < 0.001, R2  = 0.34; women: β = 0.61, p = 0.008, R2  = 0.11; sex interaction p = 0.077). Four variants and the TG-weighted genetic risk score are associated with the plasma phylloquinone response in men only. Plasma lipids are not associated with changes in biomarkers of vitamin K function (undercarboxylated osteocalcin and matrix gla protein) in either sex.

CONCLUSION

Plasma TG are an important determinant of the interindividual response of plasma phylloquinone to phylloquinone supplementation, but changes in biomarkers of vitamin K carboxylation are not influenced by lipids.

Supplementary nutrients for prevention of vascular calcification in patients with chronic kidney disease

Vascular calcification (VC) and malnutrition associated with cardiovascular disease are common in patients with chronic kidney disease (CKD) treated with dialysis. VC, which reflects vascular aging, and malnutrition are also encountered in the non-CKD elderly population. This similarity of clinical findings suggests that the progression of CKD is related to aging and the existence of a causal relationship between VC and malnutrition. To retard renal progression, a low- or very-low-protein diet is usually recommended for CKD patients. Dietary education may induce malnutrition and deficiency of important nutrients, such as vitamins K and D. Menaquinone-7, a type of vitamin K2, is under investigation for inhibiting VC in elderly patients without CKD, as well as for prevention of VC in patients with CKD. Nutritional vitamin D, such as cholecalciferol, may be considered to decrease the required dose of active vitamin D, which increases the risk of VC due to increased calcium and phosphate loads. Omega-3 fatty acids are important nutrients and their ability to inhibit VC needs to be evaluated in clinical trials. This review focuses on the ability of supplementary nutrients to prevent VC in patients with CKD, in whom dietary restriction is essential.

Vitamin K status and physical decline in older adults-The Longitudinal Aging Study Amsterdam

OBJECTIVE

We examined the association between vitamin K status and physical functioning over 13 years in the Longitudinal Aging Study Amsterdam.

STUDY DESIGN

Longitudinal cohort study of 633 community-dwelling adults from the Longitudinal Aging Study Amsterdam (LASA) aged 55-65 years (54% women).

MAIN OUTCOME MEASURES

At baseline (2002-2003), plasma desphospho-uncarboxylated matrix Gla protein (dp-ucMGP) was measured with a sandwich ELISA as a marker of vitamin K status. The outcome measures handgrip strength, calf circumference, self-reported functional limitations and functional performance were obtained at baseline and four follow-up examinations. We used generalized estimating equations to determine the relationship between dp-ucMGP tertiles and the various outcome measurements after adjusting for potential confounders. The lowest dp-ucMGP tertile reflects a high vitamin K status and was the reference.

RESULTS

Mean dp-ucMGP was 376 ± 233 pmol/L and mean follow-up was 11.1 years. Participants showed a decline in the outcome measures over time. Compared with the lowest tertile, the highest dp-ucMGP tertile had: lower handgrip strength, 1.1 kg (95% confidence interval (-2.1, -0.1; P-trend <0.001); smaller calf circumference, -0.5 cm (-0.9 -0.1; P-trend = 0.018); and, only among women, a 0.7-point poorer functional performance score (-1.1, -0.3; P-interaction = 0.002). Dp-ucMGP was not related to self-reported functional limitations. No interaction effects between time and dp-ucMGP were observed.

CONCLUSIONS

Low vitamin K status was associated with lower handgrip strength, smaller calf circumference, and, in women only, with poorer functional performance score. A low vitamin K status was however not related to the 13-year decline in these measures.

Dietary reference values for vitamin K

Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) derives dietary reference values (DRVs) for vitamin K. In this Opinion, the Panel considers vitamin K to comprise both phylloquinone and menaquinones. The Panel considers that none of the biomarkers of vitamin K intake or status is suitable by itself to derive DRVs for vitamin K. Several health outcomes possibly associated with vitamin K intake were also considered but data could not be used to establish DRVs. The Panel considers that average requirements and population reference intakes for vitamin K cannot be derived for adults, infants and children, and therefore sets adequate intakes (AIs). The Panel considers that available evidence on occurrence, absorption, function and content in the body or organs of menaquinones is insufficient, and, therefore, sets AIs for phylloquinone only. Having assessed additional evidence available since 1993 in particular related to biomarkers, intake data and the factorial approach, which all are associated with considerable uncertainties, the Panel maintains the reference value proposed by the Scientific Committee for Food (SCF) in 1993. An AI of 1 μg phylloquinone/kg body weight per day is set for all age and sex population groups. Considering the respective reference body weights, AIs for phylloquinone are set at 70 μg/day for all adults including pregnant and lactating women, at 10 μg/day for infants aged 7-11 months, and between 12 μg/day for children aged 1-3 years and 65 μg/day for children aged 15-17 years.

Bone Health and Osteoporosis: The Role of Vitamin K and Potential Antagonism by Anticoagulants

BACKGROUND

Vitamin K's effects extend beyond blood clotting to include a role in bone metabolism and potential protection against osteoporosis. Vitamin K is required for the gamma-carboxylation of osteocalcin. Likewise, this gamma-carboxylation also occurs in the liver for several coagulation proteins. This mechanism is interrupted by coumarin-based anticoagulants in both the liver and bone.

METHODS

A thorough review of the literature on vitamin K, osteocalcin and their role in bone metabolism and osteoporosis, as well as the potential bone effects of anticoagulant therapy was conducted.

CONCLUSIONS

Epidemiological studies and clinical trials consistently indicate that vitamin K has a positive effect on bone mineral density and decreases fracture risk. Typical dietary intakes of vitamin K are below the levels associated with better BMD and reduced fracture risk; thus issues of increasing dietary intakes, supplementation, and/or fortification arise. To effectively address these issues, large-scale, intervention trials of vitamin K are needed. The effects of coumarin-based anticoagulants on bone health are more ambiguous, with retrospective studies suggesting that long-term therapy adversely affects vertebral BMD and fracture risk. Anticoagulants that do not affect vitamin K metabolism are now available and make clinical trials feasible to answer the question of whether coumarins adversely affect bone. The research suggests that at a minimum, clinicians should carefully assess anticoagulated patients for osteoporosis risk, monitor BMD, and refer them to dietitians for dietary and supplement advice on bone health. Further research is needed to make more efficacious decisions about vitamin K intake, anticoagulant therapy, and bone health.

Steady-state vitamin K2 (menaquinone-7) plasma concentrations after intake of dairy products and soft gel capsules

BACKGROUND

In a previous human intervention study, we observed an improved vitamin K status after 8 weeks of intake of a yogurt that was fortified with vitamin K2 (as menaquinone-7, MK-7) and enriched with vitamins C and D3, magnesium and polyunsaturated fatty acids. It was hypothesized that the added nutrients contributed to this improvement. Here we report on a study in which we compared the fasting plasma concentrations of MK-7 from (a) yogurt enriched with MK-7, vitamins D3 and C, magnesium, n-3 poly unsaturated fatty acids (n-3 PUFA) and fish oil (yogurt Kplus), (b) yogurt fortified with MK-7 only (yogurt K) and (c) soft gel capsules containing only MK-7.

SUBJECTS/METHODS

For 42 days, healthy men and postmenopausal women between 45 and 65 years of age daily consumed either yogurt K, yogurt Kplus or capsules. Circulating MK-7, 25-hydroxy vitamin D (25(OH)D) and markers for vitamin K status (uncarboxylated osteocalcin (ucOC) and desphospho-uncarboxylated matrix Gla-protein (dp-ucMGP)) were assessed. Plasma MK-7 was also measured during the washout period of 2 weeks. MK-7 and dp-ucMGP were measured in citrated plasma, and 25(OH)D3 and ucOC were measured in the serum.

RESULTS

The increase in plasma MK-7 with the yogurt Kplus product was more pronounced than the increase in MK-7 with the capsules. Circulating dp-ucMGP and ucOC were significantly lowered after consumption of the yogurt products and the MK-7 capsules, reflecting vitamin K status improvement. No significant differences in fasting plasma concentrations of various biomarkers between the yogurts were found.

CONCLUSIONS

Dairy matrix and nutrient composition may affect MK-7 delivery and improvement of vitamin K status. Yogurt fortified with MK-7 is a suitable matrix to improve the nutritional status of the fat-soluble vitamins.

Concepts and Controversies in Evaluating Vitamin K Status in Population-Based Studies

A better understanding of vitamin K's role in health and disease requires the assessment of vitamin K nutritional status in population and clinical studies. This is primarily accomplished using dietary questionnaires and/or biomarkers. Because food composition databases in the US are most complete for phylloquinone (vitamin K1, the primary form in Western diets), emphasis has been on phylloquinone intakes and associations with chronic diseases. There is growing interest in menaquinone (vitamin K2) intakes for which the food composition databases need to be expanded. Phylloquinone is commonly measured in circulation, has robust quality control schemes and changes in response to phylloquinone intake. Conversely, menaquinones are generally not detected in circulation unless large quantities are consumed. The undercarboxylated fractions of three vitamin K-dependent proteins are measurable in circulation, change in response to vitamin K supplementation and are modestly correlated. Since different vitamin K dependent proteins are implicated in different diseases the appropriate vitamin K-dependent protein biomarker depends on the outcome under study. In contrast to other nutrients, there is no single biomarker that is considered a gold-standard measure of vitamin K status. Most studies have limited volume of specimens. Strategic decisions, guided by the research question, need to be made when deciding on choice of biomarkers.

Vitamin K Status Is not Associated with Cognitive Decline in Middle Aged Adults

OBJECTIVES

The aim of this study was to examine the association between dephospho-uncarboxylated matrix Gla protein (dp-ucMGP), an indicator of vitamin K status, and cognitive decline, and the modifying role of 25(OH)D.

DESIGN

Longitudinal study with six years follow-up.

SETTING

Community based.

PARTICIPANTS

599 participants of the Longitudinal Aging Study Amsterdam (aged 55-65 years).

MEASUREMENTS

Information processing speed and a composite Z-score by combining three domains of cognition reflecting general cognitive functioning.

RESULTS

Generalized estimating equations (GEE) showed no significant associations between dp-ucMGP and decline in general cognitive functioning. Vitamin D modified the association between dp-ucMGP and speed of information processing (p<0.05). In the group with a 25(OH)D concentration > 50 nmol/l, the highest tertile of dp-ucMGP (>406 pmol/l), which corresponds to lower vitamin K levels, was associated with 1.5 higher score on information processing speed (p=0.023) as compared to the lowest tertile of dp-ucMGP.

CONCLUSION

In contrast to our hypothesis, a suboptimal vitamin K was not associated with cognitive decline in middle-aged adults.

Yogurt drink fortified with menaquinone-7 improves vitamin K status in a healthy population

Population-based studies have shown an inverse association between dietary menaquinones (MK-n, vitamin K2) intake, coronary calcification and CHD risk, suggesting a potential role of vitamin K in vascular health. To date, the effects of increased menaquinone intake on (markers of) vascular health have been investigated using predominantly food supplements. Dairy products contain many essential nutrients and can serve as a good matrix for food fortification in order to support health. We were therefore interested to study the effects of a menaquinone-fortified yogurt drink (menaquinone as menaquinone-7 (MK-7); 28 µg MK-7/yogurt drink) on vitamin K status and markers of vascular health. The yogurt drink was also fortified with n-3 PUFA, vitamin D, vitamin C, Ca and Mg to support vascular and/or general health. Healthy men (n 32) and postmenopausal women (n 28) with a mean age of 56 (sd 5) years received either basic or fortified yogurt drink twice per d for 12 weeks. MK-7 was efficiently absorbed from the fortified yogurt drink. Levels of circulating MK-7 were significantly increased from 0·28 to 1·94 ng/ml. In accordance, intake of the fortified yogurt drink improved vitamin K status, as measured by significant decreases in uncarboxylated osteocalcin and desphospho-uncarboxylated matrix Gla-protein. No effects were, however, seen on markers of inflammation, endothelial dysfunction and lipid metabolism. In summary, consumption of a yogurt drink fortified with low doses of among others MK-7 for 3 months significantly improved vitamin K status in a healthy population.

The health benefits of vitamin K

Vitamin K has important functions within the body, some of which are still being discovered. Research has shown that vitamin K is an anticalcification, anticancer, bone-forming and insulin-sensitising molecule. Recent data indicate that subclinical vitamin K deficiency is not uncommon. Additionally, vitamin K antagonists such as warfarin may cause detrimental side effects, which may partly be blunted through vitamin K supplementation.

α-Tocopherol disappearance rates from plasma depend on lipid concentrations: studies using deuterium-labeled collard greens in younger and older adults

BACKGROUND

Little is known about α-tocopherol's bioavailability as a constituent of food or its dependence on a subject's age.

OBJECTIVE

To evaluate the α-tocopherol bioavailability from food, we used collard greens grown in deuterated water ((2)H collard greens) as a source of deuterium-labeled ((2)H) α-tocopherol consumed by younger and older adults in a post hoc analysis of a vitamin K study.

DESIGN

Younger (mean ± SD age: 32 ± 7 y; n = 12 women and 9 men) and older (aged 67 ± 8 y; n = 8 women and 12 men) adults consumed a test breakfast that included 120 g (2)H collard greens (1.2 ± 0.1 mg (2)H-α-tocopherol). Plasma unlabeled α-tocopherol and (2)H-α-tocopherol were measured by using liquid chromatography-mass spectrometry from fasting (>12 h) blood samples drawn before breakfast (0 h) and at 24, 48, and 72 h and from postprandial samples collected at 4, 5, 6, 7, 9, 12, and 16 h.

RESULTS

Times (12.6 ± 2.5 h) of maximum plasma (2)H-α-tocopherol concentrations (0.82% ± 0.59% total α-tocopherol), fractional disappearance rates (0.63 ± 0.26 pools/d), half-lives (30 ± 11 h), and the minimum estimated (2)H-α-tocopherol absorbed (24% ± 16%) did not vary between age groups or sexes (n = 41). Unlabeled α-tocopherol concentrations were higher in older adults (26.4 ± 8.6 μmol/L) than in younger adults (19.3 ± 4.2 μmol/L; P = 0.0019) and correlated with serum lipids (r = 0.4938, P = 0.0012). In addition, (2)H-α-tocopherol half-lives were correlated with lipids (r = 0.4361, P = 0.0044).

CONCLUSIONS

Paradoxically, α-tocopherol remained in circulation longer in participants with higher serum lipids, but the (2)H-α-tocopherol absorbed was not dependent on the plasma lipid status. Neither variable was dependent on age. These data suggest that plasma α-tocopherol concentrations are more dependent on mechanisms that control circulating lipids rather than those related to its absorption and initial incorporation into plasma. This trial was registered at clinicaltrials.gov as NCT0036232.

The association between vitamin K status and knee osteoarthritis features in older adults: the Health, Aging and Body Composition Study

BACKGROUND

Vitamin K-dependent (VKD) proteins, including the mineralization inhibitor matrix-gla protein (MGP), are found in joint tissues including cartilage and bone. Previous studies suggest low vitamin K status is associated with higher osteoarthritis (OA) prevalence and incidence.

OBJECTIVE

To clarify what joint tissues vitamin K is relevant to in OA, we investigated the cross-sectional and longitudinal association between vitamin K status and knee OA structural features measured using magnetic resonance imaging (MRI).

METHODS

Plasma phylloquinone (PK, vitamin K1) and dephosphorylated-uncarboxylated MGP ((dp)ucMGP) were measured in 791 older community-dwelling adults who had bilateral knee MRIs (mean ± SD age = 74 ± 3 y; 67% female). The adjusted odds ratios (and 95% confidence intervals) [OR (95%CI)] for presence and progression of knee OA features according to vitamin K status were calculated using marginal models with generalized estimating equations (GEEs), adjusted for age, sex, body mass index (BMI), triglycerides and other pertinent confounders.

RESULTS

Longitudinally, participants with very low plasma PK (<0.2 nM) were more likely to have articular cartilage and meniscus damage progression after 3 years [OR (95% CIs): 1.7(1.0-3.0), 2.6(1.3-5.2) respectively] compared to sufficient PK (≥ 1.0 nM). Higher plasma (dp)ucMGP (reflective of lower vitamin K status) was associated with higher odds of meniscus damage, osteophytes, bone marrow lesions, and subarticular cysts cross-sectionally [ORs (95% CIs) comparing highest to lowest quartile: 1.6(1.1-2.3); 1.7(1.1-2.5); 1.9(1.3-2.8); 1.5(1.0-2.1), respectively].

CONCLUSION

Community-dwelling men and women with very low plasma PK were more likely to have progression of articular cartilage and meniscus damage. Plasma (dp)ucMGP was associated with presence of knee OA features but not progression. Future studies are needed to clarify mechanisms underlying vitamin Ks role in OA.

Phylloquinone concentrations and the risk of vascular calcification in healthy women

OBJECTIVE

To investigate the association of plasma phylloquinone concentrations with coronary artery calcification (CAC) and vascular calcification.

APPROACH AND RESULTS

In a prospective cohort of 508 postmenopausal women, plasma phylloquinone concentrations were measured by high-pressure liquid chromatography. Calcification was measured in the coronary arteries, aortic valve, mitral valve, and thoracic aorta by multidetector computed tomography. To combine these calcification scores, we dichotomized each of the 4 areas into present or absent. Because of the continuous measurement of CAC, we categorized this as calcification present if Agatston score was >0, and calcification score was calculated as the sum of the calcified areas. Multivariate-adjusted prevalence ratios and odds ratios were estimated using Poisson regression and multinomial logistic regression. After 8.5 years of follow-up, 22% of the women had no calcification, whereas 5% had calcification in all measured areas. Detectable phylloquinone concentrations were associated with increased CAC compared with nondetectable phylloquinone concentrations with a prevalence ratio of 1.34 (95% confidence interval, 1.01-1.77). When dividing women with detectable phylloquinone concentrations into low detectable (>0-0.70 nmol/L) and moderate to high detectable (>0.70 nmol/L) phylloquinone concentrations versus nondetectable phylloquinone concentrations, both were associated with increased CAC with a prevalence ratio of 1.32 (95% confidence interval, 0.99-1.76) and 1.36 (95% confidence interval, 1.02-1.81), respectively. Detectable phylloquinone concentrations were not associated with the number of calcified areas with an odds ratio(no versus ≥ 3 areas calcifications) of 1.60 (95% confidence interval, 0.65-3.99; P=0.31).

CONCLUSIONS

Detectable phylloquinone concentrations are not associated with reduced vascular calcification but seemed to be associated with an increased prevalence of CAC.

Vitamin K and bone health in older adults

Vitamin K is one of several nutrients that have been linked with bone health. In particular, there is an emerging literature regarding the questionable efficacy of vitamin K supplementation in reducing age-related bone loss. This review aims to summarize the role of vitamin K in bone health in older adults and discuss the clinical implications from a select few human studies. The evidence for vitamin K supplementation in older adults is mixed. Although the observational studies have shown linkages between vitamin K intake and lower risk of fractures in this population, the current evidence from randomized controlled trials is not strongly supportive of vitamin K supplementation in older adults for the intent of improving bone health.

Association between circulating vitamin K1 and coronary calcium progression in community-dwelling adults: the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Animal studies have shown that vitamin K treatment reduced vascular calcification, but human data are limited.

OBJECTIVE

We determined the association between vitamin K status and coronary artery calcium (CAC) progression in the Multi-Ethnic Study of Atherosclerosis by using a case-cohort design.

DESIGN

Serum phylloquinone (vitamin K1) was measured in 296 participants with extreme CAC progression and 561 randomly selected participants without extreme CAC progression; all subjects had baseline and follow-up CAC measures (mean follow-up: 2.5 y). A serum vitamin K1 concentration was considered low at <1.0 nmol/L (the distribution median). Outcomes were replicated by using post hoc per-protocol analyses of a vitamin K1 supplementation trial.

RESULTS

The OR (95% CI) for extreme CAC progression for subjects with low serum vitamin K1 compared with subjects without extreme CAC progression was 1.34 (0.94, 1.90; NS) when adjusted for demographics and confounders. A significant interaction between low vitamin K1 and antihypertension medication use was detected (P = 0.016). Hypertension medication users with low serum vitamin K1 were more likely to have extreme CAC progression than were medication users without extreme CAC progression [OR (95% CI): 2.37 (1.38, 4.09)]. In replication, baseline antihypertensive medication users in the supplementation group had less CAC progression than did those in the control group [adjusted mean ± SEM of the 3-y CAC change was +5 ± 20 Agatston units (AU) in the vitamin K1 group (n = 40) and +44 ± 13 AU in the placebo group (n = 49); P < 0.01].

CONCLUSIONS

Although the point estimate of our primary analysis suggests low serum vitamin K1 is associated with greater CAC progression, the difference was NS. Low serum vitamin K1 was significantly associated with CAC progression in antihypertension medication users, which, to our knowledge, is a novel finding conditionally replicated by using an independent sample. Intervention trials are needed to determine whether improving serum vitamin K1 reduces CAC progression, especially in hypertensive individuals. This trial was registered at clinicaltrials.gov as NCT00183001.

A single measurement of serum phylloquinone is an adequate indicator of long-term phylloquinone exposure in healthy older adults

Assessment of long-term phylloquinone exposure is challenging in studies investigating vitamin K in health. Data are equivocal as to whether a single measurement of circulating phylloquinone would be adequate. The primary purpose of the present study was to validate the use of a single measurement of serum phylloquinone as a surrogate for long-term phylloquinone exposure in healthy older adults. Using data from the Québec Longitudinal Study on Nutrition and Successful Aging, the objectives were to: 1) determine the reproducibility of circulating phylloquinone over 2 y (n = 234); 2) calculate how a single measurement would rank or classify individuals and attenuate the regression coefficient between circulating phylloquinone and a health outcome; and 3) investigate the association of a single measurement of serum phylloquinone with long-term phylloquinone intakes assessed over the year prior to the blood draw (n = 228). The variance analysis based on 2 blood samples showed a fair to good reproducibility for serum phylloquinone (intra-class correlation = 0.49). The correlation coefficient between the ranking of individuals based on a single measurement of circulating phylloquinone and the "true" ranking would be 0.70. The multiple regression analysis showed that long-term phylloquinone intake was the strongest predictor of serum phylloquinone (t = 4.94; P < 0.001). The partial correlation coefficient (r = 0.32) was comparable with those reported in studies where blood sampling and diet recording were juxtaposed and/or multiple blood samples were used. The present study provides evidence that the use of a single measurement of circulating phylloquinone is adequate for assessing long-term phylloquinone exposure in healthy older adults.

Age group and sex do not influence responses of vitamin K biomarkers to changes in dietary vitamin K

Inadequate vitamin K intake has been associated with abnormal soft tissue calcification. Older adults may have insufficient intakes of vitamin K and respond less to vitamin K supplementation compared with younger adults. However, little is known about the determinants that influence the response to vitamin K supplementation. Our primary objective was to assess dietary and nondietary determinants of vitamin K status in healthy younger and older adults. In a nonrandomized, nonmasked study, 21 younger (18-40 y) and 21 older (55-80 y) men and women consumed a baseline diet (200 μg phylloquinone/d) for 5 d, a phylloquinone-restricted diet (10 μg phylloquinone/d) for 28 d, and a phylloquinone-supplemented diet (500 μg phylloquinone/d) for 28 d. Changes in vitamin K status markers in response to vitamin K depletion and repletion were studied and the influences of BMI, body fat, and circulating TG were assessed by including them as covariates in the model. Despite baseline differences in measures of vitamin K status, plasma phylloquinone tended to increase (P = 0.07) and the percentage of uncarboxylated osteocalcin and uncarboxylated prothrombin both improved with phylloquinone supplementation (P < 0.007), regardless of age group or sex. Only the excretion of urinary menadione, a vitamin K metabolite, was greater among younger adults in response to depletion than in older adults (P = 0.012), regardless of sex. Adiposity measures and circulating TG did not predict response of any measures. In conclusion, poor vitamin K status can be similarly improved with vitamin K supplementation, regardless of age group or sex.

Vitamin K nutrition, metabolism, and requirements: current concepts and future research

In 2001, the US Food and Nutrition Board concluded that there were insufficient data with which to establish a RDA for vitamin K, in large part because of a lack of robust endpoints that reflected adequacy of intake. Knowledge of the relative bioavailability of multiple vitamin K forms was also poor. Since then, stable isotope methodologies have been applied to the assessment of the bioavailability of the major dietary form of vitamin K in its free state and when incorporated into a plant matrix. There is a need for stable isotope studies with enhanced sensitivity to expand knowledge of the bioavailability, absorption, disposition, and metabolism of different molecular forms of vitamin K. Another area for future research stems from evidence that common polymorphisms or haplotypes in certain key genes implicated in vitamin K metabolism might affect nutritional requirements. Thus far, much of this evidence is indirect via effects on warfarin dose requirements. In terms of clinical endpoints, vitamin K deficiency in early infancy continues to be a leading cause of intracranial bleeding even in developed countries and the reasons for its higher prevalence in certain Asian countries has not been solved. There is universal consensus for the need for vitamin K prophylaxis in newborns, but the effectiveness of any vitamin K prophylactic regimen needs to be based on sound nutritional principles. In contrast, there is still a lack of suitable biomarkers or clinical endpoints that can be used to determine vitamin K requirements among adults.

Vitamin K status and vascular calcification: evidence from observational and clinical studies

Vascular calcification occurs when calcium accumulates in the intima (associated with atherosclerosis) and/or media layers of the vessel wall. Coronary artery calcification (CAC) reflects the calcium burden within the intima and media of the coronary arteries. In population-based studies, CAC independently predicts cardiovascular disease (CVD) and mortality. A preventive role for vitamin K in vascular calcification has been proposed based on its role in activating matrix Gla protein (MGP), a calcification inhibitor that is expressed in vascular tissue. Although animal and in vitro data support this role of vitamin K, overall data from human studies are inconsistent. The majority of population-based studies have relied on vitamin K intake to measure status. Phylloquinone is the primary dietary form of vitamin K and available supplementation trials, albeit limited, suggest phylloquinone supplementation is relevant to CAC. Yet observational studies have found higher dietary menaquinone, but not phylloquinone, to be associated with less calcification. Vascular calcification is highly prevalent in certain patient populations, especially in those with chronic kidney disease (CKD), and it is plausible vitamin K may contribute to reducing vascular calcification in patients at higher risk. Subclinical vitamin K deficiency has been reported in CKD patients, but studies linking vitamin K status to calcification outcomes in CKD are needed to clarify whether or not improving vitamin K status is associated with improved vascular health in CKD. This review summarizes the available evidence of vitamin K and vascular calcification in population-based studies and clinic-based studies, with a specific focus on CKD patients.

Serum vitamins in adult patients with short bowel syndrome receiving intermittent parenteral nutrition

BACKGROUND

Short bowel syndrome (SBS) occurs after massive intestinal resection, and parenteral nutrition (PN) therapy may be necessary even after a period of adaptation. The purpose of this study was to determine the vitamin status in adults with SBS receiving intermittent PN.

METHODS

The study was conducted on hospitalized adults with SBS who were receiving intermittent PN therapy (n = 8). Nine healthy volunteers, paired by age and sex, served as controls. Food ingestion, anthropometry, plasma folic acid, and vitamins B(12), C, A, D, E, and K were evaluated.

RESULTS

The levels of vitamins A, D, and B(12) in both groups were similar. SBS patients presented higher values of folic acid (21.3 ± 4.4 vs 14.4 ± 5.2, P = .01) and lower values of vitamin C (0.9 ± 0.4 vs 1.2 ± 0.3 mg/dL, P = .03), α-tocopherol (16.3 ± 3.4 vs 24.1 ± 2.7 µmol/L, P < .001), and phylloquinone (0.6 ± 0.2 vs 1.0 ± 0.5 nmol/L, P < .03). Eight-seven percent of patients had vitamin D deficiency, and all patients presented with serum vitamin E levels below reference values.

CONCLUSIONS

Despite all efforts to offer all the nutrients mentioned above, SBS patients had lower serum levels of vitamins C, E, and K, similar to those observed in patients on home PN. These findings suggest that the administered vitamins were not sufficient for the intermittent PN scheme and that individual adjustments are needed depending on the patient's vitamin status.

Vitamin K status in spaceflight and ground-based models of spaceflight

Bone loss is a well-documented change during and after long-duration spaceflight. Many types of countermeasures to bone loss have been proposed, including vitamin K supplementation. The objective of this series of studies was to measure change in vitamin K status in response to microgravity under a variety of spaceflight and spaceflight analog (model) conditions, including long-duration spaceflight studies (n = 15), three bed rest studies (n = 15, 49, and 24), and a 14-day saturation dive (n = 6). In crew members who flew 2-6 months on the International Space Station, in-flight and postflight plasma phylloquinone concentrations were unchanged from the preflight mean. Consistent with this finding, urinary γ-carboxyglutamic acid (GLA), a measure of vitamin K-dependent protein turnover, did not change in response to flight. Serum undercarboxylated osteocalcin (%ucOC), a measure of vitamin K function, was generally unchanged in response to flight. Spaceflight findings were corroborated by findings of no changes in phylloquinone, urinary GLA, or %ucOC during or after bed rest in three separate bed rest studies (21-90 days in duration) or after a 14-day saturation dive. The data presented here do not support either a need for vitamin K supplementation during spaceflight or the suggestion of using vitamin K as a bone loss countermeasure in spaceflight.

Adulthood obesity is positively associated with adipose tissue concentrations of vitamin K and inversely associated with circulating indicators of vitamin K status in men and women

Increased adiposity is associated with increased storage of several fat-soluble nutrients. However, the extent to which vitamin K is stored in fat and the association between vitamin K status and adiposity are unknown. Our objectives in this study were to determine whether vitamin K is stored in human adipose tissue and the association between vitamin K status and body fat in older men and women. In study A, the vitamin K concentration of subcutaneous and visceral adipose tissue was quantified in samples taken from 16 gastric bypass patients [13 women, 3 men, age 40 +/- 10 y (mean +/- SD)] using HPLC. In study B, cross-sectional associations between percent body fat (%BF) and circulating measures of vitamin K status were examined in 260 women and 183 men [age = 68 +/- 5 y]. The phylloquinone (K(1)) concentrations in subcutaneous and visceral adipose tissue were 148.2 +/- 71.8 and 175 +/- 112 nmol/kg, respectively, which is higher than the reported concentrations of other organs known to store vitamin K. There was an inverse association between %BF and plasma K(1) in women (P-trend < 0.001). Higher %BF was associated with greater circulating concentrations of uncarboxylated prothrombin, indicative of lower hepatic utilization of vitamin K in both men (P-trend = 0.02) and women (P-trend = 0.002) but not with the percentage of undercarboxylated osteocalcin. Adipose tissue contained high concentrations of vitamin K, and increased adiposity was associated with poorer vitamin K status in older adults. Additional studies are needed to further explore the relationships among body fat, storage of vitamin K in adipose tissue, and implications for vitamin K status and function.

Vitamin K absorption and kinetics in human subjects after consumption of 13C-labelled phylloquinone from kale

The absorption and plasma disappearance of vitamin K were investigated by uniformly labelling phylloquinone in kale with carbon-13, and by feeding the kale to study subjects. Seven healthy volunteers ingested a single 400 g serving of kale with 30 g vegetable oil. The kale provided 156 nmol of phylloquinone. Serial plasma samples were collected and analysed for the appearance of 13C-phylloquinone by HPLC-MS. Six of the subjects showed significant amounts of labelled phylloquinone in plasma, though one subject's plasma was not consistently enriched above the detection limit, and this subject's baseline plasma phylloquinone level was the lowest in the group. After ingestion of the labelled kale, plasma 13C-phylloquinone concentration increased rapidly to a peak between 6 and 10 h, and then rapidly decreased. Average peak plasma concentration for the six subjects with detectable 13C-phylloquinone was 2.1 nmol/l. Plasma concentration-time data were analysed by compartmental modelling. Modelling results demonstrated a mean (n 6) bioavailability of phylloquinone from kale to be 4.7%. Plasma and tissue half-times for phylloquinone were found to be 8.8 and 215 h, respectively.

The external quality assurance of phylloquinone (vitamin K(1)) analysis in human serum

The vitamin K external quality assurance scheme (KEQAS) aims to assist in the harmonization of phylloquinone (vitamin K(1)) analysis in order to improve the comparability of clinical and nutritional studies. Serum samples were despatched to 17 groups from eight countries during 2000-2006. Using pilot data (1996-1999), an analytical performance target of 20% absolute difference from the all-laboratory trimmed mean (ALTM) was assigned and formed the basis for interlaboratory comparison. Assay specificity, analytical bias and assay performance were evaluated. From 21 batches of samples distributed, 414 results were reported of which 2.7% were outliers. The mean interlaboratory absolute difference from the ALTM was 21.7% with 47% of groups consistently meeting the performance target. The mean interlaboratory coefficient of variation was 29.6%. The false positive rate for phylloquinone depleted samples was high at 35%. Bias was found to be independent of HPLC-detector type (fluorescence vs electrochemical). Assay characteristics for the measurement of phylloquinone in human serum compare favourably with methods for analytes at equivalent concentrations. The high proportion of false positive results suggest that poor assay specificity at low phylloquinone concentrations is a common problem, which in the clinical setting could lead to underreporting of vitamin K deficiency.

The effect of different meals on the absorption of stable isotope-labelled phylloquinone

Few studies have investigated the absorption of phylloquinone (vitamin K1). We recruited twelve healthy, non-obese adults. On each study day, fasted subjects took a capsule containing 20 microg of 13C-labelled phylloquinone with one of three meals, defined as convenience, cosmopolitan and animal-oriented, in a three-way crossover design. The meals were formulated from the characteristics of clusters identified in dietary pattern analysis of data from the National Diet and Nutrition Survey conducted in 2000-1. Plasma phylloquinone concentration and isotopic enrichment were measured over 8 h. Significantly more phylloquinone tracer was absorbed when consumed with the cosmopolitan and animal-oriented meals than with the convenience meal (P = 0.001 and 0.035, respectively). Estimates of the relative availability of phylloquinone from the meals were: convenience meal = 1.00; cosmopolitan meal = 0.31; animal-oriented meal = 0.23. Combining the tracer data with availability estimates for phylloquinone from the meals provides overall relative bioavailability values of convenience = 1.00, cosmopolitan = 0.46 and animal-oriented = 0.29. Stable isotopes provide a useful tool to investigate further the bioavailability of low doses of phylloquinone. Different meals can affect the absorption of free phylloquinone. The meal-based study design used in the present work provides an approach that reflects more closely the way foods are eaten in a free-living population.

Vitamin K, an example of triage theory: is micronutrient inadequacy linked to diseases of aging?

The triage theory posits that some functions of micronutrients (the approximately 40 essential vitamins, minerals, fatty acids, and amino acids) are restricted during shortage and that functions required for short-term survival take precedence over those that are less essential. Insidious changes accumulate as a consequence of restriction, which increases the risk of diseases of aging. For 16 known vitamin K-dependent (VKD) proteins, we evaluated the relative lethality of 11 known mouse knockout mutants to categorize essentiality. Results indicate that 5 VKD proteins that are required for coagulation had critical functions (knockouts were embryonic lethal), whereas the knockouts of 5 less critical VKD proteins [osteocalcin, matrix Gla protein (Mgp), growth arrest specific protein 6, transforming growth factor beta-inducible protein (Tgfbi or betaig-h3), and periostin] survived at least through weaning. The VKD gamma-carboxylation of the 5 essential VKD proteins in the liver and the 5 nonessential proteins in nonhepatic tissues sets up a dichotomy that takes advantage of the preferential distribution of dietary vitamin K1 to the liver to preserve coagulation function when vitamin K1 is limiting. Genetic loss of less critical VKD proteins, dietary vitamin K inadequacy, human polymorphisms or mutations, and vitamin K deficiency induced by chronic anticoagulant (warfarin/coumadin) therapy are all linked to age-associated conditions: bone fragility after estrogen loss (osteocalcin) and arterial calcification linked to cardiovascular disease (Mgp). There is increased spontaneous cancer in Tgfbi mouse knockouts, and knockdown of Tgfbi causes mitotic spindle abnormalities. A triage perspective reinforces recommendations of some experts that much of the population and warfarin/coumadin patients may not receive sufficient vitamin K for optimal function of VKD proteins that are important to maintain long-term health.

Roles for vitamin K beyond coagulation

Recent interest in vitamin K has been motivated by evidence of physiological roles beyond that of coagulation. Vitamin K and vitamin K-dependent (VKD) proteins may be involved in regulation of calcification, energy metabolism, and inflammation. However, the evidence for many of these proposed roles in the maintenance of health is equivocal. There is also an emerging viewpoint that the biochemical function of vitamin K may extend beyond that of a cofactor for the VKD carboxylation of glutamyl residues (Glus) to carboxylated Glus in VKD proteins.

Vitamin K, circulating cytokines, and bone mineral density in older men and women

BACKGROUND

Vitamin K modulates cytokines involved in bone turnover, including interleukin-6 (IL-6) and osteoprotegerin in vitro.

OBJECTIVE

The objective of this study was to assess 1) associations between measures of vitamin K status [plasma phylloquinone and serum percentage of undercarboxylated osteocalcin (%ucOC)] and IL-6, osteoprotegerin, and C-reactive protein (CRP) concentrations and 2) the effect of daily 500 mug phylloquinone supplementation for 3 y on cytokine concentrations.

DESIGN

Concentrations of IL-6, osteoprotegerin, and CRP and bone mineral density (BMD) were measured at baseline and after 3 y of follow-up in 379 healthy men and women (60-81 y; 58.5% women) participating in a randomized trial that studied the effect of vitamin K supplementation on bone loss.

RESULTS

Cross-sectionally, plasma phylloquinone was inversely associated with IL-6 and CRP, whereas serum %ucOC was inversely associated with IL-6. Osteoprotegerin was associated positively with plasma phylloquinone and inversely with %ucOC. No differences were observed in the 3-y change in IL-6, osteoprotegerin, and CRP concentrations between participants who received phylloquinone supplementation and those who did not. Overall, no association was observed between the 3-y changes in circulating cytokines and BMD.

CONCLUSIONS

Poor vitamin K status was associated with high concentrations of cytokines involved in bone turnover, but vitamin K supplementation did not confer a decrease in cytokine concentrations. The healthy status of this cohort may explain a lack of effect of vitamin K supplementation on cytokine concentrations. This trial was registered with www.clinicaltrials.gov as NCT00183001.

Determinants of vitamin K status in humans

To understand the role of vitamin K in human health, it is important to identify determinants of vitamin K status throughout the life cycle. Our current understanding of vitamin K physiology and metabolism only partially explains why there is wide interindividual variation in vitamin K status, as measured by various biochemical measures. Dietary intake of vitamin K is one of the primary determinants of vitamin K status, and intakes vary widely among age groups and population subgroups. How dietary sources of vitamin K are absorbed and transported varies with the form and food source of vitamin K. Likewise, the role of plasma lipids as a determinant of vitamin K status varies with the form of vitamin K ingested. There is also some evidence that other fat-soluble vitamins antagonize vitamin K under certain physiological conditions. Infants are at the greatest risk of vitamin K deficiency because of a poor maternal-fetal transfer across the placenta and low vitamin K concentrations in breast milk. During adulthood, there may be subtle age-related changes in vitamin K status but these are inconsistent and may be primarily related to dietary intake and lifestyle differences among different age groups. However, there is some suggestion that absence of estrogen among postmenopausal women may be a determinant of vitamin K, status. Genetics may explain some of the observed interindividual variability in vitamin K, but to date, there are few studies that have systematically explored the associations between individual genetic polymorphisms and biochemical measures of vitamin K status.

A stable isotope method for the simultaneous measurement of vitamin K1 (phylloquinone) kinetics and absorption

OBJECTIVES

To measure uptake and disposal kinetics and absolute absorption of vitamin K(1) using two stable isotope-labelled forms of vitamin K(1).

SUBJECTS

Ten subjects (nine women and one man) aged between 22 and 31 years, with a mean (+/-standard deviation) body mass index of 22.5+/-2.4 kg/m(2). Subjects took capsules containing 3 microg of methyl-(13)C vitamin K(1), three times a day for six days to reach a steady state for plasma vitamin K(1) isotopic enrichment. On day seven, subjects were given an intravenous dose of Konakion MM to measure disposal kinetics and at the same time, a capsule containing 4 microg of ring-D(4) vitamin K(1) to measure absorption. Plasma vitamin K(1) concentration was measured by high-performance liquid chromatography and isotopic composition by gas chromatography mass spectrometry.

RESULTS

The disposal kinetics of the intravenous dose of vitamin K(1) were resolved into two exponentials with half-times of 0.22 (+/-0.14) and 2.66 (+/-1.69) h. Absorption of oral, deuterated vitamin K(1) was 13 (+/-9)%.

CONCLUSIONS

Two-compartmental kinetic parameters observed in this study are similar to those obtained previously using radioactive tracers, but there may be additional slow-turnover body pools acting as stores of vitamin K(1). The kinetic parameters determined from the intravenous dose allowed determination of the absolute absorption of vitamin K(1) from a bolus oral dose.

Two-year randomized controlled trial of vitamin K1 (phylloquinone) and vitamin D3 plus calcium on the bone health of older women

Dietary supplementation with vitamin K(1), with vitamin D(3) and calcium or their combination, was examined in healthy older women during a 2-year, double-blind, placebo-controlled trial. Combined vitamin K with vitamin D plus calcium was associated with a modest but significant increase in BMC at the ultradistal radius but not at other sites in the hip or radius.

INTRODUCTION

The putative beneficial role of high dietary vitamin K(1) (phylloquinone) on BMD and the possibility of interactive benefits with vitamin D were studied in a 2-year double-blind, placebo-controlled trial in healthy Scottish women > or =60 years of age.

MATERIALS AND METHODS

Healthy, nonosteoporotic women (n = 244) were randomized to receive either (1) placebo, (2) 200 microg/day vitamin K(1), (3) 10 microg (400 IU) vitamin D(3) plus 1000 mg calcium/day, or (4) combined vitamins K(1) and D(3) plus calcium. Baseline and 6-month measurements included DXA bone mineral scans of the hip and wrist, markers of bone turnover, and vitamin status. Supplementation effects were tested using multivariate general linear modeling, with full adjustment for baseline and potential confounding variables.

RESULTS

Significant bone mineral loss was seen only at the mid-distal radius but with no significant difference between groups. However, women who took combined vitamin K and vitamin D plus calcium showed a significant and sustained increase in both BMD and BMC at the site of the ultradistal radius. Serum status indicators responded significantly to respective supplementation with vitamins K and D. Over 2 years, serum vitamin K(1) increased by 157% (p < 0.001), the percentage of undercarboxylated osteocalcin (%GluOC) decreased by 51% (p < 0.001), serum 25-hydroxyvitamin D [25(OH)D] increased by 17% (p < 0.001), and PTH decreased by 11% (p = 0.049).

CONCLUSIONS

These results provide evidence of a modest synergy in healthy older women from nutritionally relevant intakes of vitamin K(1) together with supplements of calcium plus moderate vitamin D(3) to enhance BMC at the ultradistal radius, a site consisting of principally trabecular bone. The substantial increase in gamma-carboxylation of osteocalcin by vitamin K may have long-term benefits and is potentially achievable by increased dietary intakes of vitamin K rather than by supplementation.

Intake and sources of phylloquinone (vitamin K1): variation with socio-demographic and lifestyle factors in a national sample of British elderly people

Intake and sources of phylloquinone (vitamin K1) were examined according to socio-demographic and lifestyle factors in free-living British people aged 65 years and over, from the 1994–5 National Diet and Nutrition Survey. Complete 4-d weighed dietary records were obtained from 1152 participants living in private households. Using newly-available, mainly UK-specific food content data, the weighted geometric mean intake of phylloquinone was estimated at 65 (95 % CI 62, 67) μg/d for all participants, with higher intakes in men than in women (70 v. 61 μg/d respectively, P<0·01). The mean nutrient densities of phylloquinone intake were 9·3 and 10·5 μg/MJ for men and women respectively (P<0·01), after adjusting for age group, region and smoking status. Of all the participants, 59 % had phylloquinone intakes below the current guideline for adequacy of 1 μg/kg body weight per d. Participants aged 85 years and over, formerly in manual occupations, or living in Scotland or in northern England reported lower phylloquinone intakes than their comparative groups. Overall, vegetables contributed 60 % of total phylloquinone intake, with cooked green vegetables providing around 28 % of the total. Dietary supplements contributed less than 0·5 % of phylloquinone intake. Participants living in northern England or in Scotland, in particular, derived less phylloquinone from vegetables than those living in southern England.

Determinants of plasma dihydrophylloquinone in men and women

Commercial hydrogenation results in the formation of trans fatty acids. An unintended consequence of the hydrogenation process is conversion of phylloquinone (vitamin K1) to dihydrophylloquinone. Plasma dihydrophylloquinone concentrations have yet to be characterized in population-based studies. Dietary determinants of plasma dihydrophylloquinone were estimated using a semi-quantitative food frequency questionnaire in 803 men and 913 women in the Framingham Offspring Study. Geometric mean dihydrophylloquinone intake was 21·3 (95 % CI 20·4, 22·3) μg/d in men and 19·4 (95 % CI 18·5, 20·2) μg/d in women. Detectable (>0·05 nmol/l) plasma dihydrophylloquinone concentrations were measured in 41 % and 30 % of men and women, respectively. The multivariate odds ratio (OR) of detectable plasma dihydrophylloquinone from the lowest to the highest quartile category of dihydrophylloquinone intake were 1 (referent), 1·13 (95 % CI 0·83, 1·53), 1·66 (95 % CI 1·21, 2·26) and 1·84 (95 % CI 1·31, 2·58), P for trend <0·001, adjusted for sex, age, body mass index, triacylglycerols, season and energy intake. Higher trans fatty acid intake was associated with higher multivariate OR for detectable plasma dihydrophylloquinone (OR comparing extreme quartiles 2·41 (95 % CI 1·59, 3·64), P for trend <0·001). There were limitations in the use of plasma dihydrophylloquinone, evident in the high proportion of the population that had non-detectable dihydrophylloquinone concentrations. Despite this caveat, higher plasma dihydrophylloquinone was associated with higher dihydrophylloquinone intake and higher trans fatty acid intake.

Comparative dietary intake and sources of phylloquinone (vitamin K1) among British adults in 1986-7 and 2000-1

Using data from 7 d weighed dietary records, dietary intake and sources of phylloquinone (vitamin K1) were examined by socio-demographic and lifestyle factors in 1916 participants aged 16-64 years from the 1986-7 Dietary and Nutritional Survey of British Adults, and 1423 participants aged 19-64 years from the 2000-1 National Diet and Nutrition Survey. Using UK-specific food content data, geometric mean phylloquinone intakes were estimated as 72 (95% CI 70, 74) and 67 (95% CI 65, 69) microg/d in 1986-7 and 2000-1 respectively (P<0.001). In 1986-7, 47% of participants had phylloquinone intakes below the UK guideline for adequacy (> or =1 microg/kg body weight per d), compared with 59% in 2000-1 (P<0.001). In both surveys, daily phylloquinone intake was higher among men than women and increased significantly with age. Participants of manual occupational social class, or who were smokers, had lower phylloquinone intake than their counterparts. Participants living in Scotland and northern England had lower phylloquinone intake than those living elsewhere in mainland Britain, particularly in 1986-7 when the contribution from vegetables was also lower than elsewhere. However, by 2000-1 this regional difference was no longer significant. Overall, vegetables contributed 63% of phylloquinone intake in 1986-7 and 60% in 2000-1, with cooked leafy green vegetables (LGV) providing 23 and 19% respectively. In both surveys, the contribution of vegetables (cooked LGV in particular) was directly associated with age. These data show a decrease in phylloquinone intake from 1986-7 to 2000-1, mainly owing to lower consumption of cooked LGV.

Plasma phylloquinone (vitamin K1) concentration and its relationship to intake in British adults aged 19-64 years

Plasma phylloquinone (vitamin K1) concentration from non-fasted blood samples was examined by season, smoking status, socio-demographic factors and phylloquinone intake in a nationally representative sample of 1154 British individuals aged 19-64 years from the 2000-1 National Diet and Nutrition Survey. Geometric mean plasma phylloquinone concentration was 0.94 (95% CI 0.88, 1.00) nmol/l, with 95% of values in the range 0.10-8.72 nmol/l. Plasma phylloquinone concentrations of 530 men were significantly higher than those of 624 women (1.13 (95% CI 1.04, 1.22) v. 0.81 (95% CI 0.74, 0.88) nmol/l; P<0.001), independent of other factors. Women aged 19-34 years had significantly lower plasma phylloquinone concentration than their older counterparts. Women were also found to have lower plasma phylloquinone concentrations during summer compared with winter and spring (each P<0.01). In contrast, plasma phylloquinone concentration in men did not vary significantly by season or any of the socio-demographic or lifestyle factors. Plasma phylloquinone concentrations were positively correlated with phylloquinone intake in men and women (r 0.26 and 0.32 respectively; each P<0.001). Overall, forward stepwise multiple regression analysis revealed that 8% of the variation in plasma phylloquinone concentration was explained by phylloquinone intake, with a further 10% of its variation explained by plasma concentrations of gamma-tocopherol (6%) and retinyl palmitate (4%). After adjustment for age and corresponding nutrient intakes, plasma phylloquinone concentration was significantly associated (each P<0.01) with plasma concentrations of total and LDL-cholesterol, alpha- and gamma-tocopherols, retinyl palmitate, beta-carotene, lycopene and lutein plus zeaxanthin in men and women.

Dietary vitamin K intake and anticoagulation in elderly patients

PURPOSE OF REVIEW

Vitamin K is an essential co-factor for the synthesis of several coagulation factors. Oral anticoagulants competitively inhibit enzymes that participate in vitamin K metabolism. The purpose of this review is to evaluate the potential interaction of dietary vitamin K and coagulation stability, particularly in the elderly patient.

RECENT FINDINGS

Recent prospective evidences suggest that dietary vitamin K plays an essential role in anticoagulation stability. Vitamin K intake of more than 250 microg/day was shown to decrease warfarin sensitivity in anticoagulated patients consuming regular diets. In a randomized crossover study, brief periods of changes on vitamin K intake also had significant effects on coagulation parameters. Patients that were allocated to an 80% decrease of intake increased International Normalized Ratio (INR) by almost 30% 7 days after the intervention. Similarly, it was estimated by dietary records that for each increase in 100 microg of vitamin K intake, the INR would be reduced by 0.2. A recent study also demonstrated that over-the-counter multivitamin supplements contain enough vitamin K1 to significantly alter coagulation parameters.

SUMMARY

Contemporary data strengthen the concept that the interaction between dietary vitamin K and coumarin derivatives is clinically relevant and plays a major role in INR fluctuations in chronic anticoagulated patients.

Effect of calcium fortified milk supplementation with or without vitamin K on biochemical markers of bone turnover in premenopausal women

OBJECTIVE

We compared the effect of supplementation with a fortified skimmed milk product (high calcium skim milk) with or without added phylloquinone (vitamin K(1)) on markers of bone formation and resorption in premenopausal women.

METHODS

Eighty-two women 20 to 35 y of age were randomly allocated to three groups. Two groups received two daily servings of high calcium skim milk (1000 mg/d of extra calcium) with or without added phylloquinone (80 microg/d) for 16 wk, and a third control group received no supplementation. Bone density was assessed at baseline and the bone markers, total osteocalcin, type I N-terminal procollagen peptide, and cross-linked C-telopeptide of type I collagen were measured at baseline and at weeks 2, 12, and 16. Serum phylloquinone and undercarboxylated osteocalcin were measured in the control and vitamin K-supplemented groups at weeks 0 and 16.

RESULTS

Baseline values for age, body mass index, and bone density did not differ across groups. In vitamin K-supplemented women, mean serum phylloquinone concentrations increased from 0.27 to 0.76 microg/L (P < 0.05) and undercarboxylated osteocalcin concentrations decreased from 9.68 to 4.46 microg/L (P < 0.05) over 16 wk. Plasma cross-linked C-telopeptide of type I collagen, total osteocalcin, and type I N-terminal procollagen peptide levels decreased significantly in both supplemented groups compared with the control group over 16 wk (cross-linked C-telopeptide of type I collagen >30%, total osteocalcin and type I N-terminal procollagen peptide >15%).

CONCLUSION

Fortified milk supplementation in premenopausal women reduced bone turnover significantly. Phylloquinone fortification substantially improved vitamin K status but had no demonstrable additive effect on bone turnover in this short-term study.

Biodisponibilidade de vitaminas lipossolúveis

O termo biodisponibilidade representa a parte do nutriente ingerido que tem o potencial de suprir as demandas fisiológicas em tecidos alvos; por definição, não corresponde, na maioria das vezes, à quantidade ingerida. Apesar da concordância entre alguns pesquisadores no que se refere ao conceito de biodisponibilidade, vários termos são comumente utilizados em trabalhos científicos como sinônimos desse, em função das peculiaridades dos métodos empregados na sua determinação. Estudos de balanço, relação dose-efeito e uso de isótopos são alguns dos métodos mais comumente utilizados para determinar a biodisponibilidade de vitaminas. Tais metodologias, além de avaliar a biodisponibilidade do nutriente, devem tanto quanto possível procurar elucidar ou levar em consideração os fatores que interferem na sua absorção e utilização. Dentre esses fatores, estão a interação com outros nutrientes ou componentes da dieta e as condições fisiológicas dos organismos submetidos ao estudo. As vitaminas lipossolúveis, devido ao seu metabolismo complexo, diversidade funcional e mecanismo de absorção relacionado a lipoproteínas, apresentam alguns problemas específicos no que se refere à avaliação de sua biodisponibilidade em alimentos ou dietas, necessitando, por ocasião dos ensaios, de um criterioso planejamento e análise de resultados. Dessa forma, ressaltaram-se, nesta revisão, alguns aspectos importantes com relação à biodisponibilidade das vitaminas lipossolúveis, como: diversidade de termos usados, metodologia para avaliação, fatores que interferem na absorção e utilização, entre outros, visto que a avaliação da biodisponibilidade de algumas vitaminas lipossolúveis ainda não possui métodos validados, gerando uma grande variação nos resultados obtidos nas pesquisas realizadas nesta área.

Intake and sources of phylloquinone (vitamin K(1)) in 4-year-old British children: comparison between 1950 and the 1990s

OBJECTIVES

To compare dietary intake and sources of phylloquinone (vitamin K1) in 4-year-old British children between 1950 and the 1990s, and report their variation by sociodemographic factors.

DESIGN

Nationally representative samples of 4-year-olds from the longitudinal Medical Research Council National Survey of Health and Development (NSHD) (1950) and the cross-sectional National Diet and Nutrition Surveys (NDNS, 1992/93 and 1997).

SETTING

Great Britain.

SUBJECTS

Subjects were 4599 children born on 3-9 March 1946 (NSHD) and 307 children in the 1990s (NDNS).

RESULTS

Geometric mean dietary phylloquinone intake was significantly higher in 1950 (39 mug day(-1), 95% confidence interval (CI) 37, 40) compared with the 1990s (24 mug day(-1), 95% CI 22, 25) (P<0.001). This difference remained when intake was expressed per MJ energy intake and per kilogram body weight, and after accounting for sex, region and occupational social class of the family. In 1950, phylloquinone intake in Scotland was significantly lower than in the rest of Britain. By the 1990s these regional differences had disappeared. Food sources of phylloquinone intake changed significantly between 1950 and the 1990s, with fats and oils contributing more and vegetables less, although vegetables contributed most (60% and 48%, respectively) to phylloquinone intake in both surveys.

CONCLUSIONS

Phylloquinone intakes of children have decreased significantly since 1950. With the suggested need for adequate phylloquinone intake for optimal development and maintenance of bone and the cardiovascular system, the substantially lower phylloquinone intakes reported in children of the 1990s, compared with 1950, may have implications for the health of these two systems in later adulthood.

Ethnic differences in osteocalcin gamma-carboxylation, plasma phylloquinone (vitamin K1) and apolipoprotein E genotype

OBJECTIVE

To investigate plasma osteocalcin gamma-carboxylation and its relationship to plasma phylloquinone concentration and apolipoprotein E (apoE) genotype in women from three ethnic groups with differing osteoporotic fracture risk.

DESIGN AND SUBJECTS

Fasted blood samples were collected from postmenopausal Gambian (n=50), British (n=31) and Chinese women (n=23), and 11 premenopausal women in each group from three cross-sectional studies.

RESULTS

After adjustment for total osteocalcin, plasma undercarboxylated osteocalcin (adjusted ucOC) was lowest in Chinese and highest in British women postmenopause (British vs Chinese 103% higher, P<0.0001; Gambian vs Chinese 66% higher, P<0.01). No differences were observed premenopause. Within each ethnic group, adjusted ucOC was similar pre- and postmenopause. Postmenopause, plasma phylloquinone was higher in Chinese women (1.0 ng/ml) than in British (0.31 ng/ml) and Gambian women (0.36 ng/ml) (P<0.0001). Premenopause, plasma phylloquinone was higher in Gambian and Chinese women (0.6 ng/ml) than in British women (0.3 ng/ml; P=0.01). Plasma phylloquinone and adjusted ucOC were inversely related in postmenopausal British women (R2=32.4%; P=0.0008). ApoE4 frequency was Gambian 32.6%, British 13.8% and Chinese 6%. A lower adjusted ucOC was associated with apoE2 genotype in British and Chinese women. Ethnic differences in adjusted ucOC persisted after adjustment for phylloquinone and apoE genotype.

CONCLUSION

These preliminary data indicate suboptimal vitamin K status in postmenopausal British compared to Chinese and Gambian women. Ethnic differences in apoE genotype may also influence osteocalcin gamma-carboxylation status. The study highlights the need for larger epidemiological investigations of ethnic differences in vitamin K status and the possible implications to bone health.

Dietary acid-base balance and intake of bone-related nutrients in Cambridge teenagers

OBJECTIVES

To evaluate the diet of 16-18-y-old boys and girls with particular reference to intakes of nutrients believed to affect bone health and dietary acid-base balance.

DESIGN

A 7-day food diary was completed between the months of October and December.

SETTING

Cambridge, UK.

SUBJECTS

A total of 111 boys and 101 girls aged 16-18 y who were recruited into the Cambridge Bone Studies.

MAIN OUTCOME MEASURES

Mean daily intakes of foods and selected nutrients (protein, calcium, phosphorus, magnesium, potassium, vitamins C and K) were calculated. Two estimates of acid-base balance were calculated from the diet using the formulae of Remer (net acid excretion, estimated indirectly; NAE(ind)) and Frassetto (protein/potassium ratio).

RESULTS

Mean calcium and phosphorus intakes were above the UK Reference Nutrient intake (RNI). In all, 39% of the boys and 36% of the girls had vitamin K intakes lower than 1 microg/kg body weight/day. Calcium intake was positively correlated with all other nutrients except vitamins C and K. Boys had a significantly higher estimated net acid excretion (NAE(ind)) than girls (P<0.001). Although a strong correlation (r=0.76, P<0.001) was found between the two methods, at higher acid levels a divergence was observed. A significant positive correlation was found between NAE(ind) and the weight consumed per day of milk, cheese, meat and cereal foods and a negative correlation was found with the weight of potatoes and fruit. Diet composition is such that a lower NAE(ind) is accompanied by a lower calcium intake.

CONCLUSIONS

The interpretation of the effects of calcium and other nutrients on bone cannot be considered in isolation from the other components of the diet. These results challenge some of the accepted perceptions about what constitutes an optimal diet for the promotion of bone health in adolescents.