Factors associated with serum/plasma concentrations of vitamins A, C, E and carotenoids in older people throughout Europe: the EUREYE study

Association between serum retinol and overall and cause-specific mortality in a 30-year prospective cohort study

How retinol as a clinical indicator of vitamin A status is related to long-term mortality is unknown. Here we report the results of a prospective analysis examining associations between serum retinol and risk of overall and cause-specific mortality. During a 30-year cohort follow-up, 23,797 deaths were identified among 29,104 men. Participants with higher serum retinol experienced significantly lower overall, CVD, heart disease, and respiratory disease mortality compared to men with the lowest retinol concentrations, reflecting 17–32% lower mortality risk (P_trend < 0.0001). The retinol-overall mortality association is similar across subgroups of smoking intensity, alcohol consumption, body mass index, trial supplementation, serum alpha-tocopherol and beta-carotene concentrations, and follow-up time. Mediation analysis indicated that <3% of the effects of smoking duration and diabetes mellitus on mortality were mediated through retinol concentration. These findings indicate higher serum retinol is associated with lower overall mortality, including death from cardiovascular, heart, and respiratory diseases.

Vitamin A, of which retinol is the major form in the circulation, is a determinant of human health but whether vitamin A status is associated with mortality is not well understood. Here the authors report that in a prospective observational analysis of 29 104 men, higher serum retinol associates with lower risk of overall and cause-specific mortality.

Whey- and Soy Protein Isolates Added to a Carrot-Tomato Juice Alter Carotenoid Bioavailability in Healthy Adults

Recent findings suggested that proteins can differentially affect carotenoid bioaccessibility during gastro-intestinal digestion. In this crossover, randomized human trial, we aimed to confirm that proteins, specifically whey- and soy-protein isolates (WPI/SPI) impact postprandial carotenoid bioavailability. Healthy adults (n = 12 males, n = 12 females) were recruited. After 2-week washout periods, 350 g of a tomato-carrot juice mixture was served in the absence/presence of WPI or SPI (50% of the recommended dietary allowance, RDA ≈ 60 g/d). Absorption kinetics of carotenoids and triacylglycerols (TAGs) were evaluated via the triacylglycerol-rich lipoprotein (TRL) fraction response, at timed intervals up to 10 h after test meal intake, on three occasions separated by 1 week. Maximum TRL-carotenoid concentration (C_max) and corresponding time (T_max) were also determined. Considering both genders and carotenoids/TAGs combined, the estimated area under the curve (AUC) for WPI increased by 45% vs. the control (p = 0.018), to 92.0 ± 1.7 nmol × h/L and by 57% vs. SPI (p = 0.006). Test meal effect was significant in males (p = 0.036), but not in females (p = 0.189). In males, significant differences were found for phytoene (p = 0.026), phytofluene (p = 0.004), α-carotene (p = 0.034), and β-carotene (p = 0.031). C_max for total carotenoids (nmol/L ± SD) was positively influenced by WPI (135.4 ± 38.0), while significantly lowered by SPI (89.6 ± 17.3 nmol/L) vs. the control (119.6 ± 30.9, p < 0.001). T_max did not change. The results suggest that a well-digestible protein could enhance carotenoid bioavailability, whereas the less digestible SPI results in negative effects. This is, to our knowledge, the first study finding effects of proteins on carotenoid absorption in humans.

Alcohol consumption and serum metabolite concentrations in young women

PURPOSE

Alcohol consumption is an established breast cancer risk factor, though further research is needed to advance our understanding of the mechanism underlying the association. We used global metabolomics profiling to identify serum metabolites and metabolic pathways that could potentially mediate the alcohol-breast cancer association.

METHODS

A cross-sectional analysis of reported alcohol consumption and serum metabolite concentrations was conducted among 211 healthy women 25-29 years old who participated in the Dietary Intervention Study in Children 2006 Follow-Up Study (DISC06). Alcohol-metabolite associations were evaluated using multivariable linear mixed-effects regression.

RESULTS

Alcohol was significantly (FDR p < 0.05) associated with several serum metabolites after adjustment for diet composition and other potential confounders. The amino acid sarcosine, the omega-3 fatty acid eicosapentaenoate, and the steroid 4-androsten-3beta,17beta-diol monosulfate were positively associated with alcohol intake, while the gamma-tocopherol metabolite gamma-carboxyethyl hydroxychroman (CEHC) was inversely associated. Positive associations of alcohol with 2-methylcitrate and 4-androsten-3beta,17beta-diol disulfate were borderline significant (FDR p < 0.10). Metabolite set enrichment analysis identified steroids and the glycine pathway as having more members associated with alcohol consumption than expected by chance.

CONCLUSIONS

Most of the metabolites associated with alcohol in the current analysis participate in pathways hypothesized to mediate the alcohol-breast cancer association including hormonal, one-carbon metabolism, and oxidative stress pathways, but they could also affect risk via alternative pathways. Independent replication of alcohol-metabolite associations and prospective evaluation of confirmed associations with breast cancer risk are needed.

A Cross-Sectional Study on Malnutrition in Inflammatory Bowel Disease: Is There a Difference Based on Pediatric or Adult Age Grouping?

BACKGROUND

Malnutrition, commonly observed in inflammatory bowel disease (IBD), is associated with increased morbidity and mortality and is attributed to multiple causes. The added energy costs of growth in the child and adolescent with IBD are an additional risk factor.

METHODS

The aim of the study was to perform a cross-sectional comparison of nutritional parameters in IBD between pediatric and adult cases.

RESULTS

We found that prevalence of undernutrition (low body mass index) and hypoalbuminemia was not different in pediatric, compared with adult patients. Anemia and iron deficiency were more often observed in pediatric subjects, compared with adults (59.1% vs 36.9%, respectively, P < 0.0001; and 37.9% vs 25.3%, P < 0.002). Vitamin B12 deficiency was significantly less common in the pediatric than in the adult group (5.4% vs 19.4%, P < 0.0001). Elevated C-reactive protein was more frequent in pediatric compared with adult cases (49.8% vs 38.4%, P < 0.01).

CONCLUSIONS

Patients with active Crohn's disease were more likely to be undernourished in both pediatric and adult populations. In both groups, predicators of undernutrition included low albumin levels (odds ratio [OR], 2.53; P < 0.006) and active disease (OR, 1.99; P < 0.03). Our results call for close surveillance of nutritional status for IBD patients, regardless of age.

Reduced aqueous humour ascorbic-acid concentration in women with smaller anterior chamber depth

Short anterior chamber depth (ACD) is considered a risk factor of endothelial-cell loss after phacoemulsification. However, whether it is an independent risk factor or not remains controversial. We investigated the relationship between ascorbic acid (AA) concentrations in the aqueous humour (AqH) and ACD. We analysed 165 AqH samples of 97 patients (42 men and 55 women) who underwent small incision cataract surgery. AqH and plasma AA concentrations were measured using a high-performance liquid chromatography - electrochemical detection method. Patient characteristics were compared between and within the sexes. As a result, age and ACD were significantly correlated with AqH AA concentrations (r = −0.206, P = 0.045; r = 0.339, P < 0.001) only in women. Moreover, plasma AA concentrations were significantly correlated with AqH AA concentrations (r = 0.420, P < 0.001; r = 0.316, P = 0.002) both in men and women. After adjusting for confounding factors (age and plasma AA concentrations), ACD was significantly and positively correlated with AqH AA concentrations (partial.r = 0.275, P = 0.009) only in women. In conclusion, AqH AA concentrations were reduced in women with smaller ACD. This may suggest that women with short ACD could be more susceptible to oxidative damage.

Correlates of the difference in plasma carotenoid concentrations between men and women

Health professionals consider the evaluation of eating habits to be challenging, given the potential biases of dietary questionnaires based on self-reported data. Circulating carotenoid concentrations are reliable biomarkers of dietary carotenoid intake and could be useful in the validation of dietary assessment tools. However, there is a sex difference in circulating carotenoids, with women displaying higher concentrations compared with men independent of intake. The aim of the present study was to identify the correlates of plasma carotenoid concentrations among men (n 155) and women (n 110) enrolled in six fully controlled dietary interventions with varying dietary carotenoid intakes. We looked at the associations of post-intervention fasting plasma carotenoid concentrations (α-carotene, β-carotene, β-cryptoxanthin, lutein, lycopene and zeaxanthin) with physical and metabolic characteristics. We found that increased body weight (r -0·47, P&lt;0·0001) and waist circumference (r -0·46, P&lt;0·0001) were associated with lower plasma total carotenoid concentrations, while elevated plasma LDL-cholesterol (r 0·49, P&lt;0·0001) and HDL-cholesterol (r 0·50, P&lt;0·0001) concentrations were correlated with higher total carotenoids in plasma. Women had significantly higher plasma total carotenoid concentrations compared with men, despite significantly lower dietary carotenoid intake. Adjustment of circulating carotenoid concentrations for plasma HDL-cholesterol eliminated sex difference in plasma carotenoid concentrations. Our results suggest that physical characteristics as well as plasma lipids are associated with circulating carotenoid concentrations and that these variables should be taken into account when using plasma carotenoids as biomarkers for food intake in men and women.

Genetic and Common Environmental Contributions to Familial Resemblances in Plasma Carotenoid Concentrations in Healthy Families

Carotenoids have shown an interindividual variability that may be due to genetic factors. The only study that has reported heritability of serum α- and β-carotene has not considered the environmental component. This study aimed to estimate the contribution of both genetic and common environmental effects to the variance of carotenoid concentrations and to test whether their phenotypic correlations with cardiometabolic risk factors are explained by shared genetic and environmental effects. Plasma carotenoid concentrations (α-carotene, β-carotene, β-cryptoxanthin, lutein, lycopene, zeaxanthin, and total carotenoids) of 48 healthy subjects were measured. Heritability estimates of carotenoid concentrations were calculated using the variance component method. Lutein and lycopene showed a significant familial effect (p = 6 × 10^-6 and 0.0043, respectively). Maximal heritability, genetic heritability, and common environmental effect were computed for lutein (88.3%, 43.8%, and 44.5%, respectively) and lycopene (45.2%, 0%, and 45.2%, respectively). Significant phenotypic correlations between carotenoid concentrations and cardiometabolic risk factors were obtained for β-cryptoxanthin, lycopene, and zeaxanthin. Familial resemblances in lycopene concentrations were mainly attributable to common environmental effects, while for lutein concentrations they were attributable to genetic and common environmental effects. Common genetic and environmental factors may influence carotenoids and cardiometabolic risk factors, but further studies are needed to better understand the potential impact on disease development.

Intrinsic and Extrinsic Factors Impacting Absorption, Metabolism, and Health Effects of Dietary Carotenoids

Carotenoids are orange, yellow, and red lipophilic pigments present in many fruit and vegetables, as well as other food groups. Some carotenoids contribute to vitamin A requirements. The consumption and blood concentrations of specific carotenoids have been associated with reduced risks of a number of chronic conditions. However, the interpretation of large, population-based observational and prospective clinical trials is often complicated by the many extrinsic and intrinsic factors that affect the physiologic response to carotenoids. Extrinsic factors affecting carotenoid bioavailability include food-based factors, such as co-consumed lipid, food processing, and molecular structure, as well as environmental factors, such as interactions with prescription drugs, smoking, or alcohol consumption. Intrinsic, physiologic factors associated with blood and tissue carotenoid concentrations include age, body composition, hormonal fluctuations, and variation in genes associated with carotenoid absorption and metabolism. To most effectively investigate carotenoid bioactivity and to utilize blood or tissue carotenoid concentrations as biomarkers of intake, investigators should either experimentally or statistically control for confounding variables affecting the bioavailability, tissue distribution, and metabolism of carotene and xanthophyll species. Although much remains to be investigated, recent advances have highlighted that lipid co-consumption, baseline vitamin A status, smoking, body mass and body fat distribution, and genetics are relevant covariates for interpreting blood serum or plasma carotenoid responses. These and other intrinsic and extrinsic factors are discussed, highlighting remaining gaps in knowledge and opportunities for future research. To provide context, we review the state of knowledge with regard to the prominent health effects of carotenoids.

Colonic Mucosal Bacteria Are Associated with Inter-Individual Variability in Serum Carotenoid Concentrations

BACKGROUND

Relatively high serum carotenoid levels are associated with reduced risks of chronic diseases, but inter-individual variability in serum carotenoid concentrations is modestly explained by diet. The bacterial community in the colon could contribute to the bioaccessibility of carotenoids by completing digestion of plant cells walls and by modulating intestinal permeability.

OBJECTIVE

To evaluate whether colonic bacterial composition is associated with serum and colon carotenoid concentrations.

DESIGN

The study was a randomized dietary intervention trial in healthy individuals who were at increased risk of colon cancer. Colon mucosal biopsy samples were obtained before and after 6 months of intervention without prior preparation of the bowels.

PARTICIPANTS/SETTING

Participants were recruited from Ann Arbor, MI, and nearby areas from July 2007 to November 2010. Biopsy data were available from 88 participants at baseline and 82 participants after 6 months.

METHODS

Study participants were randomized to counseling for either a Mediterranean diet or a Healthy Eating diet for 6 months.

RESULTS

At baseline, bacterial communities in biopsy samples from study participants in the highest vs the lowest tertile of total serum carotenoid levels differed by several parameters. Linear discriminant analysis effect size identified 11 operational taxonomic units that were significantly associated with higher serum carotenoid levels. In linear regression analyses, three of these accounted for an additional 12% of the variance in serum total carotenoid concentrations after including body mass index, smoking, and dietary intakes in the model. These factors together explained 36% of the inter-individual variance in serum total carotenoid concentrations. The bacterial community in the colonic mucosa, however, was resistant to change after dietary intervention with either a Mediterranean diet or Healthy Eating diet, each of which doubled fruit and vegetable intakes.

CONCLUSIONS

The colonic mucosal bacterial community was associated with serum carotenoid concentrations at baseline but was not appreciably changed by dietary intervention.

Use of biomarkers to assess fruit and vegetable intake

A high intake of fruit and vegetables (FV) has been associated with reduced risk of a number of chronic diseases, including CVD. The aim of this review is to describe the potential use of biomarkers to assess FV intake. Traditional methods of assessing FV intake have limitations, and this is likely to impact on observed associations with disease outcomes and markers of disease risk. Nutritional biomarkers may offer a more objective and reliable method of assessing dietary FV intake. Some single blood biomarkers, such as plasma vitamin C and serum carotenoids, are well established as indicators of FV intake. Combining potential biomarkers of intake may more accurately predict overall FV intake within intervention studies than the use of any single biomarker. Another promising approach is metabolomic analysis of biological fluids using untargeted approaches to identify potential new biomarkers of FV intake. Using biomarkers to measure FV intake may improve the accuracy of dietary assessment.

Non-Dietary Correlates and Determinants of Plasma Lutein and Zeaxanthin Concentrations in the Irish Population

OBJECTIVE

To investigate non-dietary correlates and determinants of plasma lutein (L) and zeaxanthin (Z) concentrations in The Irish Longitudinal Study on Ageing (TILDA) sample.

DESIGN

Cross-sectional study.

SETTING

Community dwelling adults in the Republic of Ireland (ROI).

PARTICIPANTS

3,681 participants aged 50 years and older.

MEASUREMENTS

TILDA is a nationally representative prospective cohort study of community dwelling adults aged 50 years and over in the ROI. Demographic and health variables were collected during a face-to-face interview carried out in the home (n=8175), and a substantial proportion of these (n=5035; 62%) also attended a study visit in a health assessment centre. Blood samples collected at baseline (wave 1, the subject of the current study), were analysed for plasma concentrations of L and Z by reversed-phase high performance liquid chromatography, and macular pigment (MP) optical density was also measured (using customized heterochromatic flicker photometry).

RESULTS

After excluding participants with eye disease, data from 3,681 participants were available for analysis. For this group of participants, plasma L and Z were inversely and significantly associated with body mass index (BMI), and were positively and significantly associated with MP, total cholesterol, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) (p<0.001, for all). Plasma L and Z were significantly lower in males, current smokers, participants reporting less physical exercise, and participants reporting lower levels of education (p<0.05, for all). Plasma L was significantly higher in participants reporting a family history of age-related macular degeneration (AMD) (p=0.001), and in the group of ≥75 years old (p<0.05). For each of these variables, the significant associations remained after controlling for other potential confounding variables.

CONCLUSION

The findings of this large study indicate that plasma concentrations of L and Z were lower in association with indicators of a poor lifestyle (high BMI, tobacco use, and less physical exercise) and in association with lower education, indicating that modifying lifestyle in a positive way is likely to be reflected in higher concentrations of plasma carotenoids, with consequential and putative health benefits.

Plasma Carotenoids, Tocopherols, and Retinol in the Age-Stratified (35-74 Years) General Population: A Cross-Sectional Study in Six European Countries

Blood micronutrient status may change with age. We analyzed plasma carotenoids, α-/γ-tocopherol, and retinol and their associations with age, demographic characteristics, and dietary habits (assessed by a short food frequency questionnaire) in a cross-sectional study of 2118 women and men (age-stratified from 35 to 74 years) of the general population from six European countries. Higher age was associated with lower lycopene and α-/β-carotene and higher β-cryptoxanthin, lutein, zeaxanthin, α-/γ-tocopherol, and retinol levels. Significant correlations with age were observed for lycopene (r = -0.248), α-tocopherol (r = 0.208), α-carotene (r = -0.112), and β-cryptoxanthin (r = 0.125; all p < 0.001). Age was inversely associated with lycopene (-6.5% per five-year age increase) and this association remained in the multiple regression model with the significant predictors (covariables) being country, season, cholesterol, gender, smoking status, body mass index (BMI (kg/m²)), and dietary habits. The positive association of α-tocopherol with age remained when all covariates including cholesterol and use of vitamin supplements were included (1.7% vs. 2.4% per five-year age increase). The association of higher β-cryptoxanthin with higher age was no longer statistically significant after adjustment for fruit consumption, whereas the inverse association of α-carotene with age remained in the fully adjusted multivariable model (-4.8% vs. -3.8% per five-year age increase). We conclude from our study that age is an independent predictor of plasma lycopene, α-tocopherol, and α-carotene.

Vitamins (A, C and E) and oxidative status of hemodialysis patients treated with HFR and HFR-Supra

BACKGROUND

Hemodiafiltration with on-line endogenous reinfusion (HFR) is an extracorporeal dialytic method that combines diffusion, convection and adsorption. HFR-Supra (HFR-S) is a second-generation system with increased convective permeability and adsorption capability. Previous studies suggested that HFR reduces oxidative stress compared to standard haemodialysis. The principal aim of the present study was to compare antioxidant vitamins behavior and oxidative status of hemodialysis patients treated with HFR and HFR-S.

METHODS

The study was designed as a multicenter, randomized, crossover trial. Forty-one patients were recruited from 19 dialysis centers and after a 4-month washout stabilization period in on-line hemodiafiltration (ol-HDF), each patient was randomized to a sequence of treatments (HFR-S followed by HFR or viceversa) with each treatment applied over 6 months. Plasma levels of Advanced Oxidation Protein Products, Total Antioxidant Status, vitamins C, A and E and their ligands (Retinol Binding Protein and total lipids) were measured at baseline and at the end of each treatment period.

RESULTS

Results show that the higher convective permeability of HFR-S with respect to HFR did not produce additional beneficial effects on the patients' oxidative status, a slight decrease of both Vitamin A and Retinol Binding Protein being the only difference registered in the long-term. However, as compared to ol-HDF, both the re-infusive techniques allowed to reduce the intradialytic loss of Vitamin C and, in the long-term, improve the patients' oxidative status and increase Retinol Binding Protein plasma values. No significant differences were found between the Vitamin C concentration of pre- and post cartridge UF neither in HFR-S nor in HFR showing that the sorbent resin does not adsorb Vitamin C.

CONCLUSION

HFR-S and HFR are almost equivalent in term of impact on antioxidant vitamins and oxidative status of hemodialysis patients. Nonetheless, as compared to ol-HDF, both treatments produced a sensible sparing of Vitamin C and may represent a new approach for reducing oxidative stress and related complications in dialysis patients. Long-term effects of re-infusive treatments on patients' cardiovascular morbidity and mortality need to be evaluated.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT01492491 , retrospectively registered in 10 December 2011.

Does the consumption of fruits and vegetables differ between Eastern and Western European populations? Systematic review of cross-national studies

BACKGROUND

Difference in fruit and vegetable consumption has been suggested as a possible reason for the large gap in cardiovascular disease (CVD) mortality rates between Eastern and Western European populations. However, individual-level dietary data which allow direct comparison across the two regions are rare. In this systematic review we aimed to answer the question whether cross-national studies with comparable individual-level dietary data reveal any systematic differences in fruit and vegetable consumption between populations in Central and Eastern Europe (CEE) and the Former Soviet Union (FSU) compared to Western Europe (WE).

METHODS

Studies were identified by electronic search of MEDLINE, EMBASE and Web of Science databases from inception to September 2014, and hand search. Studies which reported data on fruit, vegetable consumption or carotene and vitamin C intake or tissue concentrations of adult participants from both CEE/FSU and WE countries were considered for inclusion. Quality of the included studies was assessed by a modified STROBE statement. Power calculation was performed to determine the statistical significance of the comparison results.

RESULTS

Twenty-two studies fulfilled the inclusion criteria. Fruit consumption was found to be consistently lower in CEE/FSU participants compared to Western Europeans. Results on vegetable intake were less unambiguous. Antioxidant studies indicated lower concentration of beta-carotene in CEE/FSU subjects, but the results for vitamin C were not consistent.

CONCLUSION

This systematic review suggests that populations in CEE and FSU consume less fruit than Western Europeans. The difference in the consumption of fruit may contribute to the CVD gap between the two regions.

Feasibility of self-sampled dried blood spot and saliva samples sent by mail in a population-based study

BACKGROUND

In large epidemiological studies it is often challenging to obtain biological samples. Self-sampling by study participants using dried blood spots (DBS) technique has been suggested to overcome this challenge. DBS is a type of biosampling where blood samples are obtained by a finger-prick lancet, blotted and dried on filter paper. However, the feasibility and efficacy of collecting DBS samples from study participants in large-scale epidemiological studies is not known. The aim of the present study was to test the feasibility and response rate of collecting self-sampled DBS and saliva samples in a population-based study of women above 50 years of age.

METHODS

We determined response proportions, number of phone calls to the study center with questions about sampling, and quality of the DBS. We recruited women through a study conducted within the Norwegian Breast Cancer Screening Program. Invitations, instructions and materials were sent to 4,597 women. The data collection took place over a 3 month period in the spring of 2009.

RESULTS

Response proportions for the collection of DBS and saliva samples were 71.0% (3,263) and 70.9% (3,258), respectively. We received 312 phone calls (7% of the 4,597 women) with questions regarding sampling. Of the 3,263 individuals that returned DBS cards, 3,038 (93.1%) had been packaged and shipped according to instructions. A total of 3,032 DBS samples were sufficient for at least one biomarker analysis (i.e. 92.9% of DBS samples received by the laboratory). 2,418 (74.1%) of the DBS cards received by the laboratory were filled with blood according to the instructions (i.e. 10 completely filled spots with up to 7 punches per spot for up to 70 separate analyses). To assess the quality of the samples, we selected and measured two biomarkers (carotenoids and vitamin D). The biomarker levels were consistent with previous reports.

CONCLUSION

Collecting self-sampled DBS and saliva samples through the postal services provides a low cost, effective and feasible alternative in epidemiological studies.

Polymorphisms in sodium-dependent vitamin C transporter genes and plasma, aqueous humor and lens nucleus ascorbate concentrations in an ascorbate depleted setting

We have previously reported low concentrations of plasma ascorbate and low dietary vitamin C intake in the older Indian population and a strong inverse association of these with cataract. Little is known about ascorbate levels in aqueous humor and lens in populations habitually depleted of ascorbate and no studies in any setting have investigated whether genetic polymorphisms influence ascorbate levels in ocular tissues. Our objectives were to investigate relationships between ascorbate concentrations in plasma, aqueous humor and lens and whether these relationships are influenced by Single Nucleotide Polymorphisms (SNPs) in sodium-dependent vitamin C transporter genes (SLC23A1 and SLC23A2). We enrolled sixty patients (equal numbers of men and women, mean age 63 years) undergoing small incision cataract surgery in southern India. We measured ascorbate concentrations in plasma, aqueous humor and lens nucleus using high performance liquid chromatography. SLC23A1 SNPs (rs4257763, rs6596473) and SLC23A2 SNPs (rs1279683 and rs12479919) were genotyped using a TaqMan assay. Patients were interviewed for lifestyle factors which might influence ascorbate. Plasma vitamin C was normalized by a log10 transformation. Statistical analysis used linear regression with the slope of the within-subject associations estimated using beta (β) coefficients. The ascorbate concentrations (μmol/L) were: plasma ascorbate, median and inter-quartile range (IQR), 15.2 (7.8, 34.5), mean (SD) of aqueous humor ascorbate, 1074 (545) and lens nucleus ascorbate, 0.42 (0.16) (μmol/g lens nucleus wet weight). Minimum allele frequencies were: rs1279683 (0.28), rs12479919 (0.30), rs659647 (0.48). Decreasing concentrations of ocular ascorbate from the common to the rare genotype were observed for rs6596473 and rs12479919. The per allele difference in aqueous humor ascorbate for rs6596473 was -217 μmol/L, p < 0.04 and a per allele difference in lens nucleus ascorbate of -0.085 μmol/g, p < 0.02 for rs12479919. The β coefficients for the regression of log10 plasma ascorbate on aqueous humor ascorbate were higher for the GG genotype of rs6596473: GG, β = 1460 compared to carriage of the C allele, CG, β = 1059, CC, β = 1132, p interaction = 0.1. In conclusion we found that compared to studies in well-nourished populations, ascorbate concentrations in the plasma, aqueous humor and lens nucleus were low. We present novel findings that polymorphisms in SLC23A1/2 genes influenced ascorbate concentration in aqueous humor and lens nucleus.

Associations of serum retinol, α-tocopherol, and γ-tocopherol with biomarkers among healthy Japanese men

Retinol, α-tocopherol, and γ-tocopherol are fat-soluble vitamins acting as antioxidants via the prevention of lipid oxidation. Little is known about circulatory levels in healthy individuals. The present cross-sectional study aimed at elucidating the relationship between these antioxidants and clinical biomarkers in 206 male (median age 41 years, range 23-67) employees from companies located in the Okayama Prefecture, Japan. Subjects younger than 40 years (n = 94) showed a positive association of the frequency of alcohol consumption with the circulating retinol (β = 0.344, p = 0.001) and γ-tocopherol levels (β = 0.219, p = 0.041), and an inverse association of fast insulin with serum retinol (β = -0.301, p = 0.009). In participants older than 40 years (n = 112) we found that an inverse association of HOMA-R with serum retinol (β = -0.262, p = 0.021), α-tocopherol (β = -0.236, p = 0.035), and γ-tocopherol levels (β = -0.224, p = 0.052); and cigarette smoking was inversely associated with the levels of serum α-tocopherol (β = -0.286, p = 0.008) and γ-tocopherol (β = -0.229, p = 0.040). We further found negative relationships between serum ferritin and the retinol (β = -0.211, p = 0.032) and α-tocopherol levels (β = -0.223, p = 0.022) in men over 40 years of age. The present study suggests that the circulatory levels of antioxidant vitamins may modulate the action of insulin and that higher levels of iron might decrease the levels of antioxidant vitamins in the blood.

Review of nutrient actions on age-related macular degeneration

The actions of nutrients and related compounds on age-related macular degeneration (AMD) are explained in this review. The findings from 80 studies published since 2003 on the association between diet and supplements in AMD were reviewed. Antioxidants and other nutrients with an effect on AMD susceptibility include carotenoids (lutein and zeaxanthin, β-carotene), vitamins (vitamin A, E, C, D, B), mineral supplements (zinc, copper, selenium), dietary fatty acids [monounsaturated fatty acids, polyunsaturated fatty acids (PUFA both omega-3 PUFA and omega-6 PUFA), saturated fatty acids and cholesterol], and dietary carbohydrates. The literature revealed that many of these antioxidants and nutrients exert a protective role by functioning synergistically. Specifically, the use of dietary supplements with targeted actions can provide minimal benefits on the onset or progression of AMD; however, this does not appear to be particularly beneficial in healthy people. Furthermore, some supplements or nutrients have demonstrated discordant effects on AMD in some studies. Since intake of dietary supplements, as well as exposure to damaging environmental factors, is largely dependent on population habits (including dietary practices) and geographical localization, an overall healthy diet appears to be the best strategy in reducing the risk of developing AMD. As of now, the precise mechanism of action of certain nutrients in AMD prevention remains unclear. Thus, future studies are required to examine the effects that nutrients have on AMD and to determine which factors are most strongly correlated with reducing the risk of AMD or preventing its progression.