Effect of interval between serum draw and follow-up period on relative risk of cancer incidence with respect to 25-hydroxyvitamin D level; implications for meta-analyses and setting vitamin D guidelines

Multiplicative, additive, and interactive associations of 25-hydroxyvitamin D with lung and prostate cancer

Results regarding the epidemiological association of vitamin D with lung (LCA) and prostate cancer (PCA) are controversial. This study tested whether serum 25-hydroxyvitamin D [25(OH)D] concentrations have interactive epidemiological associations with smoking, the number-one risk factor for LCA, and age, the number-one risk factor for PCA. Also, this study investigated whether the associations of 25(OH)D, smoking, age, alcohol consumption, body mass index, diet (the healthy Nordic diet score), and physical activity with incident LCA and PCA are multiplicative or additive. The study of association types makes it easier to select appropriate statistical methods. The Kuopio Ischaemic Heart Disease Risk Factor Study provided the data of 2578 men with 112 LCA and 300 PCA cases over 35 years by the end of 2019. Serum 25(OH)D did not associate with LCA and PCA or interact with smoking and age. The association of smoking with LCA was additive; 13 extra cases per 1000 men every 10 years. Age and alcohol consumption multiplicatively increased the hazard of LCA (hazard ratio, 95% confidence interval for age >50: 3.56, 1.82-6.17; drink per week: 1.01, 1.00-1.03), whereas adherence to healthy Nordic diet decreased it (per score point: 0.95, 0.89-1.00). The association of age >50 with PCA was additive; 2.5 extra cases per 1000 men every 10 years. To conclude, there was no epidemiological relationship of pre-diagnostic 25(OH)D concentrations with the incidence of LCA and PCA. The respective associations of smoking and age >50 with LCA and PCA were additive rather than multiplicative.

Long Follow-Up Times Weaken Observational Diet-Cancer Study Outcomes: Evidence from Studies of Meat and Cancer Risk

For years, prospective cohort studies of diet and cancer incidence have reported smaller effects than do retrospective case-control (CC) studies. The differences have been attributed to problems with CC studies, including dietary recall bias, poor matching of cases and controls, and confounding. The hypothesis evaluated here is that long follow-up periods between ascertainment of diet and cancer incidence weaken the findings. Prospective studies of cancer incidence with respect to serum 25-hydroxyvitamin D concentration have already shown reduced benefit of higher concentrations for longer follow-up periods. Evaluating that hypothesis for dietary factors involved searching the journal literature for meta-analyses of red meat and processed meat and cancer incidence. I used findings from observational studies for bladder, breast, colorectal, and gastric cancers. To evaluate the effect of duration of follow-up time, I used two approaches. First, I plotted the relative risks for CC studies for gastric cancer with respect to consumption of 100 g/day of red meat and for bladder cancer for 50 g/day of processed meat against the interval between the dietary data and cancer incidence. Second, I compared nested CC studies of meat and cancer incidence for five breast cancer studies and one colorectal cancer study. Both approaches yielded an inverse correlation between interval or follow-up time and relative risk. My findings strongly suggest that diet near time of cancer diagnosis is more important than for longer intervals, that results from meta-analyses should be revised when possible with appropriate adjustments for duration of follow-up, and that dietary guidelines be revised accordingly.

Comparing the Evidence from Observational Studies and Randomized Controlled Trials for Nonskeletal Health Effects of Vitamin D

Although observational studies of health outcomes generally suggest beneficial effects with, or following, higher serum 25-hydroxyvitamin D [25(OH)D] concentrations, randomized controlled trials (RCTs) have generally not supported those findings. Here we review results from observational studies and RCTs regarding how vitamin D status affects several nonskeletal health outcomes, including Alzheimer’s disease and dementia, autoimmune diseases, cancers, cardiovascular disease, COVID-19, major depressive disorder, type 2 diabetes, arterial hypertension, all-cause mortality, respiratory tract infections, and pregnancy outcomes. We also consider relevant findings from ecological, Mendelian randomization, and mechanistic studies. Although clear discrepancies exist between findings of observational studies and RCTs on vitamin D and human health benefits these findings should be interpreted cautiously. Bias and confounding are seen in observational studies and vitamin D RCTs have several limitations, largely due to being designed like RCTs of therapeutic drugs, thereby neglecting vitamin D’s being a nutrient with a unique metabolism that requires specific consideration in trial design. Thus, RCTs of vitamin D can fail for several reasons: few participants’ having low baseline 25(OH)D concentrations, relatively small vitamin D doses, participants’ having other sources of vitamin D, and results being analyzed without consideration of achieved 25(OH)D concentrations. Vitamin D status and its relevance for health outcomes can usefully be examined using Hill’s criteria for causality in a biological system from results of observational and other types of studies before further RCTs are considered and those findings would be useful in developing medical and public health policy, as they were for nonsmoking policies. A promising approach for future RCT design is adjustable vitamin D supplementation based on interval serum 25(OH)D concentrations to achieve target 25(OH)D levels suggested by findings from observational studies.

Vitamin D and Cancer: An Historical Overview of the Epidemiology and Mechanisms

This is a narrative review of the evidence supporting vitamin D’s anticancer actions. The first section reviews the findings from ecological studies of cancer with respect to indices of solar radiation, which found a reduced risk of incidence and mortality for approximately 23 types of cancer. Meta-analyses of observational studies reported the inverse correlations of serum 25-hydroxyvitamin D [25(OH)D] with the incidence of 12 types of cancer. Case-control studies with a 25(OH)D concentration measured near the time of cancer diagnosis are stronger than nested case-control and cohort studies as long follow-up times reduce the correlations due to changes in 25(OH)D with time. There is no evidence that undiagnosed cancer reduces 25(OH)D concentrations unless the cancer is at a very advanced stage. Meta-analyses of cancer incidence with respect to dietary intake have had limited success due to the low amount of vitamin D in most diets. An analysis of 25(OH)D-cancer incidence rates suggests that achieving 80 ng/mL vs. 10 ng/mL would reduce cancer incidence rates by 70 ± 10%. Clinical trials have provided limited support for the UVB-vitamin D-cancer hypothesis due to poor design and execution. In recent decades, many experimental studies in cultured cells and animal models have described a wide range of anticancer effects of vitamin D compounds. This paper will review studies showing the inhibition of tumor cell proliferation, dedifferentiation, and invasion together with the sensitization to proapoptotic agents. Moreover, 1,25-(OH)₂D₃ and other vitamin D receptor agonists modulate the biology of several types of stromal cells such as fibroblasts, endothelial and immune cells in a way that interferes the apparition of metastases. In sum, the available mechanistic data support the global protective action of vitamin D against several important types of cancer.

How competing risks affect the epidemiological relationship between vitamin D and prostate cancer incidence? A population-based study

We hypothesized that controversial results regarding the epidemiological relationship between circulating 25-hydroxyvitamin D, 25(OH)D, and risk of prostate cancer (PCA) incidence are partly due to competing risks. To test the hypothesis, we studied associations across 25(OH)D, PCA and death in 2578 middle-aged men belonging to the Kuopio Ischaemic Heart Disease Risk Factor Study. The men were free of cancer at baseline, and the mean (SD) follow-up time was 23.3 (9.1) years. During this period, 296 men had a PCA diagnosis, and 1448 men died without the PCA diagnosis. The absolute risk of developing PCA was highest in the highest 25(OH)D tertile (15%), whereas that of death was highest in the lowest 25(OH)D tertile (67%). A competing risk analysis showed that belonging to the highest 25(OH)D tertile increased the risk of PCA incidence and improved survival with the respective hazard ratios (HR) of 1.35 (95% CI = 1.07-1.70) and 0.79 (95% CI = 0.71-0.89). Adjusting for 10 covariates together with 25(OH)D did not significantly change the results, but the respective adjusted HRs for PCA and death were 1.20 and 0.87. To conclude, the competing risk analysis did not eliminate the direct relationship between 25(OH)D and PCA but rather strengthened it.

Vitamin D: Promises on the Horizon and Challenges Ahead for Fighting Pancreatic Cancer

Simple Summary

Pancreatic cancer is an almost universally lethal cancer, largely due to its late diagnosis, early metastasis, and therapeutic resistance. This highlights the need to develop novel and effective intervention strategies to improve the outcomes of patients with pancreatic cancer. Vitamin D is one of the hottest topics in cancer research and clinics because of its pleiotropic functions on the hallmarks of cancer. Here we critically review past and current efforts that define the effects of vitamin D on the risk, incidence, patient survival, and mortality of pancreatic cancer. We also provide overviews on the opportunities and challenges associated with vitamin D as an economic adjunct to improve the efficacy of immunotherapy and chemo- or radiotherapy for pancreatic cancer.

Abstract

Pancreatic cancer has a dismal prognosis, while its incidence is increasing. This is attributed, in part, to a profound desmoplastic and immunosuppressive tumor microenvironment associated with this cancer and resistance to current available therapies. Novel and effective intervention strategies are urgently needed to improve the outcomes of patients with pancreatic cancer. Vitamin D has pleiotropic functions beyond calcium–phosphate homeostasis and has been extensively studied both in the laboratory and clinic as a potential preventive agent or adjunct to standard therapies. Accumulating evidence from ecological, observational, and randomized controlled trials suggests that vitamin D has beneficial effects on risk, survival, and mortality in pancreatic cancer, although controversies still exist. Recent advances in demonstrating the important functions of vitamin D/vitamin D receptor (VDR) signaling in the regulation of stromal reprogramming, the microbiome, and immune response and the emergence of checkpoint immunotherapy provide opportunities for using vitamin D or its analogues as an adjunct for pancreatic cancer intervention. Many challenges lie ahead before the benefits of vitamin D can be fully realized in pancreatic cancer. These challenges include the need for randomized controlled trials of vitamin D to assess its impact on the risk and survival of pancreatic cancer, optimizing the timing and dosage of vitamin D or its analogues as an adjunct for pancreatic cancer intervention and elucidating the specific role of vitamin D/VDR signaling in the different stages of pancreatic cancer. Nevertheless, vitamin D holds great promise for reducing risk and improving outcomes of this disease.

Plasma 25-Hydroxyvitamin D Concentrations Are Inversely Associated with All-Cause Mortality among a Prospective Cohort of Chinese Adults Aged ≥80 Years

BACKGROUND

High concentrations of plasma 25-hydroxyvitamin D [25(OH)D], a marker of circulating vitamin D, have been associated with a lower risk of mortality in epidemiologic studies of multiple populations, but the association for Chinese adults aged ≥80 y (oldest old) remains unclear.

OBJECTIVE

We investigated the association between plasma [25(OH)D] concentration and all-cause mortality among Chinese adults aged ≥80 y.

DESIGN

The present study is a prospective cohort study of 2185 Chinese older adults (median age: 93 y). Prospective all-cause mortality data were analyzed for survival in relation to plasma 25(OH)D using Cox proportional hazards regression models, with adjustments for potential sociodemographic and lifestyle confounders and biomarkers. The associations were measured with HR and 95% CIs.

RESULTS

The median plasma 25(OH)D concentration was 34.4 nmol/L at baseline. Over the 5466 person-year follow-up period, 1100 deaths were identified. Men and women were analyzed together as no effect modification by sex was found. After adjusting for multiple potential confounders, the risk of all-cause mortality decreased as the plasma 25(OH)D concentration increased (P-trend <0.01). Compared with the lowest age-specific quartile of plasma 25(OH)D, the adjusted HRs for mortality for the second, third, and fourth age-specific quartiles were 0.72 (95% CI: 0.57, 0.90), 0.73 (95% CI: 0.58, 0.93), and 0.61 (95% CI: 0.47, 0.81), respectively. The observed associations were broadly consistent across age and other subgroups. Sensitivity analyses generated similar results after excluding participants who died within 2 y of follow-up or after further adjustment for ethnicity and chronic diseases.

CONCLUSIONS

A higher plasma 25-hydroxyvitamin D concentration was associated with a reduced risk of all-cause mortality among Chinese adults aged ≥80 y. This observed inverse association warrants further investigation in randomized controlled trials testing vitamin D supplementation in this age group.

Vitamin D and Gastrointestinal Cancers: A Narrative Review

Calcitriol (1,25(OH)₂D₃) performs various activities throughout the body. Although low serum 25-hydroxyvitamin D [25(OH)D] levels are associated with several disease processes such as risk of fractures and falls, hypertension, cardiovascular disease, and diabetes mellitus, recent evidence attests that this important hormone also regulates several cellular pathways involved in cancer development and progression. Calcitriol modulates several genes controlling gut physiology and calcium homeostasis and also maintains the integrity of epithelial barriers, regulates the absorption of phosphate and calcium, and modulates host defense against pathogens and inflammatory response by interplaying with several types of secretory and immune cells. Vitamin D deficiency is significantly related to increased risk of developing certain types of cancer. This deficiency can be prevented by vitamin D supplementation which is both economical and safe. This can lower the risk of developing cancer and also improve the prognosis of patients with gastrointestinal malignancy, but epidemiological data remain inconsistent. Several retrospective observational studies have demonstrated the benefits of vitamin D supplementation, but a few randomized controlled trials have not seemingly supported the beneficial role of vitamin D supplementation in gastrointestinal cancers. Therefore, in this literature review, we aimed to examine the possible role of vitamin D in gastrointestinal malignancies, including gastric, esophageal, pancreatic, hepatic, and colorectal cancers.

Vitamin D and breast cancer: A systematic review and meta-analysis of observational studies

CONTEXT

Breast cancer (BC) is the most common malignancy among women in the US. Vitamin D status and intakes are thought to be inversely associated with BC occurrence.

OBJECTIVES

In our systematic review and meta-analysis, we evaluated evidence linking serum 25(OH)D (both in serum and diet) with breast cancer (BC) occurrence.

DATA SOURCES AND EXTRACTION

Only observational studies from databases such as PubMed and Cochrane (January 1st 2000 through March 15th, 2018) were included using PRISMA guidelines. Publication bias and consistency upon replication were assessed, while harmonizing risk ratios (RR, 95% CI) of BC, per fixed increment of 5 exposures [10 ng/mL of 25(OH)D; 100 IU/d for total/dietary vitamin D intakes; vitamin D deficiency; supplement use). RRs were pooled using random effect models.

DATA ANALYSIS

Pooled findings from 22 studies suggested a net direct association between 25(OH)D deficiency and BC, with RR_pooled = 1.91, 95% CI: 1.51-2.41, P < 0.001). Total vitamin D intake (RR_pooled = 0.99, 95% CI: 0.97-1.00, P = 0.022, per 100 IU/d) and supplemental vitamin D (RR_pooled = 0.97, 95% CI:0.95-1.00, P = 0.026) were inversely associated with BC. No evidence of publication bias was found; all 5 exposures of interest were consistent upon replication.

CONCLUSIONS

25(OH)D deficiency was directly related to BC while total vitamin D and supplemental vitamin D intakes had an inverse relationship with this outcome. Randomized clinical trials are warranted pending further evidence from primary meta-analyses of observational studies.

Plasma 25-hydroxyvitamin D concentrations and risk of incident cancer in adults with hypertension: A nested case-control study

BACKGROUND & AIMS

Evidence from epidemiologic studies on the association of circulating 25-hydroxyvitamin D [25(OH)D] concentrations with the incident risk of cancer has been inconsistent. We aimed to investigate the prospective relationship of baseline plasma 25(OH)D concentrations with the risk of cancer, and to examine possible effect modifiers.

METHODS

We employed a nested case-control study design, including 231 patients with incident cancer during a median 4.5 years of follow up, and 231 matched controls from the China Stroke Primary Prevention Trial (CSPPT).

RESULTS

The prevalence of plasma 25(OH)D <15, <20 and <30 ng/mL was 23.6%, 47.4% and 85.5%, respectively. Overall, there was an inverse relation between risk of cancer and plasma 25(OH)D. The Odds ratios (95% CI) for participants in the second (15.1 to <20.6 ng/mL), third (20.6 to <26.4 ng/mL) and fourth quartiles (≥26.4 ng/mL) were 0.45 (95% CI: 0.25-0.80), 0.53 (95% CI: 0.27-1.06) and 0.55 (95% CI: 0.27-1.10), respectively, compared with those in quartile 1. Conversely, low 25(OH)D (<15.1 ng/mL) concentrations were associated with increased risk of cancer (OR, 2.08; 95% CI: 1.20-3.59) compared to higher concentrations. These associations were consistent across subtypes of cancer. Several potential effect modifiers were identified, including plasma vitamin E concentrations and alcohol intake.

CONCLUSIONS

Low plasma 25(OH)D concentrations (<15.1 ng/mL) were associated with increased total cancer risk among Chinese hypertensive adults, compared to higher 25(OH)D concentrations. This finding and the possible effect modifiers warrant additional investigation.

Serum 25-hydroxyvitamin D and breast cancer risk by pathological subtype (MCC-Spain)

Epidemiologic evidence on the association between vitamin D and breast cancer is still inconclusive. This study analyzes the association between serum 25-hydroxyvitamin D (25(OH)D) and breast cancer risk by pathologic subtype, stage at diagnosis and specific breast cancer risk factors. We conducted a population-based multicase-control study where 546 histologically-confirmed breast cancer cases and 558 population controls, frequently matched by geographic area, age and body mass index, were recruited in 12 Spanish provinces (MCC-Spain). Information was collected by a questionnaire and plasma 25(OH)D was measured by solid-phase extraction on-line coupled to liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS). Odds ratios and 95% confidence intervals were calculated using logistic and multinomial mixed regression models. We found a clear protective effect between 25(OH)D levels and breast cancer risk, with a significant dose-response trend (OR per 10 nmol/L = 0.88; 95%CI = 0.82-0.94). While no differences were observed between pre and postmenopausal women, stage at diagnosis, or across strata of the main breast cancer risk factors, the protection was more pronounced for triple negative tumors (OR per 10 nmol/L = 0.64; p-heterogeneity = 0.038). Similar results were observed when only cases sampled in the first month after diagnosis were considered. The protective effect of vitamin D on breast cancer risk may be subtype specific, being stronger for more aggressive tumors, which provides a new approach to prevent this disease.

Vitamin D and pancreas: The role of sunshine vitamin in the pathogenesis of diabetes mellitus and pancreatic cancer

Increasing evidence suggests that vitamin D exerts multiple effects beyond bone and calcium metabolism. Vitamin D seems to play a role in pancreatic disease, including type 1 and type 2 diabetes mellitus as well as pancreatic cancer. Vitamin D's immune-modulatory action suggests that it could help prevent type 1 diabetes. In type 2 diabetes, vitamin D may influence β-cell function, insulin sensitivity, and systematic inflammation-all characteristic pathways of that disease. Data from observational studies correlated vitamin D deficiency with risk of type 1 and type 2 diabetes. Prospective and ecological studies of pancreatic cancer incidence generally support a beneficial effect of higher 25-hydroxyvitamin D concentration as well as inverse correlations between UVB dose or exposure and incidence and/or mortality rate of pancreatic cancer. This review discusses the literature regarding vitamin D's role in risk of diabetes and pancreatic cancer. The results to date generally satisfy Hill's criteria for causality regarding vitamin D and incidence of these pancreatic diseases. However, large randomized, blinded, prospective studies are required to more fully evaluate the potential therapeutic role of vitamin D in preventing pancreatic diseases.

Low vitamin D status in relation to cardiovascular disease and mortality in Swedish women - Effect of extended follow-up

BACKGROUND AND AIMS

The impact of vitamin D concentrations on subsequent cardiovascular disease (CVD) and overall mortality has been generally examined for periods under two decades. The magnitude of the association may depend on follow-up length. We aimed to investigate the relationship between baseline vitamin D and risk of total CVD, stroke and all-cause mortality over three decades of follow-up. Secondly, we aimed to assess how follow-up affects the associations.

METHODS AND RESULTS

Concentrations of 25-hydroxyvitamin D (25D) were measured in a population-based sample of 1227 middle-aged women using serum collected at baseline and categorized into low (lowest 25D quartile) vs high 25D status (upper three 25D quartiles). Hazard ratio (HR) of the endpoints was estimated for low 25D. The impact of follow-up was examined in intermediary analyses where follow-up was interrupted up to four times, each time decreasing it by five years. There were 596 cardiovascular events and 635 participants died. During the first 17 years, the low 25D group experienced a 29% higher CVD risk and 3.3-fold higher stroke risk after accounting for confounders. Longer follow-up diminished significantly these risks and 25D status had no contribution at 32 years. For mortality, the decline over time was less dramatic, with HR = 1.96 (1.25; 3.08) at 17 years and HR = 1.42 (1.17; 1.72) at 37 years.

CONCLUSION

Low 25D status increased the risk for all endpoints, but a lengthy follow-up diminished these risks towards the null. The impact of follow-up depends on the outcome. Future studies of 25D and disease should use repeated 25D assessments.

Plasma 25-hydroxyvitamin D levels, vitamin D intake, and pancreatic cancer risk or mortality: a meta-analysis

BACKGROUND

The associations between vitamin D status, including plasma 25-hydroxyvitamin D [25(OH)D] levels and vitamin D intake, and pancreatic cancer risk and mortality are inconsistent. The aims of this study are to evaluate the antitumor and therapeutic effects of vitamin D status for pancreatic cancer patients.

METHODS

A literature search for relevant studies was conducted using PubMed and Embase databases. Risk ratio (RR), hazard ratio (HR), and 95% confidence interval (CI) were used as the effect measures. All statistical analyses were performed using Stata software 12.0.

RESULTS

Our results indicated that high plasma 25(OH)D levels were inversely associated with pancreatic cancer mortality without significant heterogeneity (HR=0.81, 95% CI=0.68-0.96). However, high plasma 25(OH)D levels could not reduce pancreatic cancer risk (RR=1.02, 95% CI=0.66-1.57). Moreover, vitamin D intake was also not associated with pancreatic cancer risk (RR=1.11, 95% CI=0.67-1.86).

CONCLUSIONS

Our results indicate that high plasma 25(OH)D levels were significantly associated with improved survival in pancreatic cancer patients. However, there were no significant associations between vitamin D intake or plasma 25(OH)D levels and pancreatic cancer risk.

Vitamin D and colorectal cancer: molecular, epidemiological and clinical evidence

In many cells throughout the body, vitamin D is converted into its active form calcitriol and binds to the vitamin D receptor (VDR), which functions as a transcription factor to regulate various biological processes including cellular differentiation and immune response. Vitamin D-metabolising enzymes (including CYP24A1 and CYP27B1) and VDR play major roles in exerting and regulating the effects of vitamin D. Preclinical and epidemiological studies have provided evidence for anti-cancer effects of vitamin D (particularly against colorectal cancer), although clinical trials have yet to prove its benefit. In addition, molecular pathological epidemiology research can provide insights into the interaction of vitamin D with tumour molecular and immunity status. Other future research directions include genome-wide research on VDR transcriptional targets, gene-environment interaction analyses and clinical trials on vitamin D efficacy in colorectal cancer patients. In this study, we review the literature on vitamin D and colorectal cancer from both mechanistic and population studies and discuss the links and controversies within and between the two parts of evidence.

Do studies reporting 'U'-shaped serum 25-hydroxyvitamin D-health outcome relationships reflect adverse effects?

Several reports describe U-shaped 25-hydroxyvitamin D [25(OH)D] concentration-health outcomes, including musculo-skeletal disorders such as falls and fractures, several cancers, cardiovascular disease (CVD), cognitive function, all-cause mortality rates, birth outcomes, allergic reactions, frailty, and some other disorders. This paper reviews reports of U-shaped outcome associations with vitamin D status for evidence of underlying pathophysiological processes, or of confounding, finding that some U-shaped associations appear to be biologically meaningful, but that many could well reflect confounding by factors such as lifestyle, or hypovitaminosis D-related disease onset being masked by self-supplementation that was begun too late to correct developing health problems but before baseline vitamin D status assessment. However, the various U-shaped associations for allergic reactions may be due to vitamin D modulation of the phenotype of the immune response, shifting the Th1-Th2 balance toward Th2 formation. For prostate cancer, there seems to be little effect of 25(OH)D concentration on incidence; however, there is an inverse correlation between 25(OH)D concentration and mortality rates. Future observational studies, and randomized controlled trial data analyses, should include adjustment for data collected on prior long-term vitamin D supplementation and solar UVB exposure, as well as other potential confounders.

Essential Nutrient Interactions: Does Low or Suboptimal Magnesium Status Interact with Vitamin D and/or Calcium Status?

Although much is known about magnesium, its interactions with calcium and vitamin D are less well studied. Magnesium intake is low in populations who consume modern processed-food diets. Low magnesium intake is associated with chronic diseases of global concern [e.g., cardiovascular disease (CVD), type 2 diabetes, metabolic syndrome, and skeletal disorders], as is low vitamin D status. No simple, reliable biomarker for whole-body magnesium status is currently available, which makes clinical assessment and interpretation of human magnesium research difficult. Between 1977 and 2012, US calcium intakes increased at a rate 2-2.5 times that of magnesium intakes, resulting in a dietary calcium to magnesium intake ratio of >3.0. Calcium to magnesium ratios <1.7 and >2.8 can be detrimental, and optimal ratios may be ∼2.0. Background calcium to magnesium ratios can affect studies of either mineral alone. For example, US studies (background Ca:Mg >3.0) showed benefits of high dietary or supplemental magnesium for CVD, whereas similar Chinese studies (background Ca:Mg <1.7) showed increased risks of CVD. Oral vitamin D is widely recommended in US age-sex groups with low dietary magnesium. Magnesium is a cofactor for vitamin D biosynthesis, transport, and activation; and vitamin D and magnesium studies both showed associations with several of the same chronic diseases. Research on possible magnesium and vitamin D interactions in these human diseases is currently rare. Increasing calcium to magnesium intake ratios, coupled with calcium and vitamin D supplementation coincident with suboptimal magnesium intakes, may have unknown health implications. Interactions of low magnesium status with calcium and vitamin D, especially during supplementation, require further study.

The role of geographical ecological studies in identifying diseases linked to UVB exposure and/or vitamin D

Using a variety of approaches, researchers have studied the health effects of solar ultraviolet (UV) radiation exposure and vitamin D. This review compares the contributions from geographical ecological studies with those of observational studies and clinical trials. Health outcomes discussed were based on the author's knowledge and include anaphylaxis/food allergy, atopic dermatitis and eczema, attention deficit hyperactivity disorder, autism, back pain, cancer, dental caries, diabetes mellitus type 1, hypertension, inflammatory bowel disease, lupus, mononucleosis, multiple sclerosis, Parkinson disease, pneumonia, rheumatoid arthritis, and sepsis. Important interactions have taken place between study types; sometimes ecological studies were the first to report an inverse correlation between solar UVB doses and health outcomes such as for cancer, leading to both observational studies and clinical trials. In other cases, ecological studies added to the knowledge base. Many ecological studies include other important risk-modifying factors, thereby minimizing the chance of reporting the wrong link. Laboratory studies of mechanisms generally support the role of vitamin D in the outcomes discussed. Indications exist that for some outcomes, UVB effects may be independent of vitamin D. This paper discusses the concept of the ecological fallacy, noting that it applies to all epidemiological studies.

Emphasizing the health benefits of vitamin D for those with neurodevelopmental disorders and intellectual disabilities

People with neurodevelopmental disorders and intellectual disabilities have much greater health care needs. Mainly staying indoors, such people generally have low 25-hydroxyvitamin D (25(OH)D) concentrations. The Vitamin D Task Force of the American Academy of Developmental Medicine and Dentistry (AADMD) reviewed the evidence of 25(OH)D concentrations that benefit the health of persons with developmental disabilities. Maintaining recommended optimal serum 25(OH)D concentrations year long will benefit skeletal development in infants, children, and adolescents, and benefit musculoskeletal health and neuromuscular coordination in adult patients, and decrease risk of falls. Maintaining optimal concentrations decreases risks and severities of autoimmune diseases, cardiovascular disease, many types of cancer, dementia, types 1 and 2 diabetes mellitus, and respiratory tract infections. Other benefits include improved dental and oral health and improved physical performance. The Task Force recommends that 25(OH)D concentrations for optimal health to be in the range of 75 to 125 nmol/L, which can be achieved using between 800 and 4000 IU/day vitamin D3 and sensible exposure to solar UVB radiation. The paper also discusses the potential risks of higher 25(OH)D concentrations, the evidence from and limitations of randomized controlled trials, and the recommendations by various groups and agencies.

Vitamin D status, liver enzymes, and incident liver disease and mortality: a general population study

Vitamin D deficiency is common among patients with liver diseases. Both cholestatic and non-cholestatic liver diseases can cause vitamin D deficiency. Whether vitamin D status can also affect liver function is poorly understood. To investigate the association between vitamin D status, liver enzymes, and incident liver disease, we included a total of 2,649 individuals from the Monica10 study conducted in 1993-1994. Vitamin D status as assessed by serum 25-hydroxyvitamin, serum alanine transaminase (ALT), aspartate transaminase (AST), and gamma glutamyl transferase (GGT) were measured at baseline. Information on fatal and non-fatal liver disease was obtained from the Danish National Patient Register and The Danish Registry of Causes of Death, respectively. Median follow-up time was 16.5 years, and there were 62 incident cases of fatal and non-fatal liver disease. Multivariable Cox regression analyses with age as underlying time axis and delayed entry showed a statistically significant inverse association between vitamin D status and incident liver disease with a hazard ratio = 0.88 (95 % confidence interval 0.79-0.99) per 10 nmol/l higher vitamin D status at baseline (adjusted for gender, season, alcohol consumption, smoking, physical activity, dietary habits, education, body mass index, and ALT). The risk of having a high level of ALT, AST, or GGT tended to be higher for lower vitamin D levels, although not statistically significant. In this general population study, vitamin D status was inversely associated with incident liver disease. Further studies are needed to determine whether patients in risk of developing impaired liver function should be screened for vitamin D deficiency for preventive purposes.

The trials and tribulations of vitamin D: time for the 'sunshine' vitamin to come in out of the cold - or just more broken promises?

We are presently faced with the competing notions of modern life being a 'state of vitamin D depletion', implying a widespread need to supplement with vitamin D, or, the opposite view, which is that the present evidence can only support at best selective targeted vitamin D intervention. This is important as there is evidence that over the last 40-50 years there were downwards global trends in serum 25(OH)D concentrations, while individual consumption of vitamin D as supplements rose. For this reason and many others, a large population-based interventional study, the VITAL trial, was designed to try to establish the health value of vitamin D supplementation. VITAL is a huge primary prevention trial looking at the effects of vitamin D repletion in preventing cancer and cardiovascular disease in a fundamentally healthy population. This may seem an unusual approach given that what we mostly know about vitamin D is that is has some effects on the skeleton. This review looks to explore current knowledge about vitamin D in health and disease, and at how this is now undergoing significant reappraisal and revision. We will carefully critique the VITAL study design to see if it will allow for the construction of the detailed portfolio of clinical evidence so urgently needed to allow us better to understand role of vitamin D supplementation in health and disease.

Vitamin D intake, blood 25(OH)D levels, and breast cancer risk or mortality: a meta-analysis

Background:

Experimental studies suggest potential anti-carcinogenic properties of vitamin D against breast cancer risk, but the epidemiological evidence to date is inconsistent.

Methods:

We searched MEDLINE and EMBASE databases along with a hand search for eligible studies to examine the association between vitamin D status (based on diet and blood 25-hydroxyvitamin D (25(OH)D)) and breast cancer risk or mortality in a meta-analysis. A random-effect model was used to calculate a pooled adjusted relative risk (RR).

Results:

A total of 30 prospective studies (nested case-control or cohort) were included for breast cancer incidence (n=24 studies; 31 867 cases) or mortality (n=6 studies; 870 deaths) among 6092 breast cancer patients. The pooled RRs of breast cancer incidence for the highest vs the lowest vitamin D intake and blood 25(OH)D levels were 0.95 (95% CI: 0.88–1.01) and 0.92 (95% CI: 0.83–1.02), respectively. Among breast cancer patients, high blood 25(OH)D levels were significantly associated with lower breast cancer mortality (pooled RR=0.58, 95% CI: 0.40–0.85) and overall mortality (pooled RR=0.61, 95% CI: 0.48–0.79). There was no evidence of heterogeneity and publication bias.

Conclusions:

Our findings suggest that high vitamin D status is weakly associated with low breast cancer risk but strongly associated with better breast cancer survival.

Vitamin D status and chronic obstructive pulmonary disease: a prospective general population study

OBJECTIVES

Vitamin D deficiency is common among persons with chronic obstructive pulmonary disease (COPD). Whether vitamin D affects the development and deterioration of COPD or is a consequence of the disease lacks clarity. We investigated the association between vitamin D status and prevalent and incident COPD in the general population.

METHODS

We included a total of 12,041 individuals from three general population studies conducted in 1993-94, 1999-2001, and 2006-2008, respectively, with vitamin D measurements. Information on COPD was obtained from the Danish National Patient Register and The Danish Registry of Causes of Death.

RESULTS

There were 85 prevalent and 463 incident cases of COPD (median follow-up 9.7 years). We found a statistically significant inverse association between vitamin D status and prevalent COPD with odds ratio = 0.89 (95% confidence interval, CI: 0.79, 1.0), but no statistically significant association with incident COPD with a hazard ratio = 0.98 (95% CI: 0.94, 1.0), respectively, per 10 nmol/l higher vitamin D status, when adjusted for possible confounders.

CONCLUSIONS

We found a statistically significant inverse cross-sectional association between vitamin D status and COPD, but no association between vitamin D status and incident COPD.

Vitamin D transport proteins megalin and disabled-2 are expressed in prostate and colon epithelial cells and are induced and activated by all-trans-retinoic acid

Megalin and disabled-2 (Dab2) are essential for uptake of the 25-hydroxycholecalciferol (25D3)-vitamin D binding protein (DBP) complex in tissues. In the kidney, this mechanism regulates serum 25D3 levels and production of 1,25-dihydroxycholecalciferol (1,25D3) by CYP27B1 for systemic use. Previously, we showed that mammary epithelial cells expressing CYP27B1 express megalin and Dab2 and internalize DBP by endocytosis, indicating 25D3 was accessible for conversion to 1,25D3 in extra-renal tissues. Moreover, induction of megalin and Dab2 (protein and mRNA abundance) by all-trans-retinoic acid (RA) enhanced DBP uptake. This suggests megalin and Dab2 play a central role in uptake of vitamin D and may predict actions of vitamin D in extra-renal tissues. Here, we characterized megalin and Dab2 expression and uptake of DBP in transformed human prostate and colon epithelial cells. Megalin and Dab2 were expressed in prostate and colon epithelial cells, which was markedly enhanced following treatment with RA. Furthermore, DBP uptake was stimulated by low-dose RA supplementation in LNCaP, PC-3, and Caco-2 cells. Taken together, these are the first studies to our knowledge that have demonstrated modulated expression of megalin and Dab2, as well as an association between increased expression of endocytic proteins with DBP uptake in prostate and colon cells.

Vitamin D status and 5-year changes in urine albumin creatinine ratio and parathyroid hormone in a general population

Vitamin D is associated with cardiovascular disease and renal function but the mechanisms are as yet unexplained. Microalbuminuria is associated with a higher risk of kidney function loss, cardiovascular disease, and mortality. Parathyroid hormone is a predictor of cardiovascular mortality and negatively correlated with glomerular filtration rate. We investigated the association between vitamin D status and 5-year changes in urine albumin creatinine ratio (UACR) and parathyroid hormone (PTH). A random sample of 6,784 individuals aged 30-60 years from a general population participated in the Inter99 study in 1999-2001. Vitamin D (serum-25-hydroxyvitamin D) was measured at baseline by high-performance liquid chromatography. UACR and PTH were measured at baseline and follow-up. Increased UACR was defined as UACR >4.0 mg/g reflecting the upper quartile at baseline. We included 4,330 individuals who participated at 5-year follow-up. In multivariable linear regression analysis, a 10-nmol/l higher baseline level of vitamin D was associated with a 5-year decrease in UACR by 0.92 % (95 % confidence interval, CI 0.13, 1.71). In multivariable logistic regression analysis, the odds ratio of developing increased UACR during follow-up was 0.96 (95 % CI 0.92, 0.98) per 10 nmol/l higher baseline vitamin D level. We found a significant inverse cross-sectional (p < 0.0001) but no prospective association (p = 0.6) between baseline vitamin D status and parathyroid hormone. We found low vitamin D status to be a predictor of long-term development of increased UACR. It remains to be proven whether vitamin D deficiency is a causal and reversible factor in the development of albuminuria.

Molecular link between vitamin D and cancer prevention

The metabolite of vitamin D, 1α,25-dihydroxyvitamin D₃ (also known as calcitriol), is a biologically active molecule required to maintain the physiological functions of several target tissues in the human body from conception to adulthood. Its molecular mode of action ranges from immediate nongenomic responses to longer term mechanisms that exert persistent genomic effects. The genomic mechanisms of vitamin D action rely on cross talk between 1α,25-dihydroxyvitamin D₃ signaling pathways and that of other growth factors or hormones that collectively regulate cell proliferation, differentiation and cell survival. In vitro and in vivo studies demonstrate a role for vitamin D (calcitriol) in modulating cellular growth and development. Vitamin D (calcitriol) acts as an antiproliferative agent in many tissues and significantly slows malignant cellular growth. Moreover, epidemiological studies have suggested that ultraviolet-B exposure can help reduce cancer risk and prevalence, indicating a potential role for vitamin D as a feasible agent to prevent cancer incidence and recurrence. With the preventive potential of this biologically active agent, we suggest that countries where cancer is on the rise--yet where sunlight and, hence, vitamin D may be easily acquired--adopt awareness, education and implementation strategies to increase supplementation with vitamin D in all age groups as a preventive measure to reduce cancer risk and prevalence.

Magnesium, vitamin D status and mortality: results from US National Health and Nutrition Examination Survey (NHANES) 2001 to 2006 and NHANES III

BACKGROUND

Magnesium plays an essential role in the synthesis and metabolism of vitamin D and magnesium supplementation substantially reversed the resistance to vitamin D treatment in patients with magnesium-dependent vitamin-D-resistant rickets. We hypothesized that dietary magnesium alone, particularly its interaction with vitamin D intake, contributes to serum 25-hydroxyvitamin D (25(OH)D) levels, and the associations between serum 25(OH)D and risk of mortality may be modified by magnesium intake level.

METHODS

We tested these novel hypotheses utilizing data from the National Health and Nutrition Examination Survey (NHANES) 2001 to 2006, a population-based cross-sectional study, and the NHANES III cohort, a population-based cohort study. Serum 25(OH)D was used to define vitamin D status. Mortality outcomes in the NHANES III cohort were determined by using probabilistic linkage with the National Death Index (NDI).

RESULTS

High intake of total, dietary or supplemental magnesium was independently associated with significantly reduced risks of vitamin D deficiency and insufficiency respectively. Intake of magnesium significantly interacted with intake of vitamin D in relation to risk of both vitamin D deficiency and insufficiency. Additionally, the inverse association between total magnesium intake and vitamin D insufficiency primarily appeared among populations at high risk of vitamin D insufficiency. Furthermore, the associations of serum 25(OH)D with mortality, particularly due to cardiovascular disease (CVD) and colorectal cancer, were modified by magnesium intake, and the inverse associations were primarily present among those with magnesium intake above the median.

CONCLUSIONS

Our preliminary findings indicate it is possible that magnesium intake alone or its interaction with vitamin D intake may contribute to vitamin D status. The associations between serum 25(OH)D and risk of mortality may be modified by the intake level of magnesium. Future studies, including cohort studies and clinical trials, are necessary to confirm the findings.

Vitamin D status and incident cardiovascular disease and all-cause mortality: a general population study

Low vitamin D status has been associated with cardiovascular disease (CVD) and mortality primarily in selected groups, smaller studies, or with self-reported vitamin D intake. We investigated the association of serum vitamin D status with the incidence of a registry-based diagnosis of ischemic heart disease (IHD), stroke, and all-cause mortality in a large sample of the general population. A total of 9,146 individuals from the two population-based studies, Monica10 and Inter99, were included. Measurements of serum 25-hydroxyvitamin D at baseline were carried out using the IDS ISYS immunoassay system in Monica10 and High-performance liquid chromatography in Inter99. Information on CVDs and causes of death was obtained from Danish registries until 31 December 2008. There were 478 cases of IHD, 316 cases of stroke, and 633 deaths during follow-up (mean follow-up 10 years). Cox regression analyses with age as underlying time axis showed a significant association between vitamin D status and all-cause mortality with a HR = 0.95 (P = 0.005) per 10 nmol/l higher vitamin D level. We found no association between vitamin D status and incidence of IHD or stroke (HR = 1.01, P = 0.442 and HR = 1.00, P = 0.920, respectively). In this large general population study, the observed inverse association between serum vitamin D status and all-cause mortality was not explained by a similar inverse association with IHD or stroke.

Strong associations of 25-hydroxyvitamin D concentrations with all-cause, cardiovascular, cancer, and respiratory disease mortality in a large cohort study

BACKGROUND

Serum 25-hydroxyvitamin D [25(OH)D] concentration has been linked to mortality in several studies, but appropriate cutoffs to define risk categories are under debate.

OBJECTIVE

We aimed to conduct a repeated-measurements analysis on the association of serum 25(OH)D concentrations with all-cause and cause-specific mortality, with particular attention given to the shape of dose-response relations.

DESIGN

Concentrations of 25(OH)D were measured in n = 9578 baseline and n = 5469 5-y follow-up participants of the ESTHER study, which is a German population-based cohort aged 50-74 y at baseline. Deaths were recorded during 9.5 y of follow-up (median). Restricted cubic splines were used to assess dose-response relations, and Cox regression with time-dependent variables was used to estimate hazard ratios.

RESULTS

During follow-up, 1083 study participants died; of those, 350 individuals died of cardiovascular diseases, 433 individuals died of cancer, and 55 individuals died of respiratory diseases. The overall mortality [HR (95% CI)] of subjects with vitamin D deficiency [25(OH)D concentrations <30 nmol/L] or vitamin D insufficiency [25(OH)D concentrations from 30 to 50 nmol/L) was significantly increased [1.71 (1.43, 2.03) and 1.17 (1.02, 1.35), respectively] compared with that of subjects with sufficient 25(OH)D concentrations (>50 nmol/L)]. Vitamin D deficiency was also associated with increased cardiovascular mortality [1.39 (95% CI: 1.02, 1.89)], cancer mortality [1.42 (95% CI: 1.08, 1.88)] and respiratory disease mortality [2.50 (95% CI: 1.12, 5.56)]. The association of 25(OH)D concentrations with all-cause mortality proved to be a nonlinear inverse association with risk that started to increase at 25(OH)D concentrations <75 nmol/L.

CONCLUSIONS

In this large cohort study, serum 25(OH)D concentrations were inversely associated with all-cause and cause-specific mortality. In particular, vitamin D deficiency [25(OH)D concentration <30 nmol/L] was strongly associated with mortality from all causes, cardiovascular diseases, cancer, and respiratory diseases.

Vitamin D effects on musculoskeletal health, immunity, autoimmunity, cardiovascular disease, cancer, fertility, pregnancy, dementia and mortality-a review of recent evidence

BACKGROUND

Optimal vitamin D intake and its status are important not only for bone and calcium-phosphate metabolism, but also for overall health and well-being. Vitamin D deficiency and insufficiency as a global health problem are likely to be a risk for wide spectrum of acute and chronic illnesses.

METHODS

A review of randomized controlled trials, meta-analyses, and other evidence of vitamin D action on various health outcomes.

RESULTS

Adequate vitamin D status seems to be protective against musculoskeletal disorders (muscle weakness, falls, fractures), infectious diseases, autoimmune diseases, cardiovascular disease, type 1 and type 2 diabetes mellitus, several types of cancer, neurocognitive dysfunction and mental illness, and other diseases, as well as infertility and adverse pregnancy and birth outcomes. Vitamin D deficiency/insufficiency is associated with all-cause mortality.

CONCLUSIONS

Adequate vitamin D supplementation and sensible sunlight exposure to reach optimal vitamin D status are among the front line factors of prophylaxis for the spectrum of disorders. Supplementation guidance and population strategies for the eradication of vitamin D deficiency must be included in the priorities of physicians, medical professionals and healthcare policy-makers.

Serum 25-hydroxyvitamin D levels and overall mortality. A systematic review and meta-analysis of prospective cohort studies

OBJECTIVE

To provide a systematic review and meta-analysis of prospective, population-based cohort studies on the association of serum 25-hydroxyvitamin D (25(OH)D) and all-cause mortality.

METHODS

Relevant studies were identified by systematically searching Medline, EMBASE and ISI Web of Knowledge. Reported hazard ratios (HRs) for 25(OH)D categories were recalculated employing comprehensive trend estimation from summarized dose-response data and pooled in a random effects model meta-analysis.

RESULTS

Overall, 12 original studies were included in the review and meta-analysis comprising 32,142 mainly elderly study participants with measured 25(OH)D of whom 6921 died during follow-up. An inverse association between 25(OH)D levels and all-cause mortality was found in all but two studies that was statistically significant in several of the individual studies. In meta-analysis, 25(OH)D levels were significantly inversely associated with all-cause mortality with a pooled HR of 0.92 (95% confidence interval: 0.89-0.95) for a 20 nmol/l increase in 25(OH)D levels.

CONCLUSION

In this meta-analysis of prospective, population-based cohort studies, a 20 nmol/l increase in 25(OH)D levels was associated with an 8% lower mortality in the general elderly population. This agrees with results from meta-analyses on randomized controlled trials that found a decrease in mortality with vitamin D3 supplementation of a comparable magnitude.

Vitamin d: are we ready to supplement for breast cancer prevention and treatment?

Vitamin D deficiency is a potentially modifiable risk factor that may be targeted for breast cancer prevention and treatment. Preclinical studies support various antitumor effects of vitamin D in breast cancer. Numerous observational studies have reported an inverse association between vitamin D status, including circulating 25-hydroxyvitamin D (25(OH)D) levels, and breast cancer risk. The relationship between vitamin D and mammographic density, a strong predictor of breast cancer risk, remains unclear. Studies analyzing the link between genetic polymorphisms in vitamin D pathway genes and breast cancer incidence and prognosis have yielded inconsistent results. Vitamin D deficiency among breast cancer patients has been associated with poorer clinical outcomes and increased mortality. Despite a number of clinical trials of vitamin D supplementation, the efficacy, optimal dosage of vitamin D, and target blood level of 25(OH)D for breast cancer prevention have yet to be determined. Even with substantial literature on vitamin D and breast cancer, future studies need to focus on gaining a better understanding of the biologic effects of vitamin D in breast tissue. Despite compelling data from experimental and observational studies, there is still insufficient data from clinical trials to make recommendations for vitamin D supplementation for breast cancer prevention or treatment.

Serum 25-hydroxyvitamin D and breast cancer in the military: a case-control study utilizing pre-diagnostic serum

PURPOSE

The objective of this study was to ascertain whether a relationship exists between pre-diagnostic serum levels of 25-hydroxyvitamin D (25(OH)D) and risk of breast cancer in young women.

METHODS

About 600 incident cases of breast cancer were matched to 600 controls as part of a nested case-control study that utilized pre-diagnostic sera. Logistic regression was used to assess the relationship between serum 25(OH)D concentration and breast cancer risk, controlling for race and age.

RESULTS

According to the conditional logistic regression for all subjects, odds ratios for breast cancer by quintile of serum 25(OH)D from lowest to highest were 1.2, 1.0, 0.9, 1.1, and 1.0 (reference) (p trend = 0.72). After multivariate regression for subjects whose blood had been collected within 90 days preceding diagnosis, odds ratios for breast cancer by quintile of serum 25(OH)D from lowest to highest were 3.3, 1.9, 1.7, 2.6, and 1.0 (reference) (p trend = 0.09).

CONCLUSIONS

An inverse association between serum 25(OH)D concentration and risk of breast cancer was not present in the principal analysis, although an inverse association was present in a small subgroup analysis of subjects whose blood had been collected within 90 days preceding diagnosis. Further prospective studies of 25(OH)D and breast cancer risk are needed.

Vitamin D status and cause-specific mortality: a general population study

Background

Vitamin D deficiency is associated with an increased risk of all-cause mortality in observational studies. The specific causes of death underlying this association lack clarity. We investigated the association between vitamin D status and cause-specific mortality.

Methods

We included a total of 9,146 individuals from the two population-based studies, Monica10 and Inter99, conducted in 1993–94 and 1999–2001, respectively. Vitamin D status was assessed as serum 25-hydroxyvitamin D. Information on causes of death was obtained from The Danish Register of Causes of Death until 31 December 2009. There were a total of 832 deaths (median follow-up 10.3 years).

Results

Multivariable Cox regression analyses with age as underlying time axis and vitamin D quartiles showed significant associations between vitamin D status and death caused by diseases of the respiratory system, the digestive system, and endocrine, nutritional and metabolic diseases with hazard ratios (HRs) 0.26 (p_trend = 0.0042), 0.28 (p_trend = 0.0040), and 0.21 (p_trend = 0.035), respectively, for the fourth vitamin D quartile compared to the first. We found non-significantly lower HRs for death caused by mental and behavioural diseases and diseases of the nervous system, but no association between vitamin D status and death caused by neoplasms or diseases of the circulatory system.

Conclusion

The associations of vitamin D status and cause-specific mortality suggest that we also look elsewhere (than to cardiovascular disease and cancer) to explain the inverse association between vitamin D status and mortality.

Association between 25-hydroxyvitamin D concentration and breast cancer risk in an Australian population: an observational case-control study

The objective of this study is to examine the association between vitamin D status and risk of breast cancer in an Australian population of women. The study design is observational case-control study, performed at Westmead Breast Cancer Institute, Westmead Hospital, Sydney, Australia. 214 women newly diagnosed with breast cancer were matched to 852 controls, and their blood samples were tested at the same laboratory between August 2008 and July 2010. Circulating 25-hydroxyvitamin D (25(OH)D) concentration, was defined as sufficient (≥75 nmol/L), insufficient (50-74 nmol/L), deficient (25-49 nmol/L) or severely deficient (<25 nmol/L). The difference in median 25(OH)D concentration between cases and controls was reported, and the Mann-Whitney U test was used to determine the significance of the difference. Odds ratios and 95 % confidence intervals for the risk of breast cancer were estimated by Cox regression. Median plasma 25(OH)D was significantly lower in cases versus controls overall (53.0 vs 62.0 nmol/L, P < 0.001) and during summer (53.0 vs 68.0 nmol/L, P < 0.001) and winter (54.5 vs 63.0 nmol/L, P < 0.001). Median 25(OH)D was also lower in cases when stratified by BMI (<30, ≥30) and age group (<50, ≥50 years) compared to matched controls, although the difference failed to reach statistical significance. In a Cox regression model, plasma 25(OH)D was inversely associated with the odds ratio of breast cancer. Compared to subjects with sufficient 25(OH)D concentration, the odds ratios of breast cancer were 2.3 (95 % CI 1.3-4.3), 2.5 (95 % CI 1.6-3.9) and 2.5 (95 % CI 1.6-3.8) for subjects categorised as severely deficient, deficient or insufficient vitamin D status, respectively. The results of this observational case-control study indicate that a 25(OH)D concentration below 75 nmol/L at diagnosis was associated with a significantly higher risk of breast cancer. These results support previous research which has shown that lower 25(OH)D concentrations are associated with increased risk of breast cancer.