Vitamin D metabolism, functions and needs: from science to health claims

Background

Vitamin D is a nutrient long considered as essential for skeletal health but is now attracting interest from medical and nutritional communities as knowledge emerges of its biological function and its association with decreased risk of many chronic diseases.

Results

A question emerges: How much more vitamin D do we need for these new functions of vitamin D? This review discusses vitamin D physiology and hypovitaminosis D and presents two vitamin D dietary policies: that according to regulatory authorities and that of nutrition scientists. Scientific evidence suggests that 25(OH)D serum levels should be over 75 nmol/L; otherwise, there is no beneficial effect of vitamin D on long-latency diseases. Current regulatory authority recommendations are insufficient to reach this level of adequacy. Observational and some prospective data show that vitamin D has a role in the prevention of cancer as well as immunity, diabetes and cardiovascular and muscle disorders, which supports the actions of 1α,25(OH)2D at cellular and molecular levels. The recent assessments done by the European Food Safety Authority should lead to new health claims.

Conclusions

Vitamin D, through food fortification and supplementation, is a promising new health strategy and thus provides opportunities for food industry and nutrition researchers to work together towards determining how to achieve this potential health benefit.     

Vitamin D supplementation versus combined calcium and vitamin D in older female patients — An observational study

Background

In most developed countries overt vitamin D deficiency, characterized by rickets or osteomalacia, is now uncommon However, subclinical vitamin D insufficiency is extremely common and may contribute to the development of skeletal and non-skeletal problems. Standard practice involves supplementation with a combination of vitamin D and calcium although the benefit of adding calcium to vitamin D supplements has not been fully established and may reduce adherence due to its bulky and chalky consistency.

Purpose of study

To compare the effects of vitamin D alone versus vitamin D/calcium supplements on vitamin D levels, bone profile and parathyroid hormone level.

Population

Older (>65 years) female patients living in the community and long term care institutions.

Interventions

Either 800 iu of vitamin D3 or a composite supplement of 800 iu vitamin D3 and 1000mg calcium were given to patients in an open-labelled observational study. Serum 25-hydroxy-vitamin D, parathyroid hormone, calcium, phosphate and alkaline phosphatase levels were assessed at baseline and after 3 months of treatment.

Results

Serum 25-hydroxy-vitamin D levels rose from baseline levels of 25 ± 16 to 79 ± 16 in those treated with vitamin D alone and from 35 ± 24 nmol/L to 70 ± 24 nmol/L in those treated with vitamin D and calcium Serum PTH levels fell by similar amounts in both groups. In both community dwellers and institutionalised patients, those treated with vitamin D alone were at least as likely to achieve normalisation of serum vitamin D levels as those on combined calcium/vitamin D treatment.

Conclusion

Vitamin D alone appears as effective as combined calcium/vitamin D treatment in restoring serum vitamin D levels in older community dwelling and institutionalised patients. A prospective randomised trial would help confirm these findings.     

The influence of renal function on vitamin D metabolism in the very elderly

Objectives

Hypovitaminosis D and chronic kidney disease (CKD) are highly prevalent in older adults. The factors correlating with 25-OH-vitamin D and PTH levels were analyzed in older adults with and without CKD.

Design

We performed a cross-sectional analysis embedded within the BELFRAIL study.

Setting

A population-based prospective cohort study of the very elderly in Belgium.

Participants

325 participants, all aged 80 or older.

Measurments

Time of year and LAPAQ score were used as proxies for sunshine exposure. Vitamin D3 supplementation, gender, institutionalisation, age, level of education, and serum calcium and phosphorus level were examined as possible confounders in the analyses.

Results

There was no correlation between the presence of CKD and low 25-OH-vitamin D levels, but there was a significant (p<0. 01) correlation between CKD and high PTH levels. Among the participants with a normal eGFR, the LAPACQ score, vitamin D supplementation, season, log PTH value and eGFR were correlated with log 25-OH-vitamin D levels. Among the participants with CKD, only vitamin D supplementation, log PTH levels and serum calcium levels were correlated with log 25-OH-vitamin D levels. Gender, log 25-OH-vitamin D values, serum calcium and phosphorus levels and eGFR were correlated with log PTH values in the patients with normal eGFR. Log 25-OH-vitamin D values, serum phosphorus levels, vitamin D supplementation (p=0.07), season (p=0.10) and eGFR were correlated with log PTH values in the patients with CKD.

Conclusion

Exposure to sunshine and an active lifestyle were correlated with higher 25-OH-vitamin D levels in older adults without CKD. The PTH level in patients with CKD may be influenced by the season.     

Walk on the sunny side of life — Epidemiology of hypovitaminosis D and mental health in elderly nursing home residents

Objectives

Old age is a well-known risk factor for both depression and hypovitaminosis D, and an association between both conditions has been postulated. We document the prevalence of vitamin D deficiency in nursing home residents, and we examine the link with self-reported depressive symptoms and pharmacotherapy for depression.

Design

Cross- sectional. Setting: nursing homes in Antwerp, Belgium.

Participants

Healthy elderly (n=589), with a mean age of 84 years.

Measurements

We detected depressive symptoms by means of SF-36, a validated quality of life assessment; we registered the use of antidepressants and anxiolytics, and we measured serum 25(OH)D concentrations in all participants.

Results

Almost our entire study population appeared to be vit D deficient. Comparison of the most severely and least deficient subgroups showed a consistent tendency towards more depressive symptoms and more use of antidepressants in the group with the lowest vit D level.

Conclusion

Nursing home residents are particularly vulnerable to preventable vit D deficiency. The relevance of the association with depressive symptoms and the possibilities for treatment are critically reviewed in the discussion.     

The use of dietary supplements among older persons in Southern Germany — Results from the KORA-age study

Objectives

Current population-based surveys in Europe on the prevalence of dietary supplement (DS) use in older individuals are scarce. The aim of the present study was to investigate patterns, prevalence and determinants of non-herbal DS use in aged subjects. Furthermore, the intake amounts of vitamins and minerals from supplements were assessed.

Design

Cross-sectional.

Setting

Data on supplement use were available from an age- and sex-stratified random sample of the German population-based KORA (Cooperative Health Research in the Region of Augsburg)-Age study.

Participants

1,079 persons who were born in or before the year 1943.

Measurements

Use of dietary supplements and medications during the last seven days was recorded in a face-to-face interview in 2009. Participants were asked to bring all packages of ingested preparations to the study center. Not only vitamin/mineral supplements, but also non-vitamin non-mineral non-herbal supplements and drugs containing vitamins and minerals were coded as DS.

Results

The age-standardized prevalence of DS intake was 54.3% in women and 33.8% in men, respectively. The most commonly supplemented mineral and vitamin, respectively, was magnesium (31.9%) and vitamin D (21.5%) in women and magnesium (18.0%) and vitamin E (12.0%) in men. The highest intakes, compared to the German Dietary Reference Intakes, were reported for biotin, vitamin B₆ and B₁. Excessive intakes (equal or above the European Tolerable Upper Intake Levels (UL)) were observed especially for magnesium and vitamin E. 20.2% of the women and 32.5% of the men who took magnesium supplements regularly exceeded the UL for magnesium. In case of vitamin E this was true for 8.0% of the women and 13.6% of the men. Determinants of DS use were sex, education, smoking, physical activity, neurological diseases, and stroke.

Conclusion

A high proportion of the general population aged 65 years and older in Southern Germany uses DS, especially supplements containing vitamins/minerals. The supplementation of vitamin D can be regarded as favorable in this age group, whereas the excessive intakes of vitamin E might be a cause of concern.     

Vitamin D status among older community dwelling men living in a sunny country and associations with lifestyle factors: The concord health and ageing in men project, Sydney, Australia

Objectives

Inadequate vitamin D status (25-hydroxyvitamin D (25(OH)D) concentrations <50 nmol/L) is an increasingly important public health issue in Australia. The aim of this analysis is to describe 25(OH)D levels in community dwelling men aged ≥70 years in Sydney, Australia, and to determine associations between serum 25(OH)D levels and socioeconomic and lifestyle factors.

Design

A population-based, crosssectional analysis of the baseline phase of the Concord Health and Ageing in Men Project (CHAMP), a large epidemiological study conducted in Sydney between January 2005 and May 2007.

Participants

1659 noninstitutionalised men aged ≥70 years.

Methods

The cross-sectional analysis of the baseline phase of the Concord Health and Ageing in Men Project (CHAMP), a large epidemiological study conducted in Sydney between January 2005 and May 2007. Participants included 1659 community dwelling men who were interviewed and had clinical assessments. Main outcome measurements included serum 25(OH)D levels measured in blood samples using a radioimmunoassay kit (DiaSorin Inc., Stillwater, MN). Covariates included age, socioeconomic measures, season of blood sample, physical activity, sun exposure, vitamin D supplement use, cigarette smoking status, alcohol consumption, obesity and measures of health.

Results

Prevalence of vitamin D insufficiency was 43.0%; highest in winter (55.5%) and spring (53.9%), and was associated with season (winter and spring), low physical activity, avoidance of sun exposure, current smoking and obesity, even after adjustment for confounding factors.

Conclusion

Inadequate vitamin D status is highly prevalent among Australian older men and is associated with specific lifestyle factors. These findings emphasize the need to screen and monitor 25(OH)D levels in this population group, despite living in a sunny country such as Australia.     

Association between mortality from suicide in England and antidepressant prescribing: an ecological study

Background

There are multiple studies in different countries regarding the prevalence of vitamin D deficiency. These studies showed high prevalence of vitamin D deficiency in Asian countries. This study tries to elucidate the prevalence of vitamin D deficiency and its influencing factors in population of Tehran.

Methods

1210 subjects 20–64 years old were randomly selected. 25 (OH) D serum levels were measured. Duration of exposure to sunlight, the type of clothing and level of calcium intake and BMI were quantified based on a questionnaire.

Results

A high percentage of vitamin D deficiency was defined in the study population. Prevalence of severe, moderate and mild Vitamin D deficiency was 9.5%, 57.6% and 14.2% respectively. Vitamin D serum levels had no significant statistical relation with the duration of exposure to sunlight, kind of clothing and BMI. Calcium intake in the normal vitamin D group was significantly higher than the other groups (714.67 ± 330.8 mg/day vs 503.39 ± 303.1, 577.93 ± 304.9,595.84 ± 313.6). Vitamin D serum levels in young and middle aged females were significantly lower than the older group.

Conclusions

Vitamin D deficiency has a high prevalence in Tehran. In order to avoid complications of vitamin D deficiency, supplemental dietary intake seems essential.     

A systematic review of vitamin D status in southern European countries

Purpose

Despite an acknowledged dearth of data on serum 25-hydroxyvitamin D (25(OH)D) concentrations from Southern European countries, inter-country comparison is hampered by inconsistent data reporting. The purpose of the current study was to conduct a systematic literature review of available data on serum 25(OH)D concentrations and estimate vitamin D status in Southern European and Eastern Mediterranean countries, both at a population level and within key population subgroups, stratified by age, sex, season and country.

Methods

A systematic review of the literature was conducted to identify and retrieve scientific articles reporting data on serum 25(OH)D concentration and/or vitamin D status following standard procedures.

Results

Data were extracted from 107 studies, stratified by sex and age group, representing 630,093 individuals. More than one-third of the studies reported mean 25(OH)D concentrations below 50 nmol/L and ~?10% reported mean serum 25(OH)D concentrations below 25 nmol/L. Overall, females, neonates/ infants and adolescents had the higher prevalence of poor vitamin D status. As expected, there was considerable variability between studies. Specifically, mean 25(OH)D ranged from 6.0 (in Italian centenarians) to 158 nmol/L (in elderly Turkish men); the prevalence of serum 25(OH)D?<?50 nmol/L ranged from 6.8 to 97.9% (in Italian neonates).

Conclusions

Contrary to expectations, there was a high prevalence of low vitamin D status in the Southern Europe and the Eastern Mediterranean regions, despite abundant sunshine. These data further emphasize the need for strategies, such as fortification of foods with vitamin D and/or vitamin D supplementation, which will be tailored to the needs of specific population groups with higher risk of insufficiency or deficiency, to efficiently tackle the pandemic of hypovitaminosis D in Europe.

     

The effectiveness of a preventive health program and vitamin D status in improving health-related quality of life of older Canadians

Purpose

To assess the effectiveness of a preventive health program and vitamin D status in improving the health-related quality of life (HRQOL) of older residents of Canada.

Design

We analyzed baseline and follow-up data of 2119 volunteers of a community program that promotes healthy lifestyles and encourages vitamin D supplementation. We examined the program effect on each of the five dimensions of the EQ-5D-5L, HRQOL score, and quality-adjusted life years (QALYs) using multivariable regression methods. We further examined the specific contribution of vitamin D status as quantified by serum 25-hydroxyvitamin D (25(OH)D).

Results

Problems with mobility, usual activities, pain/discomfort, and depression/anxiety were reported less during follow-up compared to baseline. On average, participants’ HRQOL had improved by 0.018 units at 6 months and 0.025 units at 1 year of follow-up. Improvements in vitamin D status were independently associated with improvements in HRQOL and in QALYs. As per 25 nmol/L increase in 25(OH)D, there was a 0.002 increase in HRQOL and a 0.001 increase in QALYs.

Conclusions

This study documents the benefits of a real-world preventive health program to HRQOL. It is the first to reveal that improvements in vitamin D status parallel improvements in HRQOL among healthy community dwellers. The study further suggests that the preventive health program and supplementation with vitamin D are cost-effective interventions.

     

High-dose cholecalciferol supplementation significantly increases peripheral CD4+ Tregs in healthy adults without negatively affecting the frequency of other immune cells

Background

Regulatory T cells (Tregs) play a central role in the maintenance of self-tolerance. Animal and in vitro studies suggest that vitamin D is involved in reducing the risk of autoimmunity by modulating Tregs.

Methods

In a double-blind, placebo controlled study in 60 healthy volunteers, we assessed the effect of a 12-week high-dose oral cholecalciferol supplementation (140,000 IU/month) on the number and function of CD4^posCD25^highFoxP3^posCD127^dim Tregs. We also assessed the clinical safety of the supplementation and the effect on the frequency of other immune cells such as monocytes, dendritic cells, natural killer cells, natural killer T cells, B cells and subgroups of T cells. We also tested the in vitro effect of cholecalciferol on Tregs in human cell cultures.

Results

By using FACS analysis, ex vivo suppressive co-cultures and apoptosis assays, we were able to show that a cholecalciferol supplementation leads to significantly increased numbers of peripheral Tregs in vivo. Tregs function and the frequency of other immune cells remained unchanged, and no clinically relevant safety concerns were found. The in vitro exposure of human peripheral blood mononuclear cells to cholecalciferol also supported our in vivo findings.

Conclusions

Our results indicate a substantial effect of a supplementation with inactive vitamin D on the immune system of healthy humans in vivo and provide a rationale for future studies to investigate the immunomodulatory effects of vitamin D in autoimmune diseases.     

Vitamin D is not linked to folate status and mRNA expression of intestinal proton-coupled folate transporter

Purpose

In vitro studies discovered intestinal proton-coupled folate transporter (PCFT) as a vitamin D hormone-responsive gene. In vivo effects of vitamin D on PCFT and folate status are currently not available.

Methods

Three experiments were conducted. At first, vitamin D receptor knockout (VDR^?/?) mice and corresponding wild-type (WT) mice were compared for their plasma and hepatic folate concentration and PCFT mRNA expression in intestinal mucosa. In a second experiment with rats, we analyzed the folate status of offspring in response to a maternal vitamin D-adequate (1,000 IU/kg) or vitamin D-deficient (0 IU/kg) diet that was fed for 11 weeks. Finally, the plasma folate concentration of healthy individuals was studied at baseline (in winter) and in response to an oral treatment for 8 weeks with 2,000 IU vitamin D₃ per day or a placebo, respectively.

Results

Here, we show that folate status and intestinal PCFT mRNA abundance did not differ between the VDR^?/? and the WT mice. No effect of vitamin D on folate status was also found in rat dams and their offspring, and plasma folate levels of individuals did not change in response to vitamin D.

Conclusions

Current data from studies with model animals and humans provide no indication for a vitamin D effect on intestinal uptake and status of folate.     

Vitamin D supplementation,body weight and human serum 25-hydroxyvitamin D response: a systematic review

Purpose

There is considerable variation in incremental circulating 25-hydroxyvitamin D (25OHD) levels on vitamin D supplements, even when similar age groups and identical vitamin D doses are compared. We therefore aimed to investigate the importance of body weight for the dose–response relation in circulating 25OHD.

Methods

We performed a systematic review of randomized placebo-controlled vitamin D supplementation trials in all age groups ≥10 years to clarify the influence of body weight and other parameters on incremental circulating 25OHD levels (difference between baseline and in-study values) in vitamin D-deficient and non-deficient individuals.

Results

We included 144 cohorts from 94 independent studies, published from 1990 to November 2012, in our systematic review. There was a logarithmic association between vitamin D dose per kg body weight per day and increment in circulating 25OHD. In multivariable regression analysis, vitamin D dose per kg body weight per day could explain 34.5 % of variation in circulating 25OHD. Additional significant predictors were type of supplement (vitamin D₂ or vitamin D₃), age, concomitant intake of calcium supplements and baseline 25OHD, explaining 9.8, 3.7, 2.4 and 1.9 %, respectively, of the variation in circulating 25OHD.

Conclusions

This systematic review demonstrates that body weight is an important predictor of variation in circulating 25OHD in cohorts on vitamin D supplements. Our model provides an estimate of the daily vitamin D dose that is necessary for achieving adequate circulating 25OHD levels in vitamin D-insufficient or vitamin D-deficient individuals/cohorts with different body weights and ages.     

Different doses of supplemental vitamin D maintain interleukin-5 without altering skeletal muscle strength: a randomized, double-blind, placebo-controlled study in vitamin D sufficient adults

Background

Supplemental vitamin D modulates inflammatory cytokines and skeletal muscle function, but results are inconsistent. It is unknown if these inconsistencies are dependent on the supplemental dose of vitamin D. Therefore, the purpose of this study was to identify the influence of different doses of supplemental vitamin D on inflammatory cytokines and muscular strength in young adults.

Methods

Men (n = 15) and women (n = 15) received a daily placebo or vitamin D supplement (200 or 4000 IU) for 28-d during the winter. Serum 25-hydroxyvitamin D (25(OH)D), cytokine concentrations and muscular (leg) strength measurements were performed prior to and during supplementation. Statistical significance of data were assessed with a two-way (time, treatment) analysis of variance (ANOVA) with repeated measures, followed by a Tukey's Honestly Significant Difference to test multiple pairwise comparisons.

Results

Upon enrollment, 63% of the subjects were vitamin D sufficient (serum 25(OH)D ?? 30 ng/ml). Serum 25(OH)D and interleukin (IL)-5 decreased (P < 0.05) across time in the placebo group. Supplemental vitamin D at 200 IU maintained serum 25(OH)D concentrations and increased IL-5 (P < 0.05). Supplemental vitamin D at 4000 IU increased (P < 0.05) serum 25(OH)D without altering IL-5 concentrations. Although serum 25(OH)D concentrations correlated (P < 0.05) with muscle strength, muscle strength was not changed by supplemental vitamin D.

Conclusion

In young adults who were vitamin D sufficient prior to supplementation, we conclude that a low-daily dose of supplemental vitamin D prevents serum 25(OH)D and IL-5 concentration decreases, and that muscular strength does not parallel the 25(OH)D increase induced by a high-daily dose of supplemental vitamin D. Considering that IL-5 protects against viruses and bacterial infections, these findings could have a broad physiological importance regarding the ability of vitamin D sufficiency to mediate the immune systems protection against infection.     

Vitamin D and health-related quality of life in a community sample of older Canadians

Purpose

To assess how vitamin D status is associated with health-related quality of life (HRQOL) among older residents of Canada.

Design

We analysed baseline data of 1,493 Canadians aged 50 years and over in Alberta on HRQOL (EQ-5D-5L) and serum 25-hydroxyvitamin D (25(OH)D) as a measure of vitamin D status. We applied multivariable regression methods to examine the association between vitamin D status and each of the five dimensions and the summary index of the EQ-5D-5L.

Results

Participants with higher serum 25(OH)D levels were significantly less likely to report problems with mobility, usual activities, and depression and anxiety. Specifically, age- and gender-adjusted odds ratios for reporting problems with mobility, usual activities, and depression and anxiety were 0.58 (95 % confidence interval 0.44–0.78), 0.67 (0.50–0.89), and 0.67 (0.51–0.88) per 100 nmol/L increase in 25(OH)D, respectively. No significant associations were observed for problems with self-care and with pain and discomfort. HRQOL scores combining the responses of each of the five dimensions increased significantly with increasing serum 25(OH)D levels.

Conclusions

This is the first study to reveal the importance of vitamin D for the five dimensions of HRQOL in a community-based sample. The observed associations of vitamin D and HRQOL call for intervention studies to strengthen the evidence of the potential benefits of vitamin D supplementation for HRQOL among older adults.     

New perspectives on vitamin D sources in Germany based on a novel mathematical bottom-up model of 25(OH)D serum concentrations

Purpose

Up-to-date knowledge about vitamin D supply and serum concentration in Germany is not sufficient. Our purpose was to compare a novel holistic bottom-up modeling of 25(OH)D concentrations with vitamin D sources such as sunlight, food and supplements for all federal states taking seasonal and geographical variations into account. The second purpose was to update and detail vitamin D supply through food in Germany.

Methods

To confirm the model of 25(OH)D concentrations, we used the population (1,763 men and 2,267 women, 18–79 years) participated in the representative German National Health Interview and Examination Survey 1998 and the integrated German Nutrition Survey.

Results

The maximum model value is 67.5 nmol/L in July and minimum model value is 29.3 nmol/L in January, while the average model value is 45.0 nmol/L. Men have a mean daily intake of 137 IU (3.42 μg) and women of 112 IU (2.79 μg). Correlation between model and actual data is 0.77 (p = 0.003).

Conclusions

A comparison of the model data with population-based values showed good agreement. None of the vitamin D sources can provide the German population with enough vitamin D.     

Vitamin B-12 supplementation improves arterial function in vegetarians with subnormal vitamin B-12 status

Objective

Vegetarians are more vascular-healthy but those with subnormal vitamin B-12 status have impaired arterial endothelial function and increased intima-media thickness. We aimed to study the impact of vitamin B-12 supplementation on these markers, in the vegetarians.

Design

Double-blind, placebo controlled, randomised crossover study.

Setting

Community dwelling vegetarians.

Participants

Fifty healthy vegetarians (vegetarian diet for at least 6 years) were recruited. Intervention: Vitamin B-12 (500??g/day) or identical placebo were given for 12 weeks with 10 weeks of placebo-washout before crossover (n=43), and then open label vitamin B-12 for additional 24 weeks (n=41).

Measurement

How-mediated dilation of brachial artery (FMD) and intima-media thickness (IMT) of carotid artery were measured by ultrasound.

Results

The mean age of the subjects was 45+9 years and 22 (44%) were male. Thirty-five subjects (70%) had serum B-12 levels <150pmol/l. Vitamin B-12 supplementation significantly increased serum vitamin B-12 levels (p<0.0001) and lowered plasma homocysteine (p<0.05). After vitamin B-12 supplementation but not placebo, significant improvement of brachial FMD (6.3±1.8% to 6.9±1.9%; p<0.0001) and in carotid IMT (0.69±0.09mm to 0.67±0.09 mm, p<0.05) were found, with further improvement in FMD (to 7.4±1.7%; p<0.0001) and IMT (to 0.65±0.09mm; p<0.001) after 24 weeks open label vitamin B-12. There were no significant changes in blood pressures or lipid profiles. On multivariate analysis, changes in B-12 (??=0.25; p=0.02) but not homocysteine were related to changes in FMD, (R=0.32; F value=3.19; p=0.028).

Conclusions

Vitamin B-12 supplementation improved arterial function in vegetarians with subnormal vitamin B-12 levels, proposing a novel strategy for atherosclerosis prevention.     

Suboptimal maternal vitamin D status and low education level as determinants of small-for-gestational-age birth weight

Purpose

This study aimed firstly to investigate the contribution of maternal 25(OH) vitamin D to the association of maternal education and small-for-gestational-age birth weight (SGA) and secondly to examine whether the contribution of 25(OH) vitamin D differs by overweight, season, and maternal smoking.

Methods

Logistic regression analysis was carried out in this study, using data of 2,274 pregnant women of Dutch ethnicity from the ABCD study, a population-based cohort study in the Netherlands. Maternal 25(OH) vitamin D was measured in early pregnancy. Stratified analyses were conducted for overweight, season of blood sampling, and smoking.

Results

Low-educated women had lower 25(OH) vitamin D levels compared to high-educated women, and women in the lowest 25(OH) vitamin D quartile had a higher risk of SGA offspring. In addition, low-educated women had a higher risk of SGA offspring (OR 1.95 [95% CI: 1.20–3.14]). This association decreased with 7% after adjustment for 25(OH) vitamin D (OR 1.88 [95% CI 1.16–3.04]). In stratified analyses, adjustment for 25(OH) vitamin D resulted in a decrease in OR of about 17% in overweight women and about 15% in women who conceived in wintertime.

Conclusions

25(OH) vitamin D appears to be a modifiable contributor to the association between low maternal education and SGA offspring, particularly in overweight women and women who conceived in the winter period. In those women, increasing the intake of vitamin D, either through dietary adaptation or through supplementation in order to achieve the recommendation, could be beneficial.     

Antioxidant effect of zinc supplementation on both plasma and cellular red-ox status markers in a group of elderly Italian population

Objectives

The aim of this work was to evaluate the effect of long term supplementation with two moderate dose of Zn on plasma and cellular red-ox status markers in elderly volunteers.

Design, setting and subjects

In a double blind study 108 healthy volunteers, aged 70–85 years, were enrolled. They were randomly divided in 3 groups of treatment, receiving placebo, 15 mg/day and 30 mg/day of Zn for 6 months. Red-ox status markers were assessed at baseline and after 6 months evaluating carotenoids, vitamin A and E in plasma; glutathione (GSH), thiol groups (RSH), malondialdehyde (MDA), percentage of haemolysis and methemoglobin in erythrocytes.

Results

Zn supplementation had no significant effects on red-ox status markers except for vitamin A levels (from 1.94±0.44 to 2.18±0.48 μM in volunteers receiving 15 mg of Zn and from 1.95±0.46 to 2.26±0.56 μM in volunteers receiving 30 mg of Zn), which increased proportionally to zinc dose.

Conclusions

It appears that, differently from unhealthy populations, long-term supplementation with two moderate doses of Zn in a healthy elderly population, with an adequate Zn nutritive status and macro and micronutrients intakes in the range of normality, is an inefficient way to increase antioxidant defences.