Vitamin D level and its relation to muscle and fat mass in adult male Arabs

Low levels of vitamin D have been linked with increased adiposity and diminished muscle strength. Whether it is also related to fat deposition in muscle tissues is not studied well. This study explored the associations between circulating 25-hydroxyvitamin D (25(OH)D) and fat deposition in muscle tissues of adult Arab males. A total 465 adult Saudi males were included in this cross-sectional study. Anthropometrics, body composition and muscle strength were assessed. Serum 25(OH)D was determined and quantified enzymatically. They were grouped according to vitamin D status: deficient (25(OH)D < 50 nmol/l) N = 325 (69.9%) and sufficient (25(OH)D > 50 nmol/l)140 (30.1%). Mean level of lean/height², lean-arm-legs and lean-arms-legs/height² were significantly higher in 25(OH)D deficient participants (p-values 0.03; 0.05 and 0.01 respectively). Thigh strength was significantly higher in 25(OH)D sufficient participants than their deficient counterparts (p = 0.02). In all participants, a significant correlation between 25(OH)D was observed with age and thigh-strength (p-values < 0.05), while a significant inverse correlation between 25(OH)D and lean/height², lean-arms-legs, lean-arms-legs/height², fat (%) region, fat arms, fat legs, fat trunk, lean legs were noted. In conclusion, low circulating 25(OH)D is associated with enhanced fat infiltration in muscle tissues of adult Arab males.

Sunlight, UV Radiation, Vitamin D, and Skin Cancer: How Much Sunlight Do We Need?

Vitamin D is the sunshine vitamin for good reason. During exposure to sunlight, the ultraviolet B photons enter the skin and photolyze 7-dehydrocholesterol to previtamin D₃ which in turn is isomerized by the body's temperature to vitamin D₃. Most humans have depended on sun for their vitamin D requirement. Skin pigment, sunscreen use, aging, time of day, season, and latitude dramatically affect previtamin D₃ synthesis. Vitamin D deficiency was thought to have been conquered, but it is now recognized that more than 50% of the world's population is at risk for vitamin D deficiency. This deficiency is in part due to the inadequate fortification of foods with vitamin D and the misconception that a healthy diet contains an adequate amount of vitamin D. Vitamin D deficiency causes growth retardation and rickets in children and will precipitate and exacerbate osteopenia, osteoporosis and increase risk of fracture in adults. The vitamin D deficiency pandemic has other serious consequences including increased risk of common cancers, autoimmune diseases, infectious diseases, and cardiovascular disease. There needs to be a renewed appreciation of the beneficial effect of moderate sensible sunlight for providing all humans with their vitamin D requirement for health.

The DALI vitamin D randomized controlled trial for gestational diabetes mellitus prevention: No major benefit shown besides vitamin D sufficiency

BACKGROUND & AIMS

As vitamin D deficiency is associated with an increased risk of gestational diabetes mellitus (GDM), we aimed to test vitamin D supplementation as a strategy to reduce GDM risk (evaluated after fasting plasma glucose (FPG), insulin resistance and weight gain) in pregnant overweight/obese women.

METHODS

The DALI vitamin D multicenter study enrolled women with prepregnancy body mass index (BMI) ≥ 29 kg/m², ≤19 + 6 weeks of gestation and without GDM. Participants were randomized to receive 1600 IU/day vitamin D3 or placebo (each with or without lifestyle intervention) on top of (multi)vitamins supplements. Women were assessed for vitamin D status (sufficiency defined as serum 25-hydroxyvitamin D (25(OH)D) ≥ 50 nmol/l), FPG, insulin resistance and weight at baseline, 24-28 and 35-37 weeks. Linear or logistic regression analyses were performed to assess intervention effects.

RESULTS

Average baseline serum 25(OH)D was ≥50 nmol/l across all study sites. In the vitamin D intervention arm (n = 79), 97% of participants achieved target serum vitamin 25(OH)D (≥50 nmol/l) at 24-28 weeks and 98% at 35-37 weeks vs 74% and 78% respectively in the placebo arm (n = 75, p < 0.001). A small but significantly lower FPG (-0.14 mmol/l; CI95 -0.28, -0.00) was observed at 35-37 weeks with the vitamin D intervention without any additional difference in metabolic status, perinatal outcomes or adverse event rates.

CONCLUSION

In the DALI vitamin D trial, supplementation with 1600 IU vitamin D3/day achieved vitamin D sufficiency in virtually all pregnant women and a small effect in FPG at 35-37 weeks. The potential of vitamin D supplementation for GDM prevention in vitamin D sufficient populations appears to be limited.

TRIAL REGISTRATION NUMBER

ISRCTN70595832.

Serum and tissue 25-OH vitamin D3 concentrations do not predict bone abnormalities and molecular markers of vitamin D metabolism in the hypovitaminosis D kyphotic pig model

The hypovitaminosis D kyphotic pig provides a model to study maternal vitamin D (D) carryover on gross and molecular characteristics of bone abnormalities in offspring. Excess maternal D is proposed to protect offspring under nutritional challenges from developing bone abnormalities. Relationships between D sufficiency parameters and bone abnormalities were characterised. Sows (n 37) were fed diets with 0 (-D), 8·125 (+D) or 43·750 (++D) µg D3/kg throughout gestation and lactation. At weaning (3 weeks) pigs were fed diets with 0 (-D) or 7·0 (+D) µg D3/kg, each with 75 and 95 % (LCaP) or 150 and 120 % (HCaP) of the Ca and P requirements. Pigs were euthanised before colostrum consumption at birth (n 27), 3 weeks (n 27) or after the nursery period (7 weeks, n 71) for tissue analysis. At 7 weeks, differences due to maternal D were detected (P≤0·05) in pig growth, serum parameters and mRNA expression regardless of nursery diet. Prevalence of kyphosis in pigs at 13 weeks was affected by maternal D, but not prevented by only HCaP or +D nursery diets. Increased (P≤0·05) serum 25-OH-D3 concentrations in sows fed +D or ++D diets were not reflected by similar magnitudes of 25-OH-D3 in colostrum, 18-d milk, or serum and tissue concentrations in pigs. The mode of action by which maternal dietary D influences development of skeletal abnormalities warrants further investigation.

Impact of demographic, environmental, and lifestyle factors on vitamin D sufficiency in 9084 Japanese adults

BACKGROUND

Little is known about correlates of vitamin D status in Asian populations. In this study, we established the prevalence of vitamin D sufficiency in the Murakami region (latitude N38°13') in Niigata, Japan, and examined demographic, environmental, and lifestyle factors that might be associated with vitamin D sufficiency, with the aim of clarifying the relative contributions of previously described determinants of vitamin D status as well as identifying new determinants in this Japanese population.

METHODS

This study involved a cross-sectional analysis of baseline data obtained from a cohort study conducted in 2011-2013. Participants were 9084 individuals aged between 40 and 74 years who provided blood samples for the determination of plasma 25-hydroxyvitamin D [25(OH)D] concentrations. Lifestyle information was obtained from 8498 participants, with some missing values regarding different lifestyle factors. Multiple logistic regression analysis was used to obtain odds ratios for vitamin D sufficiency, which was defined as a plasma 25(OH)D concentration ≥ 75 nmol/L.

RESULTS

The prevalence of vitamin D sufficiency (i.e., plasma 25(OH)D concentration ≥ 75 nmol/L) was 9.1%, and significant associations were observed with male gender (P<0.0001; OR=2.37, 95% CI: 1.84-3.05), older age (P for trend <0.0001), lower BMI (P for trend <0.0001), higher METs score (P for trend=0.0138), higher vitamin D intake (P for trend=0.0467), summer season (P for trend <0.0001), longer duration outdoors (P for trend=0.0026), no sunscreen use (P=0.0135; OR=1.40, 95% CI: 1.07-1.82), higher salmon consumption (P for trend <0.0001), higher alcohol consumption (P for trend <0.0001), and lower coffee consumption (P for trend=0.0025). Unlike other populations previously reported, vitamin D sufficiency was associated with older age.

CONCLUSIONS

The prevalence of vitamin D sufficiency (i.e., 25[OH]D ≥ 75 nmol/L) was low (9.1%) in this Japanese population. A number of demographic, environmental, and lifestyle factors are associated with vitamin D sufficiency, and thus lifestyle modification may present an opportunity to achieve vitamin D sufficiency.

Sex-specific relationships between alcohol consumption and vitamin D levels: The Korea National Health and Nutrition Examination Survey 2009

This study assessed the association between vitamin D sufficiency (serum 25(OH)D ≥30 ng/mL) and alcohol consumption using data from the Korea National Health and Nutrition Examination Survey conducted in 2009. The following characteristics were obtained in 7,010 Korean participants ≥19-years-of-age: serum 25(OH)D level, alcohol consumption (drinking frequency, drinking number of alcoholic beverages on a typical occasion, average daily-alcohol intake), and potential confounders (age, residence, housing status, occupation, total fat and lean mass, smoking, physical activity, history of liver diseases, liver function, and daily intake of energy, protein, and calcium). After adjusting for confounders, vitamin D sufficiency in men was significantly associated with drinking frequency, number of alcoholic drinks consumed, and average daily alcohol intake; odds ratio of 1.21-1.72, 2.17-3.04, and 2.27-3.09, respectively. Increase in the three alcohol drinking-related behaviors was also linearly associated with increase in serum 25(OH)D level in men. By comparison, there was no significant association between alcohol intake and serum 25(OH)D level in women. The positive association between vitamin D sufficiency and alcohol consumption was evident only in Korean men.