Vitamin D

[funniestmama1]

I recently read on another Web site that "most people are vitamin D deficient." I do not believe there have been many people actually diagnosed with a vitamin D deficiency in the U.S. Do you have any statistics on that?

[JeffN]

Over 2/3's of Americans adults are overweight and/or obese and the numbers are similar for children. There is a direct relationship between ones weight and body fat level and their blood level of Vitamin D. As a fat soluble vitamin, it is stored in fat cells and when these subjects lose weight, their blood levels automatically go up. So, overweight and obese people may have their Vitamin D being stored in fat. I am not sure this makes them deficient just because their tested blood levels are low as a "low number" is only a sign but not a symptom of a deficiency.

More on the body fat/Vit D connection.

Association between serum 25-hydroxyvitamin D levels and body composition in postmenopausal women: the Postmenopausal Health Study.
Moschonis G, Tanagra S, Koutsikas K, Nikolaidou A, Androutsos O, Manios Y.

Menopause. 2009 Mar 6. [Epub ahead of print]
PMID: 19276997

Abstract

OBJECTIVE:: The present study examined the association between body composition measurements, using dual-energy x-ray absorptiometry and anthropometry, with serum 25-hydroxyvitamin D levels in nonosteoporotic, postmenopausal women.

METHODS:: Serum 25-hydroxyvitamin D, intact parathyroid hormone, insulin-like growth factor I levels, dual-energy x-ray absorptiometry measurements of fat and fat-free mass, anthropometric and handgrip strength measurements, dietary intake estimations, ultraviolet B radiation exposure, and physical activity levels were collected from 112 nonosteoporotic, postmenopausal women (age, 60.3 +/- 5.0,; body mass index, 29.5 +/- 4.8 kg/m).

RESULTS:: At a bivariate level, serum 25-hydroxyvitamin D levels were inversely associated with regional and total body fat mass (P < 0.05), whereas positive associations were observed with regional and total body fat-free mass (P < 0.05). After controlling for age, serum intact parathyroid hormone, insulin-like growth factor I levels, ultraviolet B radiation exposure, and physical activity levels, most of the associations observed at a bivariate level between serum 25-hydroxyvitamin D levels and body composition indices (as obtained by dual-energy x-ray absorptiometry) remained significant. No significant associations were observed between anthropometric indices of body mass and serum 25-hydroxyvitamin D levels.

CONCLUSIONS:: An independent inverse association between serum 25-hydroxyvitamin D levels and dual-energy x-ray absorptiometry measurements of total body and regional fat mass was observed in nonosteoporotic, overweight, postmenopausal women. Further clinical trials are required to come to safe conclusions on whether it is the fat mass that affects serum 25-hydroxyvitamin D levels or vice versa and whether there is a need to also take into account body composition when providing recommendations for vitamin D intake in postmenopausal women.

1) J Clin Endocrinol Metab. 2007 Aug;92(8):3155-7. Epub 2007 May 29. Reduced sun exposure does not explain the inverse association of 25-hydroxyvitamin D with percent body fat in older adults.

CONTEXT: Greater adiposity is associated with lower blood levels of 25-hydroxyvitamin D [25(OH)D]. The extent to which this results from reduced sun exposure among heavier individuals is unknown. OBJECTIVES: This analysis was conducted to determine whether sun exposure habits differ according to percent body fat (%FAT) in older adults and to what extent they explain the inverse association of adiposity with 25(OH)D in that population. DESIGN: We performed a cross-sectional analysis of baseline data from a randomized trial of calcium and vitamin D supplementation to prevent bone loss. SETTING: The study was performed at the Metabolic Research Unit at the Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging at Tufts University. PARTICIPANTS: A total of 381 generally healthy male and female volunteers age 65 and older participated in the study. Exclusion criteria included vitamin D and calcium supplement use, and medical conditions and medications known to affect bone metabolism. INTERVENTION: There were no interventions. Measurements for this analysis were made before participants received trial supplements. MAIN OUTCOME MEASURES: Plasma 25(OH)D, an indicator of vitamin D status, was measured. RESULTS: Sunscreen use, hours spent outside per week, and percent of skin exposed did not differ across quartiles of %FAT (P > 0.43). 25(OH)D decreased across %FAT quartiles (P < 0.05) and was about 20% lower in the highest compared with the lowest quartile of %FAT after adjustments for age, sex, season, and vitamin D intake. Further adjustment for sun exposure habits had little effect on estimates of 25(OH)D. CONCLUSIONS: In older adults, sun exposure habits do not vary according to adiposity and do not appear to explain lower 25(OH)D concentrations with increasing adiposity.
PMID: 17535990



2) J Clin Endocrinol Metab. 2005 Jul;90(7):4119-23. Epub 2005 Apr 26 Adiposity in relation to vitamin D status and parathyroid hormone levels: a population-based study in older men and women.P.

OBJECTIVE: In small case-control studies, obesity was associated with worse vitamin D status. Our aim was to assess the association of adiposity (anthropometric measures as well as dual energy x-ray absorptiometry) with serum 25-hydroxyvitamin D (25-OH-D) and serum PTH levels in a large population-based study including older men and women. METHODS: Subjects were participants of the Longitudinal Aging Study Amsterdam and were aged 65 yr and older. In 453 participants, serum 25-OH-D and PTH were determined, and body mass index, waist circumference, waist to hip ratio, sum of skin folds, and total body fat percentage by dual energy x-ray absorptiometry were measured. RESULTS: After adjustment for potential confounders, higher body mass index, waist circumference, and sum of skin folds were statistically significantly associated with lower 25-OH-D (standardized beta values were -0.136, -0.137, and -0.140, respectively; all P < 0.05) and with higher PTH (0.166, 0.113, and 0.114, respectively; all P < 0.05). Total body fat percentage was more strongly associated with 25-OH-D and PTH (-0.261 and 0.287, respectively; both P < 0.001) compared with anthropometric measures. Total body fat percentage remained associated with 25-OH-D after adjustment for PTH, and with PTH after adjustment for 25-OH-D. CONCLUSION: Precisely measured total body fat is inversely associated with 25-OH-D levels and is positively associated with PTH levels. The associations were weaker if anthropometric measures were used, indicating a specific role of adipose tissue. Regardless of the possible underlying mechanisms, it may be relevant to take adiposity into account when assessing vitamin D requirements.
PMID: 15855256


3) Am J Clin Nutr. 2000 Sep;72(3):690-3.
Decreased bioavailability of vitamin D in obesity.

BACKGROUND: Obesity is associated with vitamin D insufficiency and secondary hyperparathyroidism. OBJECTIVE: This study assessed whether obesity alters the cutaneous production of vitamin D(3) (cholecalciferol) or the intestinal absorption of vitamin D(2) (ergocalciferol). DESIGN: Healthy, white, obese [body mass index (BMI; in kg/m(2)) > or = 30] and matched lean control subjects (BMI </= 25) received either whole-body ultraviolet radiation or a pharmacologic dose of vitamin D(2) orally. RESULTS: Obese subjects had significantly lower basal 25-hydroxyvitamin D concentrations and higher parathyroid hormone concentrations than did age-matched control subjects. Evaluation of blood vitamin D(3) concentrations 24 h after whole-body irradiation showed that the incremental increase in vitamin D(3) was 57% lower in obese than in nonobese subjects. The content of the vitamin D(3) precursor 7-dehydrocholesterol in the skin of obese and nonobese subjects did not differ significantly between groups nor did its conversion to previtamin D(3) after irradiation in vitro. The obese and nonobese subjects received an oral dose of 50000 IU (1.25 mg) vitamin D(2). BMI was inversely correlated with serum vitamin D(3) concentrations after irradiation (r = -0.55, P: = 0.003) and with peak serum vitamin D(2) concentrations after vitamin D(2) intake (r = -0.56, P: = 0.007). CONCLUSIONS: Obesity-associated vitamin D insufficiency is likely due to the decreased bioavailability of vitamin D(3) from cutaneous and dietary sources because of its deposition in body fat compartments.
PMID: 10966885



4) J Clin Endocrinol Metab. 2003 Jan;88(1):157-61. Body fat content and 25-hydroxyvitamin D levels in healthy women.

Obesity is associated with alterations in the vitamin D endocrine system. Lower levels of serum 25-hydroxyvitamin D (25-OHD) in morbidly obese individuals may be secondary to an alteration in tissue distribution resulting from an increase in adipose mass. Therefore, morbidly obese individuals are expected to need higher doses of vitamin D supplementation than the general population. However, it is still unknown whether adiposity (or percentage body fat) should be taken into consideration while assessing vitamin D requirements in the general population. To study the relationship between 25-OHD levels and percentage body fat content in healthy women, we studied 410 healthy women between 20 and 80 yr of age with body mass index ranging from 17 to 30 kg/m2. We analyzed the correlation between serum 25-OHD level and percentage body fat measured by dual energy x-ray absorptiometry. We also analyzed the influence of season, dietary vitamin D intake, age, and race on this relationship. The levels of serum 25-OHD inversely correlated with percentage body fat. The correlation was -0.13 (P = 0.013) after adjusting for race, age, season, and dietary vitamin D intake. In a multiple stepwise regression, race and season were found to have a major influence on serum 25-OHD (cumulative R2 = 0.34), and percentage body fat, although modest (additional R2 = 0.02), also had an independent statistically significant influence on serum 25-OHD levels. We conclude, percentage body fat content is inversely related to the serum 25-OHD levels in healthy women.
PMID: 12519845


5) J Clin Invest. 1985 Jul;76(1):370-3. Evidence for alteration of the vitamin D-endocrine system in obese subjects.

Serum immunoreactive parathyroid hormone (PTH) is increased in obese as compared with nonobese subjects and declines with weight loss. To determine whether alteration of the vitamin D-endocrine system occurs in obesity and whether ensuing secondary hyperparathyroidism is associated with a reduction in urinary calcium, a study was performed in 12 obese white individuals, five men and seven women, and 14 nonobese white subjects, eight men and six women, ranging in age from 20 to 35 yr. Body weight averaged 106 +/- 6 kg in the obese and 68 +/- 2 kg in the nonobese subjects (P less than 0.01). Each of them were hospitalized on a metabolic ward and were given a constant daily diet containing 400 mg of calcium and 900 mg of phosphorus. Whereas mean serum calcium, serum ionized calcium, and serum phosphorus were the same in the two groups, mean serum immunoreactive PTH (518 +/- 48 vs. 243 +/- 33 pg/ml, P less than 0.001), mean serum 1,25-dihydroxyvitamin D [1,25(OH)2D] (37 +/- 2 vs. 29 +/- 2, P less than 0.01), and mean serum Gla protein (33 +/- 2 vs. 24 +/- 2 ng/ml, P less than 0.02) were significantly higher, and mean serum 25-hydroxyvitamin D (25-OHD) (8 +/- 1 vs. 20 +/- 2 ng/ml, P less than 0.001) was significantly lower in the obese than in the nonobese men and women. Mean urinary phosphorus was the same in the two groups, whereas mean urinary calcium (115 +/- 10 vs. 166 +/- 13 mg/d, P less than 0.01) was significantly lower, and mean urinary cyclic AMP (3.18 +/- 0.43 vs. 1.84 +/- 0.25 nM/dl GF, P less than 0.01) and creatinine clearance (216 +/- 13 vs. 173 +/- 6 liter/d, P less than 0.01) were significantly higher in the obese than in the nonobese individuals. There was a significant positive correlation between percentage of ideal body weight and urinary cyclic AMP (r = 0.524, P less than 0.01) and between percentage of ideal body weight and serum immunoreactive PTH (r = 0.717, P less than 0.01) in the two groups. The results provide evidence that alteration of the vitamin D-endocrine system in obese subjects is characterized by secondary hyperparathyroidism which is associated with enhanced renal tubular reabsorption of calcium and increased circulating 1,25(OH)2D. The reduction of serum 25-OHD in them is attributed to feedback inhibition of hepatic synthesis of the precursor by the increased serum 1,25(OH)2D.
PMID: 2991340

And losing weight increases serum levels.

Eur J Endocrinol. 2007 Aug;157(2):225-32. Vitamin D status and parathyroid hormone in obese children before and after weight loss.

OBJECTIVE: The roles of vitamin D and parathyroid hormone (PTH) are discussed controversially in obesity, and studies of these hormones in obese children are limited. Therefore, we studied the relationships between PTH, 1,25-dihydroxy-vitamin D (1,25-OH Vit D), 25-hydroxy-vitamin D (25-OH Vit D), weight status, and insulin sensitivity before and after weight loss in obese children. METHODS: Fasting serum PTH, 1,25-OH Vit D, 25-OH Vit D, inorganic phosphate, calcium, alkaline phosphatase (AP), insulin, glucose, and weight status (SDS-BMI and percentage body fat) were determined in 133 obese children (median age 12.1 years) and compared with 23 non-obese children. Furthermore, these parameters were analyzed in 67 obese children before and after participating in a 1-year obesity intervention program. RESULTS: Obese children had significantly (P < 0.001) higher PTH and lower 25-OH Vit D concentrations compared with non-obese children, while calcium, phosphate, AP, and 1,25-OH Vit D did not differ significantly. Changes of PTH (r = 0.23, P = 0.031) and 25-OH Vit D (r = -0.27, P = 0.013) correlated significantly with changes of SDS-BMI, but not with changes of insulin sensitivity (homeostasis model assessment; HOMA-B%). Reduction of overweight in 35 children led to a significant (P < 0.01) decrease of PTH concentrations and an increase in 25-OH Vit D levels. CONCLUSIONS: PTH levels were positively and 25-OH Vit D concentrations were negatively related to weight status. Since these alterations normalized after weight loss, these changes are consequences rather than causes of overweight. A relationship between PTH, vitamin D, and insulin sensitivity based on the HOMA index was not found in obese children. Further longitudinal clamp studies are necessary to study the relationship between vitamin D and insulin sensitivity.
PMID: 17656603

There are many more like this but as we can see, this is a fairly well established issue and I hope is being considered.

In Health
Jeff

[JeffN]

More on the relationship between excess weight and low levels of VItamin D

In Health
Jeff


Weight loss is associated with increased serum 25-hydroxyvitamin d in overweight or obese women.

Obesity (Silver Spring). 2012 Nov;20(11):2296-301. doi: 10.1038/oby.2012.57.

Abstract

Low circulating concentrations of vitamin D metabolites have been associated with increased risk for several diseases and clinical conditions. Large observational studies and surveys have shown that obesity is independently associated with lower serum 25-hydroxyvitamin D (25(OH)D) concentration. Few studies have examined the effect of weight loss on serum 25(OH)D concentration. The purpose of this study was to prospectively examine the effect of weight loss on serum 25(OH)D concentration. Data were collected from 383 overweight or obese women who participated in a 2-year clinical trial of a weight-loss program, in which 51% (N = 195) lost at least 5% of baseline weight by 24 months, 18% (N = 67) lost 5-10%, and 33% (N = 128) lost >10%. Women who did not lose weight at 24 months had an increase in serum 25(OH)D of 1.9 (9.7) ng/ml (mean (SD)); 25(OH)D increased by 2.7 (9.1) ng/ml for those who lost 5-10% of baseline weight; and 25(OH)D increased by 5.0 (9.2) ng/ml for those who lost >10% of baseline weight (P = 0.014). At baseline, 51% (N = 197) of participants met or exceeded the recommended serum concentration of 20 ng/ml. By study end, 64% (N = 230) of overweight or obese women met this goal, as well as 83% (N = 20) of those whose weight loss achieved a normal BMI. These findings suggest that weight loss, presumably associated with a reduction in body fat, is associated with increased serum 25(OH)D concentration in overweight or obese women.

PMID: 22402737

[JeffN]

And more.

Considering that 70% of Americans are either overweight or obese, and many have tested low in Vitamin D, the implications of this is important.

"These findings suggest that a higher BMI leads to a lower vitamin D status whereas any effects of low vitamin D status on BMI are likely to be small. That is, these findings provide evidence for obesity as a causal factor in the development of vitamin D deficiency but not for vitamin D deficiency as a causal factor in the development of obesity. These findings suggest that population-level interventions to reduce obesity should lead to a reduction in the prevalence of vitamin D deficiency ...."

In Health
Jeff

http://www.plosmedicine.org/article/inf ... ed.1001383

Abstract
Background

Obesity is associated with vitamin D deficiency, and both are areas of active public health concern. We explored the causality and direction of the relationship between body mass index (BMI) and 25-hydroxyvitamin D [25(OH)D] using genetic markers as instrumental variables (IVs) in bi-directional Mendelian randomization (MR) analysis.
Methods and Findings

We used information from 21 adult cohorts (up to 42,024 participants) with 12 BMI-related SNPs (combined in an allelic score) to produce an instrument for BMI and four SNPs associated with 25(OH)D (combined in two allelic scores, separately for genes encoding its synthesis or metabolism) as an instrument for vitamin D. Regression estimates for the IVs (allele scores) were generated within-study and pooled by meta-analysis to generate summary effects.

Associations between vitamin D scores and BMI were confirmed in the Genetic Investigation of Anthropometric Traits (GIANT) consortium (n = 123,864). Each 1 kg/m2 higher BMI was associated with 1.15% lower 25(OH)D (p = 6.52×10−27). The BMI allele score was associated both with BMI (p = 6.30×10−62) and 25(OH)D (−0.06% [95% CI −0.10 to −0.02], p = 0.004) in the cohorts that underwent meta-analysis. The two vitamin D allele scores were strongly associated with 25(OH)D (p≤8.07×10−57 for both scores) but not with BMI (synthesis score, p = 0.88; metabolism score, p = 0.08) in the meta-analysis. A 10% higher genetically instrumented BMI was associated with 4.2% lower 25(OH)D concentrations (IV ratio: −4.2 [95% CI −7.1 to −1.3], p = 0.005). No association was seen for genetically instrumented 25(OH)D with BMI, a finding that was confirmed using data from the GIANT consortium (p≥0.57 for both vitamin D scores).
Conclusions

On the basis of a bi-directional genetic approach that limits confounding, our study suggests that a higher BMI leads to lower 25(OH)D, while any effects of lower 25(OH)D increasing BMI are likely to be small. Population level interventions to reduce BMI are expected to decrease the prevalence of vitamin D deficiency.