Potassium Bicarbonate Supplementation Lowers Bone Turnover and Calcium Excretion in Older Men and Women: A Randomized Dose-Finding Trial.

The acid load accompanying modern diets may have adverse effects on bone and muscle metabolism. Treatment with alkaline salts of potassium can neutralize the acid load, but the optimal amount of alkali is not established. Our objective was to determine the effectiveness of two doses of potassium bicarbonate (KHCO3 ) compared with placebo on biochemical markers of bone turnover, and calcium and nitrogen (N) excretion. In this double-blind, randomized, placebo-controlled study, 244 men and women age 50 years and older were randomized to placebo or 1 mmol/kg or 1.5 mmol/kg of KHCO3 daily for 3 months; 233 completed the study. The primary outcomes were changes in 24-hour urinary N-telopeptide (NTX) and N; changes in these measures were compared across the treatment groups. Exploratory outcomes included 24-hour urinary calcium excretion, serum amino-terminal propeptide of type I procollagen (P1NP), and muscle strength and function assessments. The median administered doses in the low-dose and high-dose groups were 81 mmol/day and 122 mmol/day, respectively. When compared with placebo, urinary NTX declined significantly in the low-dose group (p = 0.012, after adjustment for baseline NTX, gender, and change in urine creatinine) and serum P1NP declined significantly in the low-dose group (p = 0.004, adjusted for baseline P1NP and gender). Urinary calcium declined significantly in both KHCO3 groups versus placebo (p < 0.001, adjusted for baseline urinary calcium, gender, and changes in urine creatinine and calcium intake). There was no significant effect of either dose of KHCO3 on urinary N excretion or on the physical strength and function measures. KHCO3 has favorable effects on bone turnover and calcium excretion and the lower dose appears to be the more effective dose. Long-term trials to assess the effect of alkali on bone mass and fracture risk are needed.

Effects of Hydration and Calcium Supplementation on Urine Calcium Concentration in Healthy Postmenopausal Women.

OBJECTIVE: The aim of this study was to determine whether calcium supplementation, compared with placebo, increases urine calcium concentrations to levels indicative of increased renal stone risk, and the role that fluid intake, as indicated by urine volume, may play in mitigating this risk. METHODS: This is a secondary analysis of data from a randomized placebo-controlled trial of 500 mg/d calcium supplementation to prevent bone loss. Subjects were 240 white postmenopausal women age 40 to 70 years in good general health. Effects of supplementation on 1-year changes in 24h urine calcium concentration and urine volume were examined. RESULTS: Both treatment group and urine volume were strong independent predictors of urine calcium concentration (p < 0.001). Among subjects with urine volume under 2 L/24 h, more than half of placebo subjects were at lowest risk for renal stones compared with less than 35% of calcium-supplemented subjects. Among those with higher urine volumes, all placebo subjects and more than 80% of calcium supplemented subjects were at lowest risk. CONCLUSIONS: The increased risk of renal stones with calcium supplement use may be largely eliminated with adequate fluid intake, but older adults may not spontaneously consume adequate fluids to minimize this risk and should be counseled to do so.

Dietary fat increases vitamin D-3 absorption.

BACKGROUND: The plasma 25-hydroxyvitamin D response to supplementation with vitamin D varies widely, but vitamin D absorption differences based on diet composition is poorly understood. OBJECTIVES: We tested the hypotheses that absorption of vitamin D-3 is greater when the supplement is taken with a meal containing fat than with a fat-free meal and that absorption is greater when the fat in the meal has a higher monounsaturated-to-polyunsaturated fatty acid ratio (MUFA:PUFA). DESIGN: Open, three-group, single-dose vitamin D-3 comparative absorption experiment. PARTICIPANTS/SETTING: Our 1-day study was conducted in 50 healthy older men and women who were randomly assigned to one of three meal groups: fat-free meal, and a meal with 30% of calories as fat with a low (1:4) and one with a high (4:1) MUFA:PUFA. After a 12-hour fast, all subjects took a single 50,000 IU vitamin D-3 supplement with their test breakfast meal. MAIN OUTCOME MEASURES: Plasma vitamin D-3 was measured by liquid chromatography-mass spectrometry before and 10, 12 (the expected peak), and 14 hours after the dose. STATISTICAL ANALYSES PERFORMED: Means were compared with two-tailed t tests for independent samples. Group differences in vitamin D-3 absorption across the measurement time points were examined by analysis of variance with the repeated measures subcommand of the general linear models procedure. RESULTS: The mean peak (12-hour) plasma vitamin D-3 level after the dose was 32% (95% CI 11% to 52%) greater in subjects consuming fat-containing compared with fat-free meals (P=0.003). Absorption did not differ significantly at any time point in the high and low MUFA and PUFA groups. CONCLUSIONS: The presence of fat in a meal with which a vitamin D-3 supplement is taken significantly enhances absorption of the supplement, but the MUFA:PUFA of the fat in that meal does not influence its absorption.

Association of serum 25-hydroxyvitamin D with race/ethnicity and constitutive skin color in urban schoolchildren.

The objective of this study was to determine the extent to which constitutive skin color explains racial/ethnic differences in serum 25-hydroxyvitamin D (25OHD) concentrations in urban schoolchildren. Analysis of covariance (ANCOVA) was used to determine associations of 25OHD with parent-reported race/ethnicity and constitutive skin color as measured by reflectance colorimeter [individual typology angle (ITA°; higher value corresponds to lighter skin)] in 307 Greater Boston schoolchildren aged 9-15 during October-December 2011. Nearly 60% of all children were inadequate in 25OHD (<20 ng/mL). Prevalence of inadequate 25OHD differed by race/ethnicity (p<0.001): white (46.6%), black (74.5%), Hispanic (64.7%), Asian (88.9%), and multi-racial/other (52.7%). Serum 25OHD increased 0.6 ng/mL per 10° increase in ITA° value (p<0.001). The prediction of 25OHD by race/ethnicity was slightly stronger than the prediction by skin color in separate models (R2=0.19, R2=0.16, respectively). Most of the variability in 25OHD in race/ethnicity was due to constitutive skin color in this group of racially diverse US children.

Dietary modulators of statin efficacy in cardiovascular disease and cognition.

Cardiovascular disease remains the leading cause of morbidity and mortality in the United States and other developed countries, and is fast growing in developing countries, particularly as life expectancy in all parts of the world increases. Current recommendations for the prevention of cardiovascular disease issued jointly from the American Academy of Cardiology and American Heart Association emphasize that lifestyle modification should be incorporated into any treatment plan, including those on statin drugs. However, there is a dearth of data on the interaction between diet and statins with respect to additive, complementary or antagonistic effects. This review collates the available data on the interaction of statins and dietary patterns, cognition, genetics and individual nutrients, including vitamin D, niacin, omega-3 fatty acids, fiber, phytochemicals (polyphenols and stanols) and alcohol. Of note, although the available data is summarized, the scope is limited, conflicting and disparate. In some cases it is likely there is unrecognized synergism. Virtually no data are available describing the interactions of statins with dietary components or dietary pattern in subgroups of the population, particularly those who may benefit most were positive effects identified. Hence, it is virtually impossible to draw any firm conclusions at this time. Nevertheless, this area is important because were the effects of statins and diet additive or synergistic harnessing the effect could potentially lead to the use of a lower intensity statin or dose.

Effect of supplemental vitamin D and calcium on serum sclerostin levels.

OBJECTIVE: Serum sclerostin levels have been reported to be inversely associated with serum 25OHD levels, but the effect of vitamin D and calcium supplementation on serum sclerostin levels is unknown. This study was carried out to determine whether vitamin D and calcium supplementation altered serum sclerostin levels in healthy older adults. DESIGN: We measured serum sclerostin levels at baseline and after 2 years in 279 men and women who participated in a placebo-controlled vitamin D (700 IU/day) and calcium (500 mg/day) intervention trial carried out in men and women aged ≥65 years. METHOD: Serum sclerostin levels were measured using the MesoScale Discovery chemiluminescence assay. RESULTS: In the men, sclerostin levels increased over 2 years by 4.11±1.81 ng/l (13.1%) in the vitamin D plus calcium-supplemented group and decreased by 3.16±1.78 ng/l (10.9%) in the placebo group (P=0.005 for difference in change). Adjustments for the season of measurement, baseline physical activity levels, baseline serum sclerostin levels, and total body bone mineral content did not substantially alter the changes. In the women, there was no significant group difference in change in serum sclerostin levels either before or after the above-mentioned adjustments. In both the sexes, vitamin D and calcium supplementation significantly increased serum ionized calcium levels and decreased parathyroid hormone levels. CONCLUSION: Men and women appear to have different serum sclerostin responses to vitamin D and calcium supplementation. The reason for this difference remains to be determined.

Predictors of Weight Loss in African Americans with Prediabetes or Early Diabetes.

ACKNOWLEGMENT: This study was supported by Clinical Research Grant (7-08-CR-27) from the American Diabetes Association and by a contract (58-1950-7-707) with the Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University. This article does not necessarily reflect the views or policies of the U.S. Department of Agriculture, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. government. PURPOSE: This analysis was undertaken to describe healthcare seeking, weight loss efforts and predictors of weight loss among African Americans recently identified with prediabetes or early diabetes METHODS: A secondary analysis was conducted on data collected from 89 participants who completed a previously published 12-week randomized placebo-controlled trial testing the benefit of vitamin D supplementation on blood measures predictive of diabetes risk. Information about care seeking, weight loss strategies and weight loss effort was collected by questionnaire at three data collection visits. Weight was measured by trained staff at each visit. RESULTS: More than half of the participants saw a healthcare provider during the study, but few recalled receiving advice about diet, physical activity or other strategies for weight loss. Thirty-seven % of participants maintained their weight within 1 kg of their baseline weight. Of the remaining participants, half gained >1 kg and half lost >1 kg during the study period. Age-adjusted independent predictors of weight loss included a visit to a healthcare provider for preventive care, dietary restrictions, and consistent weight loss effort. Vitamin D supplementation had no effect on weight change. CONCLUSIONS: This study reinforces the importance of preventive healthcare and sustainable changes in diet and physical activity. It also suggests that physicians need better tools for motivating and supporting their patients to adopt behaviors that can reduce diabetes risk. For the millions of Americans who are trying to lose weight to reduce their risk for chronic disease, this study reinforces the importance of sustained effort.

Ability of vitamin D to reduce inflammation in adults without acute illness.

In vitro studies and some clinical studies suggest that vitamin D plays an important role in reducing inflammation. The objective of this review was to examine recent evidence that vitamin D status influences the level of inflammation in adults without acute illness or injury. Five large cross-sectional studies and two randomized controlled trials are the focus of this review. Associations between 25-hydroxyvitamin D (25OHD) and inflammation markers are significant and inverse in study populations with low 25OHD levels (<21 ng/mL). They are also inverse in adults with relatively high inflammation levels. These associations in the few available randomized controlled vitamin D intervention trials have been null; this may be because they were not examined in populations with sufficiently low levels of 25OHD or high levels of inflammation.

Serum sclerostin levels vary with season.

CONTEXT: To establish the clinical utility of serum sclerostin levels, it is important to know whether there is seasonal variation in the measurements. OBJECTIVE: This study was done to determine whether serum sclerostin levels vary by season in healthy older men and women. METHODS: Serum sclerostin levels were measured in archived serum of 314 healthy men and women aged 65 years and older and examined for seasonal variation. Several factors known to vary by season and previously reported to be associated with serum sclerostin levels, including serum osteocalcin, physical activity, and serum PTH levels, were also measured in these subjects. Sex did not modify the association of season with sclerostin, so the men and women were analyzed together. RESULTS: Serum sclerostin levels varied significantly by season (P < .001, after adjustment for sex). Sclerostin levels in the wintertime were 20% higher than the all-year mean, the levels gradually declined through the spring and summer, and by the fall, they were 20% below the all-year mean. Adjustment for serum osteocalcin, physical activity, and serum PTH did not alter the seasonal means. Seasonal differences in serum osteocalcin, physical activity, and serum PTH were not statistically significant. CONCLUSIONS: This study documents marked seasonal variation in serum sclerostin levels. It is important to recognize this source of biological variability when considering the potential clinical utility of sclerostin measurements.

Adherence to a vitamin D supplement intervention in urban schoolchildren.

Vitamin D supplementation is an important strategy for preventing low levels of serum 25OHD and improving bone health and consequent associated health risks, especially in children at risk of deficiency. Although vitamin D supplements are recommended, there is limited research on the factors that influence adherence to taking them. In a cross-sectional sample of 256 child (aged 9 to 15 years) and parent pairs in the Boston, MA, area during January to March 2012, analysis of covariance was used to determine associations between health beliefs about vitamin D, parental vitamin D-containing supplement use, and the individual responsible for pill administration with supplement adherence measured by pill counts. Mean and median supplement pill count adherence over 3 months were 84% and 89%, respectively. Adherence was positively associated with parents' use of vitamin D-containing supplements (7% higher, P=0.008) and with combined child and parent responsibility for administration of the supplement compared with child only (9% higher, P=0.03). Parents' beliefs about vitamin D neither predicted their children's beliefs nor positively influenced children's adherence. Adherence was higher when parents took vitamin D-containing supplements and when parents and children shared responsibility for administering the supplement. Promoting child supplement use through parent involvement and role modeling may be a practical solution for registered dietitians who are aiming to improve vitamin D adherence in at-risk youth.

A randomized study on the effect of vitamin D3 supplementation on skeletal muscle morphology and vitamin D receptor concentration in older women.

CONTEXT: Studies examining whether vitamin D supplementation increases muscle mass or muscle-specific vitamin D receptor (VDR) concentration are lacking. OBJECTIVE: Our objective was to determine whether vitamin D3 4000 IU/d alters muscle fiber cross-sectional area (FCSA) and intramyonuclear VDR concentration over 4 months. DESIGN AND SETTING: This was a randomized, double-blind, placebo-controlled study in a single center. PARTICIPANTS: Participants were 21 mobility-limited women (aged ≥ 65 years) with serum 25-hydroxyvitamin D (25OHD) levels of 22.5 to 60 nmol/L. MAIN OUTCOME MEASURES: Baseline and 4-month FCSA and intramyonuclear VDR were measured from vastus lateralis muscle cross-sections probed for muscle fiber type (I/IIa/IIx) and VDR using immunofluorescence. RESULTS: At baseline, mean (±SD) age was 78 ± 5 years; body mass index was 27 ± 5 kg/m², 25OHD was 46.3 ± 9.5 nmol/L, and a short physical performance battery score was 7.95 ± 1.57 out of 12. At 4 months, 25OHD level was 52.5 ± 17.1 (placebo) vs 80.0 ± 11.5 nmol/L (vitamin D [VD]; P < .01), and change in 25OHD level was strongly associated with percent change in intramyonuclear VDR concentration-independent of group (r = 0.87, P < .001). By treatment group, percent change in intramyonuclear VDR concentration was 7.8% ± 18.2% (placebo) vs 29.7% ± 11.7% (VD; P = .03) with a more pronounced group difference in type II vs I fibers. Percent change in total (type I/II) FCSA was -7.4% ± 18.9% (placebo) vs 10.6% ± 20.0% (VD; P = .048). CONCLUSION: Vitamin D3 supplementation increased intramyonuclear VDR concentration by 30% and increased muscle fiber size by 10% in older, mobility-limited, vitamin D-insufficient women. Further work is needed to determine whether the observed effect of vitamin D on fiber size is mediated by the VDR and to identify which signaling pathways are involved.

Associations of vitamin D intake with 25-hydroxyvitamin D in overweight and racially/ethnically diverse US children.

Overweight children and minorities are at risk of vitamin D deficiency. Little information exists on whether overweight children and minorities who do not meet dietary vitamin D recommendations are at risk for low 25-hydroxyvitamin D (25OHD) status. Vitamin D intake from foods and dietary supplements was estimated in 3,310 children/adolescents who were examined as part of the 2005-2006 National Health and Nutrition Examination Survey. Weight status was dichotomized into healthy weight or overweight/obese. Parent-reported race/ethnicity was categorized as non-Hispanic white, non-Hispanic black, Mexican American, or other. Adjusted logistic regression was used to determine whether children who did not achieve the Estimated Average Requirement (EAR) were at increased risk for inadequate 25OHD. Nearly 75% of children failed to meet the EAR. Overall, not meeting the EAR was associated with inadequate 25OHD (odds ratio=2.5; 95% CI 1.4 to 4.5). However, this association differed by weight status (P=0.02) and race/ethnicity (P=0.02). Overweight/obese children who failed to meet the EAR were five times more likely to be at risk for inadequate 25OHD than overweight/obese children who met it (95% CI 2.0 to 12.7; P<0.001). Non-Hispanic blacks with intakes below the EAR were nearly four times more likely to be at risk for inadequate 25OHD than those who met the EAR (95% CI 1.5 to 9.7; P<0.01). The majority of US children failed to meet current vitamin D recommendations. Overweight/obese and non-Hispanic black children were especially likely to be at risk for inadequate 25OHD when not consuming the EAR.

Effects of alkali supplementation and vitamin D insufficiency on rat skeletal muscle.

Data on the independent and potential combined effects of acid-base balance and vitamin D status on muscle mass and metabolism are lacking. We investigated whether alkali supplementation with potassium bicarbonate (KHCO3), with or without vitamin D3 (± VD3), alters urinary nitrogen (indicator of muscle proteolysis), muscle fiber cross-sectional area (FCSA), fiber number (FN), and anabolic (IGF-1, Akt, p70s6k) and catabolic (FOXO3a, MURF1, MAFbx) signaling pathways regulating muscle mass. Thirty-six, 20-month-old, Fischer 344/Brown-Norway rats were randomly assigned in a 2 × 2 factorial design to one of two KHCO3-supplemented diets (± VD3) or diets without KHCO3 (± VD3) for 12 weeks. Soleus, extensor digitorum longus (EDL), and plantaris muscles were harvested at 12 weeks. Independent of VD3 group, KHCO3 supplementation resulted in 35 % lower mean urinary nitrogen to creatinine ratio, 10 % higher mean type I FCSA (adjusted to muscle weight), but no statistically different mean type II FCSA (adjusted to muscle weight) or FN compared to no KHCO3. Among VD3-replete rats, phosphorylated-Akt protein expression was twofold higher in the KHCO3 compared to no KHCO3 groups, but this effect was blunted in rats on VD3-deficient diets. Neither intervention significantly affected serum or intramuscular IGF-1 expression, p70s6k or FOXO3a activation, or MURF1 and MAFbx gene expression. These findings provide support for alkali supplementation as a promising intervention to promote preservation of skeletal muscle mass, particularly in the setting of higher vitamin D status. Additional research is needed in defining the muscle biological pathways that are being targeted by alkali and vitamin D supplementation.

Does vitamin D affect timing of menarche?

In a recently published prospective study, Villamor et al. found increased risk of early menarche in vitamin D-deficient girls compared to vitamin D-sufficient girls in Bogota, Columbia. The association was not fully explained by differences in body mass index-for-age z-scores. The mechanism for the association, if real, has not been elucidated, but could potentially involve vitamin D receptor polymorphisms. Early menarche and vitamin D deficiency are both associated with poor health outcomes, and further exploration of their association is important for women's health.

An evaluation of the reliability of muscle fiber cross-sectional area and fiber number measurements in rat skeletal muscle.

BACKGROUND: The reliability of estimating muscle fiber cross-sectional area (measure of muscle fiber size) and fiber number from only a subset of fibers in rat hindlimb muscle cross-sections has not been systematically evaluated. This study examined the variability in mean estimates of fiber cross-sectional area as a function of the number of fibers measured, and tested whether counting a subset of fibers in a cross-section could predict total fiber number in middle-aged rats. RESULTS: Soleus and extensor digitorum longus (EDL) muscle cross-sections from 23-month-old, male Fisher 344 x Brown Norway rats were stained for myofibrillar ATPase activity to identify muscle fiber type (either type I [slow-twitch] or II [fast-twitch]) and laminin to facilitate fiber cross-sectional measurements. We outlined the circumference of 1000 to 1600 single muscle fibers for measurement of fiber cross-sectional area within muscle sections. Mean type I fiber cross-sectional area was based on soleus muscle sections which were predominantly composed of type I muscle fibers. Mean type II fiber cross-sectional area was based on EDL muscle sections which were predominantly composed of type II muscle fibers. A bootstrapping resampling technique demonstrated that variability in sampling distribution of mean type I and II fiber cross-sectional areas decreased and gradually stabilized as the number of fibers measured increased with large declines in variability occurring at numbers below 150 fibers. Coefficients of variation for bootstrapped mean type I fiber cross-sectional areas were lower than for type II. In the same muscle sections, total fiber number was compared to fiber numbers within 1, 2, 3, and 4 fixed field areas (10x magnification; 1000 x 1500 pixels in size/field) on the cross-section. Fiber numbers from 3 to 4 fields (approximating 15 to 20% of the cross-section) provided a reasonably predictive value of total fiber number (r=0.57-0.59, P=0.003). CONCLUSIONS: These data describe a pattern of improved precision in estimating mean fiber cross-sectional area as sample size of fibers measured increases to at least 150 in this rat model. Counting 15-20% of the fibers in cross-sections provides a reasonably reliable estimate of the total fiber number.

Meal conditions affect the absorption of supplemental vitamin D3 but not the plasma 25-hydroxyvitamin D response to supplementation.

It is sometimes assumed that dietary fat is required for vitamin D absorption, although the impact of different amounts of dietary fat on vitamin D absorption is not established. This study was conducted to determine whether the presence of a meal and the fat content of the meal influences vitamin D absorption or the 25-hydroxyvitamin D [25(OH)D] response to supplemental vitamin D3 . Based on earlier studies in rats we postulated that absorption would be greatest in the low-fat meal group. Sixty-two healthy older men and women were randomly assigned to one of three meal groups: no meal, high-fat meal, or low-fat meal; each was given a monthly 50,000 IU vitamin D3 supplement with the test breakfast meal (or after a fast for the no-meal group) and followed for 90 days. Plasma vitamin D3 was measured by liquid chromatography-mass spectroscopy (LC/MS) before and 12 hours after the first dose; plasma 25(OH)D was measured by radioimmunoassay at baseline and after 30 and 90 days. The mean 12-hour increments in vitamin D3 , after adjusting for age and sex, were 200.9 nmol/L in the no-meal group, 207.4 nmol/L in the high-fat meal group, and 241.1 nmol/L in the low-fat meal group (p = 0.038), with the increase in the low-fat group being significantly greater than the increases in the other two groups. However, increments in 25(OH)D levels at 30 and 90 days did not differ significantly in the three groups. We conclude that absorption was increased when a 50,000 IU dose of vitamin D was taken with a low-fat meal, compared with a high-fat meal and no meal, but that the greater absorption did not result in higher plasma 25(OH)D levels in the low-fat meal group.

Vitamin D and its role in skeletal muscle.

This review discusses the clinical and laboratory studies that have examined a role of vitamin D in skeletal muscle. Many observational studies, mainly in older populations, indicate that vitamin D status is positively associated with muscle strength and physical performance and inversely associated with risk of falling. Clinical trials of vitamin D supplementation in older adults with low vitamin D status mostly report improvements in muscle performance and reductions in falls. The underlying mechanisms are probably both indirect via calcium and phosphate and direct via activation of the vitamin D receptor (VDR) on muscle cells by 1,25-dihydroxyvitamin D [1,25(OH)(2)D]. VDR activation at the genomic level regulates transcription of genes involved in calcium handling and muscle cell differentiation and proliferation. A putative membrane-associated VDR activates intracellular signaling pathways also involved in calcium handling and signaling and myogenesis. Additional evidence comes from VDR knockout mouse models with abnormal muscle morphology and physical function, and VDR polymorphisms which are associated with differences in muscle strength. Recent identification of CYP27B1 bioactivity in skeletal muscle cells and in regenerating adult mouse muscle lends support to the direct action of both 25-hydroxyvitamin D and 1,25(OH)(2)D in muscle. Despite these research advances, many questions remain. Further research is needed to fully characterize molecular mechanisms of vitamin D action on muscle cells downstream of the VDR, describe the effects on muscle morphology and contractility, and determine whether these molecular and cellular effects translate into clinical improvements in physical function.

Type of dietary fat is associated with the 25-hydroxyvitamin D3 increment in response to vitamin D supplementation.

CONTEXT: Mono- and polyunsaturated fats may have opposing effects on vitamin D absorption. OBJECTIVE: The purpose of this study was to determine whether intakes of different dietary fats are associated with the increase in serum 25-hydroxyvitamin D (25OHD) after supplementation with vitamin D(3). DESIGN, SETTING, AND PARTICIPANTS: This analysis was conducted in the active treatment arm of a randomized, double-blind, placebo-controlled trial of vitamin D and calcium supplementation to prevent bone loss and fracture. Subjects included 152 healthy men and women age 65 and older who were assigned to 700 IU/d vitamin D(3) and 500 mg/d calcium. Intakes of monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), and saturated fatty acids (SFA) were estimated by food frequency questionnaire. MAIN OUTCOME MEASURE: The change in plasma 25OHD during 2 yr vitamin D and calcium supplementation was assessed. RESULTS: The change in plasma 25OHD (nanograms per milliliter) during vitamin D supplementation was positively associated with MUFA, (ß = 0.94; P = 0.016), negatively associated with PUFA, (ß = -0.93; P = 0.038), and positively associated with the MUFA/PUFA ratio (ß = 6.46; P = 0.014). CONCLUSION: The fat composition of the diet may influence the 25OHD response to supplemental vitamin D(3). Diets rich in MUFA may improve and those rich in PUFA may reduce the effectiveness of vitamin D(3) supplements in healthy older adults. More studies are needed to confirm these findings.

Does vitamin D deficiency contribute to increased rates of cardiovascular disease and type 2 diabetes in African Americans?

African Americans have higher rates of type 2 diabetes (T2D) and some forms of cardiovascular disease (CVD) than do European Americans. African Americans also have much higher rates of vitamin D deficiency. There is emerging evidence that vitamin D deficiency may be a risk factor for hypertension, T2D, and CVD, but the extent to which racial disparities in disease rates are explained by racial differences in vitamin D status is uncertain. Despite a large number of observational studies and a limited number of clinical trials that examined 25-hydroxyvitamin D [25(OH)D] concentrations as a potential determinant of CVD and T2D or its precursors, it remains uncertain whether improving vitamin D status would reduce risk of these conditions in the general US population or in African Americans specifically. However, if the associations reported from the observational studies are of the estimated magnitudes and causal, vitamin D supplementation could potentially have a strong preventive effect on some of these conditions and could reduce race-related disparities in their prevalence. Because of the low 25(OH)D concentrations of many, if not most, African Americans, and the low risk associated with vitamin D supplementation, it is important to obtain more definitive answers to these questions.

Serum 25-hydroxyvitamin D concentration and physical function in adult men.

OBJECTIVE: Recent reports suggest that vitamin D status influences musculoskeletal health; yet, there are limited data in adult men. This study investigated whether serum 25-hydroxyvitamin D [25(OH)D] concentration was associated with lean body mass, muscle strength and physical performance in men. DESIGN: Population-based, observational survey. PARTICIPANTS: 1219 black, Hispanic and white randomly selected men aged 30-79 years from the Boston Area Community Health/Bone Survey. MEASUREMENTS: Lean body mass by dual-energy X-ray absorptiometry, hand grip strength, a composite physical function score (chair stand and walking speed), 25(OH)D, parathyroid hormone (PTH), testosterone, age, race, body mass index, socioeconomic status, education, smoking, arthritis, self-reported health, calcium intake, physical activity. RESULTS: The distributions of serum 25(OH)D quartiles differed by race/ethnicity, education and smoking status. After adjustment for multiple lifestyle factors, serum 25(OH)D was not related to lean body mass, grip strength or the composite physical function score (all P>0.20). There was no variation in the associations between 25(OH)D level and outcomes by race/ethnicity. The relationship between PTH and the outcomes revealed similar results. CONCLUSION: In this population-based sample of adult men with a broad age range, there was no association between serum 25(OH)D concentration and lean body mass, muscle strength and physical function after controlling for multiple lifestyle factors.