Submitted to: The Journal of the North American Menopause Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 7, 2009
Publication Date: November 1, 2009
Citation: Stewart, J.W., Alekel, D.L., Ritland, L.M., Van Loan, M.D., Gertz, E.R., Genschel, U. 2009. Serum 25-hydroxyvitamin D is related to indicators of overall physical fitness in healthy postmenopausal women. Menopause. 16:1093-1101. Interpretive Summary: Overall health and wellness in older individuals is related to levels of physical fitness and one’s ability to continue to do tasks of daily living. Research has suggested that vitamin D may be beneficial in maintenance of muscle mass and therefore strength. We examined the relationship between blood levels of vitamin D and indices of physical fitness in 242 healthy early postmenopausal women. Our results demonstrated a significant relationship between blood levels of vitamin D and upper body fat mass with lower levels of vitamin D contributing to a 1% higher level in upper body fat. Upper body fat is a marker of cardiovascular disease. The blood level of vitamin D was also a common contributor to greater lean mass, hand strength, better balance and greater back strength. Other important contributions to greater physical fitness were lower body weight, more servings of vegetables, and a lower white blood count which would be indicative of fewer infections. Because the blood level of vitamin D can be improved by sun exposure, a higher blood level may in suggestive of a “healthier” lifestyle that includes outdoor activities and thereby improved physical fitness.
Technical Abstract: Inadequate vitamin D status is related to increased adiposity, risk of falls, and muscle weakness, particularly in the elderly. We hypothesized that serum 25-hydroxyvitamin D (25(OH) vitamin D) is related to physical fitness indices (androidal fat, whole body lean mass, balance, strength) in healthy postmenopausal women. Design: Covariates for fitness indices included: age or years since menopause; weight; 25(OH) vitamin D; energy expenditure; calcium intake. Overall and regional (androidal fat mass=waist+hip fat) body composition was assessed (N=242) via dual-energy X-ray absorptiometry. Results: Regression analyses revealed that 71% of variability (P<0.0001) in androidal fat mass was accounted for by weight (53.0%, P<0.0001), white blood cell (WBC) count (2.0%, P<0.0001), supplemental calcium (1.7%, P=0.0004), years since menopause (1.1%, P=0.0034), 25(OH) vitamin D (1.0%, P=0.0051), and vegetable servings (0.6%, P=0.027); 64% of variability (P<0.0001) in lean mass was accounted for by weight (63.1.%, P<0.0001), WBC count (1.4%, P=0.0038), and 25(OH) vitamin D (1.0%, P=0.013); 12% of variability (P<0.0001) in balance (right+left leg) was accounted for by age (3.8%, P=0.0019), 25(OH) vitamin D (2.0%, P=0.025), and WBC count (1.8%, P=0.032); 14% of variability (P<0.0001) in hand grip strength (right+left) was accounted for by weight (9.3%, P<0.0001), 25(OH) vitamin D (2.4%, P=0.013), WBC count (2.1%, P=0.019), and age (1.6%, P=0.044); 22% of variability (P<0.0001) in torso strength was accounted for by site (15.0%, P<0.0001) and weight (4.6%, P=0.0003). Conclusion: Serum 25(OH) vitamin D was the common contributor to physical fitness indices (androidal fat mass, lean mass, balance, hand grip strength) in healthy postmenopausal women.