Journal Title (Medline/Pubmed accepted abbreviation): Med. Sci. Sports Exerc.
Page numbers: 266-271
doi (if applicable): 10.1249/MSS.0b013e3181ed5ec6
Summary of Background and Research Design
Background:Vitamin D has many physiologic functions. For example, it increases the amount of calcium that is absorbed from our gut. Even with modern diets, vitamin D deficiencies are prevalent. Vitamin D status many correlate with chronic health conditions including cardiovascular disease, diabetes, and depression.
Research Question: Are there separate associations between vitamin D status and: 1) cardiorespiratory fitness (CRF); 2) body mass index (BMI); 3) waist circumference (WC); 4) waist-to-hip ratio (W:Hip), and 5) percent body fat?
Subjects:2317 men; age 49.6 ± 9.9, BMI 27.9 ± 4.1, the majority were middle to upper class, and white (residing in or around Dallas, Texas)
Experimental design:no intervention
Treatments and protocol:CRF was determined using a treadmill. The pace began at 88 m/min (3.3 mph, normal walking speed) and 0% elevation. After 1 min, elevation was increased 2% and then 1% at every minute thereafter. After 25 min, elevation was held constant at 25% and speed was increased 5.4 m/min (0.2 mph) each minute until volitional fatigue. Men were labeled “fit” if they were in the upper 80% of the age-standardized CRF distribution or “unfit” if they were in the lower 20%. Vitamin D status was determined via measurement of serum 25-hydroxyvitamin D.
Summary of research findings:
Better vitamin D status appeared to correlate negatively with BMI, waist circumference, and % fat and positively with fitness (as measured by METS or metabolic equivalents). Similarly, there was a higher probability that a man would have a higher BMI, waist circumference, or waist:hip ratio if he was in lower vitamin D status. Higher vitamin D status was correlated with better performance on the treadmill exercise, implying better CRF.
Interpretation of findings/Key practice applications:
Higher vitamin D status is correlated with a leaner, more cardio-fit body type in men.
No cause and effect relationship can be implied, so it is not known, for example, whether better vitamin D status could improve inherent fitness levels or if weight loss in overweight patients could improve vitamin D status. Another explanation for the phenomenon is that more fit individuals simply consume more vitamin D because they have overall healthier lifestyles.
One must be cautious when transferring these results to other populations, especially different races and those living in regions with a lot more or a lot less sunlight. Sunlight activates the production of vitamin D from cholesterol and therefore may change vitamin D status regardless of fitness or adiposity.