To the Editor: In their randomized controlled trial, Dr Morey and colleagues1 reported that among older, long-term (≥5 years) survivors of colorectal, breast, and prostate cancer, a diet and exercise intervention reduced the rate of self-reported functional decline. The body mass index (BMI) of the participants ranged from 25 to 40 (calculated as weight in kilograms divided by height in meters squared).
Approximately 41% of men and 53% of women in the United States have levels of serum 25-hydroxyvitamin D below 28 ng/mL.2 An indicator of vitamin D status, serum 25-hydroxyvitamin D may be low in obese adults and has an inverse relationship with BMI.3 Epidemiologic studies indicate that low levels of serum 25-hydroxyvitamin D are associated with an increased risk of colon, prostate, and breast cancer, along with higher mortality from these cancers.4 Evidence also suggests that in older persons a mean serum concentration greater than 65 nmol/L of vitamin D may improve muscle performance.5