A recent study examined the vitamin D status of 3,262 Chinese people between 50 and 70 and found that 69% were deficient and 24% insufficient with their levels of 25-hydroxyvitamin D (25OHD). Researchers found that 42% of Chinese subjects with low 25OHD had the Metabolic Syndrome (MetS), which is associated with insulin resistance and increased risk of developing type 2 diabetes mellitus and cardiovascular disease.1 People in the lowest quintile of 25OHD in their blood were 52% more likely to have the MetS than the 20% with the most 25OHD. Only 6% of these older Chinese people had an adequate level of vitamin D in their tissues. These low levels of 25OHD are similar to what is seen in England and the U.S.A., where most older adults are known to have low or deficient stores of 25OHD. According to Dr. Franco, the lead researcher of this study: "Vitamin D deficiency is now recognized as a worldwide concern and metabolic syndrome has become a global epidemic."
Another study of more than 3,000 European men ages 40 to 79, found those with lower 25OHD levels in their blood did worse on a task designed to test mental ability. The results were published in the May 2009 Journal Neurology Neurosurgery and Psychiatry. This adds to growing research linking inadequate vitamin D status with an increased risk of senility.Vitamin D and its active metabolite 1,25di-OH D is a steroid hormone. A review of the literature found that low levels of vitamin D appear to reduce athletic performance. Dr. Cannell's review noted that randomized controlled trials in mostly older adults show that vitamin D supplements increase muscles. Fewer fast twitch muscle fibers appear to result from inadequate vitamin D status.2Americans should be encouraged to spend a little time in the sun several days a week. Those who live in northern states should be encouraged to take a supplement of vitamin D3 during the fall and winter months.By James J. Kenney, PhD, RD, FACN1. Diabetes Care doi:10.2337/dc09-02092. Med Sci Sports Exerc 2009;41:1102-1110