Vitamin D Emerging Information

Vitamin D is one of the most researched nutrients in recent years, with new information appearing constantly. This newsletter will explore some of the new research arriving. The importance of Vitamin D for human health cannot be overstated. In addition to its role in facilitating calcium absorption, it is involved in mood, modulates cell growth, and influences activity on over 200 genes, many of them associated with susceptibility to disease states such as multiple sclerosis and colorectal cancer. The main and best source of Vitamin D comes from exposure of the skin to sunlight. Dietary sources are not plentiful in contrast to other vitamins, however. Oily fish, dairy products, and eggs are good sources of Vitamin D3. Plant sources are scarce, with mushrooms and sunflower seeds containing relatively good amounts of Vitamin D2.

Cognitive Function/Dementia Risk

Vitamin D has been the subject of numerous large studies on cognitive function, particularly in the elderly. One study involved 400 participants with a mean age of 76 who were either cognitively normal, had mild cognitive impairment, or had dementia. Participants' serum Vitamin D was measured at the study's beginning, and deficiency or insufficiency was prevalent among 61% of them. Over five years of follow-up, Vitamin D deficient individuals experienced cognitive declines that were two-to-three times faster than those with adequate serum Vitamin D levels.

Another study from the University of Exeter Medical School, published in the medical journalNeurology, found that out of 1,658 adults studied, age 65 and over, moderately deficient individuals had a 53% increased risk of developing dementia of any kind, while severely deficient participants' risk jumped to 125%. The study cautioned that their results do not demonstrate that low Vitamin D levels cause dementia. It remains to establish whether taking Vitamin D supplements can delay or even prevent the onset of Alzheimer's disease and dementia. It is safe to extrapolate, however, that Vitamin D deficiency is associated with an increased risk of dementia and Alzheimer's in older people.

Exercise Performance

A study from the Society of Endocrinology in Edinburgh suggests that taking Vitamin D supplements may improve exercise performance and lower risk of heart disease. Previous studies suggest that Vitamin D can block the action of an enzyme needed for formation of "the stress hormone" cortisol. High cortisol levels constrict blood vessels and may raise blood pressure. As Vitamin D may reduce circulating levels of cortisol, it could
theoretically improve exercise performance and lower cardiovascular risk
factors. Thirteen healthy adults were supplemented with Vitamin D or a placebo for two weeks. The supplemented adults had lower blood pressure compared to the placebo group, as well as having lower levels of cortisol in their urine. A fitness test found that the group taking Vitamin D could cycle 6.5 km
in 20 minutes, compared to just 5 km at the start of the experiment.
Despite cycling 30% further in the same time, the group taking Vitamin D
supplements also showed lower signs of physical exertion.

Post-Menopausal Benefits

Vitamin D deficiency is a common problem in post-menopausal women,
leading to muscle weakness and thus a greater tendency for falling. A very interesting study out of Brazil showed that Vitamin D supplementation significantly increased muscle strength and reduced loss of muscle mass in post-menopausal women. At the University of Sao Paulo Medical School, a nine-month, double-blind, placebo-controlled trial showed that women receiving supplements demonstrated a 25% increase in muscle strength, while those receiving placebo lost an average of 6.8% of muscle mass. Women in the placebo group were also nearly two times as likely to fall. The lead author of the study concluded that the supplementation of Vitamin D alone provided significant protection against sarcopenia, which is a degenerative loss of skeletal muscle.