A new study, published in the Journal of Geriatric Psychology and Neurology, suggests that low levels of vitamin D may be linked to an increased risk of cognitive impairment in older adults.
Vitamin D helps the body absorb calcium and phosphorous. Recent research also suggests that vitamin D may help prevent osteoporosis, high blood pressure, cancer and several autoimmune diseases. Two forms are important in humans: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamins D2 and D3 are found in many dietary sources such as fish, eggs and fortified milk. The sun also helps the body produce vitamin D3.
As people age, their ability produce vitamin D from sunlight and to convert vitamin D into its active form decreases. Therefore, older adults have an increased risk of vitamin D deficiency.
The cross-sectional study included 1,766 adults in the Health Survey for England 2000 who were 65 years of age and older. The authors measured the participants' vitamin D blood levels and assessed their cognitive function using the Abbreviated Mental Test Score.
A total of 212 participants (about 12 percent) were considered cognitively impaired. Vitamin D levels were lower in these participants compared to those with normal cognition. In fact, about half of cognitively impaired participants had the lowest blood levels of vitamin D (8-30 nanomoles per liter of blood). According to the authors, individuals with the lowest vitamin D levels were 2.3 times more likely to develop cognitive impairment than those with the highest levels.
Early laboratory and animal studies suggest that vitamin D may have neuroprotective effects. However, human studies in this area are limited, and a potential mechanism for this effect is unclear.
This latest study is limited by its cross-section design. Additional research is warranted in this area to fully understand the potential neuroprotective effects of vitamin D.
Llewellyn DJ, Langa K, Lang I. "Serum 25-Hydroxyvitamin D Concentration and Cognitive Impairment." J Geriatr Psychiatry Neurol. 2008 Dec 10.
This article appeared in the February 2009 issue of the Integrative Medicine Newsletter published by Natural Standard.