Aside from maintaining healthy bones and boosting the immune system, vitamin D is essential to maintaining cognitive function, recent studies have shown.

In fact, vitamin D deficiency may be causing a decrease in memory retention and thinking abilities, especially among the elderly.

The study was conducted by Dr. Joshua Miller from Rutgers University and a team from the University of California Davis with 318 participants. The researchers aimed to understand the relationship between vitamin D levels and cognitive functioning.

Based on prior studies, 50 percent of Americans who were 65 years old and above were vitamin D deficient, and this decreased level of vitamin D in adults can increase the risk for dementia. Dr. Miller noted in his review that at least 70 percent of cognitively impaired patients in prior studies were vitamin D deficient.

Among Dr. Miller and his team's respondents, at least 60 percent had insufficient vitamin D, with African Americans being three times more likely to have insufficient vitamin D compared to whites and Hispanics.

Known dementia cases among the participants had less vitamin D than those without or with mild impairments. Decreased vitamin D levels are also attributed to increased difficulty in recalling general information, such as certain objects, spatial relationship recognition and reality orientation.

More severe cases exhibited a rapid decrease in their overall thinking processes and long-term memory recall capabilities. The link between vitamin D and cognitive decline remained even after considering other risk factors, such as obesity, neurovascular diseases and genetics.

"We were not particularly surprised by our findings because there is a recent and growing literature on the associations between vitamin D status and risk of Alzheimer's disease/dementia, cognitive decline, and brain atrophy," Miller said of the results. "Low vitamin D status is very common in older adults and is associated with accelerated rates of cognitive decline."

While there is no conclusive study as to whether vitamin D can help arrest or slow down cognitive function decline, knowing vitamin D levels and taking supplements only when necessary may help.

"There is a potential danger in consuming too much vitamin D as a supplement," Miller cautioned. "The upper tolerable level of daily intake (UL) for vitamin D established by the Institute for Medicine is 4000 IU/day for individuals age 9 years and older. Above this level, the risk of adverse health effects increases."

Photo: Pedro Ribeiro Simões | Flickr