Taking higher doses of Vitamin D, especially if you live in an area with long winters, can significantly improve your brain function.

In a new study, Dr. Jacqueline Pettersen, a cognitive/behavioural neurologist with the Northern Medical Program compared two groups of healthy adults from Northern BC in a randomized trial. One group took high Vitamin D doses (4000 IU/day) daily, while the other took low doses (400 IU/day), and various cognitive functions were assessed before and after 18 weeks of treatment.

Dr. Pettersen found that the high dose group performed significantly better on tasks of nonverbal (visual) memory, compared to both pre-treatment and the low dose group. She also found that the benefits were even more pronounced among those with lower levels of Vitamin D to begin with.

Vitamin D insufficiency has been estimated to affect one billion people worldwide and is particularly prevalent in the north.  Dr. Pettersen found that over 60% of participants had blood levels of vitamin D considered to be “insufficient” prior to supplementation.

“This is one of the first studies to demonstrate a positive effect of vitamin D supplementation on brain function in healthy adults,” says Dr. Pettersen. “While there has been good evidence that Vitamin D improves memory in animal models, research to date has been limited with respect to humans.”

Vitamin D, also known as the ‘sunshine vitamin’, is not produced in the body but must be either synthesized in the skin in response to the sun’s UVB rays, or else consumed through diet. However, there are few good food sources of vitamin D, and at northern latitudes there are also not enough UVB rays to help make Vitamin D during several months of the year. Unless you take a supplement during the winter (and possibly the summer as well if you take cover from the sun), you are likely to be insufficient.

“These results have implications for public health,” notes Pettersen. “For people living in Northern B.C., and other regions which experience extended winter, the findings suggest that they should be supplementing with Vitamin D during the cold weather months, and also taking a dose that is higher than the current recommended minimum daily amount.

“While 4000 IU per day (or even up to 10 000 IU per day) is considered safe, we don’t know yet if supplementing with high doses for long periods of time is recommendable, as there are likely other important factors that need to be considered. As part of my ongoing research, I am looking at what roles other nutrients may play in addition to Vitamin D, and how genetics may help some individuals benefit more than others from supplementation.”

The Institute of Medicine recommends a minimum intake of 600 IU per day for bone health. The optimal amount for cognition is not yet known, but Dr. Pettersen’s study suggests it is higher than 600 IU per day, and more in-line with recommendations from the Endocrine Society and Vitamin D Council, who suggest doses between 1500 and 5000 IU per day for other health-related outcomes in addition to bone health.

Dr. Pettersen’s research is part of a larger series of ongoing Vitamin D-related studies that she is pursuing, which includes the role of genetics and exploring the balance between vitamin D intake and the intake of other nutrients such as calcium, magnesium, zinc, vitamin A and vitamin K2.