Can taking vitamin D supplements or spending more time in the sun help prevent Alzheimer's and other forms of dementia?

Answers from David S. Knopman, M.D.

Maybe. But it's too soon to say for certain. New research suggests people with very low levels of vitamin D in their blood, known as vitamin D deficiency, are more likely to develop Alzheimer's disease and other forms of dementia.

For example, a large 2014 study published in Neurology showed people with extremely low blood levels of vitamin D were more than twice as likely to develop Alzheimer's disease or other types of dementia than those with normal vitamin D levels. But it's important to point out that the association between vitamin D deficiency and dementia risk is only observational at this point. More research is needed to show cause and effect.

Vitamin D is vital to bone metabolism, calcium absorption and other metabolic processes in the body. Its role in brain function, cognition and the aging process is still unclear. Some studies suggest vitamin D may be involved in a variety of processes related to cognition, but more research is needed to better understand this relationship.

Most of our vitamin D is produced within the body in response to sunlight exposure. Vitamin D occurs naturally in only a few foods, including fatty fish and fish liver oils. The biggest dietary sources of vitamin D are fortified foods, such as milk, breakfast cereals and orange juice. Vitamin D supplements are also widely available.

Vitamin D deficiency is common among older adults, partially because the skin's ability to synthesize vitamin D from the sun decreases with age.

It's too early to recommend increasing your daily dose of vitamin D in hopes of preventing dementia or Alzheimer's disease. But maintaining healthy vitamin D levels can't hurt and may pay off in other ways, such as reducing the risk of osteoporosis. According to the Institute of Medicine, the recommended daily dose of Vitamin D is 600 International Units (IU) per day for adults under age 70 and 800 IU per day for adults over 70.

More studies are needed to determine if vitamin D deficiency is indeed a risk factor for Alzheimer's disease and dementia, and if treatment with vitamin D supplements or sun exposure can prevent or treat these conditions.

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David S. Knopman, M.D.

May 07, 2015 See more Expert Answers