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.