A well-balanced diet is good for health, and this applies to people of any age. There are many products that are marketed to add to a deficient diet or to enhance an already good diet. Products that are claimed to help prevent or slow Alzheimer's disease (AD) are part of this market.

The Alzheimer's Association suggests there is no need for those with AD to have special diets. However, as the disease progresses, it can be difficult to make sure that a person with AD is getting all the necessary nutrition from their meals. The most prevalent reason for this is the person is just not eating.

However, a new study in JAMA Neurology indicates that not all nutritional supplements that are advocated for the treatment and prevention of Alzheimer's disease are effective.

The study, led by Richard J. Kryscio, Ph.D., from the University of Kentucky in Lexington, investigated the use of vitamin E or selenium to prevent dementia in previously asymptomatic older men. The researcers had enrolled 7,540 men who had used supplements for more than five years and compared them to 3,786 men not using supplements and who had been observed for more than five years.

The supplements had no impact on the incidence of dementia.

"The supplemental use of vitamin E and selenium did not forestall dementia and are not recommended as preventive agents," Kryscio told MedPage Today. However, he did qualify the results, stating they were "tempered by the underpowered study, inclusion of only men, a short supplement exposure time, dosage considerations and methodologic limitations in relying on real-world reporting of incident cases."

The results were met with disappointment as there had been hopes of the antioxidants being effective. The vitamins were expected to affect the generation and clearance of the type of amyloid brain deposits that contribute to Alzheimer's disease.

Vitamin E had already been shown to have no effect on the dementia with advancing age that occurs with those with Down syndrome. This study looked at a group of 337 adults with Down syndrome with one half using a vitamin E supplement and one half using a placebo over several years. The supplement had no impact on the overall rate of dementia.

There are products with nutrient supplements, including vitamins previously thought to be beneficial to prevention of dementia, on the market and under continued study. There are a lot of misconceptions about diet supplements marketed specifically for brain health and for Alzheimer's disease, including a limited number of quality products that work.

The other concern is that even if the products do not work, they are not harmless. There can be side effects to supplements, including gastrointestinal distress. A diet rich with nutrient-dense foods and eliminating foods high in fat, sugar or salt, is still a good defense against diseases of aging, including dementia.