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NCCIH Clinical Digest

for health professionals

Dietary Supplements and Cognitive Function, Dementia, and Alzheimer’s Disease: What the Science Says

June 2017

Clinical Guidelines, Scientific Literature, Info for Patients: 
Dietary Supplements and Cognitive Function, Dementia, and Alzheimer’s Disease

senior woman alzheimers dementia

Ginkgo biloba

There’s no conclusive evidence that Ginkgo biloba is efficacious in preventing or slowing dementia or cognitive decline.


Several high-quality reviews have found no convincing evidence for the efficacy of omega-3 polyunsaturated fatty acid supplements in the treatment of mild to moderate Alzheimer’s disease.

Vitamin E

A recent systematic review found no evidence that vitamin E given to people with mild cognitive impairment prevents progression to dementia, or that it improves cognitive function in people with mild cognitive impairment or dementia due to Alzheimer’s disease. However, there is moderate quality evidence from a single study that it may slow functional decline in Alzheimer’s disease.


There have only been a few clinical trials examining the effects of curcumin on cognitive function and Alzheimer’s disease, so there aren’t enough data to support the use of curcumin for this condition.

Other Natural Products

  • Research has shown that taking a multivitamin or high doses of individual vitamins, such as selenium, B vitamins, and calcium and vitamin D, doesn’t have any clear benefits for cognition in well-nourished people.
  • Although melatonin may help promote sleep in healthy people, a 2014 Cochrane review of two studies found no evidence that melatonin, either immediate- or slow-release, improved any major sleep outcome in patients with Alzheimer’s disease.
  • Coconut oil to prevent or treat Alzheimer’s disease is of interest to researchers; however, only small clinical trials have been conducted to date, and the use of coconut oil for Alzheimer’s disease is not supported by any large, rigorous clinical data.


  • Burckhardt M, Herke M, Wustmann T, et al. Omega-3 fatty acids for the treatment of dementia. Cochrane Database Syst Rev. 2016;4:CD009002.
  • DeKosky ST, Williamson JD, Fitzpatrick AL, et al. Ginkgo biloba for prevention of dementia: a randomized controlled trial. JAMA. 2008;300(19):2253-2262.
  • Farina N, Llewellyn D, Isaac MG, et al. Vitamin E for Alzheimer’s dementia and mild cognitive impairment. Cochrane Database Syst Rev. 2017;1:CD002854.
  • Fernando WM, Martins IJ, Goozee KG, et al. The role of dietary coconut for the prevention and treatment of Alzheimer’s disease: potential mechanisms of action. Br J Nutr. 114(1):1-14.
  • Klein EA, Thompson IM Jr, Tangen CM, et al. Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA. 2011;306(14):1549–1556.
  • McCleery J, Cohen DA, Sharpley AL. Pharmacotherapies for sleep disturbances in Alzheimer’s disease. Cochrane Database Syst Rev. 2014;3:CD009178.
  • Rainey-Smith SR, Brown BM, Sohrabi HR, et al. Curcumin and cognition: a randomized, placebo-controlled, double-blind study of community dwelling older adults. Br J Nutr. 115(12):2106-2113.
  • Snitz BE, O’Meara ES. Carlson MC, et al. Ginkgo biloba for preventing cognitive decline in older adults: a randomized trial. JAMA. 2009;302(24):2662-2670.
  • Sydenham E, Dangour AD, Lim W-S. Omega 3 fatty acid for the prevention of cognitive decline and dementia. Cochrane Database Syst Rev. 2012:6:CD005379.
  • Tan MS, Yu JT, Tan CC, et al. Efficacy and adverse effects of ginkgo biloba for cognitive impairment and dementia: a systematic review and meta-analysis. J Alzheimers Dis. 2015;43(2):589-603.
  • Yang G, Wang Y, Sun J, et al. Ginkgo biloba for mild cognitive impairment and Alzheimer’s disease: a systematic review and meta-analysis of randomized controlled trials. Curr Top Med Chem. 2016;16(5):520-528.

NCCIH Clinical Digest is a service of the National Center for Complementary and Integrative Health, NIH, DHHS. NCCIH Clinical Digest, a monthly e-newsletter, offers evidence-based information on complementary health approaches, including scientific literature searches, summaries of NCCIH-funded research, fact sheets for patients, and more.

The National Center for Complementary and Integrative Health is dedicated to exploring complementary health products and practices in the context of rigorous science, training complementary health researchers, and disseminating authoritative information to the public and professionals. For additional information, call NCCIH’s Clearinghouse toll-free at 1-888-644-6226, or visit the NCCIH Web site at NCCIH is 1 of 27 institutes and centers at the National Institutes of Health, the Federal focal point for medical research in the United States.


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