National Center for Complementary and Alternative Medicine (NCCAM)

NIH…Turning Discovery Into Health®

Follow NCCAM: Subscribe to our email update Subscribe to the NCCAM RSS feed Follow NCCAM on TwitterRead our disclaimer about external links Follow NCCAM on FacebookRead our disclaimer about external links

Menu

National Institutes of Health • National Center for Complementary and Alternative Medicine

NCCAM Clinical Digest. For health professionals.

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

December 2013
An old woman looks out the window.

Ginkgo

Strength of Evidence

  • Numerous studies of ginkgo have been done for a variety of conditions, including Alzheimer’s disease and dementia.

Research Results

  • A large, placebo-controlled, randomized clinical trial funded by NCCAM and NIA studying the well-characterized ginkgo product EGb-761 found it ineffective in lowering the overall incidence of dementia and Alzheimer’s disease in the elderly. Further analysis of the same data also found ginkgo to be ineffective in slowing cognitive decline, lowering blood pressure, or reducing the incidence of hypertension. In this clinical trial, known as the Ginkgo Evaluation of Memory Study, researchers recruited more than 3,000 volunteers age 75 and over who took 240 mg of ginkgo or placebo daily. Participants were followed for an average of approximately 6 years.
  • While some smaller studies of ginkgo for memory enhancement have had promising results, a trial sponsored by the National Institute on Aging of more than 200 healthy adults over age 60 found that ginkgo taken for 6 weeks did not improve memory.

Safety

  • Side effects of ginkgo may include headache, nausea, gastrointestinal upset, diarrhea, dizziness, or allergic skin reactions. More severe allergic reactions have occasionally been reported.
  • There are some data to suggest that ginkgo can increase bleeding risk, so people who take anticoagulant drugs, have bleeding disorders, or have scheduled surgery or dental procedures should use caution and talk to a health care provider if using ginkgo.
  • Fresh (raw) ginkgo seeds contain large amounts of a chemical called ginkgotoxin, which can cause serious adverse reactions—even seizures and death. Roasted seeds can also be dangerous. Products made from standardized ginkgo leaf extracts contain little ginkgotoxin and appear to be safe when used orally and appropriately.

Omega-3 Fatty Acids

Strength of Evidence

  • Omega-3 fatty acids are the subject of extensive research across NIH, in part because there is laboratory and observational evidence of potential health benefits, and in part because they are widely used by the public. Recent NCCAM-sponsored studies have been investigating whether fish oil can slow the progression of Alzheimer’s disease.

Research Results

  • Currently, there is not enough scientific evidence from these and other studies to determine whether fish oil is useful in treating Alzheimer’s disease.

Safety

  • Omega-3s appear to be safe for most adults at low-to-moderate doses. The FDA has concluded that omega-3 dietary supplements from fish are “generally recognized as safe.”
  • Some have questioned the safety of fish oil supplements because some species of fish can contain high levels of mercury, pesticides, or polychlorinated biphenyls (PCBs). However, fish oil supplements do not appear to contain these substances.
  • Fish oil supplements may cause minor gastrointestinal upsets, including diarrhea, heartburn, indigestion, and abdominal bloating.
  • In high doses, fish oil can interact with certain medications, including blood thinners and drugs used for high blood pressure.

B Vitamins

Strength of Evidence

  • Several studies have been conducted on vitamin B supplements and cognitive function in older adults.

Research Results

  • Results of short-term studies suggest that B-vitamin supplements do not help cognitive functioning in adults age 50 or older with or without dementia. The vitamins studied were B12, B6, and folic acid, taken alone or in combination.

Safety

  • There are some health risks from excessive intake of some B vitamins. In addition, vitamin B6 can interact with certain medications, and several types of medications might adversely affect vitamin B6 levels, including the antibiotic cycloserine and some anti-seizure drugs. Vitamin B12 has the potential to interact with metformin, proton pump inhibitors, the antibiotic chloramphenicol, and H2 receptor antagonists.

Asian Ginseng

Strength of Evidence

  • Asian ginseng has been widely studied for a variety of uses. Most of the evidence is preliminary—i.e., based on laboratory research or small clinical trials—but a few high-quality clinical trials have been conducted on Asian ginseng for Alzheimer’s disease.

Research Results

  • Research results to date do not conclusively support health claims associated with the herb.

Safety

  • Short-term use of ginseng at recommended doses appears to be safe for most people. Some sources suggest that prolonged use might cause side effects.
  • Asian ginseng may lower levels of blood sugar; this effect may be seen more in people with diabetes. Therefore, people with diabetes should use extra caution with Asian ginseng, especially if they are using medicines to lower blood sugar or taking other herbs, such as bitter melon and fenugreek, that are also thought to lower blood sugar.
  • The most common side effects are headaches and sleep and gastrointestinal problems.
  • Asian ginseng can cause allergic reactions.
  • There have been reports of breast tenderness, menstrual irregularities, and high blood pressure associated with Asian ginseng products, but these products’ components were not analyzed, so the cause is unclear.

Vitamin E

Strength of Evidence

  • Many laboratory and animal studies have investigated the role of vitamin E in the prevention and treatment of Alzheimer’s disease; evidence from human studies is much more limited.

Research Results

  • A 2012 Cochrane review found no convincing clinical evidence that vitamin E is of benefit in the treatment of Alzheimer’s disease or mild cognitive impairment.

Safety

  • Research has not found any adverse effects from consuming vitamin E in food. However, high doses of alpha-tocopherol supplements can cause hemorrhage and interrupt blood coagulation in animals, and in vitro data suggest that high doses inhibit platelet aggregation.
  • Recent results from the Selenium and Vitamin E Cancer Prevention (SELECT) Trial suggest that vitamin E supplements (400 IU/day) may increase the risk of prostate cancer. Follow-up studies exploring this finding are underway.
  • Vitamin E supplements have the potential to interact with several types of medications, including anticoagulant and antiplatelet medications, simvastatin and niacin, and chemotherapy and radiotherapy.

Grape Seed Extract

Strength of Evidence

  • A few preliminary studies of the effects of grape seed extract and its components on cognitive decline, Alzheimer’s disease, and other brain disorders have been undertaken.

Research Results

  • There is currently insufficient evidence to determine if grape seed extract is helpful in the prevention or treatment of cognitive decline or Alzheimer’s disease.

Safety

  • Grape seed extract is generally well tolerated when taken by mouth. It has been used safely for up to 8 weeks in clinical trials.
  • Side effects that have been reported include a dry, itchy scalp; dizziness; headache; high blood pressure; hives; indigestion; and nausea.
  • Interactions between grape seed extract and medicines or other supplements have not been carefully studied.

Curcumin

Strength of Evidence

  • A few preliminary clinical studies exploring the effects of curcumin on Alzheimer’s disease have been conducted.

Research Results

  • Evidence of benefit of curcumin on Alzheimer’s disease has not been found.

Safety

  • Curcumin is considered safe for most adults, but high doses or long-term use may cause indigestion, nausea, or diarrhea.
  • In animals, very high doses of curcumin have caused liver problems. No cases of liver problems have been reported in people.

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

The National Center for Complementary and Alternative Medicine 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 NCCAM's Clearinghouse toll-free at 1-888-644-6226, or visit the NCCAM Web site at nccam.nih.gov. NCCAM is 1 of 27 institutes and centers at the National Institutes of Health, the Federal focal point for medical research in the United States.

Subscriptions

Copyright

Content is in the public domain and may be reprinted, except if marked as copyrighted (©). Please credit the National Center for Complementary and Alternative Medicine as the source. All copyrighted material is the property of its respective owners and may not be reprinted without their permission.

Follow NCCAM on:

Twitter Twitter at twitter.com/NCCAM

Facebook Facebook at www.facebook.com/nccam

YouTube YouTube at www.youtube.com/NCCAMgov