Derived from the Curcuma long plant, curcumin is a major component of turmeric and has been used extensively in traditional Indian and Asian medicine. (Despite the similarity in name, curcumin is not related to cumin.) Although preclinical research suggests that curcumin may benefit the brain and even protect against dementia, the clinical evidence is weak. No trials have tested curcumin for dementia prevention and trials on cognition have not reported substantial benefits even with curcumin optimized for absorption.
While several clinical studies have examined the impact of curcumin on cognition for healthy individuals and Alzheimer’s patients, no study has investigated whether curcumin supplements can prevent dementia. Our search identified:
• 0 meta-analyses or systematic reviews
• 4 randomized controlled trials (2 with healthy individuals, 2 with Alzheimer’s disease patients)
• 1 observational study
• Numerous preclinical studies
An observational study in healthy elderly Asian people suggest that those who eat more curcumin (in the form of curry) may have improved cognitive function . In addition, two small clinical trials suggest that absorbable curcumin may improve some measures of cognition  in healthy older adults but the effects were miniscule and unlikely to be noticeable. No clinical studies suggest that curry, turmeric, or highly bioavailable curcumin supplements can prevent Alzheimer’s disease.
Preclinical evidence suggests that curcumin might offer several cognitive benefits, including reduced damage from oxidative stress, inflammation, and brain levels of beta-amyloid , as well as extended lifespan and improved memory . Very little clinical evidence shows whether those benefits extend to humans.
Two very small randomized clinical trials have tested curcumin as a treatment for dementia and both failed to show any benefits . Both trials, however, used forms of curcumin not easily absorbed by the human body.
Daily doses of 400 mg/day of Longvida™, a curcumin supplement, have shown to be safe for healthy elderly subjects , while doses up to 4 g daily of regular curcumin over 6 months appear safe for elderly patients with Alzheimer’s disease . Curcumin can interact with a variety of prescription and non-prescription drugs, including aspirin and other painkillers and some diabetic medications. Its potential to interact with other dietary supplements or natural products has not been fully evaluated. Nausea and upset stomach were the most common side effects reported in clinical trials, although some people had curcumin allergies. Most clinical trials have only tested short-term safety of curcumin supplements; there is less evidence regarding the safety of long-term use.
NOTE: This is not a comprehensive safety evaluation or complete list of potentially harmful drug interactions. It is important to discuss safety issues with your physician before taking any new supplement or medication.
The major dietary source of curcumin is turmeric, which usually contains 3 to 5 percent curcumin and is common in curry dishes. The form of curcumin found in turmeric (and many supplements) is not readily absorbable by the human body, but cooking and consuming it with black pepper may make it more useful . Curcumin supplements are widely available and often contain a substance called Bioperine™, a commercial form of piperine, a component of black pepper that makes ingested curcumin more available to our bodies .
Information from the Linus Pauling Institute at Oregon State University
Drug Interaction Checker from Drugs.com