The bright yellow plant extract curcumin has improved Alzheimer’s-like properties in mice, but failed to do so in humans.

Curcumin is made from turmeric, the dried root powder of the Curcuma longa plant, a  member of the ginger family. It is commonly used in curries.

Curcumin and Alzheimer’s disease

Curcumin is a mainstay of traditional Chinese and Indian herbal medicines. It is a polyphenol, or chemical compound believed to have anti-inflammatory and anti-oxidant effects.

Inflammation and oxidative stress contribute to Alzheimer’s. Oxidative stress occurs when there is an imbalance between the body’s production of potentially harmful free radicals and its ability to counter them.

But eating more curcumin-based curries is unlikely to alleviate Alzheimer’s because of curcumin’s limited bioavailability in the brain, scientists say. Bioavailability is the extent to which a therapy is available where it is needed.

The reason for curcumin’s limited bioavalability in the brain is that the liver and intestines modify it in a way that leads to the kidneys quickly flushing it from the body. This leaves little of it to work in the brain.

To overcome this problem, several companies make reformulated curcumin. The products include Sabinsa’s Curcumin C3 Complex, Verdure Sciences’ Sabinsa, and Indena’s Meriva.

Curcumin in clinical trials

Mice that consumed curcumin-based diets for five months had lower levels of amyloid beta protein — a hallmark of Alzheimer’s disease — in their brains than controls, studies have shown.

Other animal studies have suggested that curcumin can reduce tau protein clumping in the brain, slowing cognitive deterioration. Scientists have linked the clumping to Alzheimer’s in humans. Curcumin may also help protect brain cells, animals studies have shown.

Despite evidence that it can combat Alzheimer’s disease in animals, curcumin has yet to demonstrate such effects in humans.

A 24-week Phase 2 clinical trial (NCT00099710) showed that Curcumin C3 Complex failed to generate cognitive improvements in 36 people with mild to moderate Alzheimer’s. Most participants tolerated the compound well, but three had to withdraw from the trial due to gastrointestinal problems.

Chinese researchers conducted a six-month-long Phase 1/2 trial (NCT00164749) showing that a combination of curcumin and gingko extract failed to reduce amyloid beta protein levels in the blood of Alzheimer’s patients or improve their cognition. Chinese University of Hong Kong scientists did the study between 2005 and 2008.

An ongoing Phase 2 clinical trial (NCT01811381) has been investigating the combined benefits of curcumin and yoga in people with mild cognitive impairment. In the first six months, patients receive either a daily dose of curcumin or a placebo. In the next six months, they continue taking curcumin or a placebo but also engage in aerobic or yoga training.

The objectives of the trial are to see if curcumin plus exercise can improve blood biomarkers and brain images of Alzheimer’s and patients’ cognitive scores. Researchers continue to recruit trial participants in the VA Greater Los Angeles Healthcare System. The study is scheduled to end in December 2019.

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