Gut Check looks at health claims made by studies, newsmakers, or conventional wisdom. We ask: Should you believe this?

The claim:

Curcumin, a component of the spice turmeric, can prevent or treat Alzheimer’s disease.

Tell me more:

An internet search for “curcumin” and “Alzheimer’s” leads not only to commercial websites whose claims are clearly suspect but also to papers in scientific and medical journals. That’s how marketers can say “studies show” that curcumin helps immune cells suck up amyloid plaques and that people with dementia who took turmeric capsules had miraculous improvements.

Those claims make their way into the popular press when even respected universities claim that “one of the most promising new treatments for Alzheimer’s disease may already be in your kitchen” and that “curcumin has demonstrated ability to … bind and destroy the beta-amyloid plaques present in Alzheimer’s.”

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Really?

Tracing the claims feels like a neurological game of telephone, with the original message unrecognizable by the time it’s cited by later studies. One 2008 paper, for instance, claimed that curcumin “decreased Beta-amyloid plaques, delayed degradation of neurons,” and improved “the overall memory in [Alzheimer’s] patients.” Let’s trace those assertions.

The “decreased plaques” claim comes from a study in which immune cells called macrophages, taken from the blood of six people with Alzheimer’s, were grown in lab dishes. After curcumin was added to the dishes, cells from three patients devoured the main component of plaques (the sticky deposits in the brains of Alzheimer’s patients) more than curcumin-less macrophages did.

The number of red flags here rival those at Turkish national holiday celebrations. For one, cells from the other three patients showed no such effect of curcumin, and there’s no evidence this happens in real life rather than lab dishes. To happen in real life and real bodies, ingested curcumin would have to get from the gut into the bloodstream and then the brain. But “an incredibly small fraction of what you ingest even gets to where it would need to go to affect Alzheimer’s,” said Penny Dacks of the Alzheimer’s Drug Discovery Foundation, whose new website evaluates claims that various foods, drugs, and supplements protect against or treat Alzheimer’s.

Most crucially, it’s far from established that macrophages (called microglia when they’re in the brain) play an important role in Alzheimer’s. Although they might clear amyloid, they “can also activate inflammatory cascades that may accelerate damage to [brain] tissue,” said Dacks.

The “delays degradation of neurons” claim fares no better. Its source is a study that is peripheral to the claim. The study reported that curcumin reduced the number of free radicals (again, in lab dishes), and leapt from there to assert that, because free radicals attack neurons (a process that has not been shown to play an important role in Alzheimer’s), then eliminating them with curcumin (which has also not been proved in people rather than lab dishes) must delay the degradation of neurons in patients’ brains. That’s a triple play of unproved assertion stacked on unproved assertion.

The main source of the “improves memory” claim are studies reporting that people who eat a lot of curry, which contains turmeric, have better cognitive function than people who eat little. But that says nothing about cause and effect; maybe smart people eat more curry than less-smart people do. As for an oft-cited 2012 study in a journal devoted to traditional Indian medicine, which claimed miraculous improvements in three patients with dementia who took turmeric capsules: One improved from 12 to 17 on a 30-point standard mental exam; the other two had no such improvement but, the researchers reported, began recognizing family members again. Needless to say, three patients of whom only one improved on an objective scale is an awfully thin reed to hang a claim of “improves memory” on.

Two very small randomized clinical trials have tested curcumin as a treatment for dementia. Neither the 2008 study nor one in 2012 showed any benefits.

One small study in healthy adults found an effect on working memory so minuscule it wouldn’t be noticed in real life, Dacks said. Another found that curcumin boosted cognition, but only because, inexplicably, the comparison group got worse, not because the curcumin group improved.

The verdict: 

There is no rigorous evidence that curcumin does anything for Alzheimer’s.

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  • The problem with curcumin is that it is not absorbed well into the bloodstream. Various researchers are working on ways to make curcumin more bioavailable but to date there has not been a major breakthrough.

    Curcumin is a methoxyphenol and methoxyphenols are excellent antioxidants because they are good hydrogen donors. Hydrogen donors scavenge peroxynitrite–the primary oxidant in Alzheimer’s disease. They also de-nitrate amyloid plaques leading to their degradation. This is not likely important in most cases, however, as amyloid plaques (unlike other forms of amyloid) do not contribute to oxidation.

    Korean red ginseng and heat processed ginseng (Korean red ginseng steamed at higher temperature) contain two methoxyphenols–ferulic acid and syringic acid–that are better absorbed into the bloodstream. Here are the clinical trial results using these form of ginseng to treat Alzheimer’s disease

    Nutr Neurosci. 2012 Nov;15(6):278-82.
    Heat-processed ginseng enhances the cognitive function in patients with moderately severe Alzheimer’s disease.
    Heo JH, Lee ST, Chu K, Oh MJ, Park HJ, Shim JY, Kim M.

    RESULTS:
    The treatment groups showed significant improvement on the MMSE and ADAS. Patients with higher dose group (4.5 g/day) showed improvements in ADAS cognitive, ADAS non-cognitive, and MMSE score as early as at 12 weeks, which sustained for 24-week follow-up.
    DISCUSSION:
    These results demonstrate the potential efficacy of a heat-processed form of ginseng on cognitive function and behavioral symptoms in patients with moderately severe AD.

    J Ginseng Res. 2011 Nov; 35(4): 457–461.

    Improvement of Cognitive Deficit in Alzheimer’s Disease Patients by Long Term Treatment with Korean Red Ginseng
    Jae-Hyeok Heo,1 Soon-Tae Lee,2,3 Min Jung Oh,2,3 Hyun-Jung Park,2,3 Ji-Young Shim,2,3 Kon Chu,2,3 and Manho Kim2,3,*

    Abstract
    A 24-week randomized open-label study with Korean red ginseng (KRG) showed cognitive benefits in patients with Alzheimer’s disease. To further determine long-term effect of KRG, the subjects were recruited to be followed up to 2 yr. Cognitive function was evaluated every 12 wk using the Alzheimer’s Disease Assessment Scale (ADAS) and the Korean version of the Mini Mental Status Examination (K-MMSE) with the maintaining dose of 4.5 g or 9.0 g KRG per d. At 24 wk, there had been a significant improvement in KRG-treated groups. In the long-term evaluation of the efficacy of KRG after 24 wk, the improved MMSE score remained without significant decline at the 48th and 96th wk. ADAS-cog showed similar findings. Maximum improvement was found around week 24. In conclusion, the effect of KRG on cognitive functions was sustained for 2 yr follow-up, indicating feasible efficacies of long-term follow-up for Alzheimer’s disease.

  • Thanks for a voice of reason! As a dietitian, it’s amazing to me how many people continue to think an association is a cause, and that all studies deserve the same amount of consideration when it comes to health.

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