Supplemental Science: Tweaking Turmeric

A variant of the superspice makes gains as a way to stave off cognitive decline.

By Hara Estroff Marano, published March 1, 2018 - last reviewed on April 30, 2018


Over the past couple of decades, lifestyle factors such as diet have emerged as powerful weapons against disorders often thought intractable. What makes food so effective in protecting against, and even ameliorating and reversing, hard-core disease? It delivers regular, often daily hits of biologically active agents, alone or in combination, usually in small amounts but over a very long time. 

Such is the case with turmeric, a dietary staple in India long used as a medicinal as well as a flavoring agent. Its distinctive orange flesh, dried and ground, is a prime ingredient of curries, and millions of children drink it stirred into hot milk to chase away colds and the flu. 

The most prominent nutrient in turmeric is curcumin. As a polyphenol, it is one of a class of chemicals that naturally occur in plants, protecting them from solar radiation, fungal disease, and other kinds of damage. Typically highly colorful pigments, polyphenols also protect and promote longevity of the human body. 

Curcumin not only imparts flashy color to turmeric, it is a polymath of a polyphenol, with antioxidant, anti-inflammatory, and neuroprotective properties. It has become the focus of much research for its ability to fight cancer and to disrupt the cognitive decline associated with neurodegenerative disorders, particularly Alzheimer’s disease.

There are no effective therapies for Alzheimer’s disease, and available agents target only the symptoms of dementia, now known to be the late-stage manifestation of neurodegeneration underway for decades. Curcumin is clinically alluring because it is nontoxic and targets multiple processes linked to the disease.

Yet clinical studies have yielded mixed results. That may be because bioavailability is limited, neurodegeneration may be too deeply entrenched by the time dementia appears, and studies have not controlled well for intake of curcumin from dietary sources. Scientists are in hot pursuit of a synthetic variant that makes curcumin more available in the body. 

In a noteworthy advance, researchers at UCLA are testing a bioavailable form of curcumin and tracking subjects with both cognitive tests and PET scans sensitive to amyloid and tau, the toxic proteins that form the lesions seen in Alzheimer’s disease. They are the first to monitor in vivo the effects of curcumin on accumulation of amyloid plaques and tau tangles in the brain. In the American Journal of Geriatric Psychiatry, the team reports findings among 40 nondemented subjects, ages 51 to 81, randomly assigned to take curcumin or placebo twice daily for 18 months.  

Led by Gary Small, director of geriatric psychiatry at the UCLA Longevity Center, the researchers found significant memory improvement and PET scan evidence of arrested plaque accumulation in parts of the brain that modulate mood and memory. Over the 18 months, those in the curcumin group had significant gains in verbal and visual memory; those receiving placebo were unchanged. Treated subjects also tested significantly better on measures of attention and mood; placebo subjects did not.

PET scans revealed marked differences between the two groups in two regions of the brain. In the amygdala, which plays a role in memory processing, decision making, and emotional response, the curcumin-eaters displayed significantly reduced binding activity, indicating decreased deposits of pathologic proteins. Further, those changes correlated with improvements in depression scores.

In the hypothalamus, PET scans were unchanged in the curcumin group, but the placebo group had a significant increase in binding over the 18 months, indicating intensification of pathology. The hypothalamus plays a role in emotional response and influences neurons that reach cortical regions involved in Alzheimer’s.

The researchers find the results encouraging: “This relatively inexpensive and nontoxic treatment may have a potential for not only improving age-related memory decline but also preventing or possibly staving off progression of neurodegeneration and eventually symptoms of Alzheimer’s disease.” 

A Broad Range of Benefits

  • Depression
  • Anxiety
  • Working memory
  • Attention
  • Neuroprotection

Curcumin vs Alzheimer’s Disease

  • Counters inflammation
  • Inhibits oxidation of cellular agents
  • Interrupts plaque formation by promoting disaggregation of beta amyloid, the proximate cause of Alzheimer’s 
  • Activates macrophages, which dispose of amyloid
  • Counters hyperphosphorylation of tau, enhances its clearance
  • Curbs overactivation of microglia
  • Mediates insulin-signaling pathway
  • Alters expression of genes that regulate autophagy 

The Root of Brain Health

  • Curcumin is a polyphenolic component of turmeric, the root of a tropical plant of the ginger family, cultivated in India for thousands of years.
  • Turmeric contains an average of 5–10 percent curcumin.
  • Epidemiological evidence—low incidence and prevalence of Alzheimer’s disease in India—suggests curcumin is neuroprotective.
  • Curcumin displays a broad spectrum of biological activity.
  • Turmeric stimulates digestion and reduces permeability of the gastrointestinal tract.
  • Curcumin may have particular benefit against androgen-related tumors, such as prostate cancer.
  • Multiple studies show that curcumin reduces depression and anxiety in humans.
  • In its natural state, curcumin has limited bioavailability and metabolic stability; scientists are hunting for ways to retain its pharmacologic effects while overcoming its limitations.
  • Studies have found that curcumin is especially effective as a neuroprotectant when combined with the omega-3 fatty acid DHA.
  • In addition to its curcumin content, turmeric contains vitamin C, magnesium, iron, vitamin B6, potassium, and manganese, along with fiber.