New Research Links Your Brain and Your Gut

Researchers break down how, exactly, a healthy diet might lower dementia risk

Last year’s Alzheimer’s Association conference made headlines with the release of studies showing that a healthy diet, along with other lifestyle factors, can slash your risk of dementia by a third. Researchers have hunted for answers in the gut microbiome, the trillions of microorganisms that live in our digestive tracts. Changes in these bacteria have been linked to various inflammatory and autoimmune conditions:obesity, diabetes and inflammatory bowel disease. Scientists discovered that types of microbiome bacteria can promote buildup in the brain of specific proteins. In mouse studies, dietary changes that alter the microbiome in turn reduce amyloid plaques, lower inflammation and — bingo — improve memory.

Research suggests another link along the digestive tract; a person’s ability to metabolize certain lipids also can affect the risk of developing Alzheimer’s and other dementias. “If your body has trouble producing or moving lipids around, it may impact your brain structure and its function,” explains Heather Snyder of the Alzheimer’s Association.

While this research is still in its infancy, it has the potential to be game-changing. “It may help us develop better diagnostic tests for the disease in the future, as well as to better understand why some people progress rapidly over a year, and some more slowly over 15 years,” says Jagan Pillai, a neurologist at Cleveland Clinic.

What the Studies Show

Two of the studies looked at the impact of lipids on Alzheimer’s risk. One study found that low levels of a certain type of lipids, plasmalogens, are linked to higher Alzheimer’s risk. Some of these plasmalogens also contain two omega-3 fatty acids that are vital for brain health. The second study looked at 800 older adults, some healthy, some with mild cognitive impairment and some with full-blown Alzheimer’s. They also found that people with Alzheimer’s had many problems with lipid metabolism, such as difficulty absorbing lipids that contain EPA and DHA. In addition, giving these patients fish oil supplements failed to bring these lipids back to normal.

“These studies  show that if your body has trouble producing certain lipids, it impacts brain,” explains Snyder. This may explain why fish oil supplements have mixed results in clinical trials when warding off dementia. “Some people just aren’t able to absorb them, for unknown reasons,” Snyder says.

A third study examined the bile acids in older adults who either had early-stage Alzheimer’s. They found that high levels of certain bile acids were increased in people with Alzheimer’s and were linked to cognitive decline, reduced brain glucose metabolism and greater brain atrophy. “We still have a lot to tease out. Are these changes in bile acids causing changes in the brain, or is it the other way around; that something happening in the brain leads to alterations in digestion?” says Snyder. “Better diagnostic testing for Alzheimer’s could be developed based upon this information.”

There are more than 40 different risk genes associated with Alzheimer’s. The last study looked at  genetic variations and found two associated with lower levels of cholesterol components that help keep brain cell membranes healthy and strong. Alzheimer’s researchers haven’t paid much attention to these markers in the past, but this research suggests that we should. This may help us understand how these underlying mechanisms contribute to Alzheimer’s disease, and unlock strategies for more effective treatments.

The Takeaway

While much of this research is intriguing, it’s still in its infancy, cautions Small.  “The microbiome is an interesting area of study, not just for Alzheimer’s but for brain health and mood,” he notes. In the meantime, you can help keep all your organs, including your liver, GI tract — and yes, brain — in tiptop shape by eating a diet high in fruits, veggies, whole grains and healthy fats such as fatty fish and olive oil, while limiting saturated fats and sugars.

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