Diet and Mental Health

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Diet and Mental Health

In 1905, Ellen G. White said that “diet materially affects the mind and disposition” (Adventist Home, p. 252). Given her level of education and lack of scientific background, few people paid attention to her statement. It would take another century before we could fully appreciate her timeless words.

The Surprising Connection Between Brain and Gut

In 2004, a groundbreaking study found a strong correlation between postnatal gut bacteria colonization and brain plasticity. Researchers noted that these bacteria play a critical role in several areas, such as the immune system, digestion and absorption, and overall physiological response to pathogens.

In 2010, Stephen Collins, MD, and his team at McMaster University, Hamilton, Ontario, Canada, embarked on “a systematic investigation of the ability of intestinal bacteria to influence the brain and behavior” in mice. A recent Journal of the American Medical Association (JAMAreports:

Subsequent animal experiments in Collins’ laboratory bore out the researchers’ initial observations by demonstrating through both antibiotic perturbation and fecal transplants that intestinal microbiota can influence anxiety-like behaviors (Bercik P et al. Gastroenterology. 2011;141[2]:599-609). Mice treated with oral antibiotics showed a reduction in anxiety-like behavior. What’s more, swapping intestinal microbiota of mice also switched their behavioral phenotypes, where a once anxious mouse adopted the less anxious behavioral phenotype of the donor mouse and vice versa.

While these microbes seem to use various means to interact with the brain and the nervous system, JAMA highlights another team of scientists that “found that the neurochemical and behavioral effects required an intact vagus nerve, implicating this nerve as important in communicating changes in the gastrointestinal tract to the brain.”

In humans, JAMA says,

One clinical study recently looked at the potential effect of probiotics on the human brain. Gastroenterologist Emeran Mayer, MD, who has worked to understand signaling between the gut and the brain, and his team at the University of California, Los Angeles, found that giving a probiotic cocktail in a fermented dairy drink to healthy female participants could bring about changes in brain activity as measured by functional MRI (fMRI) compared with control participants (Tillisch K et al. Gastroenterology. 2013;144[7]:1394-1401).

The women carried out a face-matching attention task while they underwent fMRI before and after the 4-week intervention. They were shown pictures of human faces displaying fear or anger that normally trigger increased activity in areas of the brain involved in processing emotion. Brain activity was monitored during a resting state and while participants identified the emotions associated with human facial expressions. While executing this task, the group taking the probiotic showed less activity in brain regions involved in anxiety relative to control groups, suggesting that the brain’s reaction to negative emotional stimuli had changed.

“This was a positive proof of concept that shows if you manipulate the gut microbiota in a very subtle way, you can pick up a fairly robust brain signal that affects multiple brain regions,” said Mayer.

JAMA concludes by noting that

While the evidence is mounting that the gut microbiome is important in mental health and development, the field is still in its infancy, and there remains healthy skepticism as to whether recent work may have translational potential for treating anxiety and depression in humans.

Diet and Gut Microbes

The importance of a healthy human intestinal microbial ecology cannot be stressed enough. In 2010, the Proceedings of the National Academy of Sciences published a study that examined the role of diet in the formation of gut microbiota. The paper ended with this insightful finding: “Our results suggest that diet has a dominant role over other possible variables such as ethnicity, sanitation, hygiene, geography, and climate, in shaping the gut microbiota.”

While researchers have not determined what type of diet is most beneficial to gut microbes, growing evidence suggests that a plant-based diet offers many health advantages. The benefits of such a diet include lower risk of colon cancercardiovascular diseases, and type 2 diabetes. A plant-based diet also helps people to lose weight and maintain a healthy weight. Moreover, combining a plant-based diet with berries, especially blueberries, has been linked to a slower rate of cognitive decline and a lower risk of developing Alzheimer’s disease.

It should not be a surprise to anyone that both celebrities and politicians are joining a growing population that recognize the role of diet in our health, particularly cognitive functioning. We can truly say that Ellen G. White was a pioneer and far advanced for her time when she penned that “diet materially affects the mind and disposition.”

[Photo from Science Prose, “Gut Microbes Regulate Weight Gain”]

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About the author


Valmy Karemera is associate editor of The Compass Magazine and posts daily news updates on the Compass Twitter page. Originally from Rwanda, he now lives and works in Texas with his family.