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Diet and the Shrinking Brain

Nancy Emenaker of the National Cancer Institute told a gathering of registered dietitians, clinicians and other HRSA staff that adherence to federal dietary guidelines is improving. But poor eating habits are implicated in a wide range of mood disorders -- including anxiety, depression and dementia.
Nancy Emenaker of the National Cancer Institute told a gathering of registered dietitians, clinicians and other HRSA staff that adherence to federal dietary guidelines is improving. But poor eating habits are implicated in a wide range of mood disorders -- including anxiety, depression and dementia.

 

An "intricate communication" between the human brain and the digestive tract powerfully affects immune function, susceptibility to disease and the ability to recover from potentially catastrophic conditions like cancer, an NIH researcher told HRSA staff in a recent learning session. What you eat also can have a protective effect if you have a genetic predisposition to certain health problems.

"When we all go off the rails (at) McDonald's ... we have to keep in mind that there are some repercussions for that -- and some of these repercussions actually do impact neuro-physiology and the psychological wirings in our bodies," said research scientist Nancy Emenaker.

In short, eating the wrong foods is associated with physical changes to the human brain so pronounced that they are visible in brain scans -- and may scramble the body's main switchboard into malfunctioning to an alarming degree.

The effects are most readily seen in cancer survivors who have undergone chemotherapy, some of whom can experience cognitive loss of 17 to 75 percent as long as 20 years later because of the destructive side effects of the toxic chemicals on the brain and digestive "microbes" in the gut, Emenaker said.

But emerging research now shows that subtler conditions of the gut may contribute to "psychosocial" symptoms and conditions as varied as autism spectrum disorder, schizophrenia and Parkinson's disease -- to say nothing of chronic ailments like diabetes.

"There are shifts in neurochemicals based on whether ... we're having a fast food diet or we're eating something like a healthy salad or a chicken salad sandwich that has tomato and lettuce on it," said Emenaker, adding that consumers often are unaware of the "neurochemicals that are created by some of these food components."

"Diet plays a large role in our neuro function," she said, and "physical activity also plays a very intricate role in cognition."
 

From left, HRSA dietitians Samantha Croffut (MCHB);  Bramaramba Kowtha (BHW), who organized the March 27 event, and LT Lusi Martin- Braswell (BHW) are among more than 30 registered dietitians on the agency's staff.
From left, HRSA dietitians Samantha Croffut (MCHB);  Bramaramba Kowtha (BHW), who organized the March 27 event, and LT Lusi Martin- Braswell (BHW) are among more than 30 registered dietitians on the agency's staff.

 

"We've done a pretty good job" -- through the Dietary Guidelines for Americans, devised by HHS and the Department of Agriculture -- " at getting people to increase fruit and vegetable intake, and to reduce some of the added sugars and some of the added fats," Emenaker said. "However ... we've got a very large portion of the population that can still make substantial changes."

Nine out of 10 Americans, for example, are still consuming too much salt, and seven out of 10 are eating too much saturated fat. In general, Americans don't get enough fiber, antioxidants, or vitamins D and K. The result is a state of more or less constant inflammation of the digestive tract and altered brain chemistry.

"Unfortunately, that is leading us to the point where we're increasing risk for cardiovascular disease, diabetes and cancer," Emenaker said. "But before you're going to see that, you're going to see things like mood disorders, liver disease, hypertension," high cholesterol (or, dyslipidemia) and neurodegenerative diseases among those living with obesity.

For more than 25 years, she noted, over half of U.S. adults have been overweight or obese -- and a third of children and youth over the past decade. Perhaps most startling, 65 percent of adult women and more than two-thirds of men are living outside healthy weight limits. Most at risk are African-American adults and the poor.

"The landscape of America is changing," Emenaker said. "We're not exercising like we used to. They've taken recess out of the schools. We're not teaching people how to cook anymore. So when we're translating diet (recommendations), that information actually is being lost. The consequences of the shifting dietary patterns, in combination with a lack of exercise" are increasing rates of type-II diabetes, sleeping disorders, and the risks of cancer and mental illness, such as clinical depression and anxiety.

"Those individuals who are overweight are actually starting to notice and verbalize that they feel much less satisfied with their quality of life," she added, stoking a negative feedback loop that can increase mental stress, even as their very diets -- heavy in fatty acids, glucose and salt -- are triggering "acute inflammatory processes" that further erode mental function.

In an emerging field of study, she noted, one of the more eye-opening revelations is that the U.S.-style "Western Diet" of red meat, high-fat dairy, sugary drinks, processed meats and refined grains wreaks havoc on the brain.

One study of 4,447 men and women in Holland, concluded that "better overall diet quality is related to larger total brain volume ... these associations were not driven by one specific food group, though several food groups contributed differentially to the effect on brain changes. In particular, sufficient intake of vegetables, fruit, nuts, whole grains, dairy, and fish, and limited intake of sugar-containing beverages, were related to larger brain tissue volumes" and decreased risk of dementia over time.

Date Last Reviewed:  May 2019