What The Western Diet Does To The Immune System

Diets rich in two nutrients harm immune cells in the gut, putting people at high risk of intestinal infections.

A diet rich in fat and sugar damages particular immune cells named Paneth cells that produce antimicrobial molecules keeping inflammation and microbes under control.

Highly specialised Paneth cells are located in the small intestine where nutrients from food are absorbed and sent to the bloodstream.

Western diets are high in processed foods and fat and sugar, which cause Paneth cells to not work properly.

Paneth cell dysfunction cause abnormalities in the gut immune system which in turn leads to infections (disease-causing microbes) and inflammatory bowel disease (IBD), a study has found.

Dr Ta-Chiang Liu, the study’s first author, said:

“Inflammatory bowel disease has historically been a problem primarily in Western countries such as the U.S., but it’s becoming more common globally as more and more people adopt Western lifestyles.

Our research showed that long-term consumption of a Western-style diet high in fat and sugar impairs the function of immune cells in the gut in ways that could promote inflammatory bowel disease or increase the risk of intestinal infections.”

IBD patients often have defective Paneth cells, which are responsible for setting off inflammation in the small intestine.

For instance, Paneth cells can no longer function in patients with Crohn’s disease, which is a type of IBD and marked by fatigue, diarrhoea, abdominal pain, and anaemia.

The research team examined Paneth cells of 400 adults and found that the higher the body mass index (BMI) the worse these cells looked.

Frequent consumption of foods high in sugar and fat causes weight gain and has many health consequences.

These two macronutrients generally make up more than 40 percent of the calories of a typical Western diet.

The scientists fed mice a high sugar, high fat diet and in two months they became obese and had abnormal Paneth cells.

Dr Liu said:

“Eating too much of a healthy diet didn’t affect the Paneth cells.

It was the high-fat, high-sugar diet that was the problem.”

When a healthy diet replaced the Western diet, within four weeks, the Paneth cells were restored to normal.

Dr Liu said:

“This was a short-term experiment, just eight weeks.

In people, obesity doesn’t occur overnight or even in eight weeks.

It’s possible that if you have Western diet for so long, you cross a point of no return and your Paneth cells don’t recover even if you change your diet.

We’d need to do more research before we can say whether this process is reversible in people.”

In addition, deoxycholic acid (a secondary bile acid produce by bacteria in the gut) is involved in carbohydrate and fat metabolism.

Bile acid plays a key role regarding Paneth cell abnormality since it increases the activity of the farnesoid X receptor (involved in sugar and fat metabolism) and type 1 interferon (part of the immune system active in the antiviral responses) thus hindersing Paneth cell from working properly.

The study was published in the Cell Host & Microbe (Liu et al., 2021).

June 11, 2021        source:  Psyblog

Is a Plant-Centered Diet Better for Your Heart?

More evidence suggests the long-standing belief that eating low amounts of saturated fats to ward off heart disease may not be entirely correct.

A new study that followed more than 4,800 people over 32 years shows that a plant-centered diet was more likely to be associated with a lower risk of future coronary heart disease and stroke, compared with focusing on fewer saturated fats alone.

“It’s true that low-saturated fat actually lowers LDL [or bad] cholesterol, but it cannot predict cardiovascular disease,” says lead study author Yuni Choi, PhD, postdoctoral researcher in the Division of Epidemiology and Community Health at the University of Minnesota. “Our research strongly supports the fact that plant-based diet patterns are good for cardiovascular health.”

To assess diet patterns of study participants, the researchers conducted three detailed diet history interviews over the follow-up period and then calculated scores for each using the A Priori Diet Quality Score (APDQS). Higher APDQS scores were associated with higher intake of nutritionally rich plant foods and less high-fat meats. While those who consumed less saturated fats and plant-centered diets had lower low-density lipoprotein (LDL) levels, or lower levels of “bad” cholesterol, only the latter diet was also associated with a lower risk of heart disease and stroke over the long term.

Choi said targeting just single nutrients such as total or saturated fat doesn’t consider those fats found in healthy plant-based foods with cardioprotective properties, such as avocado, extra virgin olive oil, walnuts, and dark chocolate. Based on study results, she recommends those conscious of heart health fill their plates with vegetables, fruits, whole grains, nuts, legumes and even a little coffee and tea, which were associated with a low risk of cardiovascular disease.

“More than 80% should be plant-sourced foods and then nonfried fish, poultry, and low-fat dairy in moderation,” she says.

“I think in focusing just on nutrients, we oversimplify the heart [health] diet hypothesis and miss the very important plant component,” says research team leader David Jacobs, PhD, professor, Division of Epidemiology and Community Health at the University of Minnesota. “If you tend to eat a plant-centered diet you will tend to eat less saturated fats because that’s just the way the plant kingdom works.”

Following a plant-centered diet is consistent with the American Heart Association’s (AHA) existing recommendations to minimize saturated fats and emphasize fruits, vegetables, whole grains, legumes, nuts, and seeds, says Linda Van Horn, PhD, professor, and chief of the Department of Preventive Medicine's Nutrition Division at the Northwestern University Feinberg School of Medicine in Chicago, and a member of the AHA’s Nutrition Committee.

“There is no question that current intakes of plant-based carbohydrate, protein and fat are below what is recommended and moving in that direction would be a nutritious improvement,” she says, noting, however, that this doesn’t necessarily mean everyone needs to be on a vegetarian or vegan diet.

Given that plant-centered diets have been associated with lowering the risk of other diseases, the researchers are now looking to better understand how APDQS scores impact chronic conditions such obesity, diabetes, and kidney disease. They’ll also be researching how diet affects gut bacteria as they expect eating plant-based foods provides more fiber and promotes healthy microbiomes.

“I think that diet patterns provide a really solid base for the public and policy makers to think about what a healthy diet really is,” Jacobs says.

SOURCES

Nutrition 2021: “Which Predicts Incident Cardiovascular Disease Better: A Plant-Centered Diet or a Low-Saturated Fat Diet? The Coronary Artery Risk Development in Young Adults (CARDIA) Study.”

Yuni Choi, PhD, postdoctoral researcher, Division of Epidemiology and Community Health, University of Minnesota.

Linda Van Horn, PhD, professor, chief of the Department of Preventive Medicine's Nutrition Division, Northwestern University Feinberg School of Medicine, Chicago.

David Jacobs, PhD, professor of epidemiology and community health, University of Minnesota.7

By Rosalind Stefanac           June 10, 2021         source:   Medscape Medical News    WebMD