Ketogenic diet helps tame flu virus

A high-fat, low-carbohydrate diet like the Keto regimen has its fans, but influenza apparently isn't one of them.

Mice fed a ketogenic diet were better able to combat the flu virus than mice fed food high in carbohydrates, according to a new Yale University study published Nov. 15 in the journal Science Immunology.

The ketogenic diet -- which for people includes meat, fish, poultry, and non-starchy vegetables -- activates a subset of T cells in the lungs not previously associated with the immune system's response to influenza, enhancing mucus production from airway cells that can effectively trap the virus, the researchers report.

"This was a totally unexpected finding," said co-senior author Akiko Iwasaki, the Waldemar Von Zedtwitz Professor of Immunobiology and Molecular, Cellular and Developmental Biology, and an investigator of the Howard Hughes Medical Institute.

The research project was the brainchild of two trainees -- one working in Iwasaki's lab and the other with co-senior author Visha Deep Dixit, the Waldemar Von Zedtwitz Professor of Comparative Medicine and of Immunobiology. Ryan Molony worked in Iwasaki's lab, which had found that immune system activators called inflammasomes can cause harmful immune system responses in their host. Emily Goldberg worked in Dixit's lab, which had shown that the ketogenic diet blocked formation of inflammasomes.

The two wondered if diet could affect immune system response to pathogens such as the flu virus.

They showed that mice fed a ketogenic diet and infected with the influenza virus had a higher survival rate than mice on a high-carb normal diet. Specifically, the researchers found that the ketogenic diet triggered the release of gamma delta T cells, immune system cells that produce mucus in the cell linings of the lung -- while the high-carbohydrate diet did not.

When mice were bred without the gene that codes for gamma delta T cells, the ketogenic diet provided no protection against the influenza virus.

"This study shows that the way the body burns fat to produce ketone bodies from the food we eat can fuel the immune system to fight flu infection," Dixit said.

Too much ultra-processed food linked to lower heart health

Ultra-processed foods, which account for more than half of an average American's daily calories, are linked to lower measures of cardiovascular health, according to preliminary research to be presented at the American Heart Association's Scientific Sessions 2019 -- November 16-18 in Philadelphia.

Researchers at the U.S. Centers for Disease Control and Prevention (CDC) found that for every 5% increase in calories from ultra-processed foods a person ate, there was a corresponding decrease in overall cardiovascular health. Adults who ate approximately 70% of their calories from ultra-processed foods were half as likely to have "ideal" cardiovascular health, as defined by the American Heart Associations' Life's Simple 7®, compared with people who ate 40% or less of their calories from ultra-processed foods.

Foods were categorized into groups by the extent and purpose of industrial processing they undergo. Ultra-processed foods are made entirely or mostly from substances extracted from foods, such as fats, starches, hydrogenated fats, added sugar, modified starch and other compounds and include cosmetic additives such as artificial flavors, colors or emulsifiers. Examples include soft drinks, packaged salty snacks, cookies, cakes, processed meats, chicken nuggets, powdered and packaged instant soups and many items often marketed as "convenience foods."

"Healthy diets play an important role in maintaining a healthy heart and blood vessels," said Zefeng Zhang, M.D., Ph.D., an epidemiologist at the CDC. "Eating ultra-processed foods often displaces healthier foods that are rich in nutrients, like fruit, vegetables, whole grains and lean protein, which are strongly linked to good heart health. In addition, ultra-processed foods are often high in salt, added sugars, saturated fat and other substances associated with increasing the risk of heart disease."

Using data from the National Health and Nutrition Examination Survey (NHANES) collected between 2011 and 2016, researchers at the CDC reviewed the results from 13,446 adults, 20 years of age and older, who completed a 24-hour dietary recall and answered questions about their cardiovascular health.

Cardiovascular health is defined by the American Heart Association's Life's Simple 7 as measures of healthy blood pressure, cholesterol and blood glucose levels, avoidance of tobacco products, good nutrition, healthy body weight and adequate physical activity.

"This study underscores the importance of building a healthier diet by eliminating foods such as sugar-sweetened beverages, cookies, cakes and other processed foods," said Donna Arnett, Ph.D., past-president of the American Heart Association and dean of the College of Public Health at the University of Kentucky in Lexington. "There are things you can do every day to improve your health just a little bit. For example, instead of grabbing that loaf of white bread, grab a loaf of bread that's whole grain or wheat bread. Try replacing a hamburger with fish once or twice a week. Making small changes can add up to better heart health."