Meat and Dairy Can Rapidly Alter Gut Bacteria and Cause Inflammation

The adage “you are what you eat” might never have been truer. According to new research, your health may be determined by what you eat, and what microorganisms came along for the ride.

A new Harvard University study published in the journal Nature found that diet rapidly alters the microorganisms residing in the gut. And if what you ate was either meat or dairy, you might not be happy with their findings.  It has long been known that diet influences the type and activity of the trillions of microorganisms residing in the human gut, but Harvard scientists found that even what we eat in the short-term can have drastic effects on the type and numbers of microbes in our gut and their capacity to increase inflammation in the gastrointestinal tract (GI).

Researchers found that within two days of consuming an animal-based diet, microbes in the alistipes, bilophila, and bacteroides families increased.  Harvard scientists also discovered that microbes found in the food itself, including bacteria, fungi, and viruses, quickly colonized the gut.  And, perhaps most notably, they discovered that an animal-based diet caused the growth of microorganisms that are capable of triggering inflammatory bowel disease within only two days of eating these foods.  Earlier research showed that bilophilia overgrowth promotes inflammation.  Still further research has linked inflammation-causing microbes to serious chronic diseases, meaning that the Harvard study has potentially far-reaching implications for disease prevention and treatment.

The scientists put volunteers on a meat and cheese diet, then switched them to a fiber-rich, plant-based diet to track the effect on intestinal microbes.  They ate a breakfast of eggs and bacon, a lunch of ribs and briskets, and salami, prosciutto and assorted cheeses for dinner, along with pork rind snacks.  After a break from eating this diet the volunteers ate a plant-based diet of granola for breakfast, jasmine rice, cooked onions, tomatoes, squash, garlic, peas, and lentils for lunch and a similar dinner, with bananas and mangoes for snacks.

The scientists analyzed the volunteers’ microbes before, during, and after each meal.  The effects of the meat and cheese were immediate.  The abundance of bacteria shifted about a day after the food hit the gut. After three days on either diet, the bacteria in the gut changed their behavior.

Lead scientist Lawrence David, PhD admits that the meat and cheese diet was extreme; however, it seems to have painted a clear picture of the outcome of a diet heavy in meat and cheese—a typical diet for many people who use high protein diets to lose weight.  Dr. David said in an interview with NPR “I love meat … but I will say that I definitely feel a lot more guilty ordering a hamburger … since doing this work.”  He also indicates that the study unlocks a potentially new avenue for treating intestinal disease.  I would add that it likely unlocks ways to treat other inflammatory diseases in the body. Heart disease, diabetes, arthritis, and even cancer have been linked to inflammation in the body.

You may want to rethink that bacon-wrapped sausage hors d’oeuvre or cheese platter during the holidays … or anytime.

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Carrie-Anne Brown

thanks for sharing :)

Mac C.
mac C5 years ago

I am all for a diet that doesn't promote inflammation. Thanks for posting, Michelle, and also thanks for the link to the study.

Connie O.
Connie O5 years ago


Dawn D.
Past Member 5 years ago

Hmmm! Very interesting and for the most part true for a lot of beings.
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Elena T.
Elena Poensgen5 years ago

Thank you :)

Melinda K.
Past Member 5 years ago

Extremes always stress the body

Philipa Longley
Philipa Longley5 years ago

Interesting article, thanks for sharing.

Jennifer Blachly
Jennifer B5 years ago

Everythiing in moderation. Too much of anything can cause harm.

Dale O.

Just noticing the debate between Barbara D and Nathan W. Intriguing comments also by Heidi A as there is always some debate as to what humans began as...were we vegetarians first and all of that. Then, there are those who maintain that grains are not a natural part of the human diet and how there are some diets such as the Paleo diet that refuse to consider grains as a food to be included in the diet. Whatever happened in human evolution, we adapted to include almost everything in our diets including grains and most certainly meat. Those who are either allergic and gluten intolerant obviously exclude grains.

Mea culpa, the other day I had several tabs open with different Care2 articles. The cat that owns me was competing with me for the ownership of the keyboard (as purr-usual...purrhaps she needs her very own computer?) Anyway, I managed to type a comment onto the wrong comment board as I got distracted with four paws on the computer, so my comment just below for 6:05PM PST on Dec 27, 2013, belongs in the Meat Tax thread and not here. Oopsy! I have to sit in the Pay Attention Corner! The Shame!

Neal Jeffries

Excellent article...thanks for sharing!