Doctors Reveal What Happens In Your Body When You Stop Eating Meat

An increasing number of people are reducing the amount of meat they eat, or eliminating meat from their diets entirely. A study published in Nature in 2018 indicated that huge reductions in meat-eating worldwide were necessary to help avert climate catastrophe, and millennials in particular are changing their diets: data from The Economist found that 25% of all Americans between 25 and 34 say they're either vegan or vegetarian in 2019. If you're changing your diet to cut out meat entirely, though, you may be concerned about what happens to your body when you stop eating meat. The effects, according to experts, depend on the person — but overall, there can be benefits.

“Studies have shown that people who focus on increasing their intake of plant-based foods show lower risks of heart disease, high blood pressure, diabetes and even some forms of cancer," Dr. Penny Kris-Etherton, Ph.D., distinguished professor of nutrition at Penn State College of Health and Human Development and fellow of the American Heart Association, tells Bustle. A study of over 12,000 middle-aged Americans published in the Journal of the American Heart Association in 2019 found that cutting out meat entirely was linked to a much lower risk for cardiovascular disease and heart disease-related deaths.

However, experts tell Bustle that all meats are not created equal in this regard. "There is really solid science that cutting out red meat will reduce your risk of heart disease," Dr. Nate Favini, medical lead at Forward, a primary care medical organization, tells Bustle. "On the other hand, fish that is high in omega-3 fatty acids likely reduces the risk of heart disease, so if your diet is mostly fish, cutting that completely could have a negative impact on your health." He suggests that people contemplating giving up meat focus on plant-based sources of healthy fats, like almonds and walnuts.

Going completely meat-free can also affect your gut microbiome, experts tell Bustle. "If you cut all meat out of your diet, you would likely see a positive shift in the number of beneficial bacteria in your gut," Stephanie Papadakis, a certified holistic nutrition consultant at Gut of Integrity, tells Bustle. "Many conventionally raised animals are given hormones and antibiotics, which can shift our own beneficial bacteria in the same way taking antibiotics can."

Other gut by-products of meat consumption are reduced by eliminating meat, too. The National Institute of Health found that a compound called Trimethylamine N-oxide (TMAO), which is created in the gut microbiome, is found in high levels in people who eat red meat regularly. A study published in Nature in 2019 found that switching to a diet without any meat products and heavily reliant on plants appears to make your microbiome flourish in new ways, which could have widespread effects on other aspects of health.

However, your gut's reaction to eliminating meat may depend on how you replace it. "If you’re substituting plant foods for meat, you’ll be eating more fiber, which, when broken down by bacteria in the large intestine, produces short-chain fatty acids," Papadakis tells Bustle. "However, if you substitute with more processed and sugary foods, it could lead to an overgrowth of negative bacteria in the gut." If you cut down on meat but still eat processed meats on occasion, or replace all meat with processed vegetarian foods, it may lead to gut imbalance.

The evidence that links cutting meat from your diet to lowered risks of diabetes and cancer is compelling, but it's not clear exactly what lies behind those links. A 2019 review of nine different studies, published in JAMA Internal Medicine, discovered that there's a significant relationship between a completely plant-based diet and a lower risk of type 2 diabetes, while a 2013 study of over 2,000 people found that vegetarians were statistically less likely to develop cancer than meat-eaters, and a 2012 study of nearly 125,000 people worldwide indicated that vegetarianism may reduce the risk of cancer by 18%. There's not much evidence for the impact of lowering meat intake as opposed to going completely vegetarian or vegan.

Part of this may be caused by lowered levels of saturated fat, Dr. Kris-Etherton tells Bustle. "If you let plants — that includes fruits and veggies, as well as whole grains and legumes — become the star of the show, you’ll fuel your body with positive nutrients and reduce foods high in things like saturated fat and sodium that we know can lead to poor health if eaten too often," she says.

However, meat-free diets can change your body in other ways that could be protective against these illnesses. Studies have found that people who changed their lifestyle choices, including going meat-free, saw lengthening in their telomeres, or the small caps at the end of DNA that stop them degrading and shortening over time. Telomere shortening has been linked to breast and prostate cancers, so going meat-free might be changing your body on the genetic level — and helping to protect against cancer in the process.

Going vegetarian can change our bodies over generations, too. A 2016 study also found that primarily vegetarian populations of people can actually develop genetic mutations that help them convert plant-based foods into helpful fatty acids for their brain and heart. It only appears to occur in people whose ancestors have been vegetarian for generations, but if the planet goes plant-based, future populations may have quite different genetics to our own.

The study on meat-free diets and the gut microbiome in Nature in 2019 also identified another way in which the body changes when you cut out meat: Levels of systemic inflammation in the body often go down. "The reason for lower systemic inflammation in plant-based dieters could be due to the abundance of anti-inflammatory molecule intake and/or avoidance of pro-inflammatory animal-derived molecules," the study notes. If your diet is vegetarian or vegan, you may be avoiding meat-based foods that increase inflammation, like red meat, and eating a lot of anti-inflammatory foods like nuts and fruits.

It's possible that going vegetarian won't be automatically good for you if you don't get all your necessary nutrients. A study from the American Heart Association in 2019 found that when it comes to a healthy diet without meat, the quality of your food — how nutrient-dense and highly processed it is — matters as much as the absence of meat products. "Cutting all meat out can contribute to nutrient deficiencies," Papadakis tells Bustle. "There are certain nutrients only found in animal sources, like vitamin B12, or which have low bioavailability in plant sources, like vitamin D3, iron, zinc, and omega-3 fatty acids (EPA + DHA). You would have to supplement with B12, and be really attentive to eating plant foods high in these nutrients."

As more people go meat-free, it may have a positive effect on the planet — but its effects on the human body are highly individual, and no two people will have the same reactions. If you're considering going meat-free, it's a good idea to chat to your medical professional to make sure you're getting all your nutritional needs.

"It’s totally possible to be very healthy on a plant-based diet," Favini tells Bustle. "Your doctor or nutritionist can help customize a plan for you."

Studies referenced:

Balan, E., Decottignies, A., & Deldicque, L. (2018). Physical Activity and Nutrition: Two Promising Strategies for Telomere Maintenance?. Nutrients, 10(12), 1942. doi:10.3390/nu10121942

Huang, T., Yang, B., Zheng, J., Wahlqvist, M.L, Li, D. (2012) Cardiovascular Disease Mortality and Cancer Incidence in Vegetarians: A Meta-Analysis and Systematic Review. Annals of Nutrition and Metabolism 2012;60:233–240. https://doi.org/10.1159/000337301

Kothapalli K.S.D., Ye, K., Gadgil M.S., Carlson, S.E., O’Brien, K.O., Zhang, J.Y., Park, H.G., Ojukwu, K., Zou, J., Hyon. S.S. (2016) Positive Selection on a Regulatory Insertion–Deletion Polymorphism in FADS2 Influences Apparent Endogenous Synthesis of Arachidonic Acid. Molecular Biology and Evolution 33(7), 1726–1739. https://doi.org/10.1093/molbev/msw049

Kim, H., Caulfield, L.E., Garcia‐Larsen, V., Steffen, L.M., Coresh, J., & Rebholz, C.M.. (2019) Plant‐Based Diets Are Associated With a Lower Risk of Incident Cardiovascular Disease, Cardiovascular Disease Mortality, and All‐Cause Mortality in a General Population of Middle‐Aged Adults. Journal of the American Heart Association. https://doi.org/10.1161/JAHA.119.012865

Kim, M.S., Hwang S.S., Park E.J., Bae J.W. Strict vegetarian diet improves the risk factors associated with metabolic diseases by modulating gut microbiota and reducing intestinal inflammation. Environmental Microbiology Reports 5(5):765-75. doi: 10.1111/1758-2229.12079. Epub 2013 Jul 19.

Medawar, E., Huhn, S., Villringer, A. & Witte, A.V. (2019) The effects of plant-based diets on the body and the brain: a systematic review. Translational Psychiatry 9 (226).

Ornish D, Lin J, Daubenmier J, Weidner G, Epel E, Kemp C, Magbanua MJ, Marlin R, Yglecias L, Carroll PR, Blackburn EH. (2008) Increased telomerase activity and comprehensive lifestyle changes: a pilot study. Lancet Oncology 2008 Nov;9(11):1048-57. doi: 10.1016/S1470-2045(08)70234-1.

Qian, F, Liu G, Hu FB, Bhupathiraju SN, Sun Q. (2019) Association between plant-based dietary patterns and risk of type 2 diabetes. A systematic review and meta-analysis. JAMA Intern Medicine 179(10):1335-1344. doi:10.1001/jamainternmed.2019.2195

Springmann, M., Clark, M., Mason-D’Croz, D., Wiebe, K., Bodirsky, B.L. et al. (2019) Options for keeping the food system within environmental limits. Nature 562, 519–525.

Tantamango-Bartley Y, Jaceldo-Siegl K, Fan J, Fraser G. (2013) Vegetarian diets and the incidence of cancer in a low-risk population. Cancer Epidemiol Biomarkers Prev. 22(2):286-94. doi: 10.1158/1055-9965.EPI-12-1060.

Experts:

Penny Kris-Etherton, Ph.D., distinguished professor of nutrition at Penn State of Health and Human Development and fellow of the American Heart Association

Dr. Nate Favini, medical lead at Forward

Stephanie Papadakis, certified holistic nutrition consultant at Gut of Integrity