Plant-based meat and animal meat have similar effects on inflammation Original paper

Many people are interested in eliminating or reducing their meat consumption but are also unwilling to give up the taste of meat.^[1] To meet this demand, a growing number of plant-based imitation meat products have been developed, which resemble certain types of meat in taste and texture.

These imitation meats are usually highly processed, meeting the NOVA definition of an ultraprocessed food.^[2] This is a source of concern for many consumers, who believe the processed nature of imitation meats makes it potentially unhealthy.^[1]

One noteworthy aspect of the healthiness of a food is its effect on inflammation. Although inflammation is not inherently a bad thing, constantly elevated inflammatory signaling in the body, sometimes called chronic inflammation, has been implicated as a potential risk factor for various health conditions, including cardiovascular disease,^[3] depression,^[4] sarcopenia,^[5][6] and dementia.^[7]

This study was designed to evaluate whether animal meat and plant-based imitation meat differ in their effects on biomarkers of inflammation in order to better understand the health effects of eating imitation meat.

This 8-week randomized controlled crossover trial compared the effects of animal meat and plant-based imitation meat on markers of inflammation. It was a secondary analysis of the SWAP-MEAT study.^[8] In the trial, a total of 36 people (average age of 50, average BMI of 28) were assigned to eat at least two 3–4 ounce servings of animal meat or plant-based imitation meat per day. Each participant followed both diets in a random order.

To ensure compliance, the following foods were provided to participants:

• Plant-based imitation meat diet: burgers, beef crumbles, sausage, and chicken strips. These foods were largely composed of water, protein isolate (usually pea and/or soy), oil (usually canola, sunflower, and/or coconut oil), vegetable fiber, starch, and various flavoring agents.

• Animal meat diet: ground beef (80% lean, grass-fed), beef burger (grass-fed), pork sausage, bratwurst, and chicken breast. These meats were sometimes made with herbs and spices. The participants were allowed to add salt to the ground beef.

The participants were also instructed to avoid tofu and tempeh during both diet phases. Some fish (no more than 8 ounces per week) was also allowed, but not provided, during the animal meat phase only.

The investigators assessed blood levels of 92 proteins that are considered to be biomarkers of inflammation. Among these, particular attention was given to the biomarkers IL-6, IL-18, TNF-α, IL-12B, IL-10, and TGF-β, and the changes in these were considered the main analysis of the study.

There was no clear difference between diets for any of the 92 inflammatory biomarkers, including for the 6 biomarkers that were part of the main analysis.

Nutrient intake was fairly similar between groups, including comparable intakes of protein and sodium. The plant-based imitation meat diet resulted in a lower intake of total fat, saturated fat, and calories and a higher intake of fiber than the animal meat diet, but of these, only the difference in saturated fat was statistically significant.

Dietary intake during each diet

• Data from Crimarco et al. Am J Clin Nutr. 2020 Aug.

Many of the study details were only available in a previously published paper covering the primary outcome.^[8]

The study was funded by Beyond Meat, a company that makes plant-based imitation meats and provided the imitation meats used in this study.

A previous study reported that participants ended up weighing about 1 kg (2.2 pounds) more on the animal meat diet compared to the plant-based meat diet. The extent to which this may have influenced the results of this study is unclear.

This study compared plant-based imitation meat to animal meat and found no apparent difference in biomarkers of inflammation. With this finding in mind, it’s noteworthy that a number of researchers have suggested animal meat might cause inflammation in some contexts, but is there merit to such claims?

According to one theory, red meat and pork (but not poultry and fish) may promote inflammation in the body because these meats contain a compound called N-glycolylneuraminic acid (Neu5Gc). Consuming Neu5G is thought to be a problem because the body ultimately produces antibodies against the Neu5Gc, treating it like a foreign invader and producing chronic inflammation.^[9] In line with this part of the claim, most humans do produce such antibodies.^[10]

Experimental evidence to support the Neu5Gc theory is currently limited to rodents, specifically studies in which mice were essentially vaccinated against Neu5Gc, inducing an immune response that may not translate to what happens when the average person eats meat. Clinical trials in humans, in contrast, have frequently found no increase in inflammatory markers in response to eating more red meat^[11][12][13] or dairy products^[14] (dairy also contains Neu5Gc).

In the current study, the plant-based imitation meats were lower in saturated fat than the animal meat, although not by a substantial margin, because coconut oil is a common component of the plant-based meats used in the study. It has been suggested that saturated fat can increase the absorption of endotoxin (lipopolysaccharide, LPS), a type of bacterial fragment found in the gut which produces inflammatory effects in the bloodstream.^[15] For this reason, it is hypothesized that meat high in saturated fat may promote chronic inflammation.

However, although some studies have found that ingesting a large amounts of saturated fat (e.g., from heavy cream) can transiently increase circulating endotoxin levels,^[16][17][18] several clinical trials have found saturated fat does not reliably increase inflammatory markers compared to other types of fat.^{[18][19][20][21][22]}

While the current study found no clear difference in inflammatory markers between plant-based imitation meat and animal meat, a few clinical trials have found a reduction in inflammatory markers when legumes are eaten in place of meat (typically red meat):

• One 8-week randomized crossover trial in 31 people with type 2 diabetes compared the effect of a diet with red meat to a diet with legumes replacing two servings of red meat three days per week.^[23] Ultimately, the diet with legumes resulted in a greater reduction in levels of three inflammatory biomarkers: CRP (−1.7 mg/L vs. −1.3 mg/L), IL-6 (−1.6 pg/mL vs. −1.2 pg/mL), and TNF-α (−1.8 pg/mL vs.in1.3 pg/mL).

• A 16-week RCT in 300 people with type 2 diabetes compared the effect of hypocaloric diet with red meat to the same diet with legumes replacing one serving of red meat at least five times a week.^[24] At the end of the trial, the inflammatory biomarkers CRP, TNF-α, and IL-6 were lower in the group eating legumes.

• In an 8-week randomized crossover trial in 42 postmenopausal women, replacing one daily serving of red meat with soy nuts reduced the inflammatory biomarkers CRP and IL-18.^[25]

• An 8-week randomized controlled trial had 75 people with type 2 diabetes eat a diet with red meat or a diet that replaced two servings of red meat with either soybeans or nonsoy legumes on three days per week.^[26] At the end of the trial, CRP levels were lower in the soy group compared to the red meat group. CRP levels were also lower in the nonsoy legume group compared to the red meat group, but this was not statistically significant.

It’s difficult to determine what mediators explain these findings, but it could be attributable to a combination of the fiber,^[27] polyphenols,^[28] and magnesium^[29] found abundantly in legumes.

It’s worth emphasizing that inflammation is by no means the only factor of importance when it comes to health, so this study had a narrow focus. Many other markers of health are worth exploring when it comes to the potential effects of plant-based imitation meats. It is reassuring, though, that one previous publication from the same study reported that compared to animal meat, plant-based imitations meats had similar effects on fasting levels of insulin, glucose, HDL-C, triglycerides, and blood pressure while resulting in similar amounts of gastrointestinal issues and even reduced LDL-C.^[8]