protéines végétales moins bien assimilées

A study showed that plant proteins are less easily absorbed by the intestines

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The percentage of people adopting a meat-free diet is gradually increasing. Out of an environmental principle, out of respect for animal welfare, to reduce their expenses or to maintain their health, these people turn to plant-based alternatives based on soy and wheat proteins. However, the nutritional quality of these products is still a matter of debate within the scientific community. A new study has revealed that the proteins of vegetable alternatives are not as well absorbed as those found in meat.

According to an Ifop survey conducted in 2020 on behalf of FranceAgriMer, 68% of respondents believe that we consume too much meat in France, and 56% believe that meat production has a negative impact on the environment. However, only 2.2% of those surveyed said they had adopted a meat-free diet. Nearly a quarter of them, however, have voluntarily reduced their consumption, thus becoming resilient. But reducing meat consumption or not eating it at all means that you are eliminating an important source of protein from your diet.

However, proteins are essential for the body: they not only play a structural role (at the level of muscles and skin), but also participate in a large number of biological functions, such as immunity, digestion or transport of oxygen. According to the ANSES, healthy adults under the age of 60 should consume 0.83 grams of protein per kilogram of body weight each day. Plant protein foods are becoming popular, but it is unclear how much of this nutrient reaches human cells.

Meat alternatives considered ‘healthy’

Apart from proteins of animal origin (found in meat, fish, eggs and dairy products), the plant foods richest in protein are oilseeds, legumes, and grains. Thus, foods sold as meat substitutes are often made from soybeans or wheat. Sausages, ground beef, nuggets, and rusk chips are now in a 100% vegetarian version.

To mimic the look and feel of real meat, the plants are dried, powdered, and mixed with spices. These mixtures are then heated, moistened and processed by an extruder. Consumers of these products often think that they are healthier than animal meat. And for good reason: Consumption of red meat and deli meat is associated with an increased risk of colorectal cancer. In addition, the plants used to make meat substitutes are low in “bad” fats (the so-called saturated fats).

However, laboratory tests have shown that the plant proteins in the substitutes do not break down into peptides like those found in meat. Researchers at Ohio State University explored the question: they set out to test whether human cells could absorb as many peptides from a meat substitute as peptides from a piece of chicken.

The variant was produced by extrusion using soy protein and wheat gluten. Then they compared the physical and chemical properties, digestion in the laboratory and cellular uptake of peptides released for each of these two foods. It appears from the results that the proteins found in vegetable substitutes are not as available to cells as those found in meat.

Larger and less soluble proteins

In appearance, the two materials were similar: when slicing, the meat substitute had long fibrous pieces, just like real chicken. ” The meat counterpart showed greater toughness, but a lower degree of texture than chicken The team then cooked pieces of these two “meats,” then ground them before smashing them with a human digestive enzyme — to simulate the processes of chewing and digestion.

The meat substitute (left) is similar to chicken meat (right), but the proteins are not absorbed by human cells either. © J. Agric. Chem food.

tests in the laboratory Then cultures of Caco-2 cells—used as models of intestinal epithelial cells—were performed to quantify the amount of peptides crossing this mock intestinal wall during transit (fixed here at 4 h). The researchers reported that no cytotoxicity or inflammatory response was observed, in the case of the variant as in the case of chicken. But they noted that the variant showed lower permeability of the peptides through Caco-2 cells.

The alternative peptides had a higher molecular weight and were less soluble in water than those in chicken. Because of this, it was not absorbed by the cells either. About 2% less protein was absorbed by enterocytes in the variant condition. The difference may seem insignificant, but the researchers point out that they only used a simplified model of the gut wall here: In the real intestine, peptides must also pass through a layer of mucus before reaching the epithelial cells — and again, plant peptides can be reduced as well. It is actually absorbed.

According to the team, these findings could eventually be used to develop healthy products. In particular, it will be necessary to identify ingredients that can help stimulate the uptake of peptides from plant-based meat substitutes. In the meantime, the researchers concluded that these meat alternatives remain a good source of protein, and can be used as part of a balanced diet.

Source: D. Chen et al., J. Agric. Chem food.

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