In an article published in JAMA Network Open, researchers at the University of São Paulo's Medical School (FM-USP) report on a study involving 774 men and women who followed a vegan diet in Brazil.
Their findings show that, on average, the participants consumed the recommended amount of proteins and essential amino acids, and that their diet consisted largely of unprocessed and minimally processed foods. However, participants who consumed proportionally lower levels of industrialized products such as protein supplements and textured soy protein were more likely to exhibit inadequate protein intake, suggesting a significant reliance on nutrients from ultra-processed proteins for this population.
Coined by researchers at the same university's School of Public Health (FSP-USP), the term "ultra-processed products" refers to industrially formulated edible substances synthesized from fractionated ingredients and blended with chemical additives (colors, aromas, emulsifiers, thickeners etc.) to enhance their palatability.
"Our results contradict the stigma that a vegan diet can't provide the amount of protein and essential amino acids a person needs, and show that a vegan diet can be nutritionally adequate. Moreover, the vegans included in the study consumed ultra-processed products less than the general population," said Hamilton Roschel, last author of the article and head of the Applied Physiology and Nutrition Research Group at FM-USP's Center for Lifestyle Medicine.
The researchers measured the participants' intake of protein and essential amino acids, as well as calculating the proportions of unprocessed, processed and ultra-processed products in their meals, based on a diary kept by each participant to record everything they ate every day.
"Animal food products are known to be generally more dense in protein and essential amino acids. Meat, milk and eggs contain more protein per gram than rice or beans, for example. It was therefore important to investigate whether this requirement was met by diets consisting solely of plant protein," Roschel said.
This was the main reason for investigating whether a vegan diet affords an adequate amount of protein and acceptable levels of essential amino acids.
The analysis performed by the researchers showed that the participants mostly consumed unprocessed and minimally processed foods, which accounted for 66.5% of energy intake, while ultra-processed products accounted for 13.2%. The proportions for the general population are 44.9% and 23.7% respectively, according to IBGE's Household Budget Survey (POF).
The study also found a significant correlation between adequate protein intake and consumption of ultra-processed products. "Although this group consumed a small amount of ultra-processed products, some participants appeared to rely on them to meet their protein needs. This is partly because unprocessed foods are generally less dense in protein, a fact that paved the way for the so-called meat substitute industry, whose market share is growing," Roschel said.
Meat substitutes consist of plant protein processed to mimic different types of meat, such as vegan hamburgers, sausages and nuggets. Cheese substitutes are also available, using soy, pea, rice or potato protein. Both are considered ultra-processed products.
It is worth noting that consumption of ultra-processed products is associated with a heightened risk of weight gain, diabetes, hypertension and other cardiovascular diseases, depression, some types of cancer, and premature death. Not all the effects of plant-based ultra-processed products are known, but recent evidence suggests they too may be unhealthy.
The researchers concluded that textured soy protein (TSP) and plant-based protein supplements were the main ultra-processed products determining adequate protein intake for Brazilian vegans.
"Although they tend to be classified as ultra-processed products, TSP and protein supplements aren't necessarily unhealthy, which can't be said of ultra-processed products that contain high levels of fat, sugar, sodium, preservatives and artificial additives, for example," Roschel said.
Ultra-processed products as a broad category are considered unhealthy in many studies, but there is robust evidence that soy-derived foods do no harm to human health.
"TSP is an important source of protein and essential amino acids for vegans, even though it's classified as ultra-processed. Ultra-processed products vary considerably in terms of formulation, and despite the consensus that they should generally be avoided, it isn't reasonable to ignore the clear differences between them," he said.
As the researchers note, the same can be said about plant-based protein supplements, "an evidence-based strategy to support muscle health also associated with protein adequacy" in different contexts, such as when unprocessed and minimally processed foods do not supply sufficient protein or when a clinical condition requires a different kind of nutritional management. "In these contexts, plant-based protein plays an important role and should not be overlooked," Roschel said.
"Our findings don't show that ultra-processed products are good, and the findings should not be used to encourage their consumption. However, it would be wrong to close one's eyes to the significant differences among them and the importance of the role they play in certain contexts.
"The results of the study suggest a need for policies to facilitate access to more natural and healthy foods, as well as efforts to improve nutritional education so that this population can make better dietary choices. As the market for plant-based foods expands, regulation by the government is urgently needed to enable affordable products to be developed with transparency regarding their composition, high quality, and clearly identified health benefits."