Plant-based meat substitutes taste and chew remarkably similar to real beef, and the 13 items listed on their nutrition labels – vitamins, fats, and proteins – make them appear essentially equivalent.
But a deeper study of the nutritional content of plant-based meat alternatives by a research team at Duke University using a sophisticated scientific tool called metabolomics shows that they are as different as plants and animals.
Meat substitute makers have gone to great lengths to make the herbal product as meaty as possible by adding leghemoglobin, an iron-containing molecule from soy, as well as red berry, berry, and carrot extracts to simulate bloodiness. The texture of near-meat is thickened by adding indigestible fibers such as methyl cellulose. And to bring the vegetable meat alternatives to the protein content of meat, they use isolated vegetable proteins from soy, peas and other vegetable sources. Some meat substitutes also add vitamin B12 and zinc to further replicate the diet of meat.
However, many other components of the diet do not appear on the labels, and that is where the products differ greatly from meat, according to the study, which appears in Scientific Reports this week.
The metabolites measured by the scientists are building blocks of the body’s biochemistry, crucial for energy conversion, signal transmission between cells, the creation and breakdown of structures and a multitude of other functions. It is expected that there are more than 100,000 of these molecules in biology, and it is estimated that around half of the metabolites circulating in human blood come from our diet.
“To consumers reading nutrition labels, they may appear nutritionally interchangeable,” said Stephan van Vliet, a postdoctoral fellow at the Duke Molecular Physiology Institute who led the research. “But if you look behind the curtain with metabolomics and look at expanded nutritional profiles, we see that there are big differences between meat and a plant-based meat alternative.”
The Duke Molecular Physiology Institute’s core metabolomics lab compared 18 samples of a popular plant-based meat alternative to 18 grass-fed ground beef samples from an Idaho ranch. The analysis of 36 carefully cooked meatballs revealed that 171 of the 190 measured metabolites varied between beef and the vegetable meat substitute.
The beef contained 22 metabolites that the plant substitute did not. The vegetable substitute contained 31 metabolites that meat did not contain. The greatest differences were found in amino acids, dipeptides, vitamins, phenols, and types of saturated and unsaturated fatty acids found in these products.
Several metabolites known to be important for human health have been found in beef, either exclusively or in large amounts, including creatine, spermine, anserine, cysteamine, glucosamine, squalene and the omega-3 fatty acid DHA. “These nutrients have potentially important physiological, anti-inflammatory and / or immunomodulatory functions,” the authors say in the paper.
“These nutrients are important for our brain and other organs, including our muscles,” said van Vliet. “But some people who follow a vegan diet (no animal products) can lead healthy lives – that is very clear.” In addition, the plant-based meat alternative contained several beneficial metabolites not found in beef, such as phytosterols and phenols.
“It’s important that consumers understand that these products shouldn’t be considered nutritionally interchangeable, but that doesn’t mean one is better than the other,” said van Vliet, a self-described omnivore who eats a plant-rich diet also meat. “Plant and animal foods can complement each other because they provide different nutrients.”
He said more research is needed to determine whether the presence or absence of certain metabolites in meat and plant-based meat alternatives has short- or long-term effects.
van Vliet, S., et al. (2021) A metabolomic comparison of vegetable-based meat and grass-fed meat indicates major dietary differences, despite comparable nutritional information. Scientific reports. doi.org/10.1038/s41598-021-93100-3.