University of Minnesota nutrition and food science Professor Joanne Slavin addressed the comparative qualities of plant and animal proteins by highlighting some stark implications for product developers and vegans. in her presentation ‘Proteins for Health: Issues, Updates & Opportunities.”
“The most important macronutrient that we have in our diet is protein,” she began. “In the end, fats and carbohydrates are just calories. Proteins, however, are comprised of 20 amino acids, nine of which cannot be manufactured by a healthy adult body and are, therefore, essential nutrients.”
With protein, therefore, it isn’t just a question of quantity, but also quality and availability. This is where Slavin anticipates challenges on the food and beverage horizon.So…what do proteins do? They provide the building blocks for tissues, balance body fluids, control acidity, are integral to the immune function, produce hormones and enzymes, manage gluconeogenesis, deliver energy and signal satiety. “Whereas I can survive for a long time without most nutrients, the only two nutrients that I absolutely need in order to survive are water and protein,” Slavin said.
“We can easily calculate how much protein people need,” she added. “We know that protein needs increase during periods of growth, pregnancy and lactation. We also know that protein requirements begin to decrease after age 25.” “The Acceptable Macronutrient Distribution Range (AMDR) for protein intake is 10-35% of calories,” continued Slavin. Given that the Daily Value for protein is generally constant for individuals, reduced-calorie diets increase the required proportion of protein and vice versa. And, unless one has a kidney malfunction, “there is no upper limit for protein consumption, other than cost.”
However, individual protein intake requirements depend heavily on protein composition: A protein low in essential amino acids necessitates a higher level of intake in order to fulfill the body’s essential amino acid demand. Whereas animal proteins (eggs, milk, meat, seafood) reflect the perfect amino acid balance for humans, plant proteins do not. In addition, plant proteins are not as readily available nutritionally.
So, how to determine proteins? The FDA requires use of the Protein Digestibility-Corrected Amino Acid Score (PDCAAS) analysis for products other than for infants. It is, however, expensive and currently requires animal sacrifice (a “no-no” for many consumers).
“The only measure of protein efficiency allowed on a product label is the % Daily Value (%DV), but you must have a PDCAAS value of 1.0 before you can list your product’s %DV for protein,” stressed Slavin. This is difficult to achieve using plant proteins.
When humans lack the essential amino acids whereby to build new protein, our bodies break down existing proteins (e.g., muscle) in order to construct the “more important” proteins, explained Slavin. Consequently, a diet consisting of an adequate intake of protein can still be deficient in essential amino acids, leading to tissue breakdown.
“When people switch from animal to plant protein, it becomes more challenging,” cautions Slavin. “I think that we are going to see increasing numbers of consumers on both low-quantity, low-quality protein diets, especially among adolescent females.” Vegans take note!
The PDCASS value of plant proteins can be improved through blending and/or refining. Soy protein isolates have a PDCAAS value close to 1.0, “but only because ingredient manufacturers manufacture them that way. The only way to improve plant protein quality is by processing it…which goes against current consumer food trends favoring minimally processed whole foods.”
To conclude, even though total or average protein intakes may seem adequate, protein quality and availability must also be factored into food choices. Protein is an essential nutrient, and reduced-calorie diets, though appropriate, must necessarily contain a higher proportion of protein in order to provide essential amino acids. As consumers move from away from animal proteins toward plant proteins, they should consider how protein quantity, quality and availability affect their nutritional status.
“Eventually, consumers will discover these linkages, and they may feel misled; hopefully, it will also force the FDA to revisit its protein labeling rule requiring a PDCAAS level of 1.0 before protein %DV can be listed on packages,” she said. This will help clarify how good a source of protein the product actually is.
“Proteins for Health: Issues, Updates and Opportunities,” Joanne Slavin, Ph.D., University of Minnesota Dept. of Food Science and Nutrition, firstname.lastname@example.org
This presentation was given at the 2017 Protein Trends & Technologies Seminar — Technical Program: Formulating with Proteins.
Click here for access to the PowerPoint presentation of Proteins for Health by Joanne Slavin, Ph.D., University of Minnesota Dept. of Food Science and Nutrition
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