A segment of the population seems to be interested in protein powders derived from plants, specifically soy, peas, and even wheat. This makes sense if you're a vegan, are allergic to dairy, or your dad owns a legume farm and you get freebies, but otherwise, there's no real reason to switch from dairy proteins (whey and casein) to plant-based proteins.
Instinctively, some might also believe that plant proteins are somehow more healthful or nutritious than dairy proteins, but it's not true. Plant proteins are missing the vast majority of the vitamins, minerals, and phytochemicals that are intrinsic to the whole plant, although soy, specifically, contains just enough isoflavones to possibly cause problems.
(As I laid out in my article, Does Soy Protein Feminize You?, soy can actually exert estrogenic effects.)
Of course, dairy-based protein powders aren't exactly chockfull of vitamins and minerals, either, but in the case of whey, they at least contain immunoglobulins that can fortify human health.
But when it comes to the all-important issue of muscle protein synthesis, plant proteins don't pack on muscle the way dairy-based proteins do. Granted, not many studies have been done on the topic, but the general consensus is no, they don't – their biological value (BV) is just too low. BV is a measure of how efficiently the body utilizes protein.
While the Incredible Hulk is pea-green, it's unlikely that he got that way from pea protein, or for that matter, any other plant proteins. The results of a recent study on the anabolic effects of wheat protein, which is derived from turning gluten into free amino acids, seem to confirm this.
The researchers took 5 groups of 12 men between the ages of 65 and 80 and monitored muscle protein synthesis (MPS) after giving them varying amounts and types of protein. (Even though the test subjects were old, the results of the study also apply to younger people because of the basic "physics" of protein, as you'll see below.)
Thirty-five grams of wheat protein led to no significant increase in MPS, while ingestion of 35 grams of whey led to a 33% increase. Casein won the battle, though, leading to a 48% increase in MPS.
In short, ingesting 35 grams of casein or 35 grams of whey led to hugely greater MPS than an equivalent amount of wheat protein. In fact, it wasn't until the men ingested almost double the wheat protein – a 60-gram bolus – that MPS rates began to exceed that of whey.
Wheat protein, and all other known plant proteins, simply have poorer biological values (BV) than animal proteins. Plant proteins either have lower digestibility or are missing one or more crucial amino acids, specifically leucine, lysine, and/or methionine. Young or old, you'd have to eat a ton more of them to get the same effects as proteins from dairy or meat sources.
The researchers therefore concluded, astutely, that
"...the ingestion of a bolus of 60 g of protein does not represent a practical dietary strategy to stimulate muscle protein synthesis."
This is why the labels on most canisters of plant protein are deceiving. They might indicate that a serving contains 20 or 25 grams of protein, but the protein is invariably lacking in certain amino acids so that it's not as effective as protein from dairy. The plant-based 20 to 25 grams is not equal to the 20 to 25 grams you'd get in a canister of a quality whey, casein, or a whey/casein blend.
It's only if and when you begin to use huge quantities of the plant protein that you'd approach a more level playing field with dairy proteins and begin to experience equivocal levels of MPS.
But, as the authors of the described study suggest, having to dump in a couple of cups of vegetable protein into your oatmeal or protein drink might be practical if you're mixing wallpaper paste, but impractical if you're trying to gain muscle. This is especially true if you're trying to duplicate the muscle-building effects of the standard 40-gram serving of dairy-protein.
- Gorissen SH et al. Ingestion of Wheat Protein Increases In Vivo Muscle Protein Synthesis Rates in Healthy Older Men in a Randomized Trial. J Nutr. 2016 Sep;146(9):1651-9. PubMed.