How to Evaluate Your Protein Powder
There are several protein scoring systems. Here's the one that lifters should pay attention to.
Evaluating the quality of a protein comes down to bioavailability and amino acid profile. Bioavailability refers to how much of a particular protein you absorb. To figure this out, scientists give test subjects carefully measured amounts of protein, wait for them to poop, then measure how much nitrogen is in it.
They then use the amount of nitrogen detected to calculate how much protein was in the poop and compare it to how much was ingested. The final number is referred to as the BV, or biological value.
BV, PDCAAS, and DIAAS
The BV calculation wasn't very good because it neglected some basic human dietary mechanics. First, if the protein is fast-acting, like whey, some can be converted to glucose, particularly if you've been on a low-carb diet. Secondly, bacteria in the gut tend to "steal" some of the protein. While BV is a little outdated, protein manufacturers use it occasionally to play the "our protein is better than yours" game.
The currently accepted protein evaluation standard, used by the FDA, is the PDCAAS, or Protein Digestibility Corrected Amino Acid Score, which combines biological value with a protein's amino acid profile.
Some proteins have practically everything a human needs to sustain tissue growth. We call them "complete" proteins. They have a nearly perfect blend of essential amino acids (those we can't make ourselves) and branched-chain amino acids (BCAAs), important to muscle growth.
Other proteins are missing certain amino acids or have lousy amounts of BCAAs. Unfortunately, the PDCAAS isn't the best way to gauge a protein's quality, either. To calculate it, the scientists again measure and calculate excreted nitrogen, but the PDCAAS, like the BV, doesn't consider any protein eaten up by the bacteria in the gut.
It also requires that test subjects have an empty stomach, which exposes the test to all kinds of inaccuracies. Any food in the belly would slow down the protein's absorption or bind up some of that protein if the food has a high fiber content.
That leaves a relatively new scale: the Digestible Indispensable Amino Acid Score, or DIAAS. It measures the nitrogen content of the small intestine instead of the nitrogen in the feces. This allows researchers to get a more realistic evaluation of a protein's bioavailability because the measurement occurs before all those bacteria munch up a lot of the ingested protein. It also considers the digestibility of each amino acid instead of the overall protein. It's currently the best scoring system in use.
Got all that? If not, it doesn't matter so much. What's important is to choose the best protein based on your needs and our current best guesses as to which supports muscle and tissue growth the best.
So, How do the Various Proteins Rate?
Plant-derived proteins are the fastest-growing sector in the protein powder business. At first glance, it makes sense.
Anything associated with plants is instinctively thought to be healthier, but the thinking is a bit two-dimensional: these plant-protein fans aren't actually eating plants, but the amino acids left over when the water, fiber, chlorophyll, polyphenols, vitamins, and minerals are extracted. Your cotton underwear are probably closer in composition to an actual plant in nature than a scoop of plant-derived protein.
Also, the amino acid profile of plants isn't the same as what you'd find in human muscle. Sure, most of the amino acids are there, but usually not in the amounts you'd need to support optimal muscle growth. That said, pea and soy protein come close to being complete.
The PDCAAS shows pea protein at an impressive 0.893, while soy proteins rate from 0.95 to 1.00, depending on how they were processed. That means that pea protein is close to the highly desirable 1.0 score that most animal proteins come close to, while soy protein is neck-and-neck with them.
That's a little misleading, though. The PDCAAS must grade on a curve because they actually truncate the numbers. If they didn't do that, whey protein isolate would score 1.2 on the scale and milk protein a tad higher, meaning they're complete-PLUS.
Of course, if you compare proteins on the more sensible DIAAS scale, pea and soy protein get scores of 0.822 and 0.902, respectively, while whey protein isolate and milk protein concentrate score a superior 1.09 and 1.18.
The DIAAS shows pea and soy scoring lower than the two classic milk proteins, whey and casein, because they're a little short on the amino acid methionine and they don't quite pack the same BCAA punch as the milk (and meat-based) proteins.
Pea and soy proteins are also really high in sodium, if that's a concern. They use salt in the distillation process and a lot of it remains in the final product.
Meat Proteins are Neither Perfect nor Complete
Beef protein powders aren't common, but they seem to have a loyal customer base consisting mostly of Paleo-diet types. The assumption is that these proteins, being made from the meat of actual animals, are highly suited to building muscle in people who use them.
Not so much. These proteins are usually made mostly of the skin, bone, tendons, and other connective tissues. What you're getting is boiled-down collagen, the same stuff in Jell-O. That's not to say collagen doesn't have its merits (healthier joints, skin, etc.), but it's not the best for building muscle and it's lacking in BCAAs. While beef protein from an actual cow has a PDCAAS of .92, collagen scores 0.00.
So, What's the Verdict?
Whey isolate and milk proteins (casein, specifically) appear to be the best for muscle-building purposes, regardless of what scale you use.
Traditionally, whey protein isolate has been used for peri-workout periods as it's absorbed rather quickly, whereas casein is often preferred for all other times as it digests slowly and supplies a steady stream of amino acids. Of course, whey protein also contains some interesting immunoglobulins that appear to contribute to human health.
Given all that, it looks like a blend of fast-acting whey protein isolate and slow-digesting micellar casein (like Metabolic Drive (Buy at Amazon)) is best for strength athletes and physique athletes.
Vegetarians, however, are best served by pea protein, as soy protein often contains phytoestrogens that may affect human physiology. While the amount of these phytoestrogens is small – much less than you'd find in soy itself or soy flour – the cumulative effects can't be discounted.
References
- Hughes GL et al. "Protein Digestibility-Corrected Amino Acid Scores (PDCAAS) for Soy Protein Isolate and Concentrate: Criteria for Evaluation." J Agric Food Chem. 2011 Dec 14;59(23):12707-12. PubMed: 22017752.
- Mathai JK et al. "Values for digestible indispensable amino acid scores (DIAAS) for some dairy and plant proteins may better describe protein quality than values calculated using the concept for protein digestibility-corrected amino acid scores (PDCAAS)." Br J Nutr. 2017 Feb;117(4):490-499. PubMed: 28382889.
- Marinangeli CPF et al. "House Potential impact of the digestible indispensable amino acid score as a measure of protein quality on dietary regulations and health." Nutr Rev. 2017 Aug 1;75(8):658-667. PubMed: 28969364.
- Schaafsma G. "The Protein Digestibility-Corrected Amino Acid Score." TJ Nutr. 2000 Jul;130(7):1865S-7S. PubMed: 10867064.
- Wolfe RR et al. "Protein quality as determined by the Digestible Indispensable Amino Acid Score: evaluation of factors underlying the calculation." Nutr Rev. 2016 Sep;74(9):584-99. PubMed: 27452871.