Protein quality for vegans

Challenges and concerns for people who get their protein from plant-based sources.

Last updated: May 7, 2024

Conflicts to declare: None.

Please remember to consult with a healthcare provider prior to undertaking any of the protocols available here.

What's the issue with vegan protein relative to animal protein?

• In short: quality and bioavailability. Vegan protein doesn't have the same amino acid profile as animal protein, and it's not absorbed as effectively.

• In many cases, for the sake of practicality (e.g. total volume of food and/or total calories consumed), supplementation with vegan protein powder can help to close the gap.

• Some have raised concerns about heavy metal exposure in protein powders due to bioaccumulation associated with the preparation of animal or plant protein powders (which concentrate protein from a base animal or plant material). This study ran some simple calculations to suggest that consuming three servings of protein powder a day - ("a typical intake") would not result in adverse health effects due to heavy metals.

Okay, I understand the general principles at play. How do I put this into practice?

• For all vegans, aim for:

  • 3-4 grams of leucine per day.

  • 3-4 grams of lycine per day.

• For vegans who only need to maintain muscle mass, aim for:

  • At least 1 gram of methionine per day.

• For vegans who need to gain muscle mass, aim for:

  • 2 to 3 grams per serving, four times per day.

More on the differences between animal protein and plant protein:

From Chapter 15 of Peter Attia's Outlive:

Now, a word on plant protein. Do you need to eat meat, fish, and dairy to get sufficient protein? No. But if you choose to get all your potein from plants, you need to understand two things. First, the protein found in plants is there for the benefit of the plant, which means it is largely tied up in indigestible fiber, and therefore less bioavailable to the person eating it. Because much of the plant's protein is tied to its roots, leaves, and other structures, only about 60 to 70 percent of what you consume is contributed to your needs, according to Don Layman, professor emeritus of food science and human nutrition at the University of Illinois Urbana-Champaign, and an expert on protein.

Here we run into the first issue with plant protein: it's less bioavailable than animal protein partly because it is embedded in indigestible fibre. For plant protein powders, there is no indigestible fibre to prevent absorption, but according to other metrics (DIAAS & PDCAAS), it is still not as high quality.

Attia goes on to explain why:

Some of this can be overcome by cooking the plants, but that still leaves us with the second issue. The distribution of amino acids is not the same as in animal protein. In particular, plant protein has less of the essential amino acids methionine, lysine, and tryptophan, potentially leading to reduced protein synthesis. Taken together, these two factors tell us that the overall quality of protein derived from plants is significantly lower than that from animal products.

Here's where the nuance around plant protein supplementation comes in:

The same is true of protein supplements. Whey protein isolate (from dairy) is richer in available amino acids than soy protein isolate. So if you forgo protein from animal sources, you need to do the math on your protein quality score. In truth, this can get pretty complicated pretty quick, because you get wrapped around the axle of something called the Digestible Indispensible Amino Acid Score (DIAAS) and the Protein Digestibility-Corrected Amino Acid Score (PDCAAS). These are great if you ahve the time to comb through databases all day, but for those of us with day jobs, Layman suggests focusing on a handful of important amino acids, such as leucine, lycine, and methionine. Focus on the absolute amount of these amino acids found in each meal, and be sure to get about three to four grams per day of leucine and lycine and at least one gram per day of methionine for maintenance of lean mass. If you are trying to increase lean mass, you'll need even more leucine, closer to two to three grams per serving, four times per day.

Disclaimer: The information provided on this page is for general informational purposes only and does not constitute the practice of medicine, nursing or other professional health care services, including the giving of medical advice, and no healthcare-provider/patient relationship is formed. The content of this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment and the use of this information is provided. Prior to taking any action based on the information on this page, you should speak to your licensed healthcare provider. Our licensed PHC-Nurse Practitioner coaches can assist you with individualized implementation of this protocol and others.