The protein myth busted colon DIAAS rankings, bioavailability and plant-based muscle

Meat Eaters love to ask about protein: how do you get enough?; isn't it low quality protein?; isn't it less bio-available?; Isn't it all ultra processed?

We already know we can get plenty of protein from Whole Foods and minimally processed sources like tofu vital wheat gluten etc

But to the rest of those questions we still have good research.  Let's start with protein quality and availability. 

The bioavailability of protein is measured in something called DIAAS. This is the digestible indispensable amino acid score.  And in 2017 Marinangeli et al  published a paper in Nutrition Reviews explaining how this method does not work for a plant-based diet.

• Foods are tested in isolation. The consequence of this is that any protein source that is lower in a particular essential amino acid ends up ranking low. 

  • The problem is we don't eat foods in isolation.

  • We eat a complete diet from a variety of sources

  • The dias score cannot look at the digestibility of a complete diet.

• The test is done on pigs and sometimes rats

  •  humans are neither of those animals

• Food are normally tested raw (but not always)

  • But humans fry, bake, boil and even ferment their food. This can change the availability of the protein

That's all a bit technical and it might be easy to dismiss if we just said “well there are some flaws in the methodology”. So the next question is do we have evidence of protein deficiency in plant-based people undertaking physical exercise. That might look like significantly slower progress or ill health.  and the answer is open "no".

In fact we have evidence of quite the opposite: there is no difference when comparing vegans and omnivores who are training.

In 2021 Hevia-Larraín et al  published a randomized control trial on 38 untrained men going on two weeks of training,  splitting them in two vegans and omnivores on a diet of 1.6g protein per kilogram of body weight.

They found no difference in lean body mass, muscle biopsies, one rep max is on the leg press and the bench press. And that basically means no difference in muscle hypertrophy or strength.