A vegan diet can be as good as an omnivore diet for gains in muscle mass and strength when an adequate amount of protein is consumed. However, for vegans who do not necessarily consume a very high protein, is the current protein-recommended dietary allowance appropriate?
Overview
What did they test? The authors explored the effects of a 5-day vegan diet adhering to the recommended dietary allowance on nitrogen balance.
What did they find? The current recommended dietary allowance (0.8 grams per kilogram of body weight) was not enough to maintain a positive nitrogen balance in vegans.
What does it mean for you? Aside from aiming to consume around 1.6 grams of protein per kilogram of body weight, it is recommended to prioritize high-quality plant-based protein sources when you cannot eat more protein.
What’s the Problem?
The amount of people following a vegan diet has substantially increased in the last 5 years, with a U.S.-based survey finding that approximately 5% of people are vegans and a U.K.-based survey finding that approximately 3% of people are vegans. Following a vegan diet can be great for health, given that vegan diets are usually rich in whole foods, including plenty of fruits and vegetables; however, an omnivore diet that includes plenty of fruits and vegetables can be as healthy.
As we’ve discussed, following a vegan diet can be as good as an omnivore diet for muscle gain. A recent study by Monteyne et al. 1 found that a vegan diet resulted in the same muscle growth, muscle protein synthesis, and one-repetition-maximum increases as an omnivore diet in healthy young adults. Similarly to the findings of the Monteyne et al 1 study, Hevia-Larrain et al 2 also found that a high-protein vegan diet is equally beneficial to a protein-matched omnivorous diet for muscle mass and strength.
It’s important to note that although a vegan diet can be as good as an omnivorous diet in promoting muscle and strength gains, vegan protein sources can often have a lower biological value and an incomplete amino acid profile, which requires anyone who is following a vegan diet to be a bit more vigilant with their protein intake and sometimes even the sources of protein they choose. For example, someone who is an omnivore and consumes different types of meat and fish, as well as dairy products, gets high-quality protein daily without having to think about it. For example, in the Hevia-Larrain et al 2 study mentioned above, the researchers had participants supplement with soy protein isolate on top of their usual food intake, as soy protein is a complete source of protein, with studies showing that it can be as effective as whey protein for muscle growth when matched for leucine content 3. When they matched the two groups for leucine content, the soy protein group consumed 26 grams of protein versus 19 grams of protein that the whey group consumed, so not really a huge difference.
The current recommended dietary allowance (RDA) for adult protein intake is 0.8 grams per kilogram of body weight per day, based on a plethora of nitrogen balance studies 4.
Since protein is the only macronutrient that contains nitrogen, you can think of nitrogen balance as a seesaw for protein in your body. If you eat enough protein to match what your body uses and gets rid of, the seesaw stays level, and you're in good balance. This means your body is neither gaining nor losing protein.
If you eat more protein than your body needs, the seesaw tilts towards the high end, indicating you're storing extra protein, which can be helpful for growth or recovery.
