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At the 1936 Olympics in Berlin, a scientist named Paul Schenk surveyed the eating habits of top athletes from around the world. The Canadians reported plowing through more than 800 grams of meat per day on average; the Americans were downing more than two litres of milk daily.

While there have been plenty of changes in sports nutrition since then, the belief that meat and dairy are the best fuel for building muscle persists. These days, though, a growing number of athletes are interested in reducing or eliminating their reliance on animal proteins, for environmental, ethical or health reasons. A pair of new studies bolsters the case that it’s possible to rely on plant proteins without sacrificing training gains, as long as you pick your proteins carefully.

The standard objection to plant proteins is that they don’t have the right mix of essential amino acids needed to assemble new muscle fibres. Unlike animal proteins, most plant proteins are missing or low in at least one essential amino acid.

In particular, there’s one specific amino acid, leucine, that seems to play a special role in triggering the synthesis of new muscle. It’s particularly abundant in whey, one of the two proteins (along with casein) found in milk. That’s why whey protein is the powdered beverage of choice in gyms around the world, backed by decades of convincing research, which was often funded by the dairy industry.

But one of the reasons whey looks so good may be that we haven’t fully explored the alternatives. A 2018 study by Luc van Loon of the University of Maastricht in the Netherlands, for example, tested nine vegetable proteins including wheat, hemp, soy, brown rice, pea and corn. To their surprise, they found that corn protein contains 13.5 per cent leucine – even more than whey.

Based on that insight, van Loon decided to pit corn against milk in a direct test of muscle protein synthesis. Volunteers consumed 30 grams of one of the proteins; a series of blood tests and muscle biopsies were collected over the next five hours to determine how much of the ingested protein was being turned into new muscle fibres. The results, which appeared in the journal Amino Acids, were straightforward: Despite all the hype about whey, there was no discernible difference between them.

A second study, this one published in Medicine & Science in Sports & Exercise by a team led by Benjamin Wall of the University of Exeter in Britain, had similar findings. Instead of corn, it used a mix of 40 per cent pea, 40 per cent brown rice and 20 per cent canola proteins. Since different plants have different amino acids profiles, mixing complementary proteins has long been suggested as a way overcoming the deficiencies of any single plant protein. Sure enough, the protein blend triggered just as much new muscle synthesis as whey.

On the surface, the message from these studies is straightforward: Plant proteins are – or at least can be – as effective as even the best animal proteins for supporting muscle growth. There are a few caveats to consider, though. One is that the studies used isolated protein powders rather than whole foods. You would need nearly nine cobs of corn to get the 30 grams of protein used in van Loon’s study, compared to just three-and-a-half cups of milk.

Another is that plants are generally harder to digest, meaning that not all the amino acids will be usable. That may not be a problem for healthy young adults consuming 30 grams of protein at once, which is enough to trigger a near-maximal muscle response. But for older people, who tend to have blunted muscle-building responses to protein, or in situations where you’re getting a smaller dose of protein, the details of protein quality may become more important.

Of course, the effectiveness of plant proteins won’t be news to notable plant-based athletes such as ultrarunner Scott Jurek or basketball star Chris Paul – but it’s encouraging to see the science finally begin to catch up.

Alex Hutchinson is the author of Endure: Mind, Body, and the Curiously Elastic Limits of Human Performance. Follow him on Threads @sweat_science.

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