Stand in front of the protein shelf and the choice looks technical: whey concentrate, whey isolate, pea, soy, rice, hemp, blends of all of them, and a price range of about three to one. The honest summary of the research is that when the daily protein total is matched, the source has a small influence on the result and the total has a large one. There are still real differences between whey and plant protein, and they matter most at the margins: dose, digestion and what you are willing to keep drinking.
Protein quality matters most in muscle that has stopped responding strongly to a normal meal, which is the situation PhysioHub's guide to rehab for seniors deals with throughout.
Whey has a modest edge per gram. It is absorbed quickly, and it is unusually rich in leucine, the amino acid that acts as the trigger for muscle protein synthesis. Most plant proteins are lower in leucine and short on at least one essential amino acid, so a given scoop does slightly less work.
That edge closes with dose and blending. A larger serving of pea protein, or a pea and rice blend, delivers the same leucine and the same complete amino acid profile as a smaller serving of whey. Soy is complete on its own.
For anyone who is not chasing the last few percent of a competitive result, the deciding factors are usually digestive comfort, lactose, cost per 20g of protein, and taste. Choose the one you will actually finish the tub of.
Leucine content. Muscle protein synthesis switches on when a meal delivers enough leucine, somewhere around 2.5 to 3g. Whey is roughly 10 to 11% leucine, so a 25g serving clears the threshold comfortably. Pea protein is around 8%, rice protein lower still, so the same scoop lands closer to the line.
Completeness. Whey, casein, soy and egg contain all nine essential amino acids in useful proportions. Pea protein is low in methionine, rice protein is low in lysine, and each covers the other's gap, which is why pea and rice blends exist.
Digestibility. Scored by DIAAS, the current measure of how much of a protein is actually absorbed and usable, dairy proteins score highest, soy sits in the middle, and most other plant isolates score lower. Some of that gap is closed by processing, since isolates strip out the fibre and antinutrients that slow absorption in whole legumes.
Speed. Whey empties from the stomach quickly and produces a sharp rise in blood amino acids. Casein clots and releases slowly over hours. Plant isolates sit in between. This matters far less than the marketing suggests, since what governs the daily result is the daily total.
The question has been tested directly. A 2021 systematic review and meta-analysis in Nutrients by Lim and colleagues pooled randomised controlled trials comparing animal and plant protein supplementation, 18 studies in the review and 16 in the meta-analysis.
Protein source did not affect changes in absolute lean mass or in muscle strength. Both soy and animal proteins produced significant increases in bench press and squat one-repetition maximum in people doing resistance training, with no significant difference between them. There was a small favouring effect of animal protein on lean mass expressed as a percentage, which is the residue of the leucine and digestibility differences described above.
Read alongside the 2018 BJSM meta-analysis showing that supplementation stops adding anything above about 1.6g per kilogram per day, the practical hierarchy is clear: hit the daily total first, then worry about the source.
Three adjustments do almost all of the work.
Whole plant foods are worth counting too. Lentils, beans, tofu and wholegrains contribute meaningfully to a daily total, and they bring fibre with them.
Cost per 20g of protein. This is the number to compare, rather than the price of the tub. Divide the price by the number of servings, then adjust for the protein per serving. Whey concentrate is usually the cheapest way to buy protein in the UK, and whey isolate the most expensive per gram for a benefit most people cannot detect.
Lactose. Whey concentrate retains some lactose and causes bloating in a minority of people. Whey isolate has very little, and plant proteins have none, which is a genuine reason to switch.
Third-party testing. Supplements sit outside the regulation that applies to medicines, and contamination with substances not on the label is a documented problem. Anyone subject to drug testing in sport should use products batch-tested under a scheme such as Informed Sport. It is a reasonable precaution for everyone else too.
What is in it besides protein. Check the protein per 100g. Products in the 70 to 90% range are mostly protein; products in the 50s are carrying a lot of sugar, thickener or flavouring you are paying protein prices for.
For most people, no. Protein powder is a convenience food: a fast, cheap, portable 20 to 25g that helps a daily total add up. It has no property that food does not have.
It earns its place in three situations. When appetite is poor, which is common after surgery and during illness, a drink goes down when a meal will not. When the daily target is genuinely high, as in a heavier person training seriously, food alone becomes a lot of chewing. And when the day is structured so that one meal is reliably missed, a shake is a more realistic fix than a lifestyle change.
Outside those, the money is better spent on the food that would have provided it anyway.
The question that gets asked in the room, almost word for word, is "which one should I be buying?" It usually arrives after twenty minutes of shelf-reading and a recommendation from someone at the gym.
The answer that helps is a reframe of the question. When someone rebuilding after a shoulder repair or a knee reconstruction writes down what they actually ate last week, the shortfall is almost never in the quality of the protein and almost always in how much of it arrived before mid-afternoon. Swapping whey for pea moves the result by a percent or two. Adding 25g of protein to breakfast moves it by considerably more, and it costs nothing. At PhysioHub in Uckfield, that is the conversation the powder question usually turns into.
If you are rebuilding after an injury or an operation and want the loading and the recovery planned together, booking an assessment is the place to start.
Is whey protein better than plant protein?
Slightly, per gram, because of its leucine content and digestibility. In trials where the daily protein total is matched, the difference in lean mass and strength gains is small enough that most people will not notice it.
Is plant protein enough to build muscle?
Yes. Soy and plant blends produce significant strength gains alongside resistance training, with no significant difference from animal protein in the pooled trial evidence.
How much plant protein should I take instead of whey?
Around 30 to 40g of a pea or blended plant powder in place of 25g of whey, which brings the leucine content into line.
Which plant protein is the most complete?
Soy on its own, or a pea and rice blend, which cover each other's shortfalls in methionine and lysine.
Does whey cause bloating?
Whey concentrate contains some lactose and does upset a minority of people. Whey isolate contains very little, and plant proteins contain none.
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