Ask this question in a supplement store and you get an opinion. Ask it of the research and you get something more useful: it depends on the dose.
The reason whey has the reputation comes down to one amino acid. Leucine is the trigger for muscle protein synthesis, and after 50 that trigger has a stiffer spring — the effect researchers call anabolic resistance. Whey runs roughly 10 to 11 percent leucine and digests fast, so it produces a sharp spike in blood leucine. Pea and soy protein land closer to 8 percent and move more slowly. On paper, whey holds the advantage.
What happens when you actually test it
The most relevant trial for this audience came out of McMaster University in 2024. McKendry and colleagues gave older men whey, pea, or collagen protein above the RDA and measured muscle protein synthesis integrated over days rather than hours. Whey and pea produced similar results. Collagen fell behind, which is worth remembering if collagen is currently your protein plan — it is a poor choice for muscle.
The catch shows up in the short-window studies. When researchers compare a single modest serving — around 20 grams — a plant blend without added leucine tends to underperform whey. Fortify the plant protein with leucine, or simply give more of it, and the gap closes.
Put those two findings together and the practical rule is simple. Over a full day, at adequate intake, plant protein does the job. Inside a single serving, whey is more efficient. So if you are using plant protein, take a bigger scoop — roughly 20 to 25 percent more — or choose a blend with added leucine.
Which one should you buy?
- Whey isolate — highest leucine per gram, very low lactose, fast digesting. The default if dairy sits well with you.
- Whey concentrate — cheaper, slightly more lactose and fat. Fine for most people.
- Casein — the slow dairy protein. Its one genuine edge is before bed, covered below.
- Pea, or a pea and rice blend — the plant pick with real trial support in older adults. Aim for 25 to 30 grams per serving rather than 20.
- Collagen — good for what it is sold for elsewhere, poor for muscle. Do not count it toward your protein target.
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Send it to me →The one time casein clearly wins
A randomized controlled trial by Kouw and colleagues gave healthy older men protein before sleep and measured overnight muscle protein synthesis. It went up. Sleep is a long stretch without protein — often ten hours between dinner and breakfast — and a slow-digesting dose gives the muscle something to work with through it.
This is a small win, not a magic trick. If you are already hitting your daily total, a pre-bed serving of casein or a cup of cottage cheese is a reasonable last 10 percent. If you are 40 grams short every day, fix breakfast first.
What none of this changes
The type of protein is a rounding error next to the total. PROT-AGE recommends healthy older adults take in 1.0 to 1.2 grams per kilogram of body weight daily, more if active, alongside resistance training. Someone eating chicken, eggs and lentils to that number will do better than someone with the world's best powder and half the intake.
- Hit the daily total first.
- Get 25 to 40 grams in each sitting.
- Pick the protein you will actually take every day.
- Lift twice a week, minimum.
Not sure what your total should be? Run the protein calculator →
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Where these numbers come from
- McKendry J, et al. Whey, pea and collagen protein and myofibrillar protein synthesis in older males (AJCN, 2024)
- Kouw IWK, et al. Protein ingestion before sleep increases overnight muscle protein synthesis in older men (J Nutr, 2017)
- Salles J, et al. Circulating amino acids after pea or whey protein in young and older adults (Nutrients, 2024)
- Ely IA, et al. A focus on leucine in older adults (Clinical Nutrition, 2023)
- Bauer J, et al. PROT-AGE Study Group position paper (JAMDA, 2013)