What’s the best protein powder for muscle gain?
Whey, or soy or pea if you skip dairy. Whey has the most research, and soy did as well across 9 trials. But the type matters less than one line on the label.
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What is the best protein powder for muscle gain?
Whey, if you eat dairy. It’s the most studied powder for lifting, and it has the most leucine. Leucine is a building block that helps switch on muscle building.
No dairy? Soy did as well as whey and other animal proteins in a review of 9 trials. In one 12-week trial in young men, pea did as well as whey.
| Powder | What trials found | Suits |
|---|---|---|
| Whey | Most research and most leucine. Digests fast. | Most people who eat dairy. |
| Casein | Digests slowly. 30 to 40 g before bed raised overnight muscle building. | A shake at bedtime. |
| Soy | Matched whey and other animal proteins in a review of 9 trials. | Vegans and people who avoid dairy. |
| Pea | Matched whey in one 12-week trial in young men. | People who avoid dairy and soy. |
| Mass gainer | Protein plus extra calories. Highest heavy metal scores in one US study, still below the risk level. | Only if you struggle to eat enough. |
Sources: ISSN; Messina 2018; Babault 2015; Bandara 2020
One review found no overall difference in lean mass or strength. But adults under 50 gained about 0.41 kg more lean mass with animal protein.
So pick the one you can afford and will actually drink. Then check the label.
How much protein should a scoop give you?
That line is protein per serving. Check it in grams, not by the size of the scoop.
Sports nutrition experts at the ISSN suggest 20 to 40 g of protein at a time. Or work it out as 0.25 g for each kg you weigh. At 80 kg, that’s 20 g.
- Below 20 g per servingLess than the ISSN suggests.
- 20 up to 40 g per servingISSN: 20 to 40 g at a time.
- Above 40 g per servingAbove the ISSN amount.
Source: ISSN
Under 20 g? Use a bigger serving, or mix it with milk. A pint of semi-skimmed milk gives you about 20 g on its own.
Spread your servings out, one every 3 to 4 hours. For your total a day, see how much protein to build muscle.
Do I need protein shakes to build muscle?
No. Most of us in the UK already eat more than enough protein, the BNF says. Even with hard training, you can still get enough from food.
A shake can help if you train hard and are short of time. Food is still better where you can, as it brings other nutrients too.
And the shake is the small part. In 49 trials, training alone added about 1.1 kg of lean mass. Extra protein added about 0.3 kg on top.
Four steps before you buy a tub
- 1
Lift first
Work all your main muscles on at least 2 days a week.
- 2
Count your protein
Add up one normal day of food.
- 3
Find the gap
Compare it with your total a day for muscle.
- 4
Fill it
Food first. A scoop covers what’s left.
New to the gym? Start with a beginner gym plan, then add a little weight over time with progressive overload.
When should I drink a protein shake?
Before or after training both work. The ISSN says the boost from a workout lasts at least 24 hours, though it likely fades with time.
So drink it when it suits you. Sooner after training may help a little more.
Want one at bedtime? Pick casein, the slow one. In young men, 30 to 40 g of casein 30 minutes before sleep raised overnight muscle building.
Pick a time you can stick to, such as straight after your session.
What should I check on the label?
Five checks before you buy a protein powder
- Find the grams of protein per serving, and look for 20 to 40 g.
- Read the first ingredient. UK lists start with the main one by weight.
- Look for allergens such as milk or soya, shown in bold or a different style.
- Check for “Excessive consumption may cause a laxative effect”. Tubs with over 10% polyols, a type of sweetener, must say it.
- Compete in a tested sport? Use only batch-tested products, and check the batch number on Informed Sport.
Sources: ISSN; GOV.UK: ingredients; GOV.UK: warnings; UKAD
UK Anti-Doping says no supplement is certain to be free from banned substances. Batch testing cuts the risk.
Worried about heavy metals or organic claims? See our clean protein powder guide.
Avoiding dairy? See dairy-free protein powder.
When to speak to a GP
For healthy people who train, the ISSN found no sign of kidney or liver harm from more protein. Some people should check first. Speak to a GP if:
- You have kidney disease. People with kidney failure do better on less protein, and too much carries risks. Ask your kidney team or GP before you add a powder.
- Milk-based shakes give you tummy pain, bloating or diarrhoea, which can be a sign of lactose intolerance (you struggle to digest the sugar in milk). Go if it keeps coming back and often happens after eating. Also go if you’ve had changes in your poo, blood in your poo, or bloating and discomfort for 3 weeks. Or if you’re losing weight without trying.
- You think you may have a food allergy, such as to milk, soya or peas.
Call 999 for a serious allergic reaction, if:
- your lips, mouth, throat or tongue suddenly swell
- you’re breathing very fast or struggling to breathe
- your throat feels tight or you’re struggling to swallow
- your skin, tongue or lips turn blue, grey or pale
- you suddenly feel very confused, drowsy or dizzy
- someone faints and cannot be woken up
- a child is limp, floppy or not responding like they normally do
Want to know how your kidneys are doing? See our kidney function test guide.