In 30 seconds
- The EU authorises three claims for protein, including this one: “Protein contributes to a growth in muscle mass.”
- Across 49 trials, taking extra protein during strength training added an average of 2.5 kg more to maximal strength and 0.3 kg more lean mass.
- Above about 1.6 g per kg of body weight a day, no further gain in muscle mass was seen.
- EFSA considers it safe to take up to twice its reference intake of 0.83 g per kg.
Protein is the supplement with the most solid foundation, and also one of those surrounded by the most myths: that you need huge amounts, that it damages your kidneys, that without a shake there is no muscle. This is what the studies say.
Level of evidence by outcome
| Outcome | Evidence | What the data show |
|---|---|---|
| Growth in muscle mass | High | Authorised EU claim for foods that are at least a source of protein. |
| Maintenance of muscle mass | High | Authorised EU claim. |
| Maintenance of normal bones | High | Authorised EU claim. |
| More strength and muscle with training | Moderate | Small but consistent effect across 49 trials, larger in trained people. |
| More than 1.6 g per kg a day | No clear effect | No further gain in muscle mass above that point, with a lot of uncertainty. |
The rating is our own, based on the number of studies, their quality and the consistency of the results.
The key studies
| Study | Type | Sample | Outcome |
|---|---|---|---|
| Morton et al., 2018 | Meta-analysis | 49 trials, 1,863 people | With strength training, extra protein added 2.49 kg to maximal strength and 0.30 kg of lean mass. No further gain above 1.62 g/kg a day. 1 |
| Jäger et al. (ISSN), 2017 | Position stand | International Society of Sports Nutrition | 1.4-2.0 g/kg a day for most people who exercise, in servings of 20-40 g with 700-3,000 mg of leucine. 2 |
| EFSA, 2012 | Reference values | Expert panel | 0.83 g/kg a day for adults, including older adults. Up to twice that amount is considered safe. 3 |
What the regulations authorise
For foods that are at least a source of protein, the EU authorises these claims 5:
- Protein contributes to a growth in muscle mass.
- Protein contributes to the maintenance of muscle mass.
- Protein contributes to the maintenance of normal bones.
A varied and balanced diet and a healthy lifestyle are important.
Grams per kilo of weight a day
Daily protein: the general reference and if you train
How much you need
- If you do not train: EFSA sets a reference intake for adults, including older adults, of 0.83 g per kg of body weight a day 3. According to EFSA, the average intake of European adults is usually at or above that reference 3.
- If you train: the International Society of Sports Nutrition considers 1.4-2.0 g per kg a day sufficient for most people who exercise, in servings of 20-40 g with 700-3,000 mg of leucine 2.
Work out yours with our protein calculator.
Meta-analysis of 49 trials
What extra protein added to strength training
The large meta-analysis: 49 trials
One meta-analysis pooled 49 trials with 1,863 people doing strength training. Those who took extra protein, about 36 g a day on average, gained 2.49 kg more in their maximal strength and 0.30 kg more lean mass than those who did not 1.
Three important nuances 1:
- It adds to training. What counts most is doing strength training and reaching your daily protein.
- There is a ceiling. Above about 1.62 g per kg a day no further gain in lean mass was seen, although with a lot of uncertainty: the authors suggest up to 2.2 g per kg for anyone who wants to be sure.
- With age, the effect was somewhat smaller. But older participants were given low doses, of about 20 g a day, and the authors call for studies with more protein.
Safety
- Amount: EFSA considers it safe to take up to twice its reference intake, about 1.7 g per kg a day, an amount many active adults already get from their diet 4.
- Kidneys: if you have kidney disease, check with your doctor before increasing your protein.
- Allergies: whey protein comes from milk.
What about our protein?
Our Gourmet Isolate Protein is whey protein isolate with a chocolate flavour: 42.8 g of protein per 50 g serving, with 0.2 g of sugars.
Frequently asked questions
What is protein good for?
“Protein contributes to a growth in muscle mass.” “Protein contributes to the maintenance of muscle mass.” “Protein contributes to the maintenance of normal bones.”
How much protein should you take if you train?
The International Society of Sports Nutrition considers 1.4-2.0 g per kg of body weight a day sufficient for most people who exercise. A meta-analysis found no further muscle gain above about 1.6 g per kg.
Is it bad to take a lot of protein?
EFSA considers it safe to take up to twice its reference intake of 0.83 g per kg, that is, about 1.7 g per kg a day, an amount many active adults already get from their diet. If you have kidney disease, check with your doctor.
Does protein powder work the same way after 40?
In the meta-analysis of 49 trials, the effect on muscle mass was somewhat smaller with age. The authors point out that older participants were given low doses, of about 20 g a day, and call for studies with more protein.
Sources
- Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018;52(6):376-384. View publication
- Jäger R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20. View publication
- EFSA. EFSA sets population reference intakes for protein. Press release, 9 February 2012. View publication
- EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific opinion on dietary reference values for protein. EFSA Journal. 2012;10(2):2557. View publication
- Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. View publication
Information based on published studies. It does not replace the advice of a doctor or registered dietitian. The results describe what was measured in each study, not the properties of any specific product.
