Protein supplements: what they add to food for strength and endurance

On this page

1. What they add
2. Total intake, not the product
3. Endurance
4. Limits and product
5. How we reviewed it
6. Sources

What they add

Strength exercise and ingested protein both stimulate muscle protein synthesis, and they act synergistically when protein is taken before or after training.² The Morton et al. meta-analysis (2018) confirms a small but significant benefit of supplementing during strength programmes of at least 6 weeks in healthy adults: maximal strength +2.49 kg (95% CI 0.64-4.33), lean mass +0.30 kg (0.09-0.52).¹ These are group averages: they do not say how much you will gain.

Total intake, not the product

• Total intake: in the meta-analysis average lean-mass gains with supplementation did not increase beyond an estimated total intake of about 1.62 g/kg/day.¹ It is an estimated point on group averages, not a threshold for every person: it does not say the supplement helps below that value, nor that it cannot be useful above it.
• Age and training: the effect on lean mass falls with age and is larger in people with training experience.¹
• Timing: for the ISSN the best timing is probably a matter of individual tolerance, since benefits come both before and after; the anabolic effect of training lasts at least 24 hours but tends to fade with time.²
• Food or powder: the ISSN recognises that requirements can be met from food; a supplement is a practical way to secure quality and quantity without too many calories, for example with high training volumes. It also advises favouring foods with all the essential amino acids.² The AIS treats isolated protein as a sports food, not as an ergogenic aid.⁴

Endurance

For runners, cyclists and swimmers the ISSN position stand says the priority is adequate carbohydrate, and that adding protein may help reduce muscle damage and aid recovery.² It is not proof of better race performance. For race carbohydrate use Fuel. On BCAA and EAA see the supplements map; free-form EAA are covered there.³

Limits and product

• The sources concern healthy people who train. With medical conditions, in pregnancy or with medicines, see a doctor.
• One author of the meta-analysis declares funding from the National Dairy Council, which supported trials included in the analysis: this is a declared conflict of interest.¹
• Anti-doping and contamination: the WADA list changes every year and an unchecked product can contain banned substances.⁵⁶ WOLF LAB does not certify products or batches and does not recommend brands.

How we reviewed it

Document review: Morton 2018 meta-analysis (abstract and text), 2017 ISSN position stand, 2023 ISSN EAA, AIS and WADA pages. Not every full text. No WOLF LAB tests.

Limits. Small group-average effects. 2017 ISSN position stand. One author declares National Dairy Council funding. No dose or product. Not medical advice.

Sources

1. Morton RW 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. British Journal of Sports Medicine, 2018. PubMed.
2. Jäger R et al. International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr, 2017. PMC.
3. Ferrando AA et al. ISSN position stand: essential amino acid supplementation on skeletal muscle and performance, 2023. PMC.
4. AIS (Australian Sports Commission). Sports supplements, Group A. AIS.
5. WADA. The Prohibited List. WADA.
6. Maughan RJ et al. IOC consensus statement: dietary supplements and the high-performance athlete. British Journal of Sports Medicine, 2018. PMC.

Sources read on 31 October 2026: abstracts and main sections (ISSN 2017 in part of the text), not every full text. The ISSN position stand dates from 2017: a more recent one was not read. General information, not medical advice. No WOLF LAB tests.

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