Whey vs Plant Protein
Whey and plant protein powders compared for muscle and strength gains: what soy and pea trials found, what reviews of plant versus animal protein show, and allergen and product notes.
Content last updated . This page has not been medically reviewed.
The short answer
In longer training studies, soy and pea protein produced results broadly similar to whey for strength and muscle. Whey stimulates muscle protein synthesis more in short experiments, but that did not show up as a difference in gains over weeks of training in the studies below. Which is better for you depends more on allergies, digestion, diet, taste and cost than on a universal winner. For product types, see Whey protein and Plant protein powders.Evidence labels used here: evidence in adequately nourished people, mixed, promising but limited, insufficient evidence.
What the studies compared
| Question | What the source found | Strength of evidence |
|---|---|---|
| Short-term muscle protein synthesis | Acute studies indicate whey, likely because of its higher leucine content, stimulates muscle protein synthesis more than soy and casein. [1] | Short experiments, mechanism |
| Soy vs whey and other animal protein, 6+ weeks of resistance training | Meta-analysis of 9 studies (266 participants): strength increased in both groups, with no difference between groups for lean body mass or strength. [1] | Moderate for soy; small studies |
| Pea vs whey, 12 weeks | In 161 men aged 18 to 35 taking 25 g twice a day, muscle thickness trended toward group differences (P = 0.09), and strength increased with no group difference. [2] | One randomized trial; some authors list a company affiliation |
| Plant vs animal protein in adults 50 and over | 29 randomized trials (2,363 people) showed no significant differences in lean mass or handgrip strength; 25 of the 29 used soy. [3] | Moderate for soy; limited for other plants |
| Pea, rice, hemp and blends vs whey | Proper evidence not found in the sources we read for pooled analyses of non-soy plant blends. | Insufficient evidence |
Reading the table carefully
- Soy dominates the plant evidence. Most plant-versus-animal trials used soy, so conclusions for pea, rice or blends are less certain. [3]
- Industry link. Three authors of the pea trial list an affiliation with a company (Roquette), so industry involvement is possible. [2] Check who funded any study you rely on.
- Training does much of the work. In the pea trial, muscle thickness rose over time across the groups, so the training program itself drove a good part of the change. [2]
- Isolates, not whole foods. About four in five of the older-adult trials tested purified protein isolates rather than foods. [3]
Practical points
- Allergy and lactose. Whey is a milk protein, so people with a milk allergy need to avoid it unless a clinician says otherwise. Plant powders have their own allergens, such as soy. See Protein powder safety, allergens and contaminants.
- Complete proteins. How protein quality differs, and how blends can fill gaps, is covered in Protein quality and complete proteins.
- Whey isolate vs concentrate. Differences in lactose and protein concentration are covered on Whey protein.
- Medicines and conditions. If you have kidney disease or take regular medicines, check with a clinician first. See How interactions work.
- Goals. For training, see Protein for muscle, resistance training and recovery.
Frequently asked questions
Is whey better than plant protein for building muscle?
In the soy-versus-animal meta-analysis, supplementing resistance training with whey or soy increased strength with no difference between groups. [1] Evidence for other plant proteins is thinner.
Is pea protein as good as whey?
One 12-week trial in young men found no strength difference between pea and whey. [2] It is a single trial, and some authors list a company affiliation.
Do older adults get the same result from plant protein?
A review of 29 trials in adults 50 and over found no significant differences in lean mass or handgrip strength. [3]
Which is safer?
Neither is automatically safer. Allergies, product quality and your health conditions decide. See Protein powder safety.
References
- Messina M, et al. Int J Sport Nutr Exerc Metab 2018. No Difference Between the Effects of Supplementing With Soy Protein Versus Animal Protein on Gains in Muscle Mass and Strength in Response to Resistance Exercise. Read 2026-10-22.
- Babault N, et al. J Int Soc Sports Nutr 2015. Pea proteins oral supplementation promotes muscle thickness gains during resistance training: a double-blind, randomized, placebo-controlled clinical trial vs. whey protein. Read 2026-10-22.
- Foscolou A, et al. Clin Nutr ESPEN 2026. Plant-versus animal-derived protein and nutritional, cardiometabolic, and inflammatory outcomes in middle-aged and older adults: a systematic review and meta-analysis of randomized controlled trials. Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.