Plant protein and whey get argued about as if one must be the right answer for everyone. The research says something more useful: for building muscle, the gap is small once you match the dose, and the real differences are digestion, allergies and the environment.
This guide compares them on those points, with links to the studies, so you can pick by your body and your goals.
Quick Answer: Plant Protein vs Whey
For muscle, whey has a small edge per gram. In long-term training studies, the source makes little difference to strength and a small difference to lean mass. Whey digests quickly and has a bit more leucine per gram of protein. A 2021 meta-analysis found that animal versus plant protein did not change absolute lean mass or strength gains, though animal protein did better for percent lean mass in adults under 50. Choose whey if you tolerate dairy and want the most efficient scoop. Choose plant protein if you avoid dairy, are lactose intolerant or want a lower environmental footprint. Many people use both.
What Is Plant Protein?
Plant protein powders are made from sources such as peas, rice, soy, hemp and canola. They contain no dairy. Pea protein is lower in methionine and rice protein is lower in lysine, which is why many brands combine them. Func Lab's Plant Protein uses pea and rice protein isolate, with bromelain and papain digestive enzymes and no gums or anti-caking agents. A scoop gives about 27 to 29 g of protein.
What Is Whey Protein?
Whey is a milk protein left over from cheesemaking. It contains all nine essential amino acids and digests quickly, which is why it became the gym default. It comes in two main forms. Whey concentrate keeps some lactose and fat and gives about 22 to 25 g of protein per Func Lab scoop. Whey isolate is filtered further, with more protein per scoop (29 to 30 g in Func Lab's) and less lactose. Our beginner's guide to protein powders covers the types in more detail.
Muscle Building: Where Whey Leads and Where It Does Not
Whey has a small advantage per gram. It contains roughly 10 to 11% leucine, the amino acid that signals muscle protein synthesis, against about 8 to 8.5% in pea protein. Around 2.5 g of leucine per meal is often cited as a useful target, though it is a guideline, not a hard cutoff. A pea-based serving needs to be somewhat larger to deliver the same leucine as whey.
The studies show that dose matters more than source:
- Plant blend versus whey. In a randomized, double-blind crossover trial of 10 resistance-trained adults, 32 g of a pea, brown rice and canola protein blend produced muscle protein synthesis equivalent to whey after exercise. Blood essential amino acids were about 44% higher after whey, so the two are not identical in every measure (van der Heijden et al., Medicine & Science in Sports & Exercise, 2024).
- Soy versus whey over 12 weeks. In a randomized trial of untrained men and women, 19 g of whey isolate and 26 g of soy isolate, both giving 2 g of leucine, produced comparable gains in lean mass and strength. Note that the soy serving was larger (Lynch et al., Int J Environ Res Public Health, 2020).
- Lean mass and strength. A meta-analysis of 16 randomized trials found that protein source did not change absolute lean mass or strength. Animal protein did better for percent lean mass, and adults under 50 gained about 0.4 kg more lean mass on animal protein (Lim et al., Nutrients, 2021).
- Short-term protein synthesis. A meta-analysis of 12 studies slightly favored animal protein, with substantial uncertainty. Adults aged 65 and over showed a modest advantage for animal protein, while younger adults responded similarly (Mendes et al., Journal of the Academy of Nutrition and Dietetics, 2026).
The trials used different products and small samples, so treat them as consistent support, not proof that every plant powder matches every whey. The practical takeaway is to hit your daily protein target, train, and use a serving large enough to deliver about 25 to 30 g of protein. Our guide on how much protein you really need shows how to set that target.
Digestion and Allergens
Whey contains lactose, a sugar many adults digest poorly. The NIDDK notes that many people lose some ability to digest lactose after infancy, and that most people with lactose intolerance can handle a small amount (NIDDK). Whey isolate has less lactose than concentrate, so it is the gentler whey option.
Plant protein is lactose-free, which makes it the natural choice for dairy allergy or lactose intolerance. It is not automatically trouble-free. Some powders contain soy, gluten or added gums and sweeteners that bother sensitive stomachs, so read the label. Our label cheat sheet shows what to check, and why digestive enzymes can help with bloating explains the role of enzymes like bromelain and papain.
One caution on the plant side: independent testing has found plant-based powders tend to carry more heavy metals than whey because crops absorb them from soil. Pick a brand that publishes batch-specific lab results, and see our heavy metals guide.
Environmental Impact
Plant protein usually has the smaller footprint. A widely cited analysis of nearly 40,000 farms in 119 countries found that milk emits far more greenhouse gas per gram of protein than peas. Charted by Our World in Data, the figures are about 9.5 kg of CO2 equivalent per 100 g of protein from milk against about 0.4 kg from peas (Poore and Nemecek, Science, 2018; Our World in Data). Whey is a by-product of cheesemaking, so allocating its impact is complicated, and the size of the gap depends on how the calculation is done. If footprint matters to you, plant protein is the safer choice.
How to Choose
- Choose whey if you tolerate dairy, want the most protein per scoop and like fast, easy mixing. Use isolate if lactose is a concern, or concentrate if it is not.
- Choose plant protein if you avoid dairy, are lactose intolerant, are vegan or care about footprint. Use a full scoop of plant protein and mix it with a little more liquid. Func Lab's directions are 300 to 350 ml per scoop, against 200 to 250 ml for whey isolate. Our guide to switching to plant protein covers the practical side.
- Use both if you want flexibility: whey after training and plant protein on dairy-free days. For travel, single-serve sachets and a good shaker bottle make switching easy.
- If you are over 65, the research leans slightly toward whey, so a plant user may want a larger serving. Check protein intake with a doctor if you have kidney disease.
Frequently Asked Questions
Can plant protein build muscle as well as whey?
Close, when the dose is adequate. A 2021 meta-analysis of randomized trials found that protein source did not change gains in absolute lean mass or strength, though animal protein did better for percent lean mass, mainly in adults under 50. The practical rule is to match the protein dose, choose a well-formulated plant protein and keep training.
Which is better for weight loss, plant or whey?
Neither has a proven edge. Weight loss depends on total calories and total daily protein, and either powder helps you reach your protein target. Pick the one you digest well and will use consistently.
Can I mix plant and whey protein?
Yes. There is no safety issue with combining them, and the total protein is what counts. Many people keep both: whey isolate after training and plant protein on days they want a dairy-free shake.
Is whey isolate better than whey concentrate?
Isolate is filtered further, so it has more protein per scoop and less lactose and fat. Concentrate is a good everyday option if you tolerate dairy well. If lactose gives you trouble, start with isolate or switch to plant protein.
Is plant protein safe if I am lactose intolerant?
Plant protein contains no lactose, so it removes that trigger. Check the label for other ingredients that bother you, since sweeteners, gums and sugar alcohols can also upset the stomach.
Should I choose whey if I am over 65?
Possibly. A 2026 meta-analysis found animal protein gave a slightly larger muscle protein synthesis response than plant protein, and the gap was modest in adults aged 65 and over. Plant users in that group can compensate with a slightly larger serving, and anyone with kidney disease should check protein intake with a doctor first.
Does protein type matter if I do not lift weights?
Much less. Most of the research is in people doing resistance training. If you use powder to reach a daily protein target, digestion, taste, allergies and budget matter more than the source.
Are plant proteins tested for heavy metals?
They should be. Independent testing has found plant-based powders tend to carry more heavy metals than whey, because plants absorb them from soil. Look for batch-specific lab reports. Func Lab publishes its results on the Certified page, and our heavy metals guide explains how to read them.
The Bottom Line
Whey is slightly more efficient per gram, and plant protein is easier on dairy-sensitive stomachs and the environment. In long-term training studies the source made little difference to strength once the protein dose was matched, and a small difference to lean mass in younger adults.
Choose the one you digest well, can afford and will use every day, and make sure your total daily protein is on target. If you are unsure, keep a tub of each.
This article is for general information and is not medical advice.
