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The Truth About Plant Protein Supplements

The Truth About Plant Protein Supplements

Written by
August 29, 2019
Updated May 13, 2020

*This article has been vetted by the Onnit Advisory Board, including Scientific Adviser Vince Kreipke, PhD.


– People who strength train need up to 2 grams of protein per kilogram of body weight daily. You need even more if you’re dieting.

Plant protein powders offer a sustainable and sometimes more digestible alternative to dairy and other animal-derived protein powders.

– Most plant proteins by themselves are not complete sources, but, blended with other plant powders, they can supply the same amino acids and amounts of leucine as whey.

– Plant protein can help to control hunger, aiding weight loss.

The Truth About Plant Protein Supplements

People who wear glasses are smart. People who are overweight must be lazy. And vegetarians are all long-haired hippies that are so weak from malnutrition that a stiff breeze could knock them over.

There are some stereotypes that never seem to go away. And while the first two we listed are clearly nonsense when you think about them, the third one about vegetarians still seems to have a lot of believers—especially among athletes and muscle-seekers who think that you can’t build size and strength on a flesh-free diet. After all, huge guys are called “meatheads” for a reason.

The thing is though, it’s not meat per se that makes muscle grow, but rather the protein inside it. Protein from beans and rice can serve your purpose just as well as a rare steak can—and, in the supplement department, plant protein powders made from blends of pea, rice, or seeds can equal whey.

Nevertheless, if you’re looking to remove or reduce the amount of animal products in your diet for ethical or environmental reasons, or you’re a vegetarian/vegan who just started weight training, you may find it challenging to get all the protein you need in a day, as plant sources generally aren’t as rich in protein as animal foods are, and usually don’t contain all the necessary amino acids in amounts that make their protein complete. In this case, supplementation is helpful.

You’re about to discover the truth about plant protein supplements and muscle.

How Much Protein Do I Need?

The amount of protein you need daily depends on your goals and activity level. If you just want to get by (i.e., you don’t work out or play sports), the government’s nutrition guidelines call for a minimum of 0.8 grams of protein per kilogram of bodyweight. That’s enough to keep a sedentary person alive, and it’s not at all hard to consume. If you’re a 140-pound woman (about 64 kilos) who fits this description, you only need a little over 50 grams of protein per day.

If you want to be awesome, however—as in, muscular, strong, and athletic—you’ll need much more. The International Society of Sports Nutrition (ISSN) recommends 1.4–2 grams of protein per kilogram of bodyweight per day for those who strength train. So a 180-pound man (82 kilos) who lifts will need between 115 and 164 grams of protein daily. Still, many nutritionists recommend even more protein. If you’re a seriously dedicated lifter or bodybuilder, they’ll have you round the number up to one gram per pound of bodyweight, just to be sure your bases are covered.

If you’re dieting to lose fat, you’ll almost certainly need more—as much as 2.3–3.1 g/kg of bodyweight. For example, a 200-pound man (91 kilos) should shoot for 210–280 grams of protein to preserve muscle mass while dieting off his body fat.

That much protein can be tough to consume from whole foods alone, especially if your diet excludes meat or animal products. Vegetarians/vegans typically get their protein by way of carb-rich foods, such as beans, rice, and quinoa, so if you’re also watching your carbs, it will be even harder to get enough protein to support muscle on a plant-based diet. Conversely, if you’re trying to keep your fat in check to control calories, you won’t be able to include many nuts or seeds in your menu to hit your protein number.

For these reasons, protein supplementation is extremely beneficial, and in some cases may be necessary to ensure that you get enough protein to reach your goals. Furthermore, for those who lead busy lives and don’t have much time to prepare meals, protein powders make hitting your target protein number much more convenient and doable.

What Are The Benefits of Plant Protein Supplements?

Well-made plant protein powders can match ones derived from animals in almost every category, and offer some other benefits that whey, casein, egg, and beef protein powders can’t.

Easier Digestion

Although soy is an exception, most plant proteins digest easily and absorb well. As we reported in our guide to pea protein, pea’s digestibility rate is 94%, meaning that nearly all of it will break down in your gut. Most of it will be assimilated by your body as well—better than soy, hemp, and bean proteins are.

Rice protein’s digestibility is greater than 90%, which is higher than soy’s. According to a 2015 study, rice protein digests more easily than whey as well. If you’ve found that dairy proteins have made you feel bloated and give you gas, this shouldn’t be an issue with most plant sources.

Hemp is a burgeoning plant protein source. A study in the Journal of Agricultural and Food Chemistry found that the protein absorption rate of hempseeds is on par with that of casein, a dairy protein that’s used for its slow release of amino acids. This suggests that hemp could match casein as a great nighttime protein to take before bed, ensuring that the muscles are fed aminos at a steady rate throughout the night.

Low Risk of Allergens

Allergies and intolerances to milk/dairy, eggs, and soy are common, but most plant proteins are not offenders. Pure pea and rice proteins are known to be allergen-free.


It takes fewer natural resources to produce plant proteins than it does to farm dairy cows for whey and casein. And, unlike cattle, plants don’t burp or fart, releasing carbon into the atmosphere, or pollute waterways.

How Does Plant Protein Compare To Whey?

Whey protein is generally regarded as the gold standard for protein supplements, due to its complete amino acid profile, bioavailability, and fast digestion. However, plant protein powders aren’t necessarily inferior, especially if you combine them.

The main concern with plant proteins is that few of them are complete (soy protein is a notable exception). This means that they either don’t contain all nine essential amino acids, or they don’t provide them in adequate amounts. It’s an important distinction to make, because your body can’t produce these amino acids itself—they must be gotten from food.

But just because a plant protein isn’t complete doesn’t mean it’s useless. According to a 2018 article in The Proceedings of the Nutrition Society, you only need to consume more of it, or combine it with other plant proteins to make up the differences. Pea protein, for instance, contains all nine essential amino acids, but is low in methionine+cysteine. Rice protein has all the necessary aminos too, but is low in lysine. If you mix the two powders—or buy a product that’s combined them already—presto! Problem solved. Of course, methionine+cysteine and lysine are also found in many commonly-eaten foods among both omnivores and vegans, so simply having a protein shake along with a meal, or within a few hours of it, should balance everything out. Incidentally, pumpkin and watermelon seeds are sometimes added to plant protein blends as an inexpensive and sustainable way to round out their amino acid profiles, as both are good sources of protein.

One of whey protein’s standout features is its leucine content. Leucine is a branched-chain amino acid (BCAA), and scientists believe it’s the most important amino of all for signaling muscle growth. In fact, leucine is so powerful that it can stimulate muscle gains all by itself, and whey protein has the greatest amount of leucine of all protein sources.

According to the ISSN, the optimal amount of leucine for stimulating muscle protein synthesis is between 0.7 and 3 grams per serving of protein. One to two scoops of most whey protein powders will have this window covered, but it might take two or three scoops with soy, rice, pea, or hemp protein. So while plant proteins are not as efficient at providing leucine as whey, they’ll still get the job done. (Note: some plant protein supplements have extra leucine added to make up the deficit, so you don’t need to use more of the product to get the same amount.)

A 2015 study looked at the effect of pea protein versus whey on men 18–35 who followed the same 12-week lifting program. One group supplemented with 25 grams of pea protein twice a day, and another took the exact same amount of whey protein. Each 25-gram dose of pea protein delivered around two grams of leucine, versus 2.65 grams for whey, but both fell within the ISSN’s optimal leucine range. At the end of the 12 weeks, subjects in the pea and whey protein groups showed identical gains in biceps muscle, and both protein types showed greater results than placebo.

A Nutrition Journal study demonstrated similar results when rice protein was pitted against whey. Both groups had equal results in muscle thickness, body composition, and strength.

On the other hand, according to a review in the Journal of the American College of Nutrition, soy protein does not seem to promote muscle gains as well as whey protein, potentially due to its amino acid composition or rate of digestion. (This is interesting, since, as we noted above, soy is a complete protein just like whey.) For this reason, as well as evidence that soy protein can reduce the body’s absorption of iron and zinc (1, 2), we don’t like soy protein as much as other plant protein options.

Is Plant Protein Good For Weight Loss?

Increasing your protein consumption—whether from plants or animals—has numerous health benefits, and weight loss is near the top of the list. Protein is the most satiating of all nutrients, so it helps to control appetite. It’s also metabolically expensive for your body to digest—that is, your body burns a lot of calories processing and absorbing it.

A study in the American Journal of Clinical Nutrition showed that overweight people lost similar amounts of weight when they consumed more protein, regardless of whether it was derived from plants or animals.

Pea protein, however, seems to be particularly effective for helping to promote satiety. A Nutrition Journal study had subjects consume equal amounts of casein, whey, pea protein, egg albumin, a carbohydrate drink, or water 30 minutes before a meal. Pea protein ranked behind only casein for reducing appetite, causing subjects to consume fewer overall calories in the meal.

How Does Plant Protein Taste?

Many plant proteins have a chalky aftertaste that some people find hard to swallow (no pun intended). This is another reason why dairy proteins are more popular. But newer technology and sweeteners are making plant powders more palatable. Avocado powder may be used to help cut the chalkiness and improve mixability, while stevia and monkfruit can sweeten the powder without adding sugar, calories, or chemicals that might produce unwanted side effects.

What To Look For In a Plant Protein Supplement

Quality plant protein supplements stack up against whey powders. They should have between 100 and 150 calories per serving, and offer at least 15 grams of protein with little to no fat. Because plants are carbohydrate foods by nature, it’s normal for plant protein supplements to have three to five grams of carbs per serving, but they shouldn’t have added sugar.

To make sure you’re getting all the essential amino acids your body needs to support activity, look for a powder that blends multiple plant proteins, such as pea with rice or seeds. Getting one that also has digestive enzymes is a good idea too. A 2015 study found that ingesting enzymes along with a pea-rice protein blend improved protein absorption, bringing it closer to the rate at which whey concentrate gets soaked up by your muscles.

Sean Hyson
Sean Hyson is the Editor in Chief of Onnit. A Certified Strength and Conditioning Specialist (C.S.C.S.), he is the author of The Men's Health Encyclopedia of Muscle, and the e-book The Truth About Strength Training (
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