Our Plant Protein Testing Methodology

Plant protein is an increasingly popular alternative to whey protein in dietary supplements. That’s because it’s made with only plant-based sources of protein, including peas, soy, brown rice and seeds. While not all plant protein sources are complete proteins (i.e. containing all nine essential amino acids), most plant protein blends include at least one complete protein source.

With so many plant protein powder formulas available, we knew that finding the absolute best ones would involve more than just sorting out the good from the bad. There are a lot of high quality plant protein powders on the market, so to determine which ones stand above the rest, we developed a custom testing methodology and scoring algorithm.

When assessing individual plant protein powder formulas, we score across six categories: protein source, whether or not the source is a complete protein, macronutrient calories per serving, protein per serving, price per gram of protein and sweeteners. These categories were developed in collaboration with registered dietitian and doctor of exercise physiology Chris Mohr.

How We Score Plant Protein Powder

Our whey protein powder scoring methodology branches off of our broader nutrition product and supplement methodology. We assign each product a score of 1 out of 5 for each of the categories we test in. Those scores are then weighted based on importance and averaged to produce a cumulative score out of 5 for each product, with 1 being the lowest rating and 5 being highest.

Criteria We Evaluate

Protein source

The primary source of protein in a plant protein powder formula determines whether or not it’s a complete protein source, as well as how many calories come from protein versus carbohydrates or fats. We evaluate eight plant protein sources: soy, pea, hemp, brown rice, lentil, chia, pumpkin seed and blends.

Soy: Soy protein is a complete protein, meaning it provides all nine essential amino acids, so it gets the top score out of all plant protein sources. While most plant proteins are limited in amino acids, soy is not. It's important to note that while studies have shown that soy protein is equally capable as whey for building muscle, that’s when the two are compared for leucine content only. More soy protein is needed to provide the same benefits as whey.
Pea: While whey protein is often hailed as the gold standard when it comes to muscle protein synthesis, one study compared a variety of plant protein sources to animal protein sources and found that pea was one of the better options and is considered a complete protein. It earns a high score in this category, though not as high as soy protein.
Hemp: Hemp protein is a complete protein source, though it’s lower in the important amino acid leucine than whey protein. Hemp does offer some other unique nutrient properties, such as fiber and omega-3 fatty acids. It also receives a high rating in this category, but like pea protein, it’s not scored as high as soy.
Brown rice: Brown rice is a poor source of protein when compared to many other individual, non-animal sources. It’s specifically limited in the amino acid lysine, as well as leucine and other essential amino acids, which are key factors in muscle protein synthesis. It earns the lowest score in our methodology for testing protein sources.
Lentil: Lentil protein powder, like many other plant-based proteins, is limited in some amino acids. While still a quality source of protein, it's not comparable to whole protein sources like soy, so it earns the lowest rating like brown rice.
Chia: Chia seed protein, gram for gram, has less protein than many other types of plant protein sources, but it’s also higher in fiber and other nutrients. Even though chia seed is a complete protein source with extra nutrients, it receives a low score based on its low protein content.
Pumpkin seed: Pumpkin seed protein has less protein than many other plant-based protein types, but, like chia seeds, it’s higher in some nutrients. It could be useful in a blend to complement other plant-based options, but on its own, it earns the lowest score in this category.
Blends: Plant proteins often have a limited amino acid profile, which is why many manufacturers combine various sources. Most plant protein blends have been shown to be equally effective when it comes to muscle protein synthesis. Since plant protein blends usually yield a high protein content with all nine essential amino acids, they get the highest score in this category.

Complete protein

Complete proteins, particularly those higher in leucine, are critical in muscle protein synthesis. Protein supplements should provide all nine essential amino acids to be considered a quality source of protein because all nine are required to support muscle growth and general development.

Incomplete proteins are those that have insufficient amounts of the essential amino acids or are missing one or more amino acids. In this case, you’ll either need to take more protein to get the same level of leucine or supplement with an additional complete protein source. For this reason, incomplete proteins are scored lower than complete proteins.

Macronutrient calories per serving

Ideally, the bulk of the calories consumed through plant protein powder will come from the protein. However, depending on the protein source and other ingredients, calories can also come from carbohydrates and fats.

Carbohydrates can be used for energy and flavor. However, since most of the carbs that are in protein powders are sugar-based, we typically score products with a high source of calories from carbs lower than lower-carb alternatives.
Fat can be a great addition to a protein shake because it may help slow the absorption of the ingredients, making the satiating effect of protein last longer. It may also improve the flavor, texture and mouthfeel of the product. Plant formulas with a high percentage of calories from fat earn a higher score than carbs in this category, but less than protein.
Protein consumption is the goal of using a plant protein powder, so clearly this is the focus and key macronutrient. With that in mind, we award the highest score to formulas with the highest amount of calories from protein.

Total protein per serving

Most data suggests aiming for 25-30 grams of protein at a time. Daily protein needs vary by individual, but based on this data, 25-30 grams is optimal per serving of plant protein powder. Most plant protein supplements contain 15-30 grams of protein per serving. Here’s how we score them based on protein content:

19 grams or less per serving: This amount receives the lowest score. Not only is it below the 25-gram recommended amount, but it’s also generally not a good value.
20-25 grams per serving: This dose earns an average score because it reaches the optimal range of protein per serving, but only the lower end of that range.
26+ grams per serving: With the data suggesting the benefits (not to mention value) of higher protein per serving, this amount aligns with the research supported benefits and receives the highest marks.

Price per gram of protein

Price is an important factor for consumers, and often (though not always) reflects the quality of a product. There are high-quality plant proteins that cost below average, and relatively low quality plant protein products that cost more than average. Because of this potential discrepancy, this category receives less weight in the overall score.

Since we deem protein content to be the best measure of value for a plant protein powder, we rate each protein powder based on the price per gram of protein. Here’s the breakdown:

$0.03-$0.05 per gram: The highest marks are given to the most affordable plant protein powders.
$0.06-$0.08 per gram: This is still a relatively low cost when compared to food sources of protein, but edging slightly higher for those who use protein powders regularly. This range earns an average score.
$0.09+ per gram: Higher than $0.09 per gram is more costly compared to some other options, which could be a challenge for many consumers. For that reason, plant protein powders costing $0.09 or more per gram of protein receive the lowest marks.

Sweeteners

Sweeteners may improve the taste profile of a plant protein powder, but they don’t add nutritional value beyond sometimes being a fast-burning energy source. We prefer to see minimal sweeteners in plant protein formulas, and we prefer some over others. Here’s how we rate each sweetener:

Sugar: Added sugar is a refined carbohydrate, and an ingredient most Americans over-consume. The Centers for Disease Control and Prevention (CDC) recommend limiting added sugar to no more than 10 percent of your daily calories. For a daily 2,000-calorie diet, that means no more than 200 calories per day should come from sugar (approximately 12 teaspoons). Based on research from the U.S. Department of Agriculture, adult men consumed an average of 17 teaspoons of sugar per day, and women consumed 15 teaspoons per day from 2017-2018. To avoid health issues like obesity, type 2 diabetes and heart disease, people should limit their added sugar intake. While there often isn't much added sugar in protein supplements, limiting it as an ingredient is wise, which is why plant protein formulas with refined sugar receive the lowest score in this category.
Honey: Honey is a form of added sugar. While it's a different form of added sugar, it’s still sugar, and physiologically there are few differences between the two—none of which have clinical significance. For this reason, we score honey the same as sugar.
Agave: Similar to honey, agave is a form of added sugar with few differences from refined sugar and none that have clinical meaning. It receives the same low score as sugar and honey.
Maltodextrin: Maltodextrin is a carbohydrate derived from rice, corn, wheat and potato starch. Although it’s not sugar, it acts similarly in the body, so it shares the same low score as the other forms of sugar we evaluate (honey, agave and sugar).
Dextrose: Dextrose is marketed as a high-quality alternative to sugar, but with a glycemic index of 100, it's no different than the other added sugars. It also receives the lowest score in this category.
Sucralose, Aspartame, Acesulfame: Artificial sweeteners like sucralose, aspartame and acesulfame are non-nutritive, non-caloric sweeteners. They have repeatedly been shown to be safe in research at moderate amounts. Although a recent WHO report suggested "artificial sweeteners to be possible carcinogens", the dosing that could cause concern is equal to that in approximately nine to 14 cans of diet soft drinks and a much higher dosing than what might be in a protein supplement. Still, the lack of research on the long term use of artificial sweeteners is the reason we give them a low score, though slightly higher than the score for sugar.
Erythritol, Xylitol: Erythritol and xylitol are sugar alcohols that provide sweetness with very few calories. We rate them higher than sugar and artificial sweeteners because they contribute to oral health, including reducing plaque, alleviating constipation and triggering secretion of gut hormones that regulate satiety (the feeling of fullness after you eat). One potential downside is that too much of either sweetener may cause stomach ache, cramping, gas or even diarrhea, which is why they aren’t given the highest score.
Stevia: Stevia starts as a plant and is refined and concentrated to create a sweeter end product. Some consumers may be turned off by the sometimes bitter flavor of stevia, but it’s considered safe and is free of calories and sugar. We give it the highest score in this category.
Monk Fruit: Monk fruit is a non-caloric sweetener that comes from a fruit that's native to China. Its flavor can be less off-putting than stevia, so some appreciate its ability to provide sweetness without the bitter aftertaste. Like stevia, we give it the highest score in this category.

Bonus points

Since the supplement industry—especially protein supplements—is constantly evolving, we pay attention to products and brands that are going above and beyond to stand out. That’s why we incorporate bonus credits into our plant protein scores to recognize innovation and encourage healthy competition among all brands. All bonus credits are equally weighted and cumulatively provide a small boost to the product’s overall score.

Third-party testing

The Food & Drug Administration (FDA) doesn’t regulate dietary supplements before they’re released to the market (though they do regulate ingredients and finished products), so it’s important to look for products that have been third-party tested for purity and potency. These testing certifications show whether a dietary supplement contains what the brand says it contains in the doses advertised (potency). It also tests for harmful toxins (i.e. mold, heavy metals, etc.), and some check for banned substances (purity).

Nearly all reputable supplement companies test their products in-house for safety and label accuracy, but many brands also make the decision to have their products tested by a third party for even further quality and safety assurance. That’s why we've chosen to give brands who take on this additional responsibility bonus credits.

Smaller, newer supplement companies often can’t afford testing by high profile third-party testing labs—regardless of the purity or potency of their products—which is why third-party testing is a bonus in our scoring methodology, not a main category.

The most reputable independent testing labs include:

Informed Choice (ICFS): Informed Choice offers several certifications, the most recognizable of which is the Informed Sport badge. This certification is critical for athletes who might get drug tested for their sport.
NSF: NSF is an independent testing organization founded in 1944.
U.S. Pharmacopeia (USP): USP is an independent, non-profit scientific organization that tests medicines and supplements, founded over 200 years ago.

Enzymes for digestion

Plant protein powders, particularly those sourced from legumes, can cause gastrointestinal issues in some people. Similar to how some dairy producers are now adding the lactose enzyme to milk, enzymes are often added to plant protein powder supplements. They are thought to aid in digestion and absorption, though data doesn't necessarily support their addition in plant protein powders.

Sustainable packaging

Sports Illustrated Showcase has an ongoing commitment to sustainability. The supplement industry is known to contribute significantly to plastic manufacturing and waste. For example, protein containers are usually large one-, two- or five-pound tubs of plastic. Any company that offers sustainable packaging gets bonus credits because less plastic tubs end up in landfills.

Certified organic

While organic certification often comes with a higher price point, it may offer some consumers peace of mind about the products they're consuming. While not completely void of pesticides, organic plants are exposed to fewer pesticides and bad bacteria than non-organic plants. Organic foods may have more antioxidants and fewer nitrates (which can increase the risk of certain cancers in large amounts). Finally, organic crops reduce chemical pesticide run-off into water sources, which is better for the environment.

No proprietary blends

Transparent labeling is the only way to know exactly what's in a product. Labeling with proprietary blends offers visibility into the ingredients included in the blend, but not the specific amounts. Transparent labels enable consumers to see whether or not the key ingredients are included in clinically meaningful doses.

Summary

There are countless plant protein formulas available for consumers, and our job at Sports Illustrated Showcase is to determine which products stand above the rest in terms of quality, potency, nutrition and value. Our plant protein testing methodology involves scoring products across six categories chosen in partnership with nutrition experts. The final weighted score supports our decision to either include or exclude individual products.

For more information on our nutrition and supplement testing philosophy, please refer to Our Nutrition Products and Supplements Methodology page.