Plant-based proteins offer “complete” source of essential amino acids, experts reveal

16 Apr 2024 --- A new report aims to bust the “myth” of plant-based protein being an incomplete source of essential amino acids, arguing that many of the most popular vegan proteins contain all nine essential amino acids — histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.

Nutrition Insight meets with author Jonathan Weissberg, fitness research director at Garage Gym Reviews, to discuss the report’s suggestions. “I hope this report can help clear up some of the confusion surrounding plant-based protein and the debates on ‘complete’ vs ‘incomplete’ proteins.” 

He notes several factors have driven a “myth” of incomplete plant proteins. “In my opinion, the historical bias toward animal-based protein and a lack of clear presentation of the nutritional makeup of these protein sources to the general public are two significant factors.” 

“According to the data, consumers can support their protein intake on a plant-based diet by including a variety of protein-rich sources such as lentils, quinoa and kidney beans to help ensure a proper amount,” comments Weissberg. “Additionally, paying attention to reaching your overall caloric intake can help hit the protein goal.”

Plant-based foods  
For the report, the authors examined existing research on each plant-based source’s protein content, amino acid profile and nutritional makeup, looking at 17 food and 12 protein powder versions. 

“We went through 30 papers published in the National Library of Medicine to find the amino acid composition of the most popular vegan protein sources,” explains Weissberg. 

The research reveals that 14 of the 17 most popular plant-based protein foods contain all nine essential amino acids. The report indicates the percentage of amino acids in a 200-calorie portion for each protein source evaluated. 

According to the report, 14 of 17 popular plant-based protein foods contain all essential amino acids.When looking at plant-based food, the report indicates that lentils are the best protein source for muscle growth, containing most of the three essential amino acids associated with building muscles — leucine, methionine and valine. 

Moreover, the researchers suggest eating a portion of lentils or pumpkin seeds daily for their high methionine content — over half the daily requirement per portion. This amino acid is the most difficult to find in plant-based protein sources. 

Beans and pulses, such as lentils and kidney beans, contain the highest levels of essential amino acids per portion, while seitan is one of the few incomplete proteins, lacking in lysine, methionine and tryptophan. 

Protein powders 
Regarding protein powders, the report indicates that brown rice protein powder is the best supplement for building muscles, containing the highest levels of leucine, lysine and valine. 

Moreover, the researchers recommend adding a sacha inchi or pumpkin seed protein powder for consumers who do not regularly eat beans or pulses. These sources contain the highest concentration of methionine. 

In addition, the report finds sacha inchi the “best plant-based protein supplement for improving mood and cognition,” as it contains the highest levels of phenylalanine and tryptophan. These amino acids contribute to the creation and maintenance of neurotransmitters. 

The report recommends that older consumers supplement their diet with lentil protein, as it holds the most significant levels of threonine, which is “essential for maintaining connective tissue.”

The only incomplete protein powders identified are sunflower seed and mung bean protein powder. 

Amino acid research 
Weissberg hopes the report will be a “valuable resource for people interested in gaining a deeper understanding of plant-based protein sources, allowing them to make better-informed decisions regarding their diets.” 

Consuming various protein-rich sources, such as lentils, quinoa and kidney beans, is critical.He adds: “It’s important for readers to grasp that based on this research, you can still obtain all nine essential amino acids from plant-based protein sources, but I’d also be mindful of the quantity and variety of these sources you include.” 

There is ongoing research on the benefits and drawbacks of different types of protein amid a growing push for alternative proteins. In a recent study, partly substituting animal protein with plant-based versions was linked to increased life expectancy and carbon footprint reductions. 

For example, one study links higher plant-based protein intake to healthier aging in women. At the same time, Finnish researchers note that fava bean and pea-based products provide sufficient amino acids and protein. 

Meanwhile, last year, researchers cautioned that meat consumption supports a higher bioavailability of essential amino acids than plant-based proteins. 

Moreover, scientists have linked high protein intake — over 22% of dietary calories daily — to an increased heart disease risk due to leucine activating a specific pathway. A different research suggests that reducing intake of the isoleucine amino acid, commonly found in animal-based protein, extends the lifespan of mice. 

By Jolanda van Hal