Animal protein – particularly whey powder – is popularly endorsed as the best source of amino acids for boosting muscle strength. But a closer look at the research suggests that plant proteins could be just as effective for building and maintaining lean muscle mass.
Whey protein contains more of the amino acid leucine than plant proteins. Extensive research shows that leucine activates muscle protein synthesis – i.e. helps muscle to use the protein. This is thought to explain its superior benefits for building lean muscle and strength after resistance training.
However, the evidence derives from studies of whey protein’s short-term impact over 3 to 4 hours. A recent meta-analysis combined nine studies that compared soy protein with various animal proteins over 6 weeks or more (5 studies tested whey and 4 used beef, milk or dairy protein).
Overall, the analysis found that combining protein supplementation with resistance training exercises (bench press and squat) increased muscle strength. But the effects of soy protein did not differ from whey powder or the other animal proteins.
Looking at whole dietary patterns, the Framingham Third Generation Study found last year that people with lower protein intakes had lower lean mass and muscle strength. But they also found no difference between the different types of protein.
According to Health.com, lead author Kelsey Mangano says, “As long as a person is exceeding the recommended daily allowance for protein, no matter the source in their diet, they can improve their muscle health.”
Why is muscle health important?
Losing muscle mass is one of the biggest health challenges of aging. Lean muscle does so much more than endow our bodies with a shapely physique.
Older adults need to maintain lean muscle mass to prevent falls, a major problem in aging that results in physical injury, reduced quality of life, and death.
Muscles store glucose to provide energy and can protect against diabetes and heart disease. Age-related loss of muscle mass can lead to sarcopenia, also associated with reduced quality of life, hospital admissions and chronic conditions like poor lung function and breast cancer risk.
Proteins are made from 20 amino acids arranged in thousands of different combinations. Nine amino acids are “essential” – i.e. we need to get them through dietary sources.
Animal proteins include meat, fish, chicken, eggs, and dairy foods. Protein also derives from abundant plant foods including nuts, legumes, seeds, lentils, grains, and even hemp.
Most plant protein sources are incomplete – i.e. they don’t contain all essential amino acids. Proteins derived from animal sources are complete; hence animal protein was deemed to be superior.
However, eating combinations of plant sources provides a complete protein, and it’s now established that the body can store amino acids, so a whole amino acid contingent doesn’t need to be eaten in one meal.
Most importantly, regardless of the source, research suggests that older adults who eat 1 gram of protein per kg of body weight each day are less likely to suffer disability. Combining this with regular physical movement will yield the greatest benefits.