New research on amino acid consumption raises questions about protein’s role in muscle-building

Residents of the US are consuming the necessary amounts of essential amino acids through food and supplementation, according to a new study conducted at Pennington Biomedical Research Center in Louisiana, US. However, another recent study by the same institution has challenged the existent assumption about the role these protein-building blocks play in muscle-building and fat accumulation.

The first study found that almost everyone — more than 99% — in the US is receiving the needed amounts of essential amino acids.

“This study was the first to characterize intakes of each amino acid in the US population by gender, age, race and ethnicity. The analysis allowed us to get a picture of current amino acid intake trends in the US population. Based on our findings, US citizens are meeting and exceeding minimum recommendations for all the essential amino acids,” says Claire Berryman, author of both studies.

The second scientific paper finds that the sufficient consumption of essential amino acids is not associated with lean mass, muscle strength or physical function in older adults, while regularly eating the essential amino acids was shown to lead to fat accumulation in older females.

Barryman states that these findings were surprising for the team, warning that they “should be interpreted cautiously as they only represent a snapshot in time since we did not follow the participants for any length of time.”

“However, the findings are important and should be explored further given widespread nutritional advice to consume high protein diets and the quantity of high protein foods and supplements on the market. In addition, it is important to keep in mind that consuming any macronutrient — protein, carbohydrate or fat — in excess of calorie needs will lead to weight gain.”

Amino acids and body composition

The first study, published in the Journal of Nutrition, is an analysis of the US National Health and Nutrition Examination Survey conducted between 2001 and 2018. It looked at populations over the age of 19 and concluded that the “US population exceeds recommended minimum population requirements.”

 Regularly eating the essential amino acids was shown to lead to fat accumulation in older females.The cross-sectional study addresses the previous research gap concerning the complete amino acid composition data in food composition databases. 

The second research, published in Current Developments in Nutrition, builds on some findings from the first. It evaluated the connection between the current and usual amino acid intakes to the body composition, muscle strength and physical function of US adults aged 65 years or older.

It looked at the effects of essential amino acid intakes on older adults and how these correlate with lean mass and functions like grip strength.

“Essential” amino acids

The authors explain that the essential amino acids are named this way because the human body needs them but is unable to synthesize them. This is what makes regular and sufficient protein consumption vital. 

They highlight that this relationship between essential amino acids and body composition, muscle strength and physical function, especially among older people, had not previously been defined.

Meanwhile, a different study on the essential amino acid isoleucine, found in eggs, dairy, soy protein and several types of meat, suggested that restricting intake of this compound could promote a longer lifespan.