Excessive amino acid intake may elevate risk

Many studies have reported on associations between specific amino acids and the incidence of insulin resistance and type 2 diabetes.

“Specifically, the branched chain amino acids (BCAA) leucine, isoleucine and valine have gained attention regarding their role in insulin resistance and type 2 diabetes,” Dr. Mireille Serlie, a professor of internal medicine (endocrinology) at Yale School of Medicine, not involved in the research, told Medical News Today.

“However, results are often contradictory and causal relations have not been established in humans,” she cautioned.

Also, it is important to note that insulin resistance might affect BCAA levels and as a result, BCAA levels seem to modulate insulin sensitivity, making association studies more challenging to interpret.

“Many factors affect levels of BCAA in humans, including levels of protein synthesis and breakdown and total dietary intake,” Dr. Serlie told us.

“Protein source (animal versus plant protein) is another determinant and not always reported in clinical studies. Whether BCAA themselves or their metabolites affect glucose metabolism remains a matter of debate, and how and if insulin resistance increases levels of BCAA is still a topic of study. Therefore, the biological explanation of the association between BCAA, insulin resistance and the incidence of type 2 diabetes in humans has not been elucidated yet.”

– Dr. Mireille Serlie

Furthermore, the study did not find a significant nonlinear association between dietary amino acids and type 2 diabetes risk after adjusting for demographics and lifestyle. This shows that the association between amino acid consumption and type 2 diabetes risk is affected by other variables.

“In this study, demographics (all subjects were Iranian) and residency (urban vs. rural) likely played roles in this,” said Dr. Absalon Gutierrez, an associate professor of endocrinology, diabetes and metabolism with UTHealth Houston, not involved in this research, noted. “Also, the study relied on a questionnaire asking subjects to recall what they ate, which leaves some room for error.”

Food rich in branched chain amino acids include milk, red meat and poultry. Moreover, a large epidemiological study by has reported that pork, beef, and chicken accounted for the majority of BCAA intake, said Dr. Serlie.

“Whether reducing BCAA improves metabolic health is still unclear. Some studies showed beneficial effects of diet interventions, exercise, and weight loss while others did not observe a change in BCAA. Nevertheless, reducing meat intake and adhering to a healthy lifestyle in general is beneficial for overall health,” Dr. Serlie noted.

It is also important to note that “branched-chain amino acids (BCAAs) are types of ‘essential’ amino acids, meaning your body cannot produce them, so they have to come from food. BCAAs are in many foods, including beef, chicken, eggs, fish, nuts, and grains. Many of these foods also have the other essential amino acids,” stated Dr. Gutierrez.

To receive the benefits of amino acids and to stay consistent with the best body of evidence, Ellen Liskov, certified diabetes education and care specialist at Yale New Haven Hospital, not involved in the recent research, recommended the following:

• including fish, nuts, and legumes in the diet more often than meats, especially red meat
• consuming dairy in moderation
• avoiding amino acid supplements
• taking in sufficient protein-rich foods to get all essential amino acids
• consulting a registered dietitian for a personalized assessment and recommendations on your eating patterns.

There are numerous limitations of this study that are important to note, and many questions that remain unanswered.

“Diet studies are difficult because it is very hard to control everything a person eats,” noted Dr. Janet O’Mahony, a Baltimore-area internal medicine doctor, not involved in this research.

“We don’t eat amino acids — we eat proteins (like meat, eggs dairy) that are complex and come along with fat and sugar,“ she pointed out. “So when you make an assumption that eating a lot of amino acids in meats is bad—is that from the amino acids? Or is that from saturated fats in animal products? Or something else that we eat along with it?”

“If you draw blood levels and find high levels of BBCA’s in someone with insulin resistance, do BBCAs cause insulin resistance? Or does insulin resistance increase a person’s blood levels of BBCAs? Or maybe a person’s genetic make-up causes the increased blood levels of BBCA’s? Another possibility is that a person’s gut bacteria make these amino acids in the gut that get absorbed into the bloodstream,“ Dr. O’Mahony added.

“This study was an observation. Which means they noticed a correlation between the consumption of a lot of BBCAs and diabetes. Correlation is not equal to causation. You cannot conclude that one caused the other,” she further cautioned.

Additionally, there may be more effective research methods to consider.

“You can study this better in mice because you can feed them just the amino acids you want. It is still tricky and results are conflicting,” Dr. O’Mahony explained. “The mice might need to have a high-fat diet and high BCAA diet at the same time in order to show insulin resistance. It is not clearly cause and effect.”