Amino Acids can signal for a increase insulin levels in the human body. The branch chain amino acid leucine is specifically able to signal for an insulin increase in the human body.
The BCAAs are essential amino acids and thus cannot be manufactured in the human body, so we must get them from our diets from sources like red meat, dairy (milk cheese, and even whey protein supplements) and eggs on a somewhat regular basis.
They are in almost every source of protein that you eat. They make up almost 50% of the essential amino acids typically found in food, and are found in high levels in human muscle. There is considerable research and interest in what they can do for muscle building and overall human physiology. BCAAs have been a popular bodybuilding supplement for many years and the research is now showing that Leucine by itself may have specific effects beyond the other branched chain amino acids. Much of the diet and fitness media is still relatively unaware of the research and effects of Leucine and the specific effect it can have on insulin.
The common held belief in the mainstream fitness media is that carbohydrates are necessary for insulin release. Although it’s true that carbohydrates stimulate insulin release, they are not the only compounds that do so.
Most people know that the Branched Chain Amino Acids and specifically Leucine are important physiological regulators of metabolism and have an effect on muscle and muscle growth, but something that is not so well known is the effect that Leucine and the branched chain amino acids have on Insulin secretion.
It is well known in the scientific community that Leucine can acutely stimulate insulin secretion from the beta cells in the pancreas. This occurs in humans, rodents and all mammals. This however is not common knowledge among the diet and fitness media.
Insulin is a hormone found in the human body that is important in the regulation of carbohydrate, fat and protein metabolism. Insulin is considered a storage hormone. It’s main effect is to cause cells in liver, muscle and fat tissue to take up blood glucose, and to stop the use of fat as an energy source and promote the storage of an energy surplus in the form of body fat.
In humans, after an overnight fast even 1 gram of branched chain amino acids (containing 0.5 grams of leucine) can cause a small, temporary increase in insulin levels, peaking 15 to 30 minutes after intake.
This insulin increase is enough to decrease Plasma Free Fatty Acid concentrations, however it’s only able to slightly decrease blood glucose levels at this dosage.
Therefore even relatively small doses of the branch chain amino acids and leucine are able to signal for an increase in insulin in the human body.
The fact that protein can stimulate insulin release makes it obvious that all three macro-nutrients (Proteins, Carbohydrates and fats) are able to signal the body in multiple ways when there is an excess. It is also an indication that amino acids can signal for growth in more than just muscle, seeing as Insulin is a non-selective ’growth’ hormone - meaning it can signal for an increase fat mass just as easily (probably even to a much higher degree) then it does for an increase in muscle mass.
In truth, the amount of protein you eat really depends on your aims, goals and current training level, amount of lean mass and maybe most importantly how much protein you typically eat already. However, that being said, you do need to be aware that much of the myth about protein (such as that it can’t be stored as fat, or does not stimulate insulin) are in fact innacurate.
The bottom line is that whether your goals are to lose body-fat or gain lean mass the amount you need to eat in a day to optimize either process will fall roughly within the ranges suggested in ’How Much Protein’.
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Leucine metabolism in regulation of insulin secretion from pancreatic beta cells. Yang et al. Nutrition reviews. 2010.
Branched-Chain Amino Acid Metabolism. Harper AE. Annu Rev Nutr. 1984.
Effects of Branched-Chain amino acid supplementation on plasma concentrations of free amino acids, insulin and energy substrates in young men. Zhang Y. J Nutr Sci Vitaminol. 2011