Most people know that the three primary macronutrients are carbohydrates, fat, and protein. When asked which of the three is most commonly consumed grossly over the recommended amount in the typical American diet, the vast majority of people will answer either carbs or fat. I am not surprised by this, as Americans have been bombarded with marketing demonizing both carbs and fat for several decades. In reality, the most commonly over consumed macronutrient in America is protein. Americans are protein obsessed. Given that our protein consumption is so high, it is helpful to know how our bodies process protein, what happens to the excess protein we eat, and the resulting consequences.
Let’s begin this conversation by dispelling a common myth that continues to be thrown around about protein. It is not true that the body is only able to absorb about 30g of protein in one sitting. The next time a gym bro tries to tell you this lie, tell them they are WRONG. In reality, the body’s absorptive capacity of protein is estimated to be around 700g. Let’s move on.
What Is Protein?
Proteins are essentially a combined mixture of building blocks called amino acids. These amino acids are used not only for skeletal muscle growth, but also as components of certain hormones, enzymes, antibodies, and more.
What Is the Recommended Amount of Protein Each Day?
The recommended intake of protein for a sedentary individual is 0.8g/kg body weight. For example, a sedentary 150lbs male is recommended to consume approximately 55g of protein daily. This is equivalent to one small 3 oz chicken breast and one cup of greek yogurt. That is not a lot of food when you consider what a typical American 150lbs male eats in a day. Regularly active individuals and athletes do require a much higher protein intake to maintain and build upon skeletal muscle mass. Their recommended protein intakes are the following;
Moderate Training Volume Athletes - 1g/kg/day
Endurance Athletes - 1.2-1.4g/kg/day
Strength Athletes - Anywhere Between 1.2-2.0g/kg/day Determined An An Individual Basis
It is good to note that consuming a high amount of protein alone does not lead to increased skeletal muscle gain. Without proper strength training, that excess protein will not be used to build muscle the way you want it to.
How Much Protein is Too Much?
The upper limit for protein, or the top amount of protein that can generally be consumed without serious negative side effects, is about 2.5g/kg/day. There are several downsides to eating protein beyond the upper limit including kidney stress, dehydration, and compromised bone health from increased calcium excretion.
What Happens to the Excess Protein We Eat Beyond the Needed Amount?
The short answer is it depends on whether the body is in a state of glycogen depletion or not.
When the body is in a state of glycogen depletion, such as near the end of a long bout of endurance training, up to 15-20% of the total energy used to drive the remaining exercise may come from amino acids. In this case, excess ingested protein can be used to produce glucose through gluconeogenesis.
When the body is in a well-fed state with fully restored muscle and liver glycogen, the excess protein we consume is converted into fat through fatty acid synthesis. The idea that excess protein is simply excreted and cannot be converted into fat is another myth. It absolutely can, and it is important to understand that protein can eventually be used and/or stored as an energy source when eaten in excess.
Here Are A Few Takeaways
Our protein obsession may be misguided. Although protein is a vital aspect of everyone’s diet, it is not always true that the benefits of protein increase with increased consumption.
Excess protein that is not needed by the body for its traditional function can be used for energy by either being converted into glucose or fat.
Chronic overconsumption of protein at high levels may lead to serious health consequences including kidney stress, dehydration, and compromised bone health.
Resources:
Cornelia C. Metges, Christian A. Barth; Metabolic Consequences of a High Dietary-Protein Intake in Adulthood: Assessment of the Available Evidence, The Journal of Nutrition, Volume 130, Issue 4, 1 April 2000, Pages 886–889, https://doi.org/10.1093/jn/130.4.886
Marieb, Elaine Nicpon, et al. Human Anatomy & Physiology. Pearson Education/Benjamin Cummings, 2013.
Potgieter, S. “Sport Nutrition: A Review of the Latest Guidelines for Exercise and Sport Nutrition from the American College of Sport Nutrition, the International Olympic Committee and the International Society for Sports Nutrition.” South African Journal of Clinical Nutrition, vol. 26, no. 1, 2013, pp. 6–16., doi:10.1080/16070658.2013.11734434.