Is More Protein Always Beneficials?

More protein means more muscle – or so we were told. After a workout, everyone wants to crack open a nice Fairlife or eat their favorite protein bar. Growing teenagers and young adults often consume chicken, eggs, and yogurt with every meal to ensure they get as much protein as possible in a day to maximize their "gains." Protein additionally has far more benefits than just supporting muscle growth. So, should we consume as much protein as possible? Not quite. Just like all macromolecules, the body must have protein in moderation. In fact, excess protein can not only be problematic, it can be life-threatening.

When you eat protein, it is denatured in the stomach by an enzyme called pepsin, which breaks it down into peptides. In the small intestine, enzymes from the pancreas, such as trypsin, continue to break them into individual amino acids. Amino acids can be absorbed into the bloodstream and head toward the liver. The 20 different amino acids can be separated into essential (cannot be formed by the body and must come from food) and nonessential (can be produced by the body). These all play a role in structure, such as building muscle and hair, forming enzymes, hormones, immune defense, and even serving as a backup energy source. However, proteins cannot be stored like carbohydrates and fats. So, what happens to this excess protein and how is it used as a "backup" for energy?

Every amino acid contains an amino group with a nitrogen. Deamination is used when your body does not need an amino acid and it must get rid of the nitrogen. Enzymes called aminotransferases are used to move an amino group from one amino acid to an α-ketoglutarate. This forms glutamate which, through glutamate dehydrogenase, forms ammonia and a carbon skeleton. Ammonia is toxic and requires lots of energy to dispose of safely. Our urea cycle is the method in which the liver converts ammonia into urea, which is much safer for us to excrete. In the meantime, the carbon skeleton that the amino group was removed from feeds into our citric acid cycle, which is used for oxidative phosphorylation and producing energy.

Figure: Structure of an amino acid, showing the amino group, carboxyl group, central carbon, and variable side chain

Source: Astrochemistry Laboratory, NASA Ames Research Center (astrochem.org).

The key problem with excess protein is the toxicity of ammonia and the stress that urea production places on our bodies. This dehydration can result in kidney damage as well as kidney stones. Diets high in protein generate large amounts of acid due to the side chains of many amino acids, such as aspartic acid and glutamic acid, having low pHs. The kidneys excrete acid and use buffers to neutralize the acidic environment. Calcium is one of the best alkalines that can be used to neutralize the acidity and can be found in bones. The bones release calcium which ends up in the bloodstream and is urinated. This results in weaker bones and a higher risk of fractures. Adding on to this, urinary calcium can be a risk factor for kidney stones. Kidney stones are hard mineral and salt deposits that can cause severe pain as they pass through the urinary tract. High levels of compounds such as calcium and uric acid, due to excess protein, can become concentrated and crystallize. Being dehydrated, due to the large amounts of urea being excreted, causes these crystals to grow.

Finally, and most importantly, the diets we have that are heavy in protein are not just problematic for their impact on the kidneys. Those rich in red and processed meats can be linked to increased cancer risk. These meats contain HCAs (heterocyclic amines) and NOCs (N-nitroso compounds) which damage DNA, a critical initiator to cancer as they lead to mutations. Colon cancer is especially tied to the continuous consumption of red meat. Research has shown that an intake of more than five servings of red meat per week has a clear relationship to cancer. Furthermore, these diets are very low in fiber and high in saturated fats. On the other hand, diets that prioritize whole foods and plant proteins improve gut health, ensuring efficient digestion and nutrient absorption.

With all these risks, how much protein should one consume in a day? According to the Mayo Clinic health system and National Institute of Health, adults who regularly exercise only require 1.1-1.5 grams of protein per kilogram a day. This protein should come from real foods and protein supplements should be limited. Ultimately, protein is essential but that does not mean it is the only nutrient your body needs. While a healthy amount supports muscle growth, immunity, and hormone production, exceeding this can quietly damage your kidneys, weaken your bones, and increase long-term disease risk. The key is not just to tick off boxes or reach a number, but to look at the food as a whole and where you are getting your protein from. So, next time you reach for a scoop of protein powder, maybe think about leaving it out of your shake.

References

1. Wempen, J. Assessing Protein Needs for Performance. Mayo Clinic Health System. https://www.mayoclinichealthsystem.org/hometown-health/speaking-of-health/assessing-protein-needs-for-performance

2. Delimaris, I. (2013). Adverse Effects of High-Protein Diets: A Review. ISRN Nutrition. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4045293/

3. NASA Ames Astrochemistry Laboratory. Amino Acids. https://www.astrochem.org/sci/Amino_Acids.php