Protein

What is it?

Protein is one of the macronutrients and is necessary to survive. Proteins are made up of amino acid chains and digested into single amino acids. Nine of the amino acids are considered essential because the body cannot make them, and therefore they must be obtained from food. Those include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Protein is found in most body tissues including muscles, skin, bones, and hair. It’s important to note that not all sources of protein are created equal.

An interesting topic of discussion for protein is complete versus incomplete sources. Animal sources of protein are considered complete, meaning they provide all of the 9 essential amino acids. Soy (tofu & tempeh) and quinoa are also complete sources of protein. A complete protein can also be achieved by combining other plant-based sources, for example eating beans with rice.

What other names does protein go by?

Protein is usually referred to as protein, however it may also be called amino acid(s), polypeptide(s), or peptide(s).

What does protein do?

Protein makes up many of the enzymes that power the chemical reactions occurring throughout the body. It also makes up the hemoglobin that carries oxygen throughout the blood. In addition, protein aids in repairing and making new cells, helping to fight infections, carrying substances throughout the body, helping to keep muscles healthy, especially as people age, balancing body fluids, and helping to clot blood.

Protein, specifically amino acids, are critical for the production of cellular structures within the skin that help it to maintain its strong and taught appearance and function as an important barrier of protection. In addition, collagen, an important structural component of the skin, is a protein, and the most abundant one in the body. People tend to lose collagen as they age, however eating collagen-rich foods doesn’t necessarily result in a direct increase in collagen levels within the body. It’s important therefore to eat a balanced diet, including healthy sources of protein, not too much protein, and plenty of vitamins and minerals from fruits and vegetables. Nutrients important for supporting collagen production include Vitamin C, Proline, Glycine, Copper, and Zinc.

From a gut-health perspective, the components of protein do have a potential impact on the health and composition of the gut microbiome. The source, concentration, and balance of amino acids play a role. Consuming high amounts of protein may encourage pathogens and protein-fermenting bacteria in the gut to signal the development of disease. Likewise, the gut microbiota may play a role in how protein is digested.

What are the sources of protein?

Protein can be found in both animal and plant-based sources. The chart below lists the amount of protein per the food listed, it’s important though to consider what other nutrients are coming with the protein. Is it high in fat, saturated fat, cholesterol? Does it offer a low source of fat, cholesterol, and other important nutrients like fiber? These are important things to consider. Please note, this is not an exhaustive list.

How much is needed?

This is a question that is having a huge debate currently in the nutrition world. A general rule of thumb for adults is to get 0.8-1g of protein per kilogram of body weight, per day. For someone who is 150 pounds (68 kg), this translates into 54 – 68 grams of protein per day. For someone who is heavily active or has a diagnosed medical condition, the amount of protein needed per day may be slightly higher or lower. The challenge is that protein has been hyped up so much that most people get way too much.

Somewhere along the line the gram per kilogram guideline got translated into gram per pound. Please note, this is incorrect. If gram per pound is used in calculating the amount of protein, it is possible to get way too much.

Too much of any one nutrient, macro or micro, is not necessarily a good thing. Getting too much protein can manifest in symptoms such as kidney stones, constipation or diarrhea, fatigue, dehydration, and puts people at a higher risk of colon cancer and heart disease. A study published in February of 2024 identified a molecular mechanism by which too much protein can lead to inflammation in the body and heart disease risk. What the researchers found was that a diet high in protein, at just 22% of total caloric intake or more, creates a

alarming inflammation in the body, especially in blood vessels. They also identified Leucine, an amino acid that is found heavily in animal-derived foods like beef, milk, and eggs, was the primary culprit.

Going back to the 150 pound individual mentioned above. There is more to the equation than just grams per kg. Activity level, weight goals, disease state etc. must be accounted for. Going back to that example, let's say this person is a healthy, relatively disease-free woman who is 55 years old, 5'6", and is moderately active. She wants to lose 15 pounds of weight. Her caloric need per day may be somewhere in the 1700 kcal range. 54 - 68 grams of protein per day translates into 13 - 16% of her daily caloric needs. If we used the gram per pound calculation that has somehow taken a hold among influencers, this patient would need 135 grams of protein per day at her goal weight. That would represent 32% of her total caloric intake and have the potential to create damaging inflammation in her body, especially if that protein was coming mostly from animals.

How to get it in my diet?

Choose healthy, low saturated fat, and low cholesterol sources of protein when you can. Perhaps try to also have 1 plant-based meal during your day, or better yet, 1-2 plant-based days of eating each week!

Breakfast: 1 boiled egg = 8 g

Lunch: Salad with 4 oz roasted chicken breast = 35 g

Dinner: Tempeh stir fry = 21 g

Protein content = 64 g

References

British Nutrition Foundation. (n.d.). Protein. Retrieved from https://www.nutrition.org.uk/healthy-sustainable-diets/protein/?level=Consumer

Cleveland Clinic. (2022). Collagen. Retrieved from https://my.clevelandclinic.org/health/articles/23089-collagen

Harvard T.H. Chan School of Public Health. (n.d.). Protein. Retrieved from https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/protein/#how-much-need

Ma, N., Tian, Y., Wu, Y., & Ma, X. (2017). Contributions of the Interaction Between Dietary Protein and Gut Microbiota to Intestinal Health. Current protein & peptide science, 18(8), 795–808. https://doi.org/10.2174/1389203718666170216153505

Zhang, X., Kapoor, D., Jeong, SJ. et al. (2024). Identification of a leucine-mediated threshold effect governing macrophage mTOR signalling and cardiovascular risk. Nat Metab 6, 359–377. https://doi.org/10.1038/s42255-024-00984-2