SOUTH LAKE TAHOE, Calif. – Like dietary carbohydrates and fats, proteins differ in their quality, and individuals vary in their needs. Determining appropriate intake is not as simple as basing needs on body weight, e.g., grams protein per kilogram body weight. Instead, several factors affect how much protein a person needs. One is the source.

This article reveals what proteins are and why their source matters. The next article will explain why different people, e.g., sedentary, active, injured, growing, etc., have different protein needs and what can be done to optimize intake.

What Are Proteins?

Proteins are sequences of molecules called amino acids. Amino acids consist of smaller molecular structures, namely, an amino group (NH₂), a carboxyl group (COOH), a hydrogen atom (H), and a unique side chain.

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Through biological processes called transcription and translation, these amino acids link together in particular sequences based on genes in the DNA’s genetic code to become chains. These amino acid chains fold and bond to form larger structures.

These structures form enzymes, cell receptors, hemoglobin, antibodies, hormones, and cell structures. They also form tissues like skin, collagen (connective tissue), organs, and yes, the actin and myosin, responsible for muscle contraction.

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Only 20 amino acids are needed to make all proteins required for life. And virtually all proteins require all 20.

Although bacteria, plants, insects, reptiles, humans and all living creatures share many of the same protein enzymes, many proteins make their species distinct, such as those used to make hair and fur in mammals.

Humans can synthesize 11 of these 20 amino acids, which are known as non-essential amino acids. The remaining nine, termed essential amino acids (EAAs), must be obtained through the diet.

Most animals require roughly the same ratios of EAAs. If any EAA is missing, the organism cannot synthesize proteins, and therefore, cannot live.

Protein Quality

Protein quality refers to the degree to which a food’s protein contains the optimum ratio of EAAs humans need. Again, there is individual variation, and even one individual can vary slightly at different times depending on their stage of growth, health status, physical activity, body composition, etc.

Several established standards measure the quality of food proteins. The Amino Acid Score (AAS) is one such standard. Egg protein is commonly used as the reference because its amino acid ratio closely aligns with human needs.

Interestingly, while animals, including humans, cannot synthesize all 20 amino acids, plants and algae can and do. Like humans, fungi (e.g., mushrooms and yeast) require the same EAAs. They absorb them from their surroundings.

Because the specific protein needs of plants, algae, and fungi are different from humans, they have different ratios of human EAAs. This causes non-animal protein sources to rank lower on measures of protein quality.

Conclusion

Proteins are vital for numerous biological functions, not strictly for building muscle. They consist of various sequences of 20 amino acids, which determine their structure and function. Humans are unable to produce 9 of these amino acids, making dietary consumption essential.

The required quantities of EAAs form an optimal ratio, which differs from source to source. Plant, algae, and fungi proteins have different EAA ratios compared to animal proteins, making them less “complete” in terms of meeting human protein needs.

Generally, 0.8 to 2.2 grams of dietary protein per kg body weight is needed. However, the exact amount depends on individual needs and, as explained, the source of the protein.

The next article will explain how different sources can be strategically combined to optimize quality, when supplementation may be appropriate, why individual needs vary, and how over or under consuming can impede health goals.

Patrick Traynor, PHD, MPH, RD, CPT is a registered dietitian with an insurance-based practice, MNT Scientific in South Lake Tahoe, Sacramento, Minden, and does telehealth. Inquires can be directed to Dr. Traynor at (530)429-7363 or info@MNTScientific.com.