How your body treats protein from plant and animal sources

Kevin Farrell

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Protein is big business across the food sector these days. Despite the fact that Americans are eating far more of it than they need – just 56 grams a day for men, and 46 for women – protein enrichments are invading all manner of products in the grocery store. Protein cold brew coffee? It’s a thing. Protein cereal? Yup. Heck, there’s even protein water. But despite protein’s takeover of our daily diets, we still might not be getting the proper nutrition necessary for sustaining healthy muscle.


That’s because your body doesn’t treat all sources of protein the same. In the broadest sense, protein derived from animal and plant sources can contain many different nutritional building blocks, which are usually quite different than anything found in the protein supplements added to processed foods and nutritional aids.

The most important piece of information about any source of protein, whether a chicken breast or a bowl of edamame, is which amino acids are present. Amino acids are the genetic building blocks our bodies use to build and sustain the cardiovascular system, as well as other parts of the body.

There are 20 different types of amino acids, of which nine are categorized as essential amino acids. That’s because the human body is capable of either producing or modifying the 11 non-essential aminos all on its own. But the remaining nine – histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine, for those keeping track – can only be found outside of our bodies, in the foods we eat.

Some proteins, namely those derived from animals, are called “complete proteins,” because they contain all nine essential amino acids. If you’re consuming protein from these animal sources, in many ways, your protein needs are being met for the day. Whereas protein derived from plants, like beans or wheat, contain only a partial list of the essential amino acids necessary for our bodies to operate.

A general rule of thumb for those adhering to plant-based diets is that complete protein – the term for a mix of all nine essential amino acids – can usually be created by mixing together nearly any legume (beans, lentils, peanuts) with almost any whole grain (rice, corn, wheat). So while it isn’t difficult to cook up recipes that ensure complete proteins, a bit of mindfulness is necessary.

There are, of course, outliers to to these top-level rules about amino acid content. Soy, for example, is celebrated for containing all nine essential aminos within the relatively healthier genetic structure of a plant-based protein. Soy has thus become a global power crop, transformed into protein-rich products like tofu, soy milk, soy nuts and imitation plant-based meats like the Vivera steaks known for realistically “bleeding” when cut.

Meat, though a complete protein source, has been linked to a 400% increase in risk of death by cancer for those who consume it, compared to those who avoid animal proteins. Many animal proteins contain high levels of cholesterol, fats and even sodium – all noted for their unhealthy impact on human cardiovascular systems. They also lack the high fiber levels found in plant-based proteins, and are thus more difficult for your body to digest.

As with any part of your diet, protein consumption is just a single part of what should include a vast array of diverse nutritional sources. Part of maintaining a healthy diet means understanding what you are consuming. Here’s a brief overview of the most common protein sources to get you started.

Animal protein (land)

Common parts of many American diets include various cuts of beef, chicken and pork, along with milk, eggs, cheese and other dairy products. These proteins are complete, containing all nine essential amino acids, but overindulgence may create negative impacts on health.

Animal protein (water)

Fish, scallops, shellfish and even fish eggs (roe) are also complete proteins. Seafood is usually considered to be a healthier option, lower in cholesterol and fat than land-based animal proteins. However frequent seafood consumption may in some cases be linked to unhealthy levels of mercury consumption.

Plant-based protein

Foods like soy, wheat, quinoa, corn, tree nuts, beans, peanut butter, seeds and even some types of algae vary wildly in terms of their nutritional content and actual protein content, but are generally considered to be healthier than animal-based proteins, so long as a diverse enough array of them are consumed to account for all nine essential amino acids.

Fungus-based proteins

Technically different than plant-based proteins, mushrooms possess many of the same beneficial qualities. Fungus-based proteins are generally low in calories, high in nutrients, and are frequently used as meat substitutes for vegans and vegetarians. However, like plants, mushrooms do not contain complete proteins, and must be combined with whole grains in order to capture all nine essential amino acids.

Protein supplements/added proteins in processed foods

Oh man, where to begin? The only rule of thumb for protein-enriched foods and supplements is this: do your homework. The source of protein supplements can vary wildly, with whey, soy, casein (milk), egg, pea, and even hemp protein appearing in various combinations across products. Unless it is specifically advertised, you should never assume that protein-enriched foods are complete. As with anything you are consuming regularly, do some research to make sure what you are putting into your body is actually good for you.


Kevin Farrell

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