Protein: the basics
Protein is one of our 3 macronutrients. It offers 4 calories per gram and we should be getting at least 10% of our calories from protein. To help with muscle repair and rebuilding, athletes need more like 15% of calories coming from protein, and some strength and muscle building disciplines, like bodybuilders, require up to 20% of calories coming from protein.
We've grown to believe that the more protein the better, and marketing has led us to believe that eating animals is the best way to increase protein intake. People associate high intakes of protein with health, and protein powders, protein supplements and other protein isolates are consumed by athletes and non-athletes. We have become protein obsessed and although a 0.8 gram per kg of body weight ratio is recommended by experts (which means a 70 kilogram person should eat 60 grams of protein per day), it's super common to hear of non-athletes consuming upwards of 100-120 grams of protein per day. And although protein is considered to be a satiating macro (meaning that it makes you feel full), studies have shown that they do not lead to subsequent decreases in total caloric intake, like fiber does (more on fiber and its satiating effect in the Carbohydrates section). Protein excess simply leads to protein getting broken down and either transformed and used as carbs, or stored as energy for later use. Being a non-efficient source of energy, experts recognize that there is no logical reason to recommend excessive protein intake, since this does not improve health outcomes or athletic performance.
How they're built
Protein is made of amino acids, all joined together in a specific order. They're found throughout the body, in hair, muscles, bones. They make the enzymes that power most chemical processes keeping us alive and can also be used as fuel when needed. Of the 20 amino acids that make up protein, 9 are essential, meaning that our bodies can't synthesize them and must be obtained in our food. The others are non-essential, meaning that our bodies can make them from scratch, or modify existing ones to make new ones.
The essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. If you're eating a calorie sufficient diet coming from a variety of plants, then you're getting enough protein. The issue lots of people will raise is the fact that meat contains "complete protein", meaning that it contains all of the 20 amino acids, including the 9 essential ones. Since most plant sources don't contain all 20 amino acids, and some lack certain essential amino acids, some plant protein is said to be incomplete. Keep in mind that the human body will do exactly what other animals do, meaning that it will take bits and pieces of the different sources of plant protein, and make a complete one. In fact, all of the plants have different amounts and ratios of amino acids, meaning that all we have to do is eat a small variety of plants and the body will combine amino acids to fill in the gaps. Think of the silverback gorilla, one of the strongest animal specimens, who feeds on leaves and shoots all day.
Animal versus plant protein
Research clearly shows that the source of our protein is much more important than the amount, and protein comes pre-packaged with different compounds depending on the source. Animal sources of protein come pre-packed with inflammatory compounds, like saturated fats, heme-iron, cholesterol, sodium and zero fiber. Plant sources of protein come with fiber, antioxidants, anti-inflammatory compounds, phytonutrients, zero cholesterol and almost no saturated fat. In terms of calorie density, animal protein has an average of 1000-2000 calories per pound of food, versus plant sources of protein which have a calorie density closer to 200-600 calories per pound of food. Lots of baggage comes with animal protein, and on top of the excess calories, cholesterol, saturated fats, carcinogens and lack of fiber, we must also include the devastating environmental impacts and cruel mistreatment of animals.
Here's a quick comparison of different sources of protein:
A 4-ounce broiled sirloin steak is a great source of protein—about 33 grams worth. But it also delivers about 5 grams of saturated fat.
A 4-ounce ham steak with 22 grams of protein has only 1.6 grams of saturated fat, but it’s loaded with 1,500 milligrams worth of sodium.
A cup of cooked lentils provides about 18 grams of protein and 15 grams of fiber, and it has virtually no saturated fat or sodium, and is filled with prebiotics, vitamins and minerals like iron.
For athletes, the evidence clearly shows that plant protein is as effective as animal protein in terms of muscle and strength building potential. Even though the science is out, non-athletes still tend to consider protein supplements like whey protein a health food. Corporations, to minimize waste and increase profit, needed to find a way to reuse the milk proteins, casein and whey, which are by-products of cheese making. Cue protein powders that were marketed to athletes as the magical protein solution. Little do they know that these 2 milk proteins are linked to increased risk of hormone dependent cancers, like breast and prostate cancer. Other animal sources of protein have been found to increase systemic inflammation and oxidative stress, which in the long term, will increase risk of many inflammatory, allergic and chronic medical conditions, including cancer. In fact, the World Health Organization has issued a statement that meat and particularly processed meat, is linked to increased risk of cancer. Processed meat is classified as a class 1 carcinogen, meaning that the level of proof linking both is as strong as the association between smoking and lung cancer.
So whenever possible, consume plant sources of protein to avoid the inflammatory compounds in animal products, and to consume the anti-inflammatory ones in plant sources. It will help you avoid chronic disease, and have improved health outcomes. If you're an athlete, have no fear, because if you're eating enough calories of a variety of plant foods, you're getting sufficient and higher quality protein.
Often a source of confusion and a result of misinformation, soy protein has gotten a bad reputation over the years. But when we look at the actual science, we get a much different picture. Soy refers to products made from soybeans, a member of the legume family. Many foods are made from soy, including whole-soy products like edamame (mature soy beans), soy milk (emulsified soy beans), tofu (soy milk curds), and tempeh (fermented soybeans). Soy is also present in more processed soy products like soybean oil, soy flours, textured vegetable protein (or TVP, used in meat alternatives) and dairy substitutes like yogurts and cheeses.
The confusion stems from the fact that soy contains phytoestrogens, and the fear that these compounds could stimulate growth in hormone dependent tissues, like breasts and prostate tissues, and could eventually lead to an increased risk in cancer in these tissues. Science has debunked that a long time ago, but like autism and vaccines, the fear continues.
In its unaltered state, soy is a highly nutritious food, containing plant protein, fiber, B vitamins, iron, zinc and antioxidants. It contains no cholesterol, is low in unwanted saturated fats, and high in desirable polyunsaturated fats. People eating whole or minimally processed soy have better general health, including lower cholesterol, better fertility, less heart disease, less obesity, less osteoporosis, and better management of menopausal symptoms.
As for the cancer risk, this is a classic case of "bro-science" where the truth gets distorted into a scientifically plausible, but inaccurate theory. Let me explain. Soy doesn't contain estrogen, but rather a beneficial class of phytoestrogens called isoflavones. These compounds act as SERMs (selective estrogen receptor modulators), meaning that they bind to receptors in breast tissue where they have antagonistic effects on tissue growth. In other words, they block estrogen from binding to breast tissue and increasE hormone dependent cancers. SERMs are particular in terms that they mimic estrogen where they have beneficial effects and block estrogen in appropriate tissues. This minor detail has major significance in terms of cancer risk, where soy has protective effects instead of negative ones.
There's no need to worry about soy. It doesn't increase the risk of cancer, and populations with the highest consumption rates of soy products have the lowest rates of hormone dependent cancers. They don't hinder muscle building in the athlete or cause feminization, and are as good as animal proteins in terms of building lean muscle mass, likely better because of all the additional health benefits and nutrition attached to it. Try eating soy in its most natural forms, like edamame beans, tofu, tempeh or soy milk, and try to minimize more processed forms.
Protein is super important. It contributes to the growth and repair of all tissues and organs. Although we associate protein with muscles, it also plays an important role in immune function, enzyme synthesis and overall health, but somewhere along the way, the message of more is better got accepted as the norm. Sufficient amounts of protein are necessary, but in amounts much smaller than we're led to believe. While the recommendation for the average Joe is 0.8 grams of protein per kilogram of body weight, we still see non-athletes eating upwards of 100-120 grams of protein per day, believing that this is a healthy practice. The marketing of protein supplements and whey powders were initially directed at athletes, but now are pitched as health supplements for all.
So lay off the excessive protein intake, and consume mostly plant sources of protein, since they come packed with beneficial nutrients and are devoid of the bad stuff that comes with animal protein. To ensure our body gets all the amino acids it needs to build complete protein from all 20 amino acids, including the 9 essential ones we must get through diet, try eating a variety of plant sources of protein, like soy products, legumes, nuts and seeds, and the right amount of grams of protein, carbs and fat will magically happen without much effort.