The Protein Myth: Shattered by Science

By Deborah Schwartz

When I tell people that I only eat plants (nothing with a face or from a mother), most people ask me, "but where do you get your protein?" I appreciate the concern and wish I had time to explain what I have found through years of research.

Disclaimer: I have no formal education in any form of health care. I did spend a few years researching and reading all about nutrition after being frustrated by the contradictory advice on the shelves and shelves of nutrition books in bookstores and libraries and from news stories. I have taught graduate business statistics courses and am well-versed in experimental design and the limits and errors of statistical analysis. I believe in science: controlled, repeatable, peer-reviewed studies by highly credentialed researchers published in high quality journals. Results from one study could be a statistical anomaly, so I prefer lots of studies with the same conclusions. I tend to be skeptical of advice from people who have financial motives (e.g., authors who push vitamins, books and diet plans, physicians who recommend expensive procedures, etc.). I was concerned when I went to my annual physical at age 50 (after 25+ years of running) and my physician said, "your blood pressure, cholesterol and weight are too high ... here are some prescriptions."

What is protein?

We tend to think of protein as a single nutrient, when actually there are hundred of thousands of types of protein in our bodies (in blood, hair, skin, muscles, brains, enzymes, etc.). What we really need are amino acids, the building blocks of protein. There are 15 - 22 types of amino acids (depending on how they are counted ... for this discussion I'll say there are 20 types).  These amino acids are the building blocks of protein for all living things, such as butterflies, dogs, pine trees, etc.

Combinations of amino acids are made into protein by our bodies. Most authors use the metaphor of letters when speaking of amino acids: just like we use letters to form words to communicate, our bodies use amino acids to form strings of protein based on what we need. Our bodies are excellent at taking amino acids and forming them into the proteins needed. As adults, we have finished our growing and have minimal needs for protein, mostly for maintenance in the body through our skin, intestines, blood, etc.

Like most animals, we can produce our own amino acids from water, carbon, nitrogen, sulfur, etc. However, there are 8 - 9 (again, depending on who is counting) amino acids that we cannot produce ourselves and need to get through our diet. These are called "essential amino acids" because we can't produce them ourselves - but plants can make all 20 of the amino acids. Interestingly, rats cannot make 10 of the amino acids, so humans are better amino acid producers than rats ... and much research on diets/protein is done with rats.

When we get protein from animal sources, the animals got the original protein from plants. Most of the largest animals - cows, hippopotamus, giraffes - are herbivores, are very strong and do very well without animal foods. I digress ... when humans eat animal foods, we have to break the protein into amino acids and then use the amino acids to build the protein we need. Using the letter metaphor again, this is similar to having to cut out letters from a document and string them together again to make our own sentences. Or, as another author wrote, it is equivalent to making a wedding dress out of a used dress rather than having new fabric, thread, buttons and such.

So really, when we think of protein needs, we are really talking about amino acid needs. When our protein is from animal foods, our bodies break down the protein into amino acids and then combine the amino acids to make the proteins we need. The original sources of amino acids are the plants eaten by the animals.

Plants have protein?

The only source of all amino acids is plants. Thinking back to my schooling, I was taught that sources of protein were meat, dairy, and a little in nuts and whole grains. How could I have missed this: plants are the original sources of protein?

This knowledge is shared by all legitimate nutrition books I have read: plants have protein. Shown below is an example chart showing the essential amino acids in the left column and the amino acid content of some common vegetables:

This table is from John McDougall's website based on research done by Dr. William Rose in the 1940s at University of Illinois (this information has been around for a long time!). Note that the World Health Organization (WHO) recommendation for protein is much less than the U.S. recommended daily requirements. Many nutritionists believe the WHO is less influenced by powerful meat and dairy industry lobbyists than U.S. Department of Agriculture (USDA) and U.S. Food and Drug Administration (FDA).

Dr. Rose found there is no improvement from mixing plant foods (the myth of beans and rice) or supplements to make amino acids look more like animal foods. The beans and rice myth originated in Frances Moore Lappe's 1971 book, Diet for a Small Planet. Although much of her book was great, she did not understand the research on human protein needs and soon after her book was published, she rescinded her recommendations for combining plant food to create amino acid patterns similar to animal foods. Unfortunately, most "experts" picked up on food combining and this myth continues today. My family practice physician asked me, when learning I only ate plants, if I combined beans and rice (half of what all physician's know is wrong - they just don't know which half); just last week, my daughter's health teacher told her that as a plant-eater, she should combine foods.

Growing children need protein. Malnourished, undersized children fed a diet of local plants (sweet potatoes, rice, corn, wheat, etc.) with no animal foods quickly grow to normal size. These malnourished children were not protein deficient, they were calorie deficient. A diet of whole plant foods ("whole" meaning unprocessed, close to the plant) helped them quickly grow to normal weight.

Billions of people in the world flourish on a plant-based diet. In fact, the people on plant-based diets do not suffer from the diseases of affluence found in animal-based diet societies: cancer, obesity, diabetes, heart disease, gout, arthritis, osteoporosis, etc.

How much protein do we need?

I see many athletes taking protein supplements with the understanding that protein builds muscle. However, this is also not supported by science (note that Carl Lewis ate only plants - there is a long list of plant-eating athletes).

Since 1974, the World Health Organization has recommended a diet of 5% of calories from protein (38 grams for a man burning 3000 calories per day, 29 grams for a woman burning 2300 calories per day)- and this diet provides a large margin of safety for amino acid/protein requirements. If you are eating enough whole plant foods to meet your calorie requirements, you are getting enough protein.

Of course, on the standard American diet (SAD), we get much more protein, typically 100 - 160 grams per day. Many people have animal foods for breakfast, lunch and dinner. One tongue-in-cheek remark I remember is "if SAD really built muscle, Americans would all look like Arnold Schwarzenegger rather than Santa Claus." A visit to any mall shows us the results of SAD and the fallacy of the idea that high-protein diets build muscles.

In fact, too much protein is a huge problem. Excess nutrients are either stored (in the fat in our bodies) or eliminated. Protein is not stored in our muscles (how many of us look like body-builders?). It is eliminated in our urine after being converted by the liver and passing through our kidneys, causing wear and tear on these organs. Physicians treating patients suffering from kidney or liver failure put them on a low-protein diet - they know high protein diets harm kidneys and livers. The by-products of digesting protein are harmful to us.

Excess protein associated with animal foods (dairy and flesh) is highly correlated to rates of hip fractures and kidney stones. The lowest rates are found among people on a plant-based diet. Even osteoporosis is known to be highly correlated to high acid foods (animal foods). Our bodies use the calcium in our bones to neutralize the acidic by-products, weakening bones. The amino acids from animal foods are high in sulfur. Sulfur is essential for our health, but too much is harmful and is linked to promoting the growth of cancerous tumors, toxicity of the intestines and (minor, to be sure) foul body odor.

The question isn't "where to you get your protein?" but "am I getting too much protein?"

Why didn't I know this?

In the past, I really believed that a "good" diet was full of protein. I was surprised to learn all of this - and still am chagrined when I read Liz Applegate in Runners World recommending salmon, turkey, lean meats after all of my research. How is the scientific evidence missed? The medical journals and research is available to all, but "common knowledge" focuses on the protein myth.

While I don't believe in conspiracy theories, I do believe in the power of money. The meat and dairy industries are very powerful in this country and have everything to gain by perpetuating the myth of high protein diets (although they know what the science says). If you read John Robbins or the last third of Colin Campbell's book, you will get a better understanding of how we got to this place. Warning: reading this could make you mad!

Physicians, our typical source of health information, get little to no training in nutrition. Many of the physicians I have spoken with really believe that patients do not have the discipline and interest to use diet and exercise to keep/maintain their own health. They believe that patients demand quick, pill-based solutions (and that could be true for many people).

You should be skeptical of all health-related advice, including this. For me, after being on a plant-based diet for several years now, my blood pressure, cholesterol and weight are good. This stuff worked!  I am still learning and reading - I hope this provides some food for thought for you. I welcome your emails for a discussion.

Sources (some of my favorites)

T. Colin Campbell, Ph.D.

Ph.D. nutritionist from Cornell University. Author of The China Study, the best, science-based book on nutrition I have every read. Get it! Read it! It will change the way you think about food. Campbell grew up on a dairy farm and started his career working on ways to grow animals faster so starving children could be fed "high-quality" protein. With an open mind, he followed the evidence that maybe animal protein is not so great. In fact, based on his laboratory studies on protein, he has found an amazingly strong link between animal protein and cancer. He was lead researcher of the China Study, the first joint scientific study conducted with China (and Oxford) after diplomatic relationships were established between the U.S. and China - called the "gold standard in epidemiological research" by the New York Times.

Caldwell B. Esselstyn, Jr., MD

Hudson Valley resident and researcher/clinician at the Cleveland Clinic (the most renowned heart-surgery hospital in the country). Also an Olympic gold medalist in rowing. He has written many scientific articles in prestigious medical journals. You can get (and understand) his recent book, Prevent and Reverse Heart Disease. Interestingly, his colleagues at Cleveland Clinic rejected his offer to teach patients suffering from heart disease how to use diet to control/reverse heart disease progression (their careers and income depended on surgical interventions). However, when some of these same colleagues developed heart disease, they came to Esselstyn for treatment through diet.

John McDougall, MD

One of my favorite sources - a medical doctor practicing for over 40 years. He started practicing in Hawaii and noticed that his older patients on a traditional diet of rice and vegetables were healthy and vibrant into old age. Their middle-aged children and grandchildren, on SAD, were suffering from all the chronic diseases we have and McDougall was frustrated that American medicine only offered drugs to solve chronic diseases (note that it was not genetics that caused these chronic diseases). He has been successfully treating patients with a low fat, whole food diet. Visit his website or read his history of protein research. All of his books are great; his wife has developed thousands of recipes (some on the web site for free, some in books). We had a delicious McDougall stuffed pumpkin for Thanksgiving.

John Robbins (of the family that started Baskin-Robbins)

His book, The Food Revolution, gives lots of sources for research into the health benefits of a plant-based diet. It also includes compelling environmental and humanitarian reasons for moving away from animal foods.