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NOTE: This is a reprint of a post I wrote many years ago on blog far, far away. The subject is still relevant today, so I’m reprinting the article here.

Nick and I decided a little over a year ago to adopt a plant-based diet. That means we don’t cook with meat or animal products at home; we minimize our consumption processed foods like sugar and white flour; we avoid any food with an ingredient label containing things we don’t understand; and with the exception of half-n-half in Nick’s coffee and a dusting of Parmesan on homemade pizza we don’t eat dairy either. Instead we focus on eating a wide variety of vegetables, fruits, grains, legumes, nuts and seeds.

We chose to eat this way for a number of reasons, that maybe I’ll get into in a different post. This one, however, is an attempt to answer the question I get asked about as many times as I’ve eaten broccoli – but where do you get your protein?

People tend to be concerned about protein because, thanks to various ad campaigns, we have been brought up to believe that protein equals meat. It’s an eye-opening experience to hear, time and time again, that people believe this is the only choice as far as protein goes, even after I remind them that Popeye eats a can of spinach whenever he needs a boost in strength!

If you’re the curious type, who likes to question, research, analyze, delve deeper, and go further down the rabbit hole, then this is for you.

What is protein? And where does it come from?

A protein is a very large molecule made up of smaller molecules called “amino acids.” Each different protein is composed of various amino acids put together in varying order, with almost limitless combinations. These small units (amino acids) have a three-dimensional structure and exist in many different forms, including long chains, branched molecules, spheres, sheets, and helixes. Amino acids are the building blocks of protein, so, in reality, what we are talking about when we say protein is not a dense hunk of animal flesh per se, but about tiny little molecules that come organized into many different shapes and forms. MOLECULES! So, when we think of protein, we should now replace our mental image from whatever notion or association we have, with a new and true image, that of a complex sequence of molecules that we now know are amino acids.

Most of you reading this are thinking to yourself “tell me something I didn’t learn in 7th grade science class.” Okay smarty pants, did you know that we do not get protein directly from the foods we consume, even if they are comprised mostly of protein? Instead, our digestive system breaks down the food we eat into individual amino acids which are absorbed through the intestinal wall and carried to the liver where they are reassembled into protein our bodies use!

To accomplish this awesome feat, we need 22 amino acids. These are classified into two categories:

  • Non-essential amino acids are the ones the body is able to produce by itself. These are available and recycled from old tissue proteins already in the body.
  • Essential amino acids are the ones the body can’t make and that must be supplied by the foods we eat. That means that only 25-30% of the amino acids we need to make protein has to come from our diets.

For the record, the eight essential amino acids are isoleucine, leucine, lysine, phenylalaline + tyrosine, methionine, threonine, tryptophan, valine, and histidine.

Knowing this stuff is devilishly dangerous, though! Sometimes when people ask me where I get my protein, I’m tempted to answer “Which essential amino acid are you interested in?”

How much protein do we need?

Now that we’re on the same page regarding what protein is and the fact that only a small portion of the building blocks come from our food, the next logical question is how much do we need to consume?

Depending on the source you consult, only a small percentage of the calories we consume need to be protein. Professional estimates are as low as 2 ½ percent.1 The World Health Organization recommends about 5 to 10 percent, depending on various factors.2 And the U.S. government’s recommendation is about 9 percent, depending on calorie intake.3

This isn’t surprising, when you consider that human mother’s milk is 6 percent protein.4 We thrive on our mother’s milk when we are growing the fastest and need more protein than any other time in our lives. If all we need when we are growing rapidly is 6 percent, then as adults, we certainly need less.

Do vegetables, fruits, grains, legumes, nuts and seeds have enough protein?

In a word: yes. Whether you think our needs are 2 ½ percent or closer to 10 percent, it is nearly impossible to fail to get enough protein, provided you make sure to eat food. Looking at the chart below, you’ll see that every single whole plant food has more than 2 ½ percent protein, and they all have more than 10 percent except for fruit. Protein is one of the easiest nutrients to consume.

Average Protein Content in Food Compared to Human Need

The figures for food in this table come from the bible of nutrition data, the USDA National Nutrient Database for Standard Reference.5

The truth is: Plant foods easily supply our protein needs. In fact, when just about every single food has more than you need, how exactly could you not get enough? If you’re eating food, you’re eating protein. More than enough.

It’s meaningless to talk about a “source of protein,” because all foods have plentiful protein. In other words, every whole food is a “source of protein.” You don’t have to eat certain, special foods to get protein. You just have to eat any food. That’s it.

But don’t have to take my word for it…

“We never talk about protein anymore, because it’s absolutely not an issue, even among children,” says Marion Nestle, Ph.D., chair of the Department of Nutrition, Food and Hotel Management at New York University. “If anything, we talk about the dangers of high-protein diets. Getting enough is simply a matter of getting enough calories.6

The Myth of the Complete Protein

I hear it all the time: plant protein is “incomplete” compared to meat protein, and plant foods have to be carefully combined to make a “complete” protein.

This myth can be traced back to a best-selling book called Diet for a Small Planet. The author, Frances Moore-Lappé, promoted vegetarianism because meat production was a horrible waste of resources. She was afraid her readers would think they couldn’t get enough protein on a vegetarian diet, so she tried to reassure them by telling them that if they carefully combined various plant foods, the “inferior” plant proteins would become just as “complete” as the ones in the meat.

Moore-Lappé got this idea from 100-year-old studies on baby rats, which found that they grew best when the protein in their diet was in the same proportion found in animal food. The researchers then arbitrarily labeled animal proteins as “first-class” while plant proteins were deemed inferior. The problem with this conclusion is that it was based on the faulty assumption that baby rats had similar protein needs as humans. Rats grow very quickly; they double their birth weight in 4 ½ days. Human babies take six months to do this. To support such rapid growth rat milk is 49% protein. This is MUCH higher than human milk.

Moore-Lappé’s idea spread like wildfire. Soon the National Research Council and the American Dietetic Association joined in, without bothering to verify the theory that plant proteins were somehow inferior.7

But it wasn’t long before Lappé realized her mistake and owned up to it. In the 1981 edition of Diet for a Small Planet, she recanted:

“In 1971 I stressed protein complementarity because I assumed that the only way to get enough protein … was to create a protein as usable by the body as animal protein. In combating the myth that meat is the only way to get high-quality protein, I reinforced another myth. I gave the impression that in order to get enough protein without meat, considerable care was needed in choosing foods. Actually, it is much easier than I thought.

“With three important exceptions, there is little danger of protein deficiency in a plant food diet. The exceptions are diets very heavily dependent on [1] fruit or on [2] some tubers, such as sweet potatoes or cassava, or on [3] junk food (refined flours, sugars, and fat). Fortunately, relatively few people in the world try to survive on diets in which these foods are virtually the sole source of calories. In all other diets, if people are getting enough calories, they are virtually certain of getting enough protein.”8 [emphasis in original]

Ironic, isn’t it? Everyone who has the mistaken belief about protein combining got it from Moore-Lappé (directly or indirectly), but she took it back. I hope it means something that the person responsible for the idea being in your head in the first place said she was wrong.

The American Dietetic Association also abandoned the idea. Susan Havala Hobbs, Ph.D, R.D. describes how the ADA discarded the protein combining idea:

“There was no basis for [protein combining] that I could see…. I began calling around and talking to people and asking them what the justification was for saying that you had to complement proteins, and there was none. And what I got instead was some interesting insight from people who were knowledgeable and actually felt that there was probably no need to complement proteins. So we went ahead and made that change in the paper. [The paper was approved by peer review and by a delegation vote before becoming official.] And it was a couple of years after that that Vernon Young and Peter Pellet published their paper that became the definitive contemporary guide to protein metabolism in humans. And it also confirmed that complementing proteins at meals was totally unnecessary.”9

In addition to the American Dietetic Association, other medical and nutritional professionals who have looked at the science have come to the same conclusion:

Joel Fuhrman, M.D.
“[Y]ou don’t need to mix and match foods to achieve protein completeness. Any combination of natural foods will supply you with adequate protein, including all eight essential amino acids as well as unessential amino acids….It requires no level of nutritional sophistication to get sufficient protein, even if you eat only plant foods. It is only when a vegetarian diet revolves around white bread and other processed foods that the protein content falls to low levels. However, the minute you include unprocessed foods such as vegetables, whole grains, beans, or nuts, the diet becomes protein rich.”10

Dennis Gordon, M.Ed, R.D.:
“[C]omplementing proteins is not necessary with vegetable proteins. The myth that vegetable source proteins need to be complemented is similar to the myths that persist about sugar making one’s blood glucose go up faster than starch does. These myths have great staying power despite their being no evidence to support them and plenty to refute them.”11

Jeff Novick, M.S., R.D.:
“Recently, I was teaching a nutrition class and describing the adequacy of plant-based diets to meet human nutritional needs. A woman raised her hand and stated, ‘I’ve read that because plant foods don’t contain all the essential amino acids that humans need, to be healthy we must either eat animal protein or combine certain plant foods with others in order to ensure that we get complete proteins.’

“I was a little surprised to hear this, since this is one of the oldest myths related to vegetarianism and was disproved long ago. When I pointed this out, the woman identified herself as a medical resident and stated that her current textbook in human physiology states this and that in her classes, her professors have emphasized this point.

“I was shocked. If myths like this not only abound in the general population, but also in the medical community, how can anyone ever learn how to eat healthfully? It is important to correct this misinformation because many people are afraid to follow healthful, plant-based, and/or total vegetarian (vegan) diets because they worry about “incomplete proteins” from plant sources. …if you calculate the amount of each essential amino acid provided by unprocessed plant foods … you will find that any single one, or combination, of these whole natural plant foods provides all of the essential amino acids. …

“Modern researchers know that it is virtually impossible to design a calorie-sufficient diet based on unprocessed whole natural plant foods that is deficient in any of the amino acids. (The only possible exception could be a diet based solely on fruit.)12

John A. McDougall, M.D.:
“Many people believe than animal foods contain protein that is superior in quality to the protein found in plants. This is a misconception dating back to 1914, when Osborn and Mendel studied the protein requirements of laboratory rats.[11]… Based on these early rat experiments the amino acid pattern found in animal products was declared to be the standard by which to compare the amino acid pattern of vegetable foods. According to this concept, wheat and rice were declared deficient in lysine, and corn was deficient in tryptophan. It has since been shown that the initial premise that animal products supplied the most ideal protein pattern for humans, as it did for rats, was incorrect…. From the chart, it is clear that even single vegetable foods contain more than enough of all amino acids essential for humans…. Furthermore, many investigators have found no improvement by mixing plant foods or supplementing them with amino acid mixtures to make the combined amino acid pattern look more like that of flesh, milk, or eggs.[35-44] … People have actually lived for long periods of time in excellent health by satisfying their entire nutritional needs with potatoes and water alone.[33] … Nature has designed vegetable foods to be complete. If people living before the age of modern dietetics had had to worry about achieving the correct protein combinations in their diets, our species would not have survived for these millions of years.”13

Andrew Weil, M.D.:
“You may have heard that vegetable sources of protein are “incomplete” and become “complete” only when correctly combined. Research has discredited that notion so you don’t have to worry that you won’t get enough usable protein if you don’t put together some magical combination of foods at each meal.”14

Charles Attwood, M.D.:
“Beans, however, are rich sources of all essential amino acids. The old ideas about the necessity of carefully combining vegetables at every meal to ensure the supply of essential amino acids has been totally refuted.”15 [emphasis added]

Athletes Who Swear by Veggies

If you’re still not a believer, or if you think this information doesn’t apply to you because you are an athlete with special protein requirements, this last section is for you. Here are seven super-star, vegetarian athletes who demonstrate that you do not need meat to perform as well as the carnivorous competition.

Bill Pearl
Perhaps the world’s best-known vegetarian body builder, Pearl is a four-time Mr. Universe winner. He became a vegetarian at age 39 and won his last Mr. Universe title at age 41 – two years later. His books on body building are still considered essential reading for aspiring bodybuilders, and his vegetarianism is an inspiration to healthy athletes everywhere.

Joe Namath
Inducted into the NFL Hall of Fame, in 1985, Joe is one of the best football players of all time, period. In his words, “I have been a vegetarian for a few years. Fred Dryer of the Rams has been one for ten years. It shows you don’t need meat to play football.” Namath serves as a role model for aspiring gridironers everywhere.

Martina Navratilova
The Czech born legend Martina Navratilova is one of the greatest tennis players of the 20th century. She won 18 Grand Slam singles titles and 31 doubles titles–a record she still holds today. A vegetarian for most of her career, she’s a vocal PETA supporter–though recent reports find her occasionally venturing into fish meals.

Robert Parish
One of the greatest NBA basketball players in history, vegetarian Robert Parish played center for the Boston Celtics alongside Larry Bird. He was inducted into the Basketball Hall of Fame in 2003. Measuring over 7 feet tall, he was an imposing force on the court, yet was renowned for his versatility as well–and his high release jump shot was legendary.

Dave Scott
Scott holds the record for most Iron Man World Championship victories ever. The Iron Man, which consists of a 2.4 mile swim, a 112 mile bike ride, and a 26.2 mile run, is one of the most strenuous physical feats in the world. And Scott won six of them, all while vegetarian. He came out of retirement at 40 to compete again, and took second place. Today, at age 55, he still participates. In other words, this is one gnarly vegetarian dude.

Billie Jean King
Billie Jean King deserves a spot on the list along side Navratilova. In addition to winning 12 grand slam titles and 16 doubles titles, she’s famous for her Battle of the Sexes match, in which she defeated former men’s Wimbledon champion Bobby Riggs.

Carl Lewis
World famous track star Carl Lewis wasn’t always vegetarian. Be he eventually went even further: he adopted a vegan diet to prepare for the World Championships in 1991, where he says he ran the best meet of his life. And he wasn’t the only one who held that opinion – after seeing the results of his race, Track & Field magazine remarked, “It had become hard to argue that he is not the greatest athlete ever to set foot on track or field.” He won ABC’s Wide World of Sports Athlete of the Year in 1991 as a result. Carl Lewis earned a total of 10 Olympic medals over his career, nine of them gold medals. Here’s an interesting <a href=”http://www.ajc.com/sports/five-questions-carl-lewis-447944.html&#8221; title=”interview with Lewis”>interview with Lewis</a> published in April 2010 where he talks about his vegan diet.


1 John Robbins, Diet for a New America, 172 (1987) (citing the American Journal of Clinical Nutrition).

2 World Health Organization, Protein and Amino Acid Requirements in Human Nutrition 126 (2002). Recommendations are an “average requirement” of 0.66 g of protein per kg of ideal body weight, and a “safe level” of 0.86 g/kg. Percentages of protein vs. total calories were calculated by applying these figures for Estimated Energy Requirements as per the Dietary Reference Intakes, for a 5’5″ woman and a 5’11” man, each 30 years old and 24.99 BMI, at various activity levels.

3 Food and Drug Administration, Dietary Reference Intakes 4 . The FDA recommends men consume 56 grams of protein per day and women consume 46 grams of protein per day. If suggested caloric intake is 2301-3720 for a 5’11” man and 1816-2807 for a 5’5″ woman and a gram of protein has four calories, this works out to 8.0-12.3% protein for men and 6.6-10.1% for women.

4 USDA National Nutrient Database for Standard Reference.

5 USDA National Nutrient Database for Standard Reference. The percentage for fruit was calculated by averaging the protein in a serving of apples, pears, grapes, bananas, plums, oranges, grapefruit, watermelon, strawberries, peaches, nectarines, and cantaloupe. Vegetables protein was calculated by averaging the protein in a serving of broccoli, carrots, celery, corn, cucumber, green beans, iceberg lettuce, white mushrooms, onions, peas, potato, spinach, and tomato.

6 Debra Blake Weisenthal, Shattering the Protein Myth, Vegetarian Times (March 1995).

7 Donna Maurer, Vegetarianism: Movement or Moment?, 37 (2002).

8 Frances Moore-Lappé, Diet for a Small Planet, 162 (1982).

9 Maurer, supra note 7 at 38.

10 Joel Fuhrman, Eat to Live: The Revolutionary Formula for Fast and Sustained Weight Loss, 137 (2003).

11 Dennis Gordon, Vegetable Proteins Can Stand Alone, 96 Journal of the Am. Dietetic Ass’n, 230-231 (1996).

12 Jeff Novick, Complementary Protein Myth Won’t Go Away!, Healthy Times Newsletter (May 2003).

13 John A. McDougall, The McDougall Plan, 98-100 (1983).

14 Andrew Weil, Vegetarians: Pondering Protein? (2002).

15 Charles R. Attwood, “Complete” Proteins? (2009).