Plant protein-a complete protein

http://michaelbluejay.com/veg/protein.html

look up the numbers.

Vegetables are complete proteins
Amino acid >	Isoleu- cine	Leucine	Lysine	Phenylalaline +Tyrosine	Methionine	Threonine	Tryptophan	Valine	Histidine
Need
Brown Rice
Tomatoes
Potatoes
Green Peppers
Corn
Lettuce (iceberg)
Celery
Cucumbers
Oats
Carrots
Broccoli
Pinto Beans

Amino acid need from the World Health Organization⁴, food composition from the USDA nutrient database^4.1.





               the record straight

Vegetables have plenty of protein, and they're complete proteins as well

by Michael Bluejay • Last update: June 2013

Protein content of various foods
6.7%	Fruit
11%	Nuts & Seeds
13%	Grains
22%	Vegetables
28%	Beans
2.5% 11%	Need (Low end) Need (High end)
Protein given as a percentage of calories. Food figures are averages for several foods in each category4.1 and were taken from the bible of nutrient data, the USDA Food and Nutrient Database. Human need is from peer-reviewed research2, US govt. recommendations3, and WHO4  Chart from MichaelBluejay.com, ©2009-12

Common vegetables have much more protein than you need, and contrary to popular myth, they're complete proteins as well.¹  The reason you've heard otherwise is that the people spouting protein myths haven't bothered to look up the actual numbers.  (Anyone who thinks that vegetables don't supply enough protein or that it's incomplete for human needs should cite bona-fide science that says so.)  So let's look at what the science actually says — as well as what doctors and dietitians who are actually familiar with protein say.
We need only 2.5 to 11% of our calories from protein, according to peer-reviewed research and the official recommendations.^2,3,4  And that amount is easily supplied by common vegetables.^4.1 Vegetables average around 22% protein by calorie, beans 28%, and grains 13%.^4.1  Have a look at the chart at right.
The U.S. government's recommendation is 5-11%, based on various factors.³  The World Health Organization recommends a similar amount.⁴  And these recommendations are padded with generous safety margins, to cover people who need more protein than average.  WHO makes it clear that around 97% of people need less than their recommendations.⁴
In any event, whether you think our needs are closer to 2.5% or 11%, you can see from the chart that it's nearly impossible to fail to get enough protein, provided that you make sure to eat food.  Every single whole plant food has more than 2.5% protein, and every group averages at least 11% except for fruit.  Protein is one of the easiest nutrients to get.
The figures for food are from the bible of nutrition data, the USDA National Nutrient Database for Standard Reference. (I averaged the numbers for several foods in each category.^4.1 To find the percentage of protein for a sample, multiply the protein grams by 4 and divide by the number of calories.^4.2)
So plant foods easily supply our protein needs.  The truth is that if you're eating food, you're eating protein—and almost certainly more than enough.
It's meaningless to talk about a "source of protein", since 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 whole food. That's it.
Any well-educated health professional will tell you the same thing.  Take Marion Nestle, Ph.D, chair of the Department of Nutrition at New York University:

"We never talk about protein anymore, because it's absolutely not an issue, even among children.  If anything, we talk about the dangers of high-protein diets. Getting enough is simply a matter of getting enough calories."^4.3

Anyone who says otherwise simply hasn't bothered to look up the actual numbers.  The reason you've heard that plants are protein-deficient is because everyone is simply repeating that misinformation without looking at what the science actually says.  The science itself is clear and consistent, for anyone who cares to look. 
It's true that meat has more protein than vegetables, but the amount in vegetables is already much more than you need.  The extra protein in meat isn't better, it's useless.  If you're shopping for a car and one goes 200 miles an hour and the other goes 400, it doesn't matter, since the maximum speed limit in the U.S. is 80 mph.  Two hundred mph is more than enough for a car, and 22% protein from vegetables is more than enough when your protein needs are only 2.5 to 10%.
Oh, but you've heard that plant protein is "incomplete", right?  Well, that's not true either. Let's have a look....

Vegetables are complete proteins

We've all heard that plant protein is "incomplete" compared to meat protein, and that plant foods have to be carefully combined to make a "complete" protein.  But that's just an urban legend that was never based on science. The American Dietetic Association abandoned that idea decades ago.  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.^8.5

There's a very easy way to see the completeness of plant proteins, that most nutrition writers haven't bothered to do: Look at what's actually in the food!  It's not like this is a secret; that data has been publicly available from the USDA for decades, and now the USDA's database is even online.^4.1  Below is what it looks like when you actually look up the numbers.

Vegetables are complete proteins
Amino acid >	Isoleu- cine	Leucine	Lysine	Phenylalaline +Tyrosine	Methionine	Threonine	Tryptophan	Valine	Histidine
Need
Brown Rice
Tomatoes
Potatoes
Green Peppers
Corn
Lettuce (iceberg)
Celery
Cucumbers
Oats
Carrots
Broccoli
Pinto Beans

Amino acid need from the World Health Organization⁴, food composition from the USDA nutrient database^4.1.
Analysis is for each individual food all supplying calorie needs (closest to the "low active" category for a 5'11" 181lb. 25BMI male, as per the FDA).³

So when we compare the actual requirements to what plant foods actually contain, we find that basic plant foods aren't incomplete at all.  They have every essential amino acid, in excess of what we need.  It might not surprise you that beans are a complete protein by themselves, but even carrots are a complete protein.  Tomatoes are a complete protein.  Celery is a complete protein.  Even iceberg lettuce is a complete protein.
(Those who would object that we can't eat enough lettuce to satisfy our protein needs are wildly missing the point.  The point of using a day's worth of calories for a single food is simply to show how the food measures up, not to suggest that anyone could or should eat only a single food.  These plant foods are complete no matter how much or how little of them you eat.  That is, if only 1% of your diet is lettuce, then lettuce supplies more than 1% of your protein and amino acid requirements.)
Interestingly, the amounts for "Need" in the table are twice what they were until recently. The original recommendations in the WHO's 1973 and 1985 reports were based on William Rose's pioneering work in the 1950's, and were considerably lower.⁶  Rose determined the levels needed by his subjects by intentionally feeding them diets with a synthetic mixture of declining levels of amino acids until they became deficient.  After finding the highest amount needed by any subject, he then doubled that figure to arrive at his recommendation.⁷  And the current WHO recommendations have doubled their earlier figures again.  And even with all these increases, individual plants still measure up as fully complete.

  

Experts confirm that plant proteins are complete

Besides the American Dietetic Association, other medical and nutrition professionals who have actually looked at the science have come to the same conclusion that there is no need to carefully combine proteins.  For example: 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.⁸

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.)⁹

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.¹⁰

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.^10.5

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.¹¹

  

The original source of the protein combining myth recants!

Interestingly, it's very easy to trace the protein combining myth to its original source: A bestselling book called Diet for a Small Planet, in 1971. The author, Frances Moore-Lappé, wanted to promote meatless eating because meat production wastes horrific amounts of resources. But she knew her readers would think you couldn't get enough protein on a vegetarian diet, so she set out to reassure them, by telling them that if they carefully combined various plant foods, like rice and beans, the inferior plant proteins would become just as "complete" as the ones in meat. Lappé got her idea from studies that were done 100 years ago, on rats. The researchers found that rats grew best when the proteins in their diets were in the same proportions as found in animal foods. From this finding, animal proteins were arbitrarily labeled first-class while plant proteins were deemed inferior. The problem with this conclusion is that rats are not simply smaller vesions people.  Baby rats actually need a higher percentage of protein than baby do humans, because they grow a lot faster. People grow slowly.  It takes a baby half a year to double its birth weight.  A rat does it in only four and a half days.^4.8  So clearly rats are going to need more protein. In fact, rat milk is a whopping 49% protein^4.9 — much higher than the mere 6% found in human mother's milk.
Lappé's idea of protein combining spread like wildfire.  Soon the National Research Council and the American Dietetic Association, without bothering to verify the hypothesis, joined in by saying that plant proteins were inferior and had to be combined.^4.6
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 ar getting enough calories, they are virtually certain of getting enough protein."¹³ [emphasis in original]

Moore-Lappé has always been one of my heroes, and this is one reason why. Anyone can make a mistake, but it takes someone of integrity to own up to it. Especially when that mistake was instrumental in the person's success in the first place.  And the mistake aside, Moore-Lappé pretty much single-handedly jump-started the vegetarian movement in the U.S. in 1971, and deserves a place in history for that alone.
In any event, if you came to this page with the idea in your head that plant proteins have to be combined, I hope it means something to you that the person responsible for that idea being in your head in the first place said that she was wrong.
It's ironic, isn't it? Everyone who has the mistaken idea about protein combining got it from Moore-Lappé, directly or indirectly, but she took it back.
What's really crazy is how many people cling to the myth even after learning that Moore-Lappé admitted she was wrong. It would be akin to the news reporting that there was an earthquake in Japan, then correcting themselves and saying that the earthquake was actually in China, but people insisting on believing the earthquake was in Japan simply because that's what the news said first.  Likewise, most people insist on believing that plants are incomplete even though the person responsible for getting that thought into their heads in the first place now says it's not true.

Digestibility is not a problem

Some critics have screamed at me that plant protein isn't digested as well as animal protein.  Once again, these critics haven't bothered to look up the numbers.

The protein in beef and fish in 94% digestible.  That's actually less than the digestibility than plant foods like white flour (96%) and peanut butter (95%).  Peas, rice, whole corn, soy flour, oatmeal, and whole wheat flour aren't far behind (86-88%).  Beans, despite their high protein content, are a bit further down on the digestibility scale (78%).³ (By the way, the WHO report didn't list other vegetables, or I would have listed them here.)

This shows that digestibility isn't a problem at all, in practical terms.  Plant foods still provide more than enough protein, even after considering lower digestibility.  From the numbers above, the protein in meat is digested 20.5% better than that of beans.  If we take someone with a higher than average need for protein (10% of calories), and add 20.5% to that figure to account for lower digestibility, we now need 12.5% protein instead of 10%.  And again, grains average 13% protein and vegetables average 22%—more than enough.

Protein quality is not a problem

Some critics have pointed to various measures of protein quality, such as PDCAAS, which say that plant protein is inferior.  Such critics are missing the obvious:  The quality measures are mostly based on the amounts of amino acids in foods, and I've already explained in detail, with a nice chart, using numbers from official sources, that vegetables absolutely contain as much or more than you need of each individual amino acid.  That is, plant foods provide more than enough protein even after you account for any differences in digestion or protein quality.  Your body doesn't care whether the protein quality of what you're eating is "very high" vs. simply "high".  It's concerned only that you eat enough.  As long as your body is getting as much protein as it actually needs, it doesn't matter what form the protein comes in.

Critics are confusing more with better.  Yes, animal foods have more protein, but that's not a benefit.  There's absolutely no advantage to eating way more protein than your body can use.  If you need 2500 calories a day, would you be healthier with 3000 calories a day?  No.  In fact, eating that much more than you need would be detrimental to your health.  The same is true of eating too much protein.  Excess protein intake has been linked to bone loss, osteoporisis, kidney damage, kidney stones, immune dysfunction, arthritis, cancer promotion, low-energy, and overall poor health.^13.3  The science on this is very clear.

Vegan diets supply plenty of protein for building muscle

Vegan bodybuilders shatter the myth that vegans are skinny and malnourished.  (Pictured: Avi Lehyani, anonymous, Ryan Wilson, Robert Cheeke)

Plant foods supply plenty of protein even for athletes and those trying to build muscle. In a recent study older adults doing either lower-body or whole-body resistance training increased their muscle strength and mass on the US RDA for protein of only 0.36 g per lb. of body weight.^14.5 For a 120-lb. person eating 2000 calories or a 180-lb. person eating 2500 calories, that's 8.6% to 10.4% of their diets as protein. And remember, vegetables average 22% protein and beans 28%. Another study suggested that established bodybuilders need around 0.48 g of protein per pound of body weight per day (1.05 g/kg).¹⁵ (Incidentally, it also found that bodybuilders required 1.12 times and endurance athletes required 1.67 times more daily protein than sedentary controls.) For an 180-lb. athlete the 0.48 g/lb. figure is 90 grams (360 calories from protein). For a 3000-calorie diet, that's 12% of calories from protein. And again, vegetables average 22% and beans 28%.
Those starting a muscle-building program may need more protein, 0.77 g/lb. (1.7 g/kg).¹⁶ For a 180-lb. athlete that's 139 grams (556 calories). On a 3000-calorie diet, that's 18.5%, still less than supplied by common vegetables.
If the athlete eats more than 3000 calories a day, or weighs less than 180 lbs., then the percentage of protein required goes down even more.
In 2009 three major health organizations endorsed the 0.5 to 0.8 g/lb. (1.2-1.7 g/kg) figures above (American Dietetic Association, Dietitians of Canada and the American College of Sports Medicine)¹⁷
More is not better. As one paper said, "Ingesting more protein than necessary to maintain protein balance during training (e.g., >1.8 g/kg/d) does not promote greater gains in strength or fat-free mass."^17.5.
Jack Norris, RD points out that nutrient recommendations are always "padded" with safety margins. That is, most people need less:

Considering the information reviewed above...it seems reasonable to conclude that the protein needs of most vegan bodybuilders are somewhere between 0.8 and 1.5 g/kg (0.36 and 0.68 g/lb) of body weight.... The Food and Nutrition Board, which sets the RDA, reviewed Lemon et al.'s study and others and concluded there is no sufficient evidence to support that resistance training increases the protein RDA of 0.80 g/kg [0.36 g/lb] for healthy adults.¹⁸

For more on protein and muscle-building, see my separate article on Protein & Strength.

Other objections

I get lots of misinformed objections to this article, but some of it is really wacky.  One particular objection is that my use of recommendations from the World Health Organization (WHO) is wrong, because supposedly the WHO's recommendations are designed only to prevent extreme malnourishment among impoverished third-world residents.

Such critics have apparently never actually read a WHO report, since WHO reports say the exact opposite.  For example:

• "The levels of energy intake recommended by this expert consultation are based on estimates of requirements of healthy, well-nourished individuals."^18.5 (emphasis in original)
• "[T]he objective of this report is to make recommendations for healthy, well-nourished populations..."^18.5
• "The requirement...can be accepted as the best estimate of a population average requirement for healthy adults."³

A number of people have also complained about my statement that lettuce has more than enough protein (26%), because, they say, to get a day's worth of calories from it (e.g., 2000 calories), you'd have to eat 31 pounds of it.  Others suggest that even for higher-calorie foods, it would be boring to eat just one food.  Here's an example of such criticism:

How to lie with (food) statistics: [To] get 2000 calories out [lettuce], you would need to eat more than 14 kilos of the stuff. [Bluejay's] article cites 19 different sources. Yet by a single bullcannon claim - a true one! - it utterly fails the common sense test. Hint: DO NOT USE water-lettuce to boost yer average fer protein levels in veggies. This is on a par in stupidity level with suggesting that just because 7-UP isn't alcoholic you can still get drunk on it if you have at least 50 litres. (source)

I'm hesitant to answer this, because if the answer isn't already glaringly obvious to these critics or those who believe them, can they even understand the explanation? But here goes anyway:

The reason we look at the protein you'd get by eating an entire day's worth of calories from a single food is that this is simply a handy method of comparing the protein content of various foods, not to suggest that anyone should or even could eat 31 pounds of lettuce.  Sure, you can't eat 31 pounds of lettuce in a day, but whatever amount of lettuce you do eat helps (and doesn't hurt) your protein intake.  You could certainly eat 1% of your calories as lettuce, and if you did, that lettuce would supply more than 1% of your protein needs.  Ergo, lettuce supplies sufficient protein.

The "getting drunk on 7-UP" analogy is ridiculous.  7-UP doesn't have any alcohol, but lettuce does have protein.  (And more protein than you need, calorie per calorie.)

It's really meat that's incomplete

When you think about it, it's kind of silly to single out protein, just one of the many nutrients, just so we can declare plant proteins to be incomplete (although they're not). Why aren't we declaring meat to be an incomplete vitamin? Because it is, you know.  For example, beef is completely devoid of Vitamin C, an essential nutrient without which you'd die.  And beef doesn't just have a lower level of this essential nutrient, it has zero. So why didn't the authorities ever caution us that we need to combine various foods to get a complete vitamin? But actually, no combination of meat will make a complete vitamin, since every single kind of common meat has zero Vitamin C.  And it's deficient in other vitamins as well.  So while plants aren't actually deficient in protein, meat is definitely deficient in vitamins.  But I'm sure you never heard about vitamin deficiency in animal foods.  All you've heard about is the supposed deficiency of protein in plants.
And speaking about biases, the whole protein-combining idea supposes that vegetarians are eating just one food, which is allegedly incomplete.  Okay, how many people do you know who eat one food?  And since nobody eats just one food, the whole idea of protein combining would be unnecessary anyway, even if it were true.  So here again, what would be the point of harping on protein combining when it doesn't matter?

Using some common sense

The largest land animals in the world, elephants, are exclusively vegetarian. They grow up to 10,000 pounds, by eating nothing but plant matter.  They couldn't grow so big if plants weren't loaded with protein. Amazingly, many readers have protested this by saying "But we're not elephants!", as though they've made some sort of point.  If they mean to suggest that elephants don't need protein, they're wrong: Every living creature on the planet does. Elephants don't have some magical superpower which allows them to live and grow without eating protein. They need it, eat it, and use it, like everyone and everything else.
Perhaps the point was supposed to be that elephants utilize protein differently? Not in any meaningful way.  All protein, whether plant or animal, is broken down into the individual amino acids before the body uses it.  And that goes for any body, elephant, human, or otherwise.
Maybe the idea was that elephants get enough protein from plants only because they eat so much?  No, because once you adjust for body weight, elephants eat less than we do.  Per 100 lbs. of body weight, Americans eat about 3 lbs. of food per day, while elephants eat only 1.9. ^13.5
And elephants aren't the only huge vegetarian animals roaming the planet. There are also horses, camels, giraffes, elk, rhinos, cattle, and more. Clearly if these massive animals are eating only plants, then plants have more than sufficient protein.

Ignoring common sense

We've seen what answers we get when we use credible resources and common sense. What happens if we just draw ridiculous conclusions? I studied nutrition at the University of Texas at Austin, one of the largest universities in the country. They taught us that vegetarian or natural-foods diets were only for the stupid or naïve. I remember in particular one page from our textbook, which had three pie charts, each showing the proportion of macronutrients in vegetables, meat, and a human being, respectively. And by golly, the charts for the meat and for the human being were nearly identical! The implication was that meat is an ideal food, because it matches our body type so well.
It was at that point I realized I paid too much for my college education. Of course the charts were the same, because human beings are simply walking, talking meat. A body is a body, after all. By the logic presented in the textbook, if someone is white then they should eat white food.
And what about all the other animals? Elephants, giraffes, and horses would all have a pie chart that looks exactly like the one in the book. Shouldn't they be eating meat, too? Stupid elephants!  You know, I really should go find a horse and try to get her to eat some meat. If she's not interested, I should show her the textbook so she can see that beef has the same makeup of her own body type. If that doesn't convince her, I should at least implore her to combine her proteins to make a complete protein.

Changing our vocabulary

Now that we know the truth about protein, it's time to start changing the way we talk about it. Here are some common ways in which the word protein is misused.

"Are beans a good source of protein?"

This question misses the point. When all whole foods have plentiful protein, it's meaningless to talk about a "source" of it. Food is a good source of protein.  We don't ask whether certain foods are good sources of calories, because all foods have calories.

"I try not to eat a protein until lunchtime."

That's pretty much impossible, unless this person is not eating at all, since all whole foods contain protein, and they generally contain more than what you need.

There is no food that is "a protein".  Foods contain various nutrients, and protein is just one of them.  It's disparaging to food to identify it by just one of the nutrients it contains.  Would you call peanut butter a protein?  Because it's actually mostly fat, much more fat than protein.  Would you then call it a fat?  Why so, since it has more protein than you need?  We have to stop equating foods with individual nutrients.  Foods contain nutrients, they contain a collection of nutrients (not just one), and in any event, all whole foods contain protein.

"Try to eat three servings of lean protein."

There is no such thing as "lean protein". There is only food, all of which contains protein. We know that all food has protein, so something caled "lean protein" should at least be low in fat, right? Think again. The National Institutes of Health says "lean protein" can have up to 3 grams of fat per 55 calories.¹⁴ That's up to 49% fat! Forty-nine percent is lean to these people?! Lean would be something like 10%. Half-fat would not.
So "lean protein" is wrong on two counts. First it assumes that only certain foods have protein, or that a food can be "a protein" (rather than being food), and second, "lean protein" isn't even lean.

Ask them for their sources!

I know that other sources say that vegetarians have a hard time getting protein, and that they have to carefully combine them to make "complete" proteins. I heard that line in my nutrition class at the university, and just today I saw the complete protein myth in the booklet that came with my Omron Body Fat Analyzer. With all the people talking about complete proteins, you'd think there was really something to it. But it's one thing to say something, and it's another to back it up. When those espousing the need to carefully combine plant proteins are asked for their evidence, they're never able to produce any. Case in point:  After the American Heart Association printed the "complete proteins" myth in its journal, John A. McDougall, MD insisted that they back up their assertion. The AHA couldn't do so.¹⁹
So the first thing to ask someone who says that plant foods don't have more than abundant protein is, what percentage of protein do they think we need in our diets? If they don't have a specific, concrete answer then you can stop there, because they clearly don't know what they're talking about.
But let's say they answer, and their answer is higher than the ~10% recommended by the expert scientists at the Institute of Medicine and the World Health Organization.  Ask them why they think we need more than expert scientists say that we need.  While you're at it, ask them how it is they're more knowledgeable about human protein needs than nutrition scientists, and what their plans are for contacting the scientists to let them know they're wrong.
If their answer is 10% or less, ask them how much protein is in vegetarian food. Here again, if they don't know, then they don't know what they're talking about, and you can easily dismiss their position as being based on mere opinion and guessing. If they give an answer lower than the figures provided by the USDA summarized in the table above, ask them how it is they know better than the USDA.
If they say that we can't look at protein percentages because plant proteins are incomplete, ask them why looking at the actual numbers says the exact opposite. And ask them for their own data, from official sources, that backs their position. (They can't produce it, because it doesn't exist.)
Many people ask me, why are so many authorities giving out blatantly false information? You'll have to ask them, not me, since they're the ones giving it out. But I'll say that I think the answer has a lot more to do with psychology and sociology than it does with nutrition. And while you're at it, ask them for their sources. Anyone can say anything, but can they back it up? I tried to back up all the assertions I made in this article, with official, credible sources. I'm afraid those portraying plant proteins as inadequate or inferior haven't done the same.

---

Corrections

In an earlier version of this article, I mentioned that human breast milk is a mere 5.9%, supplying plenty of protein when we're growing the fastest, which suggests that we wouldn't need more than that as adults when we're not growing so fast.  However, as The Vegan RD points out, a comparison to babies on a percentage-of-calories basis is problematic, because babies consume lots more calories than adults.  Adjusting for a first-month baby's voracious appetite (i.e., assuming s/he consumes the same number of calories per pound of body weight as adults, but needs as much protein as a baby does), I calculate that a baby's protein consumption would look more like 16.5% of calories.  So it's not right to conclude that since mother's milk for fast-growing babies is only 5.9% protein, we therefore need less than 5.9% protein from our diets as adults.  But we could certainly conclude that we need less than 16.5% of calories as protein, and that's in fact what the official sources say.  Even so, common vegetables average more than 16.5% protein, even after adjusting for bioavailability. 

Further reading:

• Dr. McDougall on protein
• The Milk Letter: A message to my patients, by Robert M. Kradjian, M.D.                 

•