The myth of protein deficiency

When­ev­er I hear peo­ple talk­ing about how nutri­tious a food is, I usu­al­ly hear them talk about the amount and “qual­i­ty” of the pro­tein it con­tains. It’s as if peo­ple real­ly are get­ting sick from eat­ing low-pro­tein foods or foods with low-qual­i­ty pro­tein. They’re not. In real­i­ty, it’s prac­ti­cal­ly impos­si­ble to avoid get­ting enough pro­tein, includ­ing enough of all of the essen­tial amino acids, as long as you are eat­ing enough food to get enough calo­ries.

To get a pro­tein defi­cien­cy while get­ting enough calo­ries, you’d have to eat noth­ing but a low-pro­tein fruit (such as apples) or noth­ing but refined sug­ars and fats. If you eat enough of any sort of unre­fined grains and veg­eta­bles, your pro­tein require­ments will be eas­i­ly met.

What about the “qual­i­ty” of the pro­tein? Peo­ple often talk about pro­tein sources that are “high-qual­i­ty” or “com­plete.” They often warn that plant pro­teins are “incom­plete.” Although there are some impor­tant nutri­tion­al dif­fer­ences between plant pro­teins and ani­mal pro­teins, you sim­ply don’t have to wor­ry about the “com­plete­ness” of the pro­tein in plant foods. The only “incom­plete” pro­tein that peo­ple are like­ly to find on their din­ner plate is gelatin, which is extract­ed from ani­mal bones.

Gelatin is incom­plete because the caus­tic chem­i­cals used in the extrac­tion process break down some of the essen­tial amino acids. You couldn’t sur­vive if gelatin were your only source of pro­tein, but the pro­teins in plant foods are “com­plete” as far as human pro­tein require­ments go.

What is protein?

Pro­teins are huge mol­e­cules made up of small­er mol­e­cles called amino acids. The amino acids orig­i­nal­ly came from plants, which string them togeth­er to make their own pro­teins. When we digest a pro­tein, we break it apart into indi­vid­ual amino acids again. Then our cells use the amino acids to make their own pro­teins.

How pro­teins are made and digest­ed

Each of our genes is just a recipe that tells the cell which amino acids to use, and in what order, when mak­ing pro­teins. If there’s a short­age of any of the amino acids, the cell can’t make that pro­tein. Although the recipes in our genes can call for up to 20 dif­fer­ent amino acids, we need to get only 8 of them from our food. Our bod­ies can make the oth­er ones, some­times out of one of the oth­er amino acids. The­o­ret­i­cal­ly, if there’s a short­age of any of the essen­tial amino acids, it would be a lim­it­ing fac­tor for an animal’s growth.

How much protein do people need?

Sci­en­tists tend­ed to fol­low one of three basic approach­es to fig­ur­ing out how much pro­tein peo­ple need:

  • Ask peo­ple how much pro­tein they would like to eat, if they could afford to eat as much as they want­ed
  • Study rats, and then assume that rats and peo­ple are alike
  • Study what peo­ple are eat­ing and how it affects their health

Each approach gives you a dif­fer­ent answer, but only the third approach gives you a reli­able answer.

People want more protein than they need

Carl von Voit was a 19th cen­tu­ry Ger­man sci­en­tist who is con­sid­ered to be the “father” of mod­ern dietet­ics. From his clin­i­cal stud­ies, Voit knew that men need­ed about 50 grams of pro­tein per day. How­ev­er, he based his rec­om­men­da­tions for pro­tein intake on the amount of meat that work­ing­men would like to eat, if they could afford as much as they want­ed. So Voit came up with a rec­om­men­da­tion of near­ly 120 grams per day for men. Voit’s rec­om­men­da­tion was very pop­u­lar, because it was based on what peo­ple want­ed, not what was good for their health. When peo­ple eat as much meat as they want, they end up at risk for obe­si­ty, heart dis­ease, and gout.

Why do peo­ple want to eat an unhealthy amount of pro­tein? I think it’s main­ly because they like to eat an unhealthy amount of fat. When you ana­lyze ani­mal-based foods, you’ll find that most of the calo­ries come from fat. Fat­ty foods are a con­cen­trat­ed source of calo­ries. Since star­va­tion was the main dietary chal­lenge that our species has always faced, it makes sense that we’d want to eat as much fat­ty food as we could get. Occa­sion­al­ly gorg­ing on fat may have helped our ances­tors sur­vive long enough to repro­duce, but con­tin­u­al­ly gorg­ing on fat is pre­vent­ing a lot of peo­ple today from liv­ing long enough to get to know their grand­chil­dren.

Rats need far more protein than people do

One of the main dif­fer­ences between peo­ple and rats is the rate of growth. Peo­ple grow amaz­ing­ly slow­ly, and rats grow unbe­liev­ably fast. If a woman and a rat con­ceive on the same day, the rat will prob­a­bly give birth before the woman is even sure that she’s preg­nant. There are about 6 to 12 babies in a lit­ter of rats, and the babies them­selves can start breed­ing when they’re about 65 days old. As long as the food sup­ply holds out and there are no preda­tors, the sheer weight of the rat pop­u­la­tion can grow explo­sive­ly. It takes a lot of pro­tein to pro­duce all those pounds of rat bod­ies in so short a time.

You can stunt the growth of rats by feed­ing them plants instead of ani­mal-based foods. That’s because rats need so much pro­tein. They also need a high­er “qual­i­ty” of pro­tein than peo­ple need. Rats need to get ade­quate amounts of 10 dif­fer­ent “essen­tial” amino acids from the diet. The idea of com­bin­ing dif­fer­ent kinds of plant pro­teins to improve the “qual­i­ty” of the pro­tein came from stud­ies of rats. These com­bi­na­tions are also impor­tant for oth­er fast-grow­ing ani­mals, such as pigs and broil­er chick­ens.

Although a high-pro­tein diet and sup­ple­ments of spe­cif­ic amino acids are use­ful for max­i­miz­ing the growth of rats, pigs, and chick­ens, they are sim­ply unnec­es­sary for human beings. If you feed peo­ple any more pro­tein than they real­ly need, they just burn it for ener­gy. So all those pro­tein sup­ple­ments are noth­ing but a dirty form of sug­ar. Ordi­nary unre­fined starch­es and veg­eta­bles, such as rice or pota­toes, pro­vide all the pro­tein that human beings need. We don’t even need to com­bine dif­fer­ent kinds of plant foods to get a “com­plete” pro­tein. The only “incom­plete” pro­tein that human beings are like­ly to find on their plate is gelatin, which comes from ani­mal bones.

It’s practically impossible to get a protein deficiency

As long as you are eat­ing any rea­son­able selec­tion of unre­fined plant foods, if you take care of the calo­ries, the pro­tein takes care of itself. The sci­en­tif­ic evi­dence has been clear for over a cen­tu­ry. In order to get a defi­cien­cy of pro­tein, or any of the essen­tial amino acids, you’d have to eat a bizarre diet. You’d have to eat noth­ing but apples, or noth­ing but extract­ed sug­ars and fats, or (as is much more like­ly) noth­ing but alco­hol.

If you aren’t get­ting enough calo­ries, you will burn pro­tein for ener­gy. Pro­tein sup­ple­ments will do a starv­ing per­son lit­tle good unless you give them enough calo­ries that they stop hav­ing to burn up pro­tein for ener­gy. Since human beings grow so slow­ly, they can get by with a sur­pris­ing­ly low-pro­tein diet. This fact is reflect­ed in the rel­a­tive­ly low pro­tein con­tent of human breast milk.

About 20 years ago, while I was edit­ing the man­u­script of a nutri­tion text­book, I learned that pro­tein defi­cien­cy is a myth. As long as peo­ple get enough calo­ries from any rea­son­able diet, they auto­mat­i­cal­ly get enough pro­tein. The only peo­ple in the Unit­ed States who were get­ting a pro­tein defi­cien­cy despite eat­ing enough calo­ries were peo­ple who were get­ting noth­ing but glu­cose IVs, or babies who were being fed some bizarre sub­sti­tute for breast milk, or alco­holics who were get­ting too many of their calo­ries from booze. To see if that sto­ry had changed, I did a search on MEDLINE, which is an enor­mous data­base of med­ical and sci­en­tif­ic jour­nal arti­cles. It includes just about any arti­cle of any impor­tance and stretch­es back to the mid 1960s.

Sure enough, when I searched for “pro­tein defi­cien­cy,” I found that most of the arti­cles dealt with pigs and chick­ens. When I lim­it­ed the search to arti­cles on human beings, I found that most of the “hits” were for arti­cles about peo­ple who weren’t get­ting enough calo­ries either, or peo­ple who were los­ing pro­tein through their dam­aged kid­neys, or peo­ple who couldn’t digest their food prop­er­ly because there was some­thing wrong with their pan­creas or some oth­er part of the diges­tive sys­tem. I found lots of arti­cles about alco­holics. But I didn’t find any arti­cles that sup­port­ed the idea that pro­tein defi­cien­cy is some­thing for veg­e­tar­i­ans or even veg­ans to wor­ry about. Even when I looked up the adverse effects of veg­e­tar­i­an diets, I found arti­cles about vit­a­min B12 defi­cien­cy, but noth­ing about peo­ple get­ting sick from pro­tein defi­cien­cy.

Nor was I able to find any arti­cles about peo­ple who had trou­ble from eat­ing “incom­plete” plant pro­teins. I found reports of peo­ple dying from a fad diet whose sole pro­tein source was gelatin. How­ev­er, gelatin is a processed food that comes from ani­mals.

The Great Protein Fiasco

The sci­en­tif­ic evi­dence has shown since the ear­ly 20th cen­tu­ry that human pro­tein needs are small and eas­i­ly met by ordi­nary plant-based foods. Unfor­tu­nate­ly, the peo­ple who made nutri­tion pol­i­cy got con­fused by a dis­ease from Africa called kwash­iorkor. It was a form of star­va­tion that tend­ed to strike neglect­ed chil­dren in very poor pop­u­la­tions. Instead of being sim­ply scrawny, these poor chil­dren were hor­ri­bly swollen and their skin was peel­ing off like flaky paint. The British-trained Jamaican pedi­a­tri­cian who first described this con­di­tion sus­pect­ed that it might be due to a defi­cien­cy of pro­tein or one of the amino acids. Today, we still aren’t sure what caus­es kwash­iorkor, but the the­o­ry that it results from pro­tein defi­cien­cy in peo­ple who are get­ting enough calo­ries has fall­en out of favor. The peo­ple with kwash­iorkor aren’t get­ting enough calo­ries, either.

In the late 1950s, the experts at the Unit­ed Nation’s World Health Orga­ni­za­tion and Food and Agri­cul­ture Orga­ni­za­tion mis­tak­en­ly con­clud­ed that pro­tein defi­cien­cy was the sin­gle most impor­tant nutri­ent defi­cien­cy in the devel­op­ing world. Their over­es­ti­ma­tion of the amount of pro­tein peo­ple need cre­at­ed an imag­i­nary “pro­tein gap” in the Third World, thus launch­ing what lat­er was called the Great Pro­tein Fias­co. Researchers worked hard to fig­ure out ways to increase people’s intake of ani­mal pro­tein in poor coun­tries. This was an eco­nom­ic and envi­ron­men­tal and nutri­tion­al dis­as­ter, for sev­er­al rea­sons.

First, the focus on an imag­i­nary pro­tein gap obscured the real prob­lem, which was a short­age of food and thus a short­age of calo­ries and oth­er nutri­ents. The mal­nour­ished peo­ple in poor coun­tries are mal­nour­ished because they can’t afford to eat enough food, not because the foods the local peo­ple nor­mal­ly eat is too low in pro­tein. Poor peo­ple also tend to depend too heav­i­ly on a sin­gle sta­ple food, which meant that they are at greater risk for vit­a­min and min­er­al defi­cien­cies. Because of poor san­i­ta­tion, the peo­ple in poor coun­tries are also at high risk for par­a­site infec­tions, which could drain nutri­ents from their body, thus caus­ing ane­mia and oth­er prob­lems. None of these prob­lems are caused by pro­tein defi­cien­cy, and none of them can be solved by pro­tein sup­ple­ments.

The attempt to pro­vide pro­tein sup­ple­ments or to encour­age peo­ple to grow and eat more meat didn’t solve these prob­lems. Instead, they tend­ed to make them worse. The pro­tein sup­ple­ments tend­ed to be more expen­sive than people’s nor­mal food, so the peo­ple would end up being able to afford even few­er calo­ries. Since the prob­lem was lack of calo­ries, the peo­ple would be worse off than before. The same thing would hap­pen if peo­ple were encour­aged to grow and eat more meat. It would be far more effi­cient to eat grain your­self than to feed it to ani­mals and then eat the ani­mals.

Diet for a small planet

One response to the Great Pro­tein Fias­co of the 1960s and ear­ly 1970s was a best­selling book, Diet for a Small Plan­et. Its author, France Moore Lap­pé, was con­cerned about the prob­lem of world hunger. She argued, cor­rect­ly, that it is far more effi­cient to eat grains and soy­beans our­selves than to feed them to ani­mals and then eat the bod­ies, milk, and eggs of the ani­mals. How­ev­er, she was untrained in nutri­tion and was unaware how eas­i­ly human beings can get enough of all of the essen­tial amino acids from plant foods.

Lap­pé came up with a sys­tem by which peo­ple could com­bine dif­fer­ent plant foods with­in the same meal, so that togeth­er they would pro­vide a high­er “qual­i­ty” of pro­tein. For exam­ple, grains such as corn are rel­a­tive­ly low in lysine but have rel­a­tive­ly large amounts of methio­n­ine. beans con­tain lots of lysine but are rel­a­tive­ly lit­tle methio­n­ine. The­o­ret­i­cal­ly, you could get a bet­ter bal­ance of amino acids if you ate beans and corn togeth­er in the same meal.

Since Lappé’s book became a best­seller, many veg­e­tar­i­ans in the Unit­ed States have wor­ried about “com­bin­ing their pro­teins” in order to get a “com­plete” pro­tein. In real­i­ty, corn con­tains enough lysine and beans enough methio­n­ine to meet human nutri­tion­al needs. You don’t have to eat both of them. And you cer­tain­ly don’t have to wor­ry about eat­ing them in the same meal. In fact, if you work hard to com­bine plant pro­teins so that they have the same amino acid bal­ance as ani­mal pro­teins, you end up with some of the same draw­backs as ani­mal pro­teins, espe­cial­ly a high­er risk for can­cer pro­mo­tion.