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Protein in the Vegan Diet

by Reed Mangels, PhD, RD

From Simply Vegan 5th Edition

Summary

It is easy for a vegan diet to meet recommendations for protein, as long as calorie intake is adequate. Strict protein combining is not necessary; it is more important to eat a varied diet throughout the day.

Some Americans are obsessed with protein. Vegans are bombarded with questions about where they get their protein. Athletes used to eat thick steaks before competition because they thought it would improve their performance. Protein supplements are sold at health food stores. This concern about protein is misplaced. Although protein is certainly an essential nutrient which plays many key roles in the way our bodies function, we do not need huge quantities of it. Only about one calorie out of every 10 we take in needs to come from protein. Vegan athletes, especially in the early stages of training, may have higher protein needs than vegans who exercise moderately or who are not active. Vegan athletes’ protein needs can range from 0.36 to 0.86 grams of protein per pound. [2] Protein supplements are not needed to achieve even the highest level of protein intake.

How much protein do we need? The RDA recommends that we take in 0.8 grams of protein for every kilogram that we weigh (or about 0.36 grams of protein per pound that we weigh) [1]. This recommendation includes a generous safety factor for most people. When we make a few adjustments to account for some plant proteins being digested somewhat differently from animal proteins and for the amino acid mix in some plant proteins, we arrive at a level of 0.9 gram of protein per kilogram body weight (0.41 grams per pound). 

If we do a few calculations we see that the protein recommendation for vegans amounts to close to 10% of calories coming from protein. [For example, a vegan male weighing 174 pounds could have a calorie requirement of 2,600 calories. His protein needs are calculated as 174 pounds x 0.41 g/pound = 71 grams of protein. 71 grams of protein x 4 calories/gram of protein = 284 calories from protein. 284 divided by 2,600 calories = 10.9% of calories from protein.] If we look at what vegans are eating, we find that, typically, between 10-12% of calories come from protein [3]. This contrasts with the protein intake of non-vegetarians, which is close to 14-18% of calories.

So, in the United States it appears that vegan diets are commonly lower in protein than standard American diets. Remember, though, with protein, more (than the RDA) is not necessarily better. There do not appear to be health advantages to consuming a high protein diet. Diets that are high in protein may even increase the risk of osteoporosis [4] and kidney disease [5].

Table 2 shows the amount of protein in various vegan foods and also the number of grams of protein per 100 calories. To meet protein recommendations, the typical moderately active adult male vegan needs only 2.2 to 2.6 grams of protein per 100 calories and the typical moderately active adult female vegan needs only 2.3 to 2.8 grams of protein per 100 calories. These recommendations can be easily met from vegan sources.

It is very easy for a vegan diet to meet the recommendations for protein. Nearly all vegetables, beans, grains, nuts, and seeds contain some, and often much, protein. Fruits, sugars, fats, and alcohol do not provide much protein, so a diet based only on these foods would have a good chance of being too low in protein. However, not many vegans we know live on only bananas, hard candy, margarine, and beer. Vegans eating varied diets containing vegetables, beans, grains, nuts, and seeds rarely have any difficulty getting enough protein as long as their diet contains enough energy (calories) to maintain weight. [See Feeding Vegan Kids, Pregnancy and the Vegan Diet, and the section on lactation (page 186, in Simply Vegan), for details about protein needs during these special times.]

What about combining or complementing protein? Doesn’t that make the protein issue much more complex? Let’s look at a little background on the myth of complementing proteins. Protein is made up of amino acids, often described as its building blocks. We actually have a biological requirement for amino acids, not for protein. Humans cannot make nine of the twenty common amino acids, so these amino acids are considered to be essential. In other words, we must get these amino acids from our diets. We need all nine of these amino acids for our body to make protein.

Some people say that eggs, cow’s milk, meat, and fish are high quality protein. This means that they have large amounts of all the essential amino acids. Soybeans, quinoa (a grain), and spinach also are considered high quality protein. Other protein sources of non-animal origin usually have all of the essential amino acids, but the amounts of one or two of these amino acids may be low. For example, grains are lower in lysine (an essential amino acid) and legumes are lower in methionine (another essential amino acid) than those protein sources designated as high quality protein.

Frances Moore Lappé, in her book Diet for a Small Planet [6] advocated the combining of a food low in one amino acid with another food containing large amounts of that amino acid. This got to be a very complicated process, with each meal having specific amounts of certain foods in order to be certain of getting a favorable amino acid mix. Many people got discouraged with the complexity of this approach. Actually, Lappe was being overly conservative to avoid criticism from the “Nutrition Establishment.” She has since repudiated strict protein combining, saying, “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”. [7]

We recommend eating a variety of unrefined grains, legumes, seeds, nuts, and vegetables throughout the day, so that if one food is low in a particular essential amino acid, another food will make up this deficit. [8] [9]

As an extreme example, even if you only ate one kind of grain, bean, potato, or vegetable as a protein source, and ate enough of that food, you could meet your protein and amino acid needs. Admittedly, it would be a very monotonous way to eat and you might miss out on other nutrients. We point this out, however, to illustrate the idea that almost all non-animal protein sources contain all of the essential amino acids. Table 3 above shows the amount of rice, corn, potatoes, or tofu that an adult male would need to eat if he relied on only one food as a protein source. Women would need about 20% less food because of women’s lower protein requirements.

See Gluten free diet and protein sources. [[blog]]

References