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 1: Sample Menus Showing How Easy It Is To Meet Protein Needs

Protein (grams)
Breakfast: 1 cup Oatmeal 6
  1 cup Soy Milk 7
  1 medium Bagel 10
Lunch: 2 slices Whole Wheat Bread 7
  1 cup Vegetarian Baked Beans 12
Dinner: 5 oz firm Tofu 12
  1 cup cooked Broccoli 4
  1 cup cooked Brown Rice 5
  2 Tbsp Almonds 4
Snack: 2 Tbsp Peanut Butter 8
  6 Crackers 2
TOTAL   77 grams
Protein Recommendation for Male Vegan 63 grams
[based on 0.9 gram of protein per kilogram body weight for 70 kilogram (154 pound) male]

Breakfast: 2 slices Whole Wheat Toast 7
  2 Tbsp Peanut Butter 8
Lunch: 6 oz Soy Yogurt 6
  2 Tbsp Almonds 4
  1 medium Baked Potato 3
Dinner: 1 cup cooked Lentils 18
  1 cup cooked Bulgur 6
Snack: 1 cup Soy Milk 7
TOTAL   59 grams
Protein Recommendation for Female Vegan 52 grams
[based on 0.9 gram of protein per kilogram body weight for 57.5 kilogram (126 pound) female]
Additional food should be added to these menus to provide adequate calories and to meet requirements for nutrients besides protein.

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.

Table 2: Protein Content of Selected Vegan Foods

FOOD AMOUNT PROTEIN PROTEIN
   (gm) (gm/100 cal)

Tempeh 1 cup 31 9.6
Soybeans, cooked 1 cup 29 9.6
Seitan 3 ounces 21 17.5
Lentils, cooked 1 cup 18 7.8
Black beans, cooked 1 cup 15 6.7
Kidney beans, cooked 1 cup 15 6.8
Chickpeas, cooked 1 cup 15 5.4
Pinto beans, cooked 1 cup 15 6.3
Lima beans, cooked 1 cup 15 6.8
Black-eyed peas, cooked 1 cup 13 6.7
Veggie burger 1 patty 13 18.6
Veggie baked beans 1 cup 12 5.0
Tofu, firm 4 ounces 11 10.6
Tofu, regular 4 ounces 10 10.7
Bagel 1 med. (3.5 oz)10 3.9
Quinoa, cooked 1 cup 8 3.7
Peas, cooked 1 cup 8 6.6
Textured Vegetable Protein (TVP), cooked 1/2 cup 8 15.0
Peanut butter 2 Tbsp 8 4.1
Veggie dog 1 link 8 13.3
Spaghetti, cooked 1 cup 8 3.7
Almonds 1/4 cup 8 3.7
Soy milk, commercial, plain 1 cup 7 7.0
Whole wheat bread 2 slices 7 5.2
Almond butter 2 Tbsp 7 3.4
Soy yogurt, plain 8 ounces 6 4.0
Bulgur, cooked 1 cup 6 3.7
Sunflower seeds 1/4 cup 6 3.3
Cashews 1/4 cup 5 2.7
Spinach, cooked 1 cup 5 13.0
Broccoli, cooked 1 cup 4 6.7
Sources: USDA Nutrient Database for Standard Reference, Release 24, 2011 and manufacturers’ information.
The recommendation for protein for adult male vegans is around 63 grams per day; for adult female vegans it is around 52 grams per day.

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 Lappe, 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.

Table 3: Amounts of Foods Providing Recommended Amounts of Essential Amino Acids

12-3/4 cups of cooked corn OR 8 large potatoes OR 2-1/2 cups of tofu OR 15-1/2 cups of cooked brown rice
Any one of the above foods, eaten in the amount specified, would provide the recommended amounts of all essential amino acids for an adult male. Women would need about 20% less of each food due to lower recommendations. This concept is illustrated below:
Food Try Thr Iso Leu Lys Met+Cys Phe+Tyr Val
Adult RDA,154 lb male (1) 350 1400 1330 2940 2660 1330 2310 1680
12-3/4 cups corn 437 2527 2527 6801 2679 1824 5339 3629
8 large potatoes 646 2057 2033 2990 3277 1723 3971 3134
2-1/2 cups tofu 780 2045 2480 3808 3298 1333 4112 2530
15-1/2 cups cooked rice 907 2569 2962 5773 2660 2418 6237 4111
Source: USDA Nutrient Database for Standard Reference, Release 24, 2011.
Notes: Amounts of amino acids are in milligrams. Try=tryptophan, Thr=threonine, Iso=isoleucine, Leu=leucine, Lys=lysine, Met+Cys=methionine+cysteine, Phe+Tyr=phenylalanine+tyrosine, Val=valine

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.

References

  1. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: National Academy Press, 2002.
  2. Rodriguez NR, DiMarco NM, Langley S. Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance. J Am Diet Assoc 2009;109:509-27.
  3. Mangels R, Messina V, Messina M. The Dietitian’s Guide to Vegetar-ian Diets, 3rd ed. Sudbury, MA: Jones and Bartlett Learning, 2011.
  4. Sellmeyer DE, Stone KL, Sebastian A, et al. A high ratio of dietary animal to vegetable protein increases the rate of bone loss and the risk of fracture in postmenopausal women. Am J Clin Nutr 2001;73:118-22.
  5. Knight EL, Stampfer MJ, Hankinson SE, et al. The impact of protein intake on renal function decline in women with normal renal function or mild insufficiency. Ann Intern Med 2003;138:460-7.
  6. Lappe FM. Diet for a Small Planet. New York: Ballantine Books, 1971.
  7. Lappe FM. Diet for a Small Planet, 10th anniversary edition. New York: Ballantine Books, 1982.
  8. Young VR, Pellett PL. Plant proteins in relation to human protein and amino acid nutrition. Am J Clin Nutr 1994;59 (suppl):1203S-1212S.
  9. Craig WJ, Mangels AR. Position of The American Dietetic Association: Vegetarian Diets. J Am Diet Assoc 2009;109:1266-82.