Potent Proteins

by Martina M. Cartwright, PhD, RD on Sep 13, 2013

Diet Facts


Not all proteins are created equal. We divide them into the “complete” proteins like soy and animal sources, which contain all nine essential amino acids (EAA), and the incomplete proteins found in most vegetables and grains, which lack one or more EAAs. This would seem to complicate life for vegans, but it turns out that building complete dietary proteins is easy for those who know how to “complement.”

Proteins are ranked according to amino acid content and digestibility, typically via the Protein Digestibility Corrected Amino Acid Score (PDCAAS). The highest PDCAAS for a food is 1.0, meaning that after digestion, it provides at least 100% of the recommended amount of essential amino acids per unit of protein. Whey, milk, casein, egg whites and soy all score 1. Vegetable proteins can be combined to create a perfect score (Schaafsma 2012).

Meat, Fish, Eggs and Dairy

Packed with all nine EAAs, animal proteins are complete proteins, abundant in essential nutrients like B12, calcium, zinc and iron. On the downside, higher-fat varieties contain artery-clogging saturated fats. Good choices include low-fat dairy and lean meats. An ounce of beef or chicken provides 7-10 grams of protein and a cup of milk contains nearly 8 grams. A large egg has 6 grams of protein, with nearly equal amounts in the yolk and white (USDA 2013).

Six ounces of yogurt has 6 grams of protein. Most Greek yogurts contain double the protein of regular versions. Yogurt also is a good source of calcium, B vitamins and live active probiotic cultures (NYA 2013).

Super Seeds

All seeds are incomplete proteins. Flax, sesame and sunflower seeds provide 2-5 grams of protein per ounce. Ditto with trendy hemp and chia seeds. Potent pumpkin seeds triumph with about 9 grams per ounce. Seeds are good sources of healthy fats, vitamin E and essential minerals like magnesium, copper and zinc (USDA 2013).


Almonds, walnuts and cashews provide 6-8 grams of incomplete protein per ounce. Packed with healthy fats, fiber, vitamin E and minerals, nuts are an integral part of the Mediterranean Diet (Guasch-Ferre et al. 2013). Nut-rich diets can lower cholesterol (Damasceno et al. 2011); the FDA allows the claim, “Scientific evidence suggests, but does not prove, that eating 1.5 ounces per day of most nuts (e.g.: almonds, hazelnuts, peanuts, pecans, some pine nuts, pistachio nuts and walnuts) as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease” (FDA 2013).


Alfalfa, clover, peas, beans, lentils, carob, soy and peanuts are well-known legumes. Of these, soy contains the most protein with about 43 grams per 100-gram (3.5-ounce) serving. Edamame, tofu and soy milk are complete vegan proteins (Hughes et al. 2011). Beans and lentils are good sources of incomplete protein, with the added benefits of high fiber and B vitamins.

Great Complements

If you shun soy and avoid meat, it’s still easy to create complementary proteins by mixing and matching vegetarian proteins like these:

  • Lima beans and corn
  • Rice and beans
  • Hummus on whole-grain bread
  • Whole grain noodles with peanut sauce
  • Beans and tortillas
  • Peanut butter on whole-grain crackers


Damasceno, N.R., et al. 2011. Crossover study of diets enriched with virgin olive oil, walnuts or almonds. Effects on lipids and other cardiovascular risk markers. Nutrition, Metabolism and Cardiovascular Disease, 21 (1, Suppl.), S14-20.

FDA (U.S. Food and Drug Administration). 2013. Summary of Qualified Health Claims Subject to Enforcement Discretion. Nuts & heart disease. www.fda.gov/Food/IngredientsPackagingLabeling/LabelingNutrition/ucm073992.htm#nuts; retrieved August 19, 2013.

Guasch-Ferre, M., et al. 2013. Frequency of nut consumption and mortality risk in the PREDIMED nutrition intervention trial. BMC Medicine, 11, 164.

Hughes, G.J., et al. 2011. Protein digestibility-corrected amino acid scores (PDCAAS) for soy protein isolates and concentrate: criteria for evaluation. Agricultural and Food Chemistry, 59 (23), 12707-12712.

NYA (National Yogurt Association). 2013. Live and Active Culture Yogurt. www.aboutyogurt.com/Live-Culture; retrieved August 18, 2013.

Schaafsma, G. 2012. Advantages and limitations of the protein digestibility-corrected amino acid score (PDCAAS) as a method for evaluating protein quality in human diets. British Journal of Nutrition, 108 (2, Suppl.), s333-336.

USDA (U.S. Department of Agriculture). 2013. National Agricultural Library National Nutrient Database for Standard Reference. Release 26. http://ndb.nal.usda.gov/ndb/search/list; retrieved August 19, 2013.

Photography: Janet Hudson

IDEA Food and Nutrition Tips, Volume 2, Issue 5

© 2013 by IDEA Health & Fitness Inc. All rights reserved. Reproduction without permission is strictly prohibited.

About the Author

Martina M. Cartwright, PhD, RD

Martina M. Cartwright, PhD, RD IDEA Author/Presenter

Martina Cartwright is a registered dietitian (R.D.) with a Ph.D. in Nutritional Science and Biomolecular Chemistry from the University of Wisconsin-Madison. She has more than 20 years experience in me...


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  • Pat Pomerantz

    Good article. I'm vegan, so of course, I would say to stay away from animal products and soy is not the answer. Sorry folks. People always want to know how you get your protein as a vegan, and the mixing and matching food complements was spot on. Thank you. P.S. I am adamant about this since my husband has overcome Stage 4 Pancreatic Cancer by becoming vegan.
    Commented Sep 22, 2013
  • Christopher Williams

    Artery clogging saturated fats? I can't wait until the day the saturated fat misconception finally dies for good.
    Commented Sep 20, 2013

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