Plant-based living

Why Eating a Variety of Protein Sources Matters

Different foods supply different amino acids. Here's why variety matters, what complete and incomplete proteins are, and why you don't need to combine them at every meal.

Updated · 2 min read

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We've written before about why protein matters and how much you need. Here's a short follow-up with one practical tip: while you're getting enough protein, mix up where it comes from. Here's why variety matters, especially if you eat mostly plants.

Why does the source of your protein matter?

Proteins are built from about 20 amino acids, and each food contains them in different proportions. Your body breaks protein down into those amino acids and uses them to build and repair tissue. Some amino acids do even more: they help regulate key metabolic pathways that affect health and growth and act as signals that regulate gene expression. Different sources bring different amino acid profiles, so variety helps you cover them all.

What's the difference between complete and incomplete proteins?

A complete protein contains all nine essential amino acids, the ones your body can't make, in useful amounts. Animal foods such as meat, fish, eggs and dairy are complete proteins, as is soy.

Most individual plant proteins are lower in at least one essential amino acid. In a comparison of plant protein isolates, methionine and lysine were typically lower in plant proteins than in animal proteins. That makes plant proteins "incomplete" on their own, but it's easily solved: grains tend to be lower in lysine and legumes lower in methionine, so foods such as rice and beans complement each other. Mixtures of plant proteins can serve as a complete and well-balanced source of amino acids.

Do you need to combine proteins at every meal?

No. This is one of the most persistent myths about plant-based eating. According to MedlinePlus, you don't need to eat essential and nonessential amino acids at every meal; what matters is getting a balance of them over the whole day. If one food is low in an amino acid, another food later in the day can make up for it, as long as you're eating a range of protein sources rather than relying on one or two.

The Academy of Nutrition and Dietetics agrees that appropriately planned vegetarian and vegan diets are healthful and nutritionally adequate at all stages of life.

How do you add more variety to your protein?

Rotate through legumes (beans, lentils, chickpeas), soy (tofu, tempeh, edamame), whole grains (quinoa, oats, brown rice), and nuts and seeds. Our list of everyday vegan protein options has protein counts for common foods, and our recipes have plenty of ideas.

Want a shortcut? So Lean & So Clean pairs organic pea and rice protein for 23g of complete plant protein per serving, with all nine essential amino acids and no added sugar. For more on individual amino acids, see what BCAAs are.

Frequently asked questions

What is a complete protein?

A protein that contains all nine essential amino acids in useful amounts. Meat, fish, eggs, dairy and soy are complete proteins.

Are plant proteins incomplete?

Most individual plant proteins are lower in at least one essential amino acid, often lysine or methionine, but combining different plant proteins provides a complete amino acid supply.

Do I need to combine rice and beans at the same meal?

No. Getting a balance of amino acids over the whole day is enough, as long as you eat a variety of protein sources.

Is pea and rice protein a complete protein?

Together, yes. Pea protein is higher in lysine and rice protein supplies more methionine, so a blend covers each one's gap.

References

  1. Wu G. Functional amino acids in growth, reproduction, and health. Adv Nutr. 2010;1(1):31-7. https://pubmed.ncbi.nlm.nih.gov/22043449/
  2. Kimball SR, et al. Amino acids as regulators of gene expression. Nutr Metab (Lond). 2004;1(1):3. https://pubmed.ncbi.nlm.nih.gov/15507151/
  3. MedlinePlus. Amino acids. U.S. National Library of Medicine. https://medlineplus.gov/ency/article/002222.htm
  4. Gorissen SHM, et al. Protein content and amino acid composition of commercially available plant-based protein isolates. Amino Acids. 2018;50(12):1685-1695. https://pubmed.ncbi.nlm.nih.gov/30167963/
  5. Young VR, et al. Plant proteins in relation to human protein and amino acid nutrition. Am J Clin Nutr. 1994;59(5 Suppl):1203S-1212S. https://pubmed.ncbi.nlm.nih.gov/8172124/
  6. Melina V, et al. Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. J Acad Nutr Diet. 2016;116(12):1970-1980. https://pubmed.ncbi.nlm.nih.gov/27886704/