
Answer:
Many foods — including ones that are plant-based — are good sources of protein, although not all are good sources of complete protein. A complete protein (also sometimes referred to as "high-quality") refers to one that contains all nine essential amino acids (i.e., those that can't be produced by the body) in proportions needed by the human body and in a form that is readily digestible and can be absorbed (Hertzler, Nutrients 2020).
As discussed in detail in our full article, all animal proteins are complete but consuming more meat-based foods may not be the best way to go.
Pros and cons of animal proteins
All dietary animal protein sources are complete proteins. This includes meat, fish, poultry, eggs, and milk (Day, Trends Food Sci Technol 2022). However, some animal proteins may be more healthful than others. For example, fish meat is one of the most healthful sources of animal-based protein because there is typically less saturated fat in fish than in other meats such as red meat. Greek yogurt can also be a good food source of protein, although it does contain somewhat less calcium than regular yogurt.
Pros and cons of plant proteins
Not all plant-based proteins are complete, but people following a vegetarian or vegan diet can still meet protein requirements by considering the following: First, plant-based proteins typically contain a lower ratio of total essential amino acids to total protein compared to animal-based proteins. This means that a person may need to eat more of a plant-based protein to obtain the same amount of essential amino acids found in animal protein (Gorissen, Amino Acids 2018). Second, not all plant-based proteins are complete and those that are may be low in one or more specific amino acid. For instance, soy and hemp protein are "complete" proteins because they contain all nine essential amino acids, although soy is low in methionine and hemp is low in leucine and lysine. Other plant-based proteins such as rice and wheat protein are not considered to be complete proteins (Gorissen, Amino Acids 2018; Marsh, Med J Aust 2013; Craig, J Am Diet Assoc 2009). Fortunately, adding a complementary plant protein that contains higher amounts of the essential amino acid that's lacking may be beneficial. See our Protein Supplements Review for details about plant-based protein combinations that could be taken together to ensure that essential amino acid requirements are met. The Protein Supplements Review also includes our Top Picks among protein powders (which includes whey and casein as well as plant-based powders).
Also see our article "Top 8 vitamins and nutrients for vegetarians and vegans" to learn about other nutrients that might be inadequate in a strict vegetarian or vegan diet.
Can you get too much of an amino acid from food?
It may be possible to get too much of certain amino acids from high-protein foods, although the risk appears to depend on the type of high protein food. Sign in as a member for details.
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eve21916
February 07, 2025Food combining at the same meal is not necessary to obtain complete protein as long as you get them all in a day. Which is very easy
You are correct! We explain this in the Protein section of our article, "Top 8 vitamins and nutrients for vegetarians and vegans"
https://www.consumerlab.com/answers/eight-supplements-for-vegetarians-and-vegans/vegetarians-and-vegans/
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Martin21382
December 10, 2024Very good article, but there are, in my opinion, some discrepancies in how a "complete" protein is described. A "complete protein" typically refers to one containing all nine essential amino acids in sufficient amounts, not merely present (because they always are) but also in adequate proportions as defined by FAO/WHO standards. Moreover it is highly questionable, that methionin is limiting in the soy protein, if we take raw soybeans, cystein + methionin is limiting by 0,09 g/100 g of the reference protein, but who eats raw soybeans? If we take tofu on the other hand, all essential amino acids are more than sufficient (sources: fooddatacentral, FAO/WHO). So keep up with your good work and articles like that.
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Stan21233
November 30, 2024What is the relationship (if any) between sulfur-containing amino acids methionine and cysteine found mainly in beef, pork, chicken, and fish and cruciferous vegetables that are a rich source of sulfur?
We've added information to answer your question in the following section of our article: https://www.consumerlab.com/answers/getting-high-quality-protein-from-food/complete-protein-from-food/#vegetables-with-sulfur
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Bruce21038
November 05, 2024So that suggested limit of the two sulfur-containing amino acids means 1.33 G per day of each, or 1.33 G per day combined?
Great question! The 1.33-gram limit is for the two amino acids, combined.
njb
November 08, 2024Well all listed contain more than 1.33g!! Can't eat any??!!
As shown in the third column of the table in our article, all of the listed foods contain more than 1.33 grams of total protein per serving, but none of the products contain more than 1.33 grams of sulfur-containing amino acids per serving. However, some foods do contain close to this amount.
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JoAnna21033
November 05, 2024You did not mention lamb, or eggs in your protein list
We appreciate your feedback. The table in our article has been updated to include details on the protein content and sulfur-containing amino acids found in lamb and eggs.
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Ron21032
November 05, 2024Is there any data, observational or otherwise, suggesting that N-Acetylcysteine (NAC) possesses the same toxicity?
Please see our N-Acetyl Cysteine Supplements Review for information about side effects and safety concerns linked with NAC: https://www.consumerlab.com/reviews/n-acetyl-cysteine-nac-supplements/n-acetyl-cysteine/#cautions
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Steven20889
October 15, 2024Is L-arginine the only amino acid with potential health risks if we get too much? I thought I saw recent findings about one of the aminos beeing risky.
Great question! Please see the following section of our article for information about getting too much of an amino acid from food: https://www.consumerlab.com/answers/getting-high-quality-protein-from-food/complete-protein-from-food/#too-much-amino-acid
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Mary20886
October 15, 2024I like broth better than protein shakes -- for me, anyway. I don't buy store-bought, make my own, no idea how much protein is in a serving, but it's great first thing in the morning and even (after water) after a workout.
You can see how much protein and collagen we found in popular bone broths in our Bone Broth Review https://www.consumerlab.com/reviews/bone-broth-review/bone-broth/.
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