The Myth of Incomplete Protein – Resolved!

The Myth of Incomplete ProteinThe Myth of Incomplete Protein from plants is going to get it’s final nail in this post and laid to rest for good. Only not in peace I imagine. So much of our food economy and our cultural eating habits are based on false claims about protein, and industry “milks” it. 

But as you see in this recent post from Jeff Novick MS, RD, the myth will finally be resolved, if it wasn’t already.  

Q. You stated that “any single whole natural plant food, or any combination of them, if eaten as one’s sole source of calories for a day, would provide all of the essential amino acids”. So if one elected to eat only cauliflower (or broccoli or carrots or any other vegetable) for an entire day though one would obviously miss some of the necessary nutrients for a healthy diet there would always be enough of the 8 EAA’s to produce the required proteins? 

If they were consuming enough calories to maintain a healthy weight, yes.

Q.  You also said, “The only possible exception could be a diet based solely on fruit. Which amino acids are missing in fruit?

None. It is just that the total might be low if all they ate were sweet fruits.

Q. However, in order for your gentle readers to enlighten family and friends not versed in the benefits of WFPB (whole foods, plant based) “nutrient rich” nutrition one can’t simply say it is a fact because Jeff Novick and John McDougall said it was so. We will need a brief scientific explanation to support this conclusion.

Though I am sure that most of the conclusions in your articles are patently obvious to you most of your readers lack your extensive nutritional background so a little assistance in the area of scientific method would be helpful. A sentence of explanation or a footnote source supporting your position would prove extremely helpful. It would allow us to easily research the topic further as necessary.

It was only a blog, edited down from a general article in my newsletter and not an in depth review article on the topic. 

The data is there and has been there for many years and I will include some of it below. 

However, it is really not just about scientific studies per see, but a simple analysis of the content of food.   If you go to the USDA Database Standard Reference 25 and look up the analysis of any one whole plant food, you will see that all the amino acids exist in the food and if you calculated the amount one would get at ~2300 calories, you would see all the amino acids in the right amounts.  So, what more do you need?

In a way, it is like asking for proof that an 8 cylinder car has 8 cylinders just because many people think it only has 6. 

Just open the hood and look. 🙂


However,  because you asked, here are a few references…

Position of the American Dietetic Association: vegetarian diets. 

Craig WJ, Mangels AR; American Dietetic Association.

J Am Diet Assoc. 2009 Jul;109(7):1266-82.

PMID: 19562864

Young VR, Pellett PL. Plant proteins in relation to human protein and amino acid nutrition. Am J Clin Nutr. 1994;59(suppl):1203S–1212S. MEDLINE

Rand WM, Pellett PL, Young VR. Meta-analysis of nitrogen balance studies for estimating protein requirements in healthy adults. Am J Clin Nutr. 2003;77:109–127. MEDLINE

Young VR, Fajardo L, Murray E, Rand WM, Scrimshaw NS. Protein requirements of man: Comparative nitrogen balance response within the submaintenance-to-maintenance range of intakes of wheat and beef proteins. J Nutr. 1975;105:534–542. MEDLINE

FAO/WHO/UNU Expert Consultation on Protein and Amino Acid Requirements in Human Nutrition. Protein and Amino Acid Requirements in Human Nutrition: Report of a Joint FAO/WHO/UNU Expert Consultation. Geneva, Switzerland: World Health Organization; 2002;WHO Technical Report Series No. 935.

Messina V, Mangels R, Messina M. The Dietitian’s Guide to Vegetarian Diets: Issues and Applications. 2nd ed.. Sudbury, MA: Jones and Bartlett Publishers; 2004;.

Tipton KD, Witard OC. Protein requirements and recommendations for athletes: Relevance of ivory tower arguments for practical recommendations. Clin Sports Med. 2007;26:17–36. Full Text | Full-Text PDF (218 KB) | CrossRef

From the American Journal Of Clinical Nutrition.

Plant Proteins in relation to human protein and amino acid nutrition.  Vernon R Young & Peter L Pellet.  Amer J Clin Nutr  1994;59(s):1230s-1212s

“… One reason for discussing amino acid complementation is to introduce the question of ingestion of complimentary proteins. There is some concern, at least at the consumer level, about the need to ingest different plant proteins at the same time, or within the same meal, to achieve maximum benefit and nutritional value from proteins with different, but complementary, amino acid patterns.  This concern may also extend to the question of the need to ingest a significant amount of protein at each meal, or whether it is sufficient to consume protein in variable amounts at different meals as long as the daily average intake meets or exceeds the recommended or safe protein intakes.

According to FAO/WHO/UNU, estimates of protein requirements refer to metabolic needs that persist over moderate periods of time.  Although protein and amino acid requirements are conventionally expressed as daily rates (of intake), this is no implication that these amounts must be consumed each and every day.  Therefore, it is not essential, at least in adults, that daily intakes of protein, or presumably of each indispensable amino acid, must equal of exceed the physiological requirement: it is apparently sufficient for the average intake over a number of days to achieve this level.  This pattern of intake would allow maintenance of an adequate protein nutritional state.

(NOTE:  this part is in regard to the value of the original studies done on rats and then pigs)

Earlier work in rapidly growing rats suggested that delaying the supplementation of a protein with its limiting amino acids reduces the value of the supplement.  Similarly the frequency of feeding of diets supplemented with lysine in growing pigs affects overall efficiency and utilization of dietary protein.  There are few data available from human studies to assess the significance of these findings. However the relevance of rat and pig studies can be questioned in view of the profoundly  different qualitative and quantitative characteristics of protein metabolism in in rats and pigs compared to human subjects.   

(NOTE: this part is discussing the amino acid pool and using lysine as their example, since it is often thought of as one of the more “limiting” amino acids)

…. it is of interest and relevance that in the skeletal musculature, there is a sizable pool in the intracellular space of free amino acids, particularly of lysine. The size of the pool responds to changes, both in acute and chronic,in the amount of lysine ingested  (43) Based on the data of Bergstrom et all (44) we calculate that after a protein rich meal 60% of the adult daily requirement for lysine may be deposited in this intracellular pool within 3 hours.  Hence, a protein with a relatively low lysine content (corn) could be ingested some hours later than a complementary, higher lysine containing protein (soy) and the free-lysine pool in the muscle would buffer the low lysine content of the amino acid mixture derived from the digestion of the corn.  Overall, the nutritional quality of the combined meals would be high.  We conclude that it is not necessary to balance the amino acid profile at each meal, especially under conditions where intakes of total protein substantially exceed minimum physiological requirements.

Summary and Conclusions

Thus, we conclude that consumers do not have to be at all concerned about amino acid imbalances when the dietary amino acid supply is from the plant food proteins that make up our usual diets. 

43 Munro HN Free amino acid pools and their role in regulation.  In Murno HN ed, Mamaliam protein metabolism. Vol 4. New York. Academic Press, 1970:299-386

44.  Bergstrom J. et al. Effect of a test meal, without and with protein, on muscle and plasma free amino acids.  Clin Sci. 1990;79:331-7

It is even adequate in athletes…

From Physical fitness and vegetarian diets: is there a relation?

Am J Clin Nutr. 1999 Sep;70(3 Suppl):570S-575S.

The available evidence supports neither a beneficial nor a detrimental effect of a vegetarian diet on physical performance capacity, especially when carbohydrate intake is controlled for. Concerns have been raised that an emphasis on plant foods to enhance carbohydrate intake and optimize body glycogen stores may lead to increases in dietary fiber and phytic acid intake to concentrations that reduce the bioavailability of several nutrients, including zinc, iron, and some other trace minerals. There is no convincing evidence, however, that vegetarian athletes suffer impaired nutrient status from the interactive effect of their heavy exertion and plant-food based dietary practices to the extent that performance, health, or both are impaired. Although there has been some concern about protein intake for vegetarian athletes, data indicate that all essential and nonessential amino acids can be supplied by plant food sources alone as long as a variety of foods is consumed and the energy intake is adequate. There has been some concern that vegetarian female athletes are at increased risk for oligoamenorrhea, but evidence suggests that low energy intake, not dietary quality, is the major cause. In conclusion, a vegetarian diet per se is not associated with improved aerobic endurance performance. Although some concerns have been raised about the nutrient status of vegetarian athletes, a varied and well-planned vegetarian diet is compatible with successful athletic endeavor.

From one of the resources responsible for the promotion of the myth….

DIET FOR A SMALL PLANET, Tenth Anniversary Edition, Frances Moore Lappe, p 161-162:

“When I first wrote DIET FOR A SMALL PLANET in 1971, the idea that

people could live well without meat seemed much more controversial

than it does today.  I felt I had to prove to nutritionists and doctors that because we could combine proteins to create foods equal in protein usability to meat, people could thrive on a non-meat or low-meat diet.  Today, few dispute that people can thrive on this kind of diet.  In fact, more and more health professionals are actually advocating less meat precisely for health reasons, reasons I discussed in ‘America’s Experimental Diet.’

“In 1971 I stressed protein complementary because I assumed that the only way to get enough protein (without consuming too many calories) was to create a protein as usable by the body as animal protein.  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.”

So, Plant foods are not incomplete proteins in regard to “incomplete” meaning “missing” amino acids.  All plant food contain all the EAAs, The only known commonly consumed food product that is truly an incomplete protein is an animal food, gelatin.

Plant foods are not incomplete proteins either in regard to having “limiting” amounts of amino acid.  Plant foods therefore do not have to be combined in certain combinations at each meal (or at all) to meet some reference EAA profile that is considered ideal.  While some plant foods may have lower amounts of one or two EAAs when compared to some animal foods, these amounts are still adequate amounts to meet human needs.

  •  The body has a dynamic circulating pool of AA’s, which includes the EAAs, that are readily available and can be drawn upon when necessary. 
  •  The original “reference” and “standard” protein (egg) was established on feeding experiments on young rats, which have completely different protein and amino acid needs than humans, so the whole concept is flawed from the beginning.By Jeff Novick, MS, RD

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