I’ve read on the back of a container of soy milk, that soy is one of the few vegetable sources of “complete protein”. I was a little surprised at this statement. I’ve checked it out on the internet and have seen this claim repeated with no further details. I had always thought there is no single vegetable containing all of the amino acids that are necessary for human life; in other words, there isn’t one vegetable you could pick to eat and expect to last for very long, whereas you could survive on meat forever.
If it is true that soy protein is “complete”, why is it complete where other bean sources are not? What other single vegetable source has a “complete” set of amino acids that we need to survive?
Complete protein is generally defined as containing sufficient quantities of the essential amino acids in a reasonable consumable portion.
Vegetables, legumes and grains contain some of these EAAs - but generally require combining in order to create the full array. The amount of food one must consume to be equivalent to animal protein is fairly large - and not what most people would find enjoyable to eat.
Soy is the one non-animal protein source that is reasonably complete on its own, afaik.
I thought what you just stated is common knowledge, and implied in my original question.
Why would soy be the one? I’m looking for a little proof beyond just the statements that I’ve found thus far. I was always under the impression (I was taught this in school) that there are NO vegetable sources of complete protein (in one vegetable).
Soy protein is OK, but it’s a little deficient in methionine. The ‘completeness’ of proteins is measured by their BV (biological value), which is the comparison of the protein’s amino acid profile against a reference standard. The reference standard is given an arbitrary score of 100, and proteins are measured according to how closely they match its profile. The reference standard in the United States is chicken eggs, and the Europeans use a different scale which uses human lactalbumin as the reference standard. Proteins from animal sources usually have a much higher BV than do vegetable sources, but there are a few notable exceptions, soybeans being one of them. As far I know, rice has the highest BV of any non-animal protein, with a BV of 84.
When I was younger I used to make my own homemade soy milk and fortify it with methionine to improve its BV. I used to know the exact amount to use, but unfortunately that knowledge is long gone. I might be able to figure it out again by poking around on the web—I’ll see what I can do. Methinoine fortified soy protein is commercially available and is distributed in third world countries both as a substitute for mother’s milk and for famine relief purposes.
The whole soy milk/tofu thing really turns my stomach, however I am totally in love with edamame: really young green soybeans that you suck out of the pod to eat.
I wonder if these have even more nutrients, being unprocessed?
Just wanted to add that “complete” proteins really only matter if you’re trying to survive on a single source of protein and have no other foods with amino acids available. Eating a varied diet should provide any vegetarian or vegan with sufficient amino acids each day.
Exactly. The amount of protein that a healthy adult needs every day to maintain nitrogen balance is ridiculously small. The RDA is .8 g/kg. of body weight, and for all intents and purposes you can do fabulously on about a third of this. The bottom line is that a normal healthy adult needs about an ounce of high quality protein a day to replace turnover losses. Unless you’re a vegan, it’s essentially a non-issue. And all vegans have to do is follow a few very simple and easily learned techniques to ensure that they have an adequate protein intake. Protein malnutrition in healthy adults is essentially nonexistent in industrialized nations.
Ok, Ok, I guess I should have posted a hypothetical; here it is:
If I were to be put on an island and allowed only one cultivar as a source of protein, and no animals, which plant should it be? Please assume for the sake of discussion that conditions on the island can be adjusted to be favorable for whatever plant I bring.
If I were forced into that situation, my unequivocal choice would be rice. Not only does rice contain the most complete protein of any known plant source, it is quite close to being the perfect food. As we all know, there is no ‘perfect’ naturally occurring food. In other words, there is no food that would keep you alive if you ate nothing but that food. Everything is missing something. But brown rice comes quite close. I’d have to really sit down with a calculator and an exhaustive table of food composition, but just off the top of my head, I’d say that a human could live on a diet consisting entirely of brown rice, if it were supplemented with an ounce of beef liver and a half cup of orange juice a day. (Although folic acid and EFA’s might present a problem—I’d have to look it up). Brown rice is about 7.5 % protein by dry weight, about 2% fat, and the other 90% or so a mixture of digestible and indigestible carbohydrates. The glycemic index of brown rice is beautiful—the response curve is damn near flat. It’s a slow and clean burning fuel. This simple, inexpensive and ubiquitous grain is really one the best foods you can possibly eat.
I take it that you’re talking about unpolished/unbleached/brown rice. I wonder how many societies take advantage of this knowledge? My relatives in India refuse to eat brown rice. To them, it’s garbage food; they’ll eat only white rice.
Just wanted to add, if it tasted bitter to you it probably was not properly prepared. Quinoa needs to be washed thoroughly before cooking to get rid of the bitter taste. I am a big fan, I cook it up as one would risotto and add stuff like cheese and sun dried tomatoes. Yum!
You mean no “vegetable” food, right? There are non-vegetarian foods that could keep you alive indefinitely without deficiencies, certain kinds of fresh meat, for example. Just ask Ernest Shackleton and his men.
Thanks for the information. I actually had no idea that rice was a “complete” food, I thought it was severely one-sided in the amino acid department, even as brown rice. I thought rice was mostly carbohydrate, actually.
While you could stay alive for quite a long period of time consuming nothing but animal flesh, you wouldn’t want to. It would be a pretty miserable existence. And you would eventually die from scurvy. There really is no naturally occurring complete food. If you tried to live off of one food only you would eventually die, unless it were an artificially constructed food such as Purina Monkey Chow, which is marketed for primate consumption and can be used as a stand-alone food. Chances are that a human could also live indefinitely off of dry dog food, since all commercial dog foods contain ascorbic acid. And you could probably live entirely off of brown rice if you supplemented it with vitamins A, C, and B12. Your skin might eventually start to lose its integrity from lack of arachidonic acid, but there might be enough in brown rice to stave this off indefinitely.