Complementary Protein and Diet

The book

Lappé, Francis Moore. 1991. Diet for a Small Planet. 20th Anniv. Ed. Ballantine Books, New York.

is used as a supplemental text for this lecture. Much of the material included in this lecture comes from this source. There are several diagrams from the book that will also be discussed in class and for which you will be held responsible on the next test.

Essential Amino Acids
Hypothetical Levels Needed
Low Lysine Intake
Low Lysine Intake
Limits Use of All Others
Limits Usefulness of All
We need protein in our diets. More specifically, each of us needs amino acids in a specific ratio to each other. Our bodies can make about half of the needed amino acids given proper starting materials including a source of nitrogen (such as other amino acids). There are eight amino acids we can’t make, so they must be present in our diets in a specific ratio to each other. These eight are collectively known as the essential amino acids and include:

  1. valine,
  2. leucine,
  3. isoleucine,
  4. the sulfur-containing amino acids: methionine and cysteine,
  5. the aromatic amino acids: phenylalanine and tyrosine,
  6. tryptophan,
  7. threonine, and
  8. lysine.

Our bodies use amino acids in a specific ratio to each other, so if a person doesn’t get enough of one of them to match with the rest, the rest can only be used at a level to balance with that low one. Most of these amino acids are fairly easy to get in a reasonably well-balanced diet. However, there are three that are a little harder to get than the rest, thus it is important to make sure you’re getting enough of these three. These three are called limiting amino acids, because if a person’s diet is deficient in one of them, this will limit the usefulness of the others, even if those others are present in otherwise large enough quantities. The three limiting amino acids include the sulfur-containing ones (methionine and cysteine), tryptophan, and lysine.

The sulfur-containing amino acids are grouped together because if your body has enough of one of them, it can change part of the excess into the other amino acid if needed. The same is true for the aromatic amino acids. The term “aromatic” does not refer to the smell of these, but is a term that chemists use for molecules which contain a structure known as a benzene ring. A ninth amino acid, histidine, is essential for very young children, whose bodies are not yet mature enough to manufacture it.

Because of publicity from certain agricultural industries, many people in our culture have been taught to think that it is necessary to eat meat to get protein, but this is not true! People in many other cultures do not eat meat yet do get enough protein in their diets. It is true that there are areas of the world where people need to raise cattle and eat meat to survive. For example, in certain arid areas of Africa where almost nothing grows, cattle can graze on the meager grass that’s there that people can’t eat, and the people can eat the milk and meat from those cattle. In our country, the climate is much better, and we can raise many varieties of edible plants, thus we have available alternate (and often better) sources of protein. Some plant protein sources, like soybeans, have a better amino acid balance for humans than meat.

In general, foods that were designed to be the sole food source for some organism, especially a new, growing baby one, tend to be very high in protein. Since these were designed as food sources for that specific (baby) organism, the amino acids in their protein may not be in the best ratio for an adult human, and some come closer than others. Eggs and milk were designed to be the sole foods of the baby cattle and developing chicks they nourish, thus they are high in protein and have fairly good amino acid ratios, although not exactly what’s needed by an adult human. Additionally, various seeds store nutrients needed by the new embryo plant until it gets out of the ground, so they have lots of protein, too. Since plants are not as closely related to humans, their amino acid ratios are a little farther off from that needed by adult humans. However, since some are low in certain amino acids and high in others while other seeds have the opposite composition, it is possible to combine seeds to obtain a better protein source. For dietary protein purposes, plant seeds fall into several major categories:
 legumes peas, beans, lentils, peanuts, alfalfa
 whole grain wheat, rice, corn, oats, rye
 seeds and nuts sesame, sunflower (others are too high in oil)

So, why should you consider these alternative protein sources? One factor might be cost: quite often a meal of beans and grains is cheaper than a meal of steak. Other people just like something different for a change. Additionally, Ms. Lappé points out that beef production as done on major US beef farms is expensive, wasteful, and often cruel. I know that a number of you live on small farms here in in Clermont Co., and occasionally raise a few beef cattle. Typically, these cattle are allowed to eat grass like they were meant to do and are not given a lot of drugs. This is not the case, however, in this country’s big beef ranches. Cattle are held in small pens so they don’t get exercise and “burn off” their food. They are fed lots of high-protein soybeans and corn so they will put on weight faster (often fat, not muscle) and can be sold sooner. Frequently they are given hormones to make them grow faster, insecticides to keep flies off, antibiotics and other drugs to prevent or cure illnesses caused by over-crowding, and various other chemicals. Here are some statistics on this beef production cited in Diet for a Small Planet and/or Diet for a New America:

Combining Foods
Combining Plant Protein Sources
Protein complementation is combining plant protein sources to achieve a better amino acid balance than either would have alone. Because of differences in amino acid make-up, when plant sources are combined, the strengths of one make up for the deficiencies in another. For example, many grains are notoriously low in lysine, but beans are high in lysine. On the other hand, beans are low in the sulfur-containing amino acids, while grains like wheat contain much of these. Thus, by eating beans and grains “together,” the strengths of one make up for the deficiencies of the other, making a source of complete protein.

Actually an interesting discussion/debate among the experts in this area has been, “How close together must foods be eaten to complement each other?” From what I’ve read, it sounds like most of the experts are saying complementary protein foods don’t have to be consumed exactly together in the same meal, but rather sometime within a few hours or the same day.

In any food, because of amino acid balance and other factors, not all of the ingested protein in food is used/usable. Net protein utilization (NPU) is the percentage of ingested protein in a given food item that is actually used by the body. Most whole grains alone and most legumes alone have NPUs in the same range as meat.

Here are NPU values (from Diet for a Small Planet) for some selected foods:
Food NPU
 most meats  65-57% 
 eggs  94% 
 milk  82% 
 soybeans (alone)  61% 
 other legumes alone  50-60% 
 brown rice  70% 
 other whole grains  50-60% 

Cross Section of Wheat Berry
Cross Section of Wheat Berry or Rice Grain
For grains, use of the whole grain is important because of nutrients contained in the various parts of the seed. The bran (the outer “wrapper”) contains lots of fiber and minerals such as iron. The germ or embryo contains a number of vitamins, notably many of the B vitamins and the fat soluble vitamins like Vitamin E, a number of minerals, and much protein that is of high quality (very usable by the human body). The endosperm is mostly short-chain starch, with a small quantity of low quality protein (which is not as useful by humans), and almost no vitamins nor minerals. Note that when wheat is milled to produce white flour, the bran and germ are removed leaving only the endosperm. These isolated short-chain starches are too easily converted to sugar, thus can be a problem for hypoglycemics. When the left-over endosperm is further chemically reacted (“bleached”) to make it appear even whiter for bleached white flour, even more of whatever nutrients might still be present are destroyed. Interestingly, back in 1943, our government decided this might cause nutritional deficiencies, so by law, manufacturers of white flour must artificially add back in three specific B vitamins (Thiamine or B1, Riboflavin or B2, and Niacin or B3) and iron out of all the nutrients that were removed, thus the bleached white flour is “enriched.” I have heard that the government regulations were recently changed to require that manufacturers include folacin, another B vitamin, in enriched flour. While whole wheat contains around 16 minerals and 11 vitamins, most are removed in processing white flour, yet these few synthetically-produced vitamins and iron source are all that must be added back in.

Complementary Protein
Complementary Protein
Fortunately, it’s not as hard to combine proteins as it sounds like it might be. Diet for a Small Planet includes a diagram like this to illustrate protein complementation. “Fat” arrows are especially good combinations and “thin” arrows are satisfactory combinations. Legumes and grains together (refried beans on tortilla in Central America, falafel made from chick peas in whole wheat pita in the Middle East, soybeans and whole rice in the Far East, cornbread and pinto beans down South, peanut butter on whole wheat bread) make complete protein. Dairy and whole grains (oatmeal and milk, whole wheat macaroni and cheese, cheese sandwich on whole grain bread) are also complete protein. Seeds and legumes (Middle Eastern dip known as hummous made from sesame seeds ground up like peanut butter and cooked chick peas) also make a complete protein. Nutritious “three-way” combinations are also good: pizza with a whole wheat and soy crust and cheese on top, cheese and refried beans on a corn tortilla, or a peanut butter on whole wheat sandwich with a glass of milk.

It’s amazing how many cultures instinctively came up with local ideas for complementary protein dishes without even knowing there were any “rules” for doing so. If you’re interested in trying some new recipes, Diet for a Small Planet includes a bunch of recipes for foods that contain complete protein from complementary protein sources, and there are a number of other books and Web sites with information on this topic.

Lentils and Rice
Click for Lentils and Rice Recipe
Here’s a recipe for one of my favorite Middle Eastern dishes. Its “real” name is M’judra (which is probably spelled and pronounced slightly differently in the various Middle Eastern countries). I hear many people say that they don’t eat home-cooked dried beans because they take so long to cook. This dish has probably one of the shortest cooking times for dried beans and grains: it takes only about an hour. You could start a pot and study your biology while it’s cooking. The traditional way of serving this is to sauté a sliced onion until it is brown, crispy, and sweet. Mix half the onion into the lentils and rice when it’s done, and save the other half to sprinkle on top for a garnish. If you like yogurt, this is really good with a spoonful of plain yogurt (instead of sour cream – tastes the same, lower in fat, higher in protein) on top. At home, we usually just throw some dried onion flakes in with the lentils and rice while it’s cooking. We often make a double batch, then freeze some and put some in the refrigerator. A quick, nutritious meal “on-the-go” is a scoop or two of this stuff with cheese slices (real cheese, please) placed on top, then the whole thing warmed in the microwave. If you’re into salt, you may wish to add some while the lentils and rice are cooking (and/or experiment with adding herbs of your choice).

Popcorn Recipe
Click for
Here’s another recipe for Fankhauser Popcorn Seasoning. Here, brewer’s yeast, kelp, and popcorn combine to form a complete protein. Typically, students served this popcorn soon learn that the more speckly the pieces of corn, the better the taste.

I know that most of you are not going to change your eating habits overnight, nor is it a good idea to try to do so. Any changes you make should be gradual. Try a new recipe now, and another later, gradually working them into your family’s routine. Many of you may not want to change much at all, but occasionally want something different to eat. Others may be looking for ways to save some money on groceries. Some may be concerned about fats and cholesterol in your own diets. Others may be concerned about what your children are eating, and perhaps what sorts of additives might be contributing to hyperactivity. Quite often this way of eating lower on the food chain is cheaper, more nutritious (more fiber, vitamins, and minerals with less fat), and more ecologically sound.

Other Dietary Protein Sources to Consider:

While not complementary protein, there are other sources of dietary protein which some of you may wish to try. These foods are not knowingly consumed in this country on a regular basis, but are important protein sources for people in many other cultures. The book,

Taylor, Ronald L. 1975. Butterflies in My Stomach. Woodbridge Press Publ. Co. Santa Barbara, CA.

includes the following statistics:

Food SourceProtein
(% of weight)
(% of weight)
KCal/100 gVit. A
IU/100 g
Vit. D
IU/100 g
Beef17.4 - 19.415.8 - 25.1225 - 30130 - 50?
Pork14.6 - 16.722.7 - 31.4276 - 346??
Chicken20.6 - 23.41.9 - 4.7117 - 13060 - 150?
Fish (dep. on species)18.3 - 20.91.2 - 10.0100 - 168440?
Cow Milk3.53.7 - 3.966150 - 16041 (added)
Chicken Egg12.911.51631180?
Sundried Grasshoppers49.7 - 75.010.1 - 18.4???
Silkworm Pupae23.114.2207“ample”?
Honeybee Larvae15.43.71?8900 - 11,900613,000 - 743,000
Honeybee Pupae18.22.39?4930 - 5330507,000 - 526,000

Notice how much higher in protein (and comparable or lower in fat) dried grasshoppers are than the meats most people eat. Dried grasshoppers can be ground into flour and incorporated into other foods, unseen. The RDA for vitamin D is 400 IU. By law, vitamin D is added to milk such that one 8-oz. glass supplies 100 IU so drinking four glasses/day will supply 400 U (plus an appropriate amount of calcium). About 0.055 to 0.065 g (= 55 to 65 mg) of honeybee larvae would supply the same amount. A “Quarter-Pounder” made from honeybee larvae would contain a 5-year supply of vitamin D — enough to make a person very ill if consumed all at once.


Borror, Donald J. 1960. Dictionary of Root Words and Combining Forms. Mayfield Publ. Co.

Lappé, Francis Moore. 1991. Diet for a Small Planet. 20th Anniv. Ed. Ballantine Books, New York.

Marchuk, William N. 1992. A Life Science Lexicon. Wm. C. Brown Publishers, Dubuque, IA.

Robbins, John. 1987. Diet for a New America. Stillpoint Publ., Walpole, NH.

Taylor, Ronald L. 1975. Butterflies in My Stomach. Woodbridge Press Publ. Co. Santa Barbara, CA.

Copyright © 1996 by J. Stein Carter. All rights reserved.
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