For purposes of survival and good health, the protein that you eat needs to meet two conditions:
(a) sufficient total protein, and,
(b) sufficient quantities of each essential amino acid.
A. Total Protein
The US RDA for total protein is 46 grams of protein for adult women, and 56 grams of protein for adult men, per day. Protein is composed of a chain of amino acids. But the calculation of total protein includes any and all essential amino acids. It tells you nothing about whether or not that protein has all of the right amino acids in the right proportions.
B. Essential amino acids
Your body can make most of the amino acids that you need. Only certain amino acids are unable to be manufactured by the body; they must be provided in the diet. These are called essential amino acids. There are 8 essential amino acids.
But in practical terms, we can simplify the need for essential amino acids. Almost any normal diet, with sufficient total protein, will have plenty of each essential amino acid, with three exceptions: lysine, tryptophan, methionine. These are the only essential amino acids that are at all likely to be lacking in any diet. Lysine tends to be lacking in grain-based diets. Methionine tends to be lacking in legumes and some roots/tubers. Tryptophan is lacking in various foods (no particular category).
If you are growing food in a survival garden, you might have to depend on the protein from that garden if/when other food sources fail. So it would be good to have sources of protein in your garden that are complete: sufficient total protein and sufficient amounts of all essential amino acids, especially lysine, tryptophan, methionine. This prepping and survival blog post lists 12 garden food sources that offer plenty of protein and all essential amino acids in sufficiently high quantities and proportions.
1. Quinoa — the ancient cereal that was a staple food for the Inca civilization. Quinoa is higher than wheat in total protein and has an excellent essential amino acid profile: all essential amino acids in ideal proportions, including lysine.
2. Amaranth — another cereal from South America. Amaranth is also a complete protein, with plenty of lysine. It is easy to grow, drought-tolerant, and easy to harvest. Neither quinoa nor amaranth has hulls. So after threshing the grain, simply wash the grain (thoroughly wash quinoa to remove the bitter saponin coating) and cook.
3. Dried peas — The fresh sweet peas that are so popular with gardeners are not a complete protein. But the not-so-sweet starchy “soup peas”, harvested after they dry on the vine, are a complete protein. The former are too low in methionine; the latter have a perfect essential amino acid profile.
4. Soybeans — The same principle applies. “Edamame” soybeans, harvested green and fresh, are not a complete protein and are lower in protein. The mature soybeans, dried on the vine, have all essential amino acid and plenty of lysine, and are higher in total protein. If you take fresh soybeans or other legumes and dry them, the essential amino acid profile does not change. The protein still has the same proportion of amino acids.
5. Cowpeas — this legume is not a pea, but a bean. Dried mature cowpeas are high in protein (24%) and a complete protein. Unlike many other legumes, cowpeas are also a complete protein when picked fresh. The protein content in the fresh cowpeas is lower, due to higher water content, but fresh (immature) cowpeas have an excellent essential amino acid profile.
6. Chickpeas — also called Bengal gram or garbanzo beans. Mature dried chickpeas have nearly 20% protein and are high in lysine. The essential amino acid profile is excellent, including plenty of methionine (which is lacking in many other legumes).
7. Kidney beans — this legume is a complete protein; the mature dried seeds have about 24% total protein and plenty of lysine and methionine.
8. Yardlong beans — this bean is popular in gardens; the bean pods are a foot or two long, and rather thin. The pods are edible and offer a complete protein, but low total protein (2.8%). The mature seeds, dried on the vine, are high in protein and also a complete protein.
9. Lima beans — the immature (fresh) beans are not a complete protein (too little methionine). But the mature (dried on the vine) beans are a complete protein, with more methionine and a higher total protein. Many other beans are not a compete protein, even when mature.
10. Pumpkin seeds — Choose a hulless variety for easy harvesting. The seeds are high in total protein at 24.5% and have an excellent essential amino acid profile. Pumpkin seeds are high in lysine, and so they complement a grain diet well.
11. Sunflower seeds — This source of protein as 88% of the ideal percent of lysine, but otherwise is high in essential amino acids. The seeds are about 20% protein, and make an enjoyable snack. They are difficult to hull, though, so hulless pumpkin seeds are a better choice for the backyard garden.
12. Peanuts — You can grow your own peanuts, even using raw in-the-shell peanuts from the supermarket as a seed source. This legume is high in total protein and has plenty of essential amino acids. However, the percent of lysine is only 70% of ideal. Given the high protein content and the high palatability of this food (you can eat a lot more peanuts in a week than dried beans), you can obtain plenty of all essential amino acids from peanuts, despite the lower percent of lysine.
Rice also has 70% of the ideal proportion of lysine. Rice is 7 to 8% protein; peanuts are 25.8% protein. A person can survive in good healthy with rice as his main protein source. It takes about two cups of dried rice to provide just under 1 gram of lysine. You need 2 to 3 grams of lysine per day. A cup of peanuts provides 1.35 grams of lysine.
Foods that don’t quite make the cut:
Wheat and Rice are somewhat deficient in lysine, and so they are not complete proteins. However, the amount of lysine is enough for survival and health.
Maize is typically too low in total protein and lysine to be your main source of protein for survival. Always supplement maize as a staple food with crops high in lysine, like soybeans, adzuki beans, other legumes, peanuts, pumpkin seeds, etc.
Fresh beans tend to have a lower protein content and a poorer essential amino acid profile. In general, if you want the highest protein content and best essential amino acid profile, let your legumes reach maturity by drying them on the vine. Snap beans are low in total protein and low in methionine. The same is true for snap peas and snow peas (“edible-podded peas”).
Potatoes are low in total protein at about 2%, but have a fairly good essential amino acid profile. If you eat enough potatoes, you will have enough protein in your diet, but the low total protein means that you should supplement potato with foods high in protein, like legumes or seeds.