Recently I became curious about what foods contain complete essential nutrients we could survive on eating them alone. Interesting enough, the first food that came up (and continued to come up in other sources) on my internet search was HEMP SEED. The seed of cannabis sativa contains all the amino acids and essential fatty acids to maintain human life. No other single plant that is easily digestible can compare to the perfect ratio to meet human nutritional needs. There is some very complicated information on this subject, but more simply explained, the amino acids which convert to enzymes (globular proteins) in our bodies carry out the mechanics of living.
Although there is controversy about humans consuming milk of animals, the fact is, cows mild is a good source of calcium, protein and also one of the most nutritionally complete foods. Of course mother's milk for a baby is the most complete food from time of birth until 6months old.
As i researched further, I discovered that there is no single food that qualifies, although the jury is still out about hemp seeds or cows milk. There are food sources that excel high in some areas of nutrition, but fall short in others as far as sustaining healthy human life for a long period of time. The following suggestion is the best I can come up with.
Seaweed not only adds flavor & salt to dishes, but is also one of the most complete foods. It is high in potassium, calcium, iron, magnesium, iodine, and selenium. It is also rich in B vitamins and omega 3 fatty acids, which also reduce risk of cancer and cardiovasculardisease.
Soy beans are a complete plant protein that is equivalent to animal protein. Soy foods contain 9 essential amino acids in the ratio for human needs.
Potatoes contain protein, fiber, calcium, magnesium, phosphorus, iron, and 6 fatty acids, vitamins C, B, K, and A. They only lack in vitamin D and E.
Beans in every color contains protein, iron, magnesium zinc, potassium, and fiber in high amounts. They are also a rich source of vitamins, minerals, and foliate. Beans together with rice forms a complete protein.
So, in all this research, some of my preconceived ideas that there was one or more foods that were a complete source of nutritional needs for human life, were proven wrong. You must eat a variety of foods to maintain health, although combining only a few of them will work even though a little boring.