We cannot live on grains alone because they do not contain enough amino acids, the building blocks that make protein. There are 20 kinds of amino acids. Our bodies naturally make some of these acids and get the rest from food.
Meat provides all the protein we need, but many people wish to eliminate or reduce their meat consumption for ethical, financial, environmental or health reasons. No single plant food contains all the essential amino acids to manufacture protein, so we can get enough only by combining them.
One of the most important amino acids we need is lysine. It’s scarce in wheat, corn, rice, oats, sorghum and millet protein. However, all these crops contain other essential amino acids, such as methionine. Other plant foods, including beans, are rich in lysine but have little methionine. These foods complement one another, with one providing amino acids the other lacks, to provide complete protein.
When people in early civilizations started growing grains for nutrition, nobody knew anything about protein. But they learned what foods to eat by using trial and error. Traditional diets evolved by combining complementary proteins. For example, corn and beans became staples in Mexico, and Indian people relied on rice and dal.
The gluten-free diet has brought attention to some interesting alternatives to the familiar grains. Amaranth, quinoa and buckwheat contain a high proportion of lysine, and amaranth is unusually high in many essential amino acids. This is good news for avid bakers going gluten free. They’re already experts at blending flours to achieve the right flavors and textures. Using amaranth, quinoa, buckwheat and legume (bean or chickpea) flour can also help round out the protein content to make these recipes more nutritious.