I frequently hear from people who are considering becoming vegetarian that they aren't sure what to eat. They wonder about protein sources and usually mention that they find the idea of combining foods to get "complete proteins" very daunting. If this has been a barrier for you, let me explain why it shouldn't be!
What are "complete proteins"?
The building blocks of protein consist of 22 different amino acids. Nine of those (the "essential amino acids") must be supplied by our food intake. The remaining 13 can be constructed in our bodies. Each protein is custom-built to meet its specific function from the 22 building blocks.
What is food combining and where did this idea come from?
In her book Diet for a Small Planet (originally published in 1971), Frances Moore Lappe emphasized the need for vegetarians to eat a variety of foods to meet their protein requirements. It was believed, at the time, that it was necessary to get all of the essential amino acids by combining different foods (e.g. beans and rice) to get "complete proteins" in each meal.
Do I need to combine foods at every meal to meet my protein needs?
No. When we eat a variety of foods, the amino acids from those foods are stored in our bodies. Those amino acids are then used to create proteins as needed. Some but not all foods provide all of the essential amino acids, however, by eating a assortment of plant proteins over the course of the day our needs can easily be met. Incidentally, the source of the amino acids (animal foods or plant foods) is indistinguishable in our bodies. In fact, the amino acids in all animal foods are derived from the plants (think cows eating grains or grass).
What do I need to do?
There is no need to carefully plan each day's meals. Simply enjoy eating a variety of plant-based foods.
Are you curious about what amino acids are in the foods that you eat? I'll give you a link but you must promise me that you're not going to use this to control-freak your meal planning, ok? LINK
If you are considering making the switch to a plant-based diet, here are two excellent books that will help to answer many of your questions:
The New Becoming Vegetarian
(Both by Brenda Davis, R.D. & Vesanto Melina, M.S., R.D.)