Are we back to complementing proteins?
Bioavailable Methionine Assessed Using the Indicator Amino Acid Oxidation Method Is Greater When Cooked Chickpeas and Steamed Rice Are Combined in Healthy Young Men, The Journal of Nutrition, 9 April 2020
When chickpeas are the main protein source in the diet of young adult men, the combination of rice and chickpeas in a 3:1 ratio is recommended to improve dietary protein quality.
The idea of combining foods that contain complementary amino acids was promulgated by Frances Moore Lappé in her 1971 book, Diet for a Small Planet. It has since been challenged. Lappé herself retracts the notion in her later editions.
While it’s true that all the essential amino acids exist in plant foods – you don’t need to eat animal foods to get them* – that doesn’t take into account absorption. This study took that into account.
If you’re going to eat rice and you’re going to eat beans it would not be a bad idea to get them into your stomach around the same time.
* You do need to eat sufficient calories, keeping in mind that fruit is a poor source of protein.