Frequently Asked Questions

Protein

I have read in many places that a serving of rice and beans provides complete protein - more complete than a serving of beef. Recently a woman disputed this and I thought it might be a good idea to check it out before I tell anyone again.

Theresa

Answer

Dear Teresa

High Quality (complete) Proteins are dietary proteins that contain sufficient quantities of all essential amino acids (present in animal foods only - the only plant food that is a complete protein is soy).

Low Quality (incomplete) Proteins are Dietary proteins that are low or lack one or more essential amino acids (usually in plant foods eg wheat and rice lacks lysine, corn lacks lysine and tryptophan, legumes (except soy) and nuts lack methionine.

When incomplete proteins are combined in the same meal e.g cereals are eaten with egumes, they become complete proteins, equivalent to protein quality of meat (but not better than meat).

New evidence suggests that there is no need to combine incomplete proteins at every meal - as long as one consumes a variety of protein containing foods across the day.

The position paper by the American Dietetic Association has more information on the evidence.

Regards,
Healthy Eating Team

Last Updated: October 30, 2001.