All plants contain protein. By eating a wide spectrum of plants, I get all the protein and other nutrients I need. I do not take any protein or other nutritional supplements, with one exception -- a B12 supplement is recommended for everyone following a plant-based diet.
Americans on the SAD consume six-to-10 times more protein than they need. That excess protein overworks the liver and kidneys, causing both these organs to become enlarged and injured. Excess protein consumption causes the kidneys to pull large quantities of calcium from the body, causing bones to weaken and kidney stones to form. (Dr. John McDougall).
I’m actually asked this question several times per day, and rather than go through my elevator speech, sometimes I find the best response is just to ask, “Do you think I need more protein?” Then I show a muscle, such as my calves, pictured below.