Cooked brown rice contains five grams of protein per cup, and compared with other similar plant protein sources, brown rice is the second highest in BCAAs after quinoa. Brown rice is missing the essential amino acid lysine. However, this is easily made up in other places in the diet and isn’t a limiting factor in the gym. Brown rice protein powder is another popular plant-based protein supplement. A soon-to-be-published study from the University of Tampa found that a rice protein supplement yielded similar muscle-building benefits to whey when taken after weight training.