Leucine can be used as a nutritional supplement and flavoring agent. The best sources of leucine include brown rice, beans, meat, nuts, soy meal, and whole grains. Since it is an essential amino acid, this means the body cannot produce it on its own, only through the diet. People engaged in high levels of physical activity and low protein diets should consider taking a white acid supplement. Although independent supplements are available, they are best taken with isoleucine and valine. Therefore, it is more convenient to choose a combination supplement.