Riboflavin (B2) also plays an important role in the body's production of energy, acts as an antioxidant, and promotes cell growth. It also works synergistically with various enzymes to help the body metabolize proteins, carbohydrates, and fats. Healthy skin, hair, and nails all depend on adequate amounts of riboflavin, as does good vision.

One of the best food sources of riboflavin is Brewer's yeast. Organ meats, milks, eggs, cheese, green leafy vegetables, millet, wild rice, legumes, and oily fish such as mackerel and trout, are other good sources. Riboflavin is also produced by intestinal bacteria. Sunlight destroys riboflavin, as does stress and alcohol consumption, and some health experts say riboflavin deficiencies are more common than deficiencies for any other nutrient, especially among the elderly, people with poor eating habits, and alcoholics. Deficiency symptoms include mouth and tongue sores, eye fatigue and redness, sensitivity to light, hair loss, digestive problems, dermatitis, and general fatigue.