Thiamine helps convert food into energy. It is essential for skin, hair, muscle health and brain function. In its absence, burning sensation, weakness in the arms and legs, palpitations, swelling, nausea, fatigue, and gastrointestinal problems may occur. It is found in asparagus, lettuce, mushrooms, beans, lentils, spinach, peas, eggplant, Brussels sprouts, tomatoes, tuna, whole wheat, soybeans.