Vitamin is an essential nutrient that helps the body to function properly. Vitamins are divided into two categories: fat-soluble and water-soluble. Thiamin, also known as Vitamin B1, is a water-soluble vitamin that helps the body to convert carbohydrates into energy. PILL is a form of medication that is taken orally. Niacin, also known as Vitamin B3, is a water-soluble vitamin that helps the body to break down fats and proteins. Biotin, also known as Vitamin B7, is a water-soluble vitamin that helps the body to metabolize carbohydrates, fats, and proteins.