Malic acid contributes to the pleasant, slightly sour taste of fruits and is used as a food additive for this reason. It is present in grapes and in most wines (it gives some varieties of wines their slightly tart taste) and most other fruits and vegetables..
The body produces malic acid when it converts carbohydrates into energy. Some people take malic acid by mouth with magnesium for treating pain and tenderness associated with fibromyalgia. Formulations with malic acid are also topically applied by some to the skin for moisturizing, for treating acne, and to help smooth skin.