The body synthesizes malic acid during the process of converting carbohydrates to energy. Extremely preliminary evidence suggests that individuals with the disease fibromyalgia(a disorder that involves fatigue and pain in the muscles) might have difficulty creating or utilizing malic acid.1 Such a deficiency could interfere with normal muscle function.

Based on this supposition, products containing malic acid and other nutrients were widely offered for sale to people with fibromyalgia. However, there is as yet no evidence that these products are in fact helpful.

The body produces its own malic acid. Many fruits and vegetables also supply malic acid, most notably apples.