Malic acid is a substance found in some fruits and also made by your body when it turns the carbohydrates you eat into energy, while magnesium is an essential mineral. They are sometimes combined in one supplement and marketed to people who suffer from chronic fatigue syndrome or fibromyalgia. Evidence on the effectiveness of this supplement for treating any condition is preliminary and conflicting, however. Speak with your doctor before taking malic acid and magnesium to make sure it is safe for you.
A theory based on preliminary evidence suggests magnesium and malic acid may help treat fibromyalgia, a condition that causes fatigue, tender muscles and generalized pain. A study published in the "Journal of Korean Medical Science" in October 2011 found that women with fibromyalgia had lower levels of magnesium. The New York University Langone Medical Center also notes that people with fibromyalgia may have trouble creating malic acid, which could cause problems with muscle function, but states that there isn't enough evidence yet on the benefits of malic acid supplements for treating this condition.
A classic study published in the "Journal of Rheumatology" in May 1995 on fibromyalgia pain found no treatment benefits after four weeks of using a supplement containing magnesium and malic acid, but people allowed to increase the dose for longer periods of time experienced some decrease in pain. Further research is necessary to verify these potential benefits.
Chronic Fatigue Syndrome
The University of Maryland Medical Center notes that magnesium may help with chronic fatigue syndrome. A review article published in "The American Journal of Psychiatry" in February 2003 noted that at least one well-designed study showed magnesium helps with chronic fatigue syndrome, but it noted that later studies didn't show the same benefits. More research is necessary to verify any potential benefits.
High doses of a magnesium and malic acid supplement may cause loose stools, which is most likely due to the magnesium in the supplement. Magnesium may also cause upset stomach, nausea, diarrhea, vomiting, low blood pressure and irregular heartbeat. Pregnant women, people with kidney and liver disease and children shouldn't take these supplements because they haven't been well studied in these populations. Magnesium may also interact with some medications, including antibiotics, blood thinners, high blood pressure medications, diabetes medications, the heart medication digoxin, water pills and muscle relaxants.