The most common vitamins and minerals that require sufficient stomach acid to be properly absorbed are magnesium, zinc, calcium, iron, vitamin B12 and folic acid. 13 common symptoms of low stomach acid: 1  Bloating, belching and flatulence immediately after meals. 2  Indigestion, diarrhea or constipation. 3  Soreness, burning or dryness of the mouth. 4  Heartburn. 5  Multiple food allergies.