Symptoms of an underactive stomach include bloating and gas, diarrhea and/or constipation, undigested food in the stool, candidiasis, chronic dysbiosis (imbalanced gut flora), and mineral deficiency (most commonly iron and zinc). Individuals may also experience increasing food sensitivities/allergies; nausea after taking supplements; weak, peeling, cracked fingernails; and dull hair or hair loss as a result of stomach acid deficiency. Improving symptoms of an underactive stomach can be done using raw, unfiltered, organic apple cider vinegar. Add one tablespoon to a cup of room temperature or hot water (cold water inhibits digestion), and drink it 15 to 30 minutes before meals.