Your brain needs iron. Iron helps with cognitive functions—for example, children who have an iron deficiency tend to do worse on math and language tests. Recent studies show that even minor levels of iron deficiency can have negative effects on brain function. Iron is necessary for the production of myelin, the insulating sheath around neurons (nerve cells), which helps speed the rate at which cells convey impulses. Without appropriate myelination, the nervous system, including your brain, cannot function correctly. If you have an iron deficiency, you may need to rely on supplementation rather than diet to raise your iron content to normal levels. But don’t overdo it. Taking iron supplements can cause side effects such as nausea, vomiting, constipation, diarrhea, dark-colored stools, and/or abdominal distress. To minimize these side effects, follow your doctor’s recommendations and take with food.