Folic acid requires vitamin B12, niacin and vitamin C to be converted to its biologically active form. High vitamin C intake can increase folic acid excretion. Cautions Large amounts of folic acid can mask anemia caused by vitamin B12 deficiency. Although this is rare, in some cases it may lead to permanent nerve damage. Amounts greater than 400 mcg per day should not be taken in cases of anemia unless a diagnosis of pernicious anemia is ruled out. Folic acid can interfere with the effectiveness of anticonvulsant drugs such as phenytoin and can result in an increase in seizure activity if large doses are taken. The body needs vitamins in tiny amounts for normal functioning.
If it does not get them, deficiency diseases develop. (These are very rare in our society.) In addition to their basic roles in metabolism, some vitamins, taken in larger amounts, have other effects that are ignored by many nutritionists and doctors. These other actions may make them useful as treatments for particular problems. First I want to give you some general advice about vitamins. Vitamin pills and powders can cause nausea, heartburn, and other gastric disturbances, especially when taken on an empty stomach. Always take them after a meal, with food in the stomach. If they do not agree with you in the morning, try taking them later in the day. There is no important difference between natural and synthetic vitamins, unless the natural forms provide traces of other substances that might enhance their activity. Different brands of vitamins vary widely in cost. Buy the cheapest brands you can find that are as free as possible of fillers and additives. Very expensive, fancy vitamins are likely to be of greater benefit to the manufacturer than to you.