The B vitamin folacin, or folic acid, works closely with vitamin B12 to produce red blood cells. Folic acid is vital to proper cell division and prevents damage to cellular DNA, helping to reduce the risk of colon polyps, colorectal cancer and cervical cancer.

Many studies show that folic acid also prevents birth defects. Women planning to have children should supplement with 400 micrograms of folic acid daily to prevent neural tube defects such as spina bifida and anencephaly. This amount may also lower homocysteine levels in the blood as high levels of homocysteine are associated with increased risk of heart attack and stroke.

"Folic acid is necessary for proper brain function, being concentrated in the spinal and extracellular fluids. It is essential for mental and emotional health...In surveys conducted, it was shown to be one of the nutrients most often deficient in our diets."

Folic acid in supplement form is twice as available to the body as the folate found in foods. The vitamin has a low toxicity. A one-thousand-fold increase in the daily requirement may be consumed with no harmful effects. Daily doses of 15 mg are non-toxic. If excess is ingested, the extra is excreted in the urine.

Birth control pills increase the body's demand for folic acid and may result in folic acid deficiency. Phenytoin (Dilantin) competes with folic acid for absorption.