Folic acid, otherwise known as vitamin B9, is essential to cell production and plays a vital role in the development of the fetus. In fact, studies have shown that supplementing with folic acid can reduce birth defects by 72 to 100 percent. Folic acid also plays a role in the metabolism of protein and formation of amino acids. This vitamin is also been shown to help with mental health and the digestive and nervous systems.

Because most foods besides liver are a poor source of folic acid, you may have a deficiency unless you happen to eat quite a bit of liver and leafy greens. Signs of a deficiency include an inflamed tongue, shortness of breath, loss of appetite, forgetfulness and mental sluggishness. These can also be signs of many other problems, and it is best to seek the advice of a physician if you have any of these symptoms.

In addition to your diet, there are conditions that might deplete your body or block absorption of B vitamins, including folic acid. Celiac disease, alcoholism and irritable bowel syndrome are three things that can contribute to a deficiency.

Folate may also play a role in depression, as studies in elderly people have shown. The three vitamins B6, B12 and B9 must work together to improve depression and should be taken in a multivitamin supplement or administered by a doctor. These vitamins decrease the amount of homocysteine in your body. Homocysteine is thought to play a role in causing depression.