Folic acid, also known as folate or Vitamin B9, aids the conversion of food into fuel for the body, producing energy. Deficiencies in this key supplement have been linked to a heightened risk of depression. Folic acid increases the receptiveness of depression patients to antidepressant medication. Research indicates that together with a B12 supplement, folic acid can lower the risk of stroke due to its key role in managing homocysteine levels (raised levels of this hormone can put one at risk of developing cardiovascular conditions).