Folic acid -- also known as folate and as vitamin B-9 -- is a vitamin you need to help maintain normal cellular function. While you need it all the time, it's of particular importance during pregnancy, and pregnant women generally take larger quantities than non-pregnant women. Despite the word "acid" in its name, it doesn't contribute to acid reflux.
There are many different B vitamins, of which folic acid is only one. While they all have different functions in the body, most participate in energy metabolism -- chemical reactions in the cells leading to production of energy -- to some extent. Folic acid also helps you make red blood cells, explains PubMed Health, and deficiencies can lead to anemia. If you're pregnant, your developing embryo needs folic acid to help form the neural tube, which becomes the brain and spinal cord.
Acid reflux occurs when stomach acid -- a strongly acidic mixture of hydrochloric acid, water, and other digestive juices -- backs up through the cardiac sphincter into the esophagus. The cardiac sphincter is a tight ring of muscle that normally prevents stomach contents from moving upward. While the stomach's lining is tough and protected against acid, the delicate esophagus is not, and acid reflux causes a painful burning sensation in the chest.
The misconception that folic acid -- in food or in the form of supplements -- leads to increased acid reflux may come from the fact that pregnant women often begin experiencing acid reflux shortly after they begin taking folic acid supplements. This is a coincidence, however, and stems from the fact that you're advised to take folic acid supplements when you find out you're pregnant, if you're not already doing so. You also have increased acid reflux during pregnancy, explain Heidi Murkoff and Sharon Mazel in their book "What To Expect When You're Expecting."
Whether or not you're pregnant, there's no reason to stop taking your folic acid supplements if you're experiencing acid reflux; there's no scientific evidence to support any connection between the two. Instead, continue taking your supplements and treat your acid reflux by avoiding foods that cause it to worsen, and by remaining upright for 30 minutes after eating. You can also try antacids containing calcium carbonate, sodium bicarbonate, or magnesium hydroxide to lessen your symptoms.