Constant brain fog, nagging headaches and heavy fatigue that never seems to go away – it's easy to shrug these symptoms off as nothing more than not sleeping enough, eating too much fast food or simply getting older.But experts believe they could be a sign of a little-known vitamin deficiency: folate.Folate, also known as vitamin B9, is crucial for helping the body produce and repair DNA, as well as form red blood cells that carry oxygen to major organs. It also helps break down the amino acid homocysteine, which circulates in the blood and, at high doses, raises the risk of blood clots and heart attacks. However, the body can't produce folate on its own, and must get the vitamin from foods such as dark leafy greens and Brussels sprouts. Fortified cereals and supplements contain the synthetic version of vitamin B9 called folic acid.Folate and folic acid are especially crucial for pregnant women, as the nutrient builds the baby's neural tube that eventually grows into the brain and spinal cord. While estimates suggest that true folate deficiency is rare, one in five Americans doesn't get enough, including men, non-pregnant women and older adults. Experts told the Daily Mail that folate deficiency can lead to fatigue, brain fog and shortness of breath