Folate is essential and Folic Acid is commonly available

Folate (L-methylfolate or vitamin B9) and Folic Acid:

Food Sources of Folate, the bioactive natural form, include:

beans, black eyed peas, green peas,
peanuts and other nuts and seeds,
whole grains,
asparagus, most dark green vegetables,
orange juice, citrus fruits.
Fortified cereal and rice are sources of folic acid, the supplemental form.

Folate is the natural form; Folic Acid is in supplements & fortified foods.

Folate is the form of the vitamin found in food and is more bioactive. Folic acid is the form that is commonly available as a supplement and in fortified foods, however it is less bioactive, less able to function until methyl groups are added which requires adequate supplies of vitamin B12. A genetic difference may exist in some individuals that prevent the body from being able to convert the inactive folic acid form into folate, the methylated bioactive form of the vitamin. [More about methylation.]

Symptoms of Folate deficiency include:

Deficiency of folate can cause megaloblastic / macrocytic anemia which is characterized by red blood cells that are over-sized and ineffective. Anemia symptoms include being short of breath and feeling tired and weak. The symptoms are due to a shortage of normal red blood cells and reduced ability to transport oxygen with each breath.
Folate is needed for DNA synthesis and for DNA methylation which may be important for preventing cancerous changes from occurring in the DNA.
Lack of folate may increase heart disease risks due to less breakdown of homocysteine. Vitamin B6 and B12 are also necessary, a deficiency of any one of the three might cause an accumulation of homocysteine.
Folate is important during pregnancy for fetal development. Spina bifida and cleft palate are birth defects that may be caused by folate deficiency.
Deficiency of several of the B vitamin group can cause changes in the appearance and surface texture of the tongue. B vitamins that can cause changes in the tongue are mentioned in the following excerpt and include “niacin (B3), riboflavin (B2), pyridoxine (B6), folic acid (folate/B9), and vitamin B12”:
“Deficiencies of niacin, riboflavin, pyridoxine, folic acid, or vitamin B12, resulting from poor diet or from the administration of antagonists, may cause a sore, beefy-red tongue without a coat. In the chronic vitamin deficiency state, the tongue may become atrophic and smooth.” – “The Tongue – Clinical Methods – NCBI bookshelf https://www.ncbi.nlm.nih.gov/books/NBK236/
See the post on Vitamin B6 for more information about how the group of B vitamins work together in energy metabolism and cell growth.

Reference used for food sources & symptoms of Folate deficiency:

An Evidence-based Approach to Vitamins and Minerals: Health Benefits and Intake Recommendations, 2nd Ed., by J. Higdon & V. Drake, (Thieme, Stuttgart / New York, 2012)
A description and source for purchasing the text: http://www.thieme.com/books-main/complementary-medicine/product/1040-an-evidence-based-approach-to-vitamins-and-minerals
A review of the text: http://ajcn.nutrition.org/content/79/5/892.full

Other References used for the food sources of Folate and Folic Acid:

Disclaimer: Opinions are my own and the information is provided for educational purposes within the guidelines of fair use. While I am a Registered Dietitian this information is not intended to provide individual health guidance. Please see a health professional for individual health care purposes.