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Vitamin B9 (Folate) and your healthFolate - or vitamin B9 - deserves an extra dose of your attention. It is one of the essential nutrients most often deficient in the diet. And its "resume" shows very clearly that it is not to be neglected. As a part of various coenzymes, it plays important role in the metabolism, synthesis of amino acids, formation of red blood cells, DNA and RNA. It is also needed for proper functioning of the digestive tract (production of hydrochloric acid), immune and nervous systems.
Another important function of folate is assisting conversion of homocysteine to methionine. Since the body constantly produces homocysteine - an intermediary amino acid form in the SAM (S-adenosyl metyhionine) cycle - folate deficiency can result in its accumulation in the blood (more so if combined with vitamin B6 deficiency). High homocysteine levels are linked to cardiovascular diseases and liver damage.
The two main form of vitamin B9 are folates, vitamin's natural form that includes a number of molecularly homologous compounds, and its synthetic form, folic acid (also existing in natural form, but present in foods in very low levels).
While present in variable amounts in most of foods, vitamin B9 is, like most other B-vitamins, fragile and easily lost in food processing and preparation (it is rapidly destroyed by exposure to heat and light). An additional natural source is friendly intestinal bacteria, which is capable of synthesizing vitamin B9. However, it is unsure what portion of it is absorbed by the body; also, the level and activity of friendly intestinal bacteria varies significantly from one individual to another.
Unlike natural forms, which are generally chemically unstable, easily destroyed in food processing, and significantly degraded in foods within weeks, or even days, the synthetic B9 form, folic acid, remains stable for months, even years. For that reason, it is a form of choice for vitamin B9 supplements, and frequently added to processed foods.
In 1998, the Food and Drug Administration made it mandatory to fortify all enriched grain foods (enriched breads, flours, cereals, pastas, etc.) with specified amounts of folic acid. The primary goal was to reduce the incidence of neural tube defect (birth defect), thought to be caused mainly by mother's folate deficiency.
While FDA's goal was to increase average individual folic acid intake by about 100μg (micrograms) per day, actual increase is likely significantly higher, in the 215-240mg range (Johnson et al, Effect of food fortification on folic acid intake in the United States, 2003), mainly due to higher than expected volume of consumption of fortified foods. Such a high proportion of B9 form that is naturally very low in comparison to other, unstable forms of the vitamin, are a legitimate reason for concern, and more so with even higher level of mandatory folic acid fortification being considered.
Risks and possible symptoms of folate deficiency are anemia, atrophy of thymus glands and lymph nodes (compromising the immune function), elevated homocysteine levels, psychological disturbances (confusion, irritability, depression) and mental disorders, high blood pressure and higher incidence of cancer. Deficiency risk increases in pregnancy, due to the greater need for the vitamin. It can result in complications and congenital abnormalities (specifically, neural tube defect).
Excessive intake of vitamin B9 can cause gastrointestinal discomfort, kidney damage, worsening of bad-to-good cholesterol ratio, and potentiate zinc and potassium deficiency in individuals with marginal intakes of these nutrients. It can also mask symptoms of pernicious anemia caused by vitamin B12 deficiency.
Some recent studies have linked high folic acid level with increased risk of developing certain forms of cancer (breast, prostate, colorectal, lung); no such association has been indicated for the natural B9 form, folate. While the differences in risk ratios are relatively low, it is prudent to avoid significant intake of the synthetic B9 form (folic acid).
Vitamin B9 DRI (Dietary Reference Intakes, the most recent set of dietary recommendations set by the government) for an average healthy adult is 0.4mg (400mcg) of folate equivalents a day. Since folate is a natural form of vitamin B9, about half as active as its synthetic form - folic acid - the appropriate daily dose for the latter is about 0.2mg, or 200mcg. Recommended daily intake in pregnancy and lactation are higher, 0.6mg and 0.5mg of folate equivalents a day, respectively.
Best natural food sources of vitamin B9 are wheat germ, avocado, beans, fruit, cheese and vegetables in general, particularly green leafy vegetables.