Sunday, January 24, 2010

Folic acid: an essential B vitamin with a warning on overdose

Folate is the naturally occurring form of vitamin B9, while folic acid is the synthesized form. This vitamin is essential in the synthesis and repair of DNA, in the production of red and white blood cells, in the synthesis of important amino acids, and in any period of rapid cell growth, such as childhood and pregnancy.

The urgent need for Folate in pregnancy Neural tube defects are among the most dreaded birth defects, affecting 1 in 1500 births in the US today. The baby is born without a major portion of its brain and skull (and dies shortly after birth) or with incomplete closure of the spinal cord in the back, leading to some degree of paralysis, pain, and problems with bowel and bladder function. Insufficient folate in the diet (along with genetic and unknown factors) plays a role in this problem, and supplementation of the mother’s diet can decrease the incidence of neural tube defects by more than 70%. The folic acid supplement, as well as adequate dietary intake of folate, should start even before the beginning of pregnancy, as the neural tube starts developing in the first month. It is extremely important for young women to take a multivitamin containing 400 micrograms (mcg) of folic acid on a regular basis; even if she does not plan to become pregnant (at least 50% of pregnancies are unplanned; in celibate or lesbian women the multi will also help with a possibly haphazard diet.) More folate is needed during pregnancy and lactation. Because not all girls and young women take vitamins, the FDA mandated the fortification of refined grain products (white flour, pasta, breakfast cereals) with folic acid in 1998. It is estimated that young women get about 100 mcg a day of folic acid from fortified cereal grains – which is an improvement, but insufficient. An excellent diet and/or a multivitamin is still important. Studies show an approximate 50% reduction in neural tube defects in the US since fortification in 1998. Similar programs of fortification have taken place in Costa Rica and many European countries. Other problems in pregnancy, such as fetal cleft lip, premature delivery and serious bleeding at delivery from placental detachment, have been associated with folate deficiency. See for Nicolas Kristof’s opinion page article on the benefits of micronutrient enrichment of foods in Honduras and elsewhere.

Homocysteine: Homocysteine is an amino acid that used to be associated with higher rates of heart disease amd stroke; it can be lowered by conversion into methionine (another amino acid) by folic acid, vitamins B6 and B12. However, studies from two Canadian Universities in 2006 showed that lowering homocysteine levels with these B vitamins did not decrease the risk of heart attack or death from heart disease, but did significantly decrease the risk of stroke. Studies also show that lowering homocysteine levels with B vitamins in people with former strokes lowers their risk of hip fractures.

Anemia: People with a low intake of folate from food, or with chronic alcoholism, can develop a kind of anemia characterized by large, malformed red blood cells. This anemia is akin to ‘pernicious anemia’ related to vitamin B12 deficiency, and can have serious consequences. Medical care is essential.

Cancer: There is growing controversy over the effects of giving high dose folic acid supplements to prevent cancer or other diseases, since recent clinical trials have shown an increase in lung cancer and polyps of the colon. Animal experiments show that small amounts of folic acid supplements can decrease cancer risk, and high amounts can increase it. However, no amount of folate in foods is dangerous and studies show a decreased cancer risk, including breast cancer, among those with the highest dietary intakes.

Foods containing folate: All forms of green leafy vegetables, broccoli, avocado, asparagus, peas, beans of all kinds, lentils, peanuts, wheat germ, oranges and other citrus fruits, and many other whole foods contain folate. You will benefit from folate by making vegetables and fruits the center of your diet. Cooking can destroy folate, so it is best to steam or stir fry vegetables lightly, or cook them in a microwave. Avoid boiling in abundant water.

What’s the bottom line with folate and folic acid supplements?
Keep eating as many vegetables and fruits as possible, and include raw salads in your daily fare. You will be ingesting plenty of folate, which is a very good thing. Young women who might become pregnant should take a daily multi with 400 mcg of folic acid and special vitamins during pregnancy. Adult multivitamins with 400 mcg of folic acid should be taken by people with high risk of stroke or a prior stroke, and by those dependent on alcohol. For other adults, a multi is probably safe, if it contains no more than 400 mcg of folic acid. Who said it would be simple?
Sadja Greenwood, MD, MPH past issues on this blog

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