US study shows that folic acid fortification decreases neural tube def
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《英国医生杂志》
The incidence of neural tube defects in infants fell by about a third in some ethnic groups when the United States gradually increased enrichment of grain products with folic acid in the 1990s, a study has found (Pediatrics 2005;116:580-6).
The March of Dimes, a charity active in efforts to prevent birth defects, has called for a doubling of fortification of food with folic acid to further reduce neural tube defects. In 1996 the charity recommended that grain products should be enriched with 350 micrograms for each 100 g of grain. Two paediatricians argue in a commentary to the paper that the concentration of folic acid in grain products in the US should be at least doubled from the current level of 140 micrograms per 100 g of grain and that vitamin B-12 should also be added to flour (Pediatrics 2005:116:753-5). The paediatricians argued that such fortification was worthwhile, because fears that folic acid supplementation might mask vitamin B-12 deficiency in elderly people were based on a misunderstanding of the biochemistry involved.
The paper抯 lead author, Sonja Rasmussen, told the BMJ that in the US about 3000 pregnancies a year were affected by neural tube defects such as spina bifida and anencephaly (the number of live births a year in the US is about four million). Dr Rasmussen, a clinical geneticist with the National Center on Birth Defects and Developmental Disabilities at the Centers for Disease Control and Prevention, in Atlanta, Georgia, said the national figure was derived from state data because national data were not available. Surveillance systems whose data included pregnancies where a neural tube defect was diagnosed antenatally and the pregnancy was terminated indicate that the current risk that a pregnancy would be affected with such a defect was about 0.75 per 1000, which translates into 3000 pregnancies a year.
Spina bifida and anencephaly are more common among Hispanic people than other ethnic groups and least common among black Americans. Several studies have shown that consumption of a supplement of 400 micrograms a day of folic acid, one of the B complex vitamins, around the time of conception reduced a woman抯 risk of giving birth to a baby with a neural tube defect by 50% to 70%.
In 1992 the US Public Health Service, a part of the Department of Health and Human Services, recommended that women of reproductive age consume 400 micrograms of synthetic folic acid every day to prevent the development of spina bifida and anencephaly in fetuses. Many women do not get enough folic acid from their diets. Its natural form, folate, is found in leafy green vegetables, orange juice, and legumes.
In 1996 the Food and Drug Administration required folic acid fortification of grain products, labelled as "enriched," to provide about 100 micrograms a day. This fortification, Dr Rasmussen said, still did not provide the 400 micrograms a day recommended by the Public Health Service for women of childbearing age. Therefore efforts were made to increase women抯 intake, through a multivitamin pill containing folic acid, taking a folic acid supplement, or eating a breakfast cereal fortified with 100% of the recommended daily intake of folic acid every day.
The study looked at 21 population based surveillance systems that recorded trends in the prevalence of spina bifida and anencephaly between 1995 and 2002. About 35% to 40% of all births in three ethnic groups in the US were included: Hispanic, non-Hispanic white, and non-Hispanic black people. The studies covered about 11 million births. There were 4468 cases of spina bifida and 2625 cases of anencephaly.
The rate of neural tube defects found was about 0.64 per thousand pregnancies, a lower figure than the rate of 0.75 per 1000 pregnancies estimated as being the national rate, because 12 of the 21 surveillance studies in the analysis were unable to ascertain cases of neural tube defects when the abnormality was diagnosed prenatally and the pregnancy was terminated.
The prevalence of neural tube defects declined from 1995 and 1996, before fortification was introduced, to 1998, a period when fortification was optional. The prevalence declined further from 1998 to 2002, when fortification became mandatory.
Dr Rasmussen said the decline in the prevalence of neural tube defects was significant in the Hispanic and non-Hispanic white groups (respective declines of 26% and 29% for anencephaly, and 36% and 34% for spina bifida). However, in the black group the decline in prevalence of anencephaly was not significant, and that of spina bifida was borderline significant.
She said that differences in diet and the prevalence of obesity and diabetes, as well as genetic factors, influenced the risk of a woman giving birth to a child with a neural tube defect. For example, she said, white women were more likely than Hispanic women to eat breakfast cereal enriched with folic acid and that Hispanic women were more likely to have a genetic polymorphism that affects folate metabolism. The risk of giving birth to a child with a neural tube defect among women who were obese was about double that among women who were not obese, she said. Similarly, the risk among women with diabetes was also about double that in women without diabetes.
Andrew Russell, executive director of the UK Association for Spina Bifida and Hydrocephalus, said that fortification of flour with folic acid wasn抰 mandatory in Britain, despite a long campaign to have it introduced. In 2000 the government抯 scientific advisory committee on nutrition had recommended fortification at 240 micrograms per 100 g of flour, but in 2002 the Food Standards Agency rejected this advice out of caution over masking deficiency of vitamin B-12 in elderly people. The committee is reviewing its advice at the moment and is expected to report shortly.
Mr Russell said that fortification at the level suggested by the committee in 2000 would prevent about 300 of the 1000 elective abortions carried out on women each year because of neural tube defects.(Janice Hopkins Tanne)
The March of Dimes, a charity active in efforts to prevent birth defects, has called for a doubling of fortification of food with folic acid to further reduce neural tube defects. In 1996 the charity recommended that grain products should be enriched with 350 micrograms for each 100 g of grain. Two paediatricians argue in a commentary to the paper that the concentration of folic acid in grain products in the US should be at least doubled from the current level of 140 micrograms per 100 g of grain and that vitamin B-12 should also be added to flour (Pediatrics 2005:116:753-5). The paediatricians argued that such fortification was worthwhile, because fears that folic acid supplementation might mask vitamin B-12 deficiency in elderly people were based on a misunderstanding of the biochemistry involved.
The paper抯 lead author, Sonja Rasmussen, told the BMJ that in the US about 3000 pregnancies a year were affected by neural tube defects such as spina bifida and anencephaly (the number of live births a year in the US is about four million). Dr Rasmussen, a clinical geneticist with the National Center on Birth Defects and Developmental Disabilities at the Centers for Disease Control and Prevention, in Atlanta, Georgia, said the national figure was derived from state data because national data were not available. Surveillance systems whose data included pregnancies where a neural tube defect was diagnosed antenatally and the pregnancy was terminated indicate that the current risk that a pregnancy would be affected with such a defect was about 0.75 per 1000, which translates into 3000 pregnancies a year.
Spina bifida and anencephaly are more common among Hispanic people than other ethnic groups and least common among black Americans. Several studies have shown that consumption of a supplement of 400 micrograms a day of folic acid, one of the B complex vitamins, around the time of conception reduced a woman抯 risk of giving birth to a baby with a neural tube defect by 50% to 70%.
In 1992 the US Public Health Service, a part of the Department of Health and Human Services, recommended that women of reproductive age consume 400 micrograms of synthetic folic acid every day to prevent the development of spina bifida and anencephaly in fetuses. Many women do not get enough folic acid from their diets. Its natural form, folate, is found in leafy green vegetables, orange juice, and legumes.
In 1996 the Food and Drug Administration required folic acid fortification of grain products, labelled as "enriched," to provide about 100 micrograms a day. This fortification, Dr Rasmussen said, still did not provide the 400 micrograms a day recommended by the Public Health Service for women of childbearing age. Therefore efforts were made to increase women抯 intake, through a multivitamin pill containing folic acid, taking a folic acid supplement, or eating a breakfast cereal fortified with 100% of the recommended daily intake of folic acid every day.
The study looked at 21 population based surveillance systems that recorded trends in the prevalence of spina bifida and anencephaly between 1995 and 2002. About 35% to 40% of all births in three ethnic groups in the US were included: Hispanic, non-Hispanic white, and non-Hispanic black people. The studies covered about 11 million births. There were 4468 cases of spina bifida and 2625 cases of anencephaly.
The rate of neural tube defects found was about 0.64 per thousand pregnancies, a lower figure than the rate of 0.75 per 1000 pregnancies estimated as being the national rate, because 12 of the 21 surveillance studies in the analysis were unable to ascertain cases of neural tube defects when the abnormality was diagnosed prenatally and the pregnancy was terminated.
The prevalence of neural tube defects declined from 1995 and 1996, before fortification was introduced, to 1998, a period when fortification was optional. The prevalence declined further from 1998 to 2002, when fortification became mandatory.
Dr Rasmussen said the decline in the prevalence of neural tube defects was significant in the Hispanic and non-Hispanic white groups (respective declines of 26% and 29% for anencephaly, and 36% and 34% for spina bifida). However, in the black group the decline in prevalence of anencephaly was not significant, and that of spina bifida was borderline significant.
She said that differences in diet and the prevalence of obesity and diabetes, as well as genetic factors, influenced the risk of a woman giving birth to a child with a neural tube defect. For example, she said, white women were more likely than Hispanic women to eat breakfast cereal enriched with folic acid and that Hispanic women were more likely to have a genetic polymorphism that affects folate metabolism. The risk of giving birth to a child with a neural tube defect among women who were obese was about double that among women who were not obese, she said. Similarly, the risk among women with diabetes was also about double that in women without diabetes.
Andrew Russell, executive director of the UK Association for Spina Bifida and Hydrocephalus, said that fortification of flour with folic acid wasn抰 mandatory in Britain, despite a long campaign to have it introduced. In 2000 the government抯 scientific advisory committee on nutrition had recommended fortification at 240 micrograms per 100 g of flour, but in 2002 the Food Standards Agency rejected this advice out of caution over masking deficiency of vitamin B-12 in elderly people. The committee is reviewing its advice at the moment and is expected to report shortly.
Mr Russell said that fortification at the level suggested by the committee in 2000 would prevent about 300 of the 1000 elective abortions carried out on women each year because of neural tube defects.(Janice Hopkins Tanne)