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Neural tube defects and extra folate in bread

Study
Results
Comment

Anyone who lived in South Wales or Ireland in the 1950s and 1960s and who had their eyes and ears open can attest that neural tube defects of spina bifida and anencephaly were common. There were about 90 cases per 10,000 births, three times the number in Southern England, and ten times higher than in South Asia or Africa. Bandolier remembers attending lectures where association with tea-drinking and bad potatoes were suggested as possible causes.

Now rates are much, much, lower. Now we know about the importance of folic acid in the prenatal and early days of pregnancy, in the crucial period when the neural tissue is forming. Newer and better methods of detecting neural tube defects, with blood and ultrasound screening, means that many affected pregnancies are terminated.

Better than termination is prevention. Prevention involves ensuring that women of child-bearing age have adequate or supplemented folic acid in their diet. One of the changes in previously badly-affected regions was the advent of the chain food stores with fresh and frozen vegetables all year round - the 'Tesco effect'. In the United States mandatory fortification of cereal grain products went into effect in January 1998. The effect of this comes from a report from the Centres of Disease Control [1].

Study

Eight population-based surveillance systems provided data from sources performing diagnostic prenatal ultrasound as part of their surveillance programmes. The number of spina bifida and anencephaly-affected pregnancies were added together to provide an estimated total of neural tube defect (NTD) affected pregnancies, and prevalence multiplied by US births for total numbers in the USA. The number of affected pregnancies included live births, stillbirths, foetal deaths, and elective terminations.

Two periods were studied, a 24-month pre-fortification period in 1995 and 1996, and a 24-month post-fortification period in 1999-2000.

Results

Table 1 shows prevalence and numbers for the two periods. The estimated number of affected pregnancies fell by 27%.



Table 1: Prevalence and numbers of neural tube defects in the United States estimated from sites with diagnostic prenatal ultrasound before and after cereal fortification with folic acid



Spina bifida
Anencephaly
 
Prevalence
(per 10,000 live births)
Number
(USA)
Prevalence
(per 10,000 live births)
Number
(USA)
Total NTD
(USA)
Before fortification (1995-1996)
6.4
2,490
4.2
1,640
4,130
After fortification (1999-2000)
5.1
1,980
3.5
1,380
3,020


Comment

Fortification of cereal products with folic acid increases blood folate levels. In Chile [2], fortification of bread to an average level of 2 mg folic acid per kilogram of bread raised serum and red cell folate substantially (Figure 1).



Figure 1: Serum and red cell concentrations (log scale) in Chilean women before and after fortification of bread





It would be wonderful if every woman of child-bearing age ate enough fruit and vegetables that supplementation before pregnancy was unnecessary, but that is baying for the moon. Folic acid consumption in diet and supplements has a strong dose response, and better ways have to be found to get the message across. Perhaps food supplementation with folic acid would be useful across the population, given its general antioxidant properties? The targets would be heart disease and cancer, as well as neural tube defects. It would be worth taking a look at the evidence when it is available.

References:

1 P Mersereau et al. Spina bifida and anencephaly before and after folic acid mandate - United States, 1995-1996 and 1999-2000. MMWR 2004 53: 362-365.

2 F Hertrampf et al. Consumption of folic acid-fortified bread improves folate status in women of reproductive age in Chile. Journal of Nutrition 2003 133: 3166-3169.

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