Folic acid has been added to cereal-grain products in the United States (US) for more than 20 years. Since 1998, enriched cereal grain products have been compulsory in order to improve folate status in women of reproductive age and subsequently reduce the risk of neural tube birth defects (NTDs).
Neural Tube Defects
Neural tube defects (NTDs) are birth defects of the brain, spine or spinal cord. They occur to the foetus when the spinal cord and/or surrounding vertebrae fails to close properly or becomes damaged – with folate being involved with cell division and this closure.
NTDs happen in the first month of pregnancy, often before a woman even knows that she is pregnant. The two most common neural tube defects are spina bifida and anencephaly. In spina bifida, the foetal spinal column doesn’t close completely, usually resulting in some paralysis of the legs. In anencephaly, most of the brain and skull do not develop, resulting in stillborn babies or babies who die shortly after birth.
The exact causes of neural tube defects aren’t known. However, consuming enough folic acid, before and during pregnancy, is known to prevent most neural tube defects.
Folate and Folic Acid
Folate is a water-soluble B vitamin, known as vitamin B9, which is essential for the formation of red blood cells (RBCs). The folate form that naturally occurs in food is called folate. Folic acid is the synthetic form of folate and can be used in the fortification of food and within food supplements.
The levels of folate in an individual differs by age and population. Folate deficiency isn’t a major problem for individuals eating a balanced diet, though there are many people that do not achieve the recommended intakes. This is most problematic in women of childbearing age, where a consequence of folate deficiency is that pregnant women are at greater risk of giving birth to babies with NTDs. Furthermore, with NTDs occurring in the first month of pregnancy, this is before many women know that they are pregnant and consequently begin supplementation when it is already too late.
Folic Acid Fortification in the US
Enriched cereal-grain products have been fortified in the US since 1998, which is estimated to additionally provide an average intake of 115µg of folic acid per day in women of reproductive age from enriched cereal-grain products and ready-to-eat cereals.
Cross-sectional serum and RBC folate data has been assessed from the National Health and Nutrition Examination Survey (NHANES) from 1999-2016 by the Centre of Disease Control (CDC) and published in the American Journal of Clinical Nutrition in August 2019.
The prevalence of folate insufficiency in women of reproductive age decreased from 59% pre-fortification (1988–1994) to 15% (1999–2006), 23% (2007–2010) and 18.6% (2011-2016) post-fortification. This is likely to be due to the fact that the concentrations of serum folate and RBC folate sharply increased from pre- to post-fortification, followed by minor fluctuations during the post-fortification survey periods (1999–2016). Furthermore, it has been established that overall, a 28% reduction in anencephaly and spina bifida at birth was observed from pre- to post-fortification, with this reduction in NTDs remaining fairly stable during for the 13-year period up to 2011.
It is worth noting that in the United Kingdom (UK) folic acid is not added presently added to foods, although the UK government are have undertaken a consultation on whether folic acid should be added to flour.
As such, the UK is currently pre-fortification and the UK National Diet and Nutrition Survey Rolling Programme Years 7 and 8 has reported folate insufficiency at 91% in women aged 16 to 49. Data from the US could indicate that a compulsory folic acid fortification programme in the UK may be an effective way of reducing the prevalence of folate insufficiency and subsequent NTDs in foetuses. The US data shows that post-fortification has kept folate insufficiency levels at a fairly constant level of about 20%.
Discussion
The long-term monitoring of folate status in the US has provided vital information, with results indicating that folate insufficiency rates appear to be stable at approximately 20%. This data, however, did not account for women with higher folate requirements e.g. those with genetic polymorphisms, diabetes nor previous pregnancies affected by NTDs.
These findings still show, however, that 1 in 5 US women have insufficient folate status. On this note folic acid flour fortification should not been seen as a substitute for healthy and balanced diets nor preconception supplementation strategies.
It is also important to continue advising on the importance of planning and preparing the body nutritionally prior to conception and not relying solely on fortification strategies.
References
Pfeiffer CM et al (2019). Folate status in the US population 20 y after the introduction of folic acid fortification. Am J Clin Nutr. Aug 27
Proposal to add folic acid to flour: consultation document
https://www.gov.uk/government/consultations/adding-folic-acid-to-flour/proposal-to-add-folic-acid-to-flour-consultation-document
National Diet and National Survey: time trend and income analyses for Years 1 to 9
https://www.gov.uk/government/statistics/ndns-time-trend-and-income-analyses-for-years-1-to-9
