The early days and weeks following conception are critical to human life. During this period an embryo goes from being a tiny ball of identical cells to a complex array of specialised cells and structures, ready to develop into the organs that will support life.
The formation of the spinal cord and brain occurs during the first 28 days of pregnancy as a flattened sheet of cells curls up to form a cylinder called the neural tube. From this tube the brain begins to develop at one end, and at the other, the spinal cord forms. In one or two of every 1000 pregnancies this formation doesn’t happen properly, and produces a neural tube defect (NTD).
A spectrum of health conditions can result from this including severely disabling conditions such as Spina bifida, or the ultimately fatal condition of anencephaly.
Randomised controlled trials in the 1990’s showed conclusively that folic acid could prevent NTDs. Folate, the natural form of folic acid, is found at low levels in foods such as leafy vegetables, yeast extract such as marmite, and legumes, such as beans and peanuts. Achieving the recommended daily intake (RDI) of 400ug of folic acid during pregnancy from diet alone is difficult.
As a result, women are told to take supplements of folic acid to boost their levels if they are trying for a baby or in the first trimester of pregnancy.
During the first few weeks of pregnancy, folic acid reduces the risk of developing an NTD
This poses a real problem for the 55% of pregnancies that are not planned. Women often don’t know they are pregnant until near the end of the critical early 28 day window at the beginning of pregnancy where the neural tube is formed and NTDs can be prevented – so by the time they know to begin taking supplements the critical time has passed.
To get around this issue, it has been recommended that folic acid should be added to flour. Mandatory folic acid supplementation of flour has been introduced in 81 countries around the world. This is at a level that should help the general population to reach the recommended intake during pregnancy. For example, in the USA they have mandatory fortification which has boosted women’s consumption in the US by around 100-200ug a day and there has been a reduction of 25-50% in the incidence of NTD affected babies.
In the UK the average adult takes in around 250ug of folic acid per day from dietary sources, but adding folic acid to flour could help women reach the RDI of 400ug of folic acid if they are pregnant.
Adding folate to flour could ensure women who are unknowingly pregnant are still able to meet the RDI for folic acid
There have been some worries over folic acid fortification, as the safe upper limit was set at 1000ug a day. The main concern is that if your intake of folic acid is too high, a deficiency in another important dietary component, Vitamin B12, would be difficult to diagnose. This is because some of the main symptoms associated with a folate deficiency, or a B12 deficiency, are also caused by anaemia.
A high intake of folate can resolve these symptoms, even when the person is deficient in Vitamin B12. So, when people with a high folate intake go to the doctor with a problem, including other symptoms associated with B12 deficiency, the deficiency in B12 may still remain undiagnosed.
Failure to diagnose and treat B12 deficiency may expose people, often the elderly to more severe symptoms such as neuropathy as the condition worsens before diagnosis.
The inherent ethical problem in this scenario is that measures to prevent illness in young members of the population could entail a risk to older member’s health, as a side effect.
Recently, scientists have found that the likelihood of this side effect has been miscalculated; high levels of folic acid are not associated with increased numbers of people suffering from neuropathy with B12 deficiency.
This suggests that there should not be concern about higher levels of folic acid intake, since the benefits are clear and the risks disproven. As a result, people are calling for folic acid to be added to flour in the UK, just like in many countries around the world, as an important preventative measure against the development of NTDs.
RSB supports the use of bioscience evidence to guide public policy, including on folic acid supplementation. You can keep up to date with all of our policy activities and sign up to our science policy newsletter.