Children are the ones most likely to overdose on folic acid
Dr Clare Craig
| Key points The safe upper limit for a child aged one to three is 200 micrograms of folic acid a day. For an adult it is 1,000. The limit is precautionary because no safety trials have ever been done. At the level chosen, the government’s own modelling shows 4.4 per cent of one to three year olds would be exposed over their limit, compared to 0.6 per cent of the whole population. Allowing for under-recording of consumption in young children could raise that to about 6 per cent. Capping folic acid in breakfast cereals, spreads and supplements could cut the toddlers at risk of over exposure almost six-fold. The regulations did not cap anything. Prior to fortification the fifth of childbearing women with the lowest intakes are all below the recommended intake and after fortification sixty per cent of them still will be. |
Folic acid is being added to flour from December 2026 with the aim of reducing pregnancies affected by neural tube defects. On the government’s own modelling, the group most at risk of exceeding its upper limit is children who were never at risk and have no possibility of benefiting. In addition, fortification has the least impact on the target women with the lowest folate levels and even after intervening in a way that affects the whole population most of this group will be left short of the government recommended intake.
What is the safety limit
For an adult the ceiling is 1,000 micrograms of folic acid a day. For a one to three year old it is 200 micrograms.
| Age | Safe upper limit for folic acid |
| 1 to 3 years | 200 micrograms a day |
| 4 to 6 years | 300 |
| 7 to 10 years | 400 |
| 11 to 14 years | 600 |
| 15 to 17 years | 800 |
| 18 and over | 1,000 |
Upper limits used in the government’s modelling. The adult figure is the Guidance Level set by the Expert Group on Vitamins and Minerals in 2003. The children’s figures come from the Scientific Committee for Food.
There has been no safety measure in adults or in children. The Expert Group on Vitamins and Minerals declined to set a Safe Upper Level for folic acid even in adults in 2003 because they did not have the evidence on adverse effects to enable them to do so. Instead they set a Guidance Level of 1 mg a day, based on the risk of a dosage that could mask vitamin B12 deficiency leading to permanent neuropathies or dementia. For children it could not even set a guidance level. The children’s figures in the table are the European ones, scaled down from the adult limit to fit smaller body sizes. The government had to use these numbers in their modelling because they had nothing else to use.
To be clear, the upper exposure limit for a toddler is a number derived from an adult neurological damage risk and then divided by weight.
Who is already over the limit
The government has attempted to measure exposure using food diaries. Before any flour was fortified, 38 people in their survey were already above their age-specific limit. Fifteen of them were children aged ten or under.
For every adult the overdose could be prevented by stopping supplements. Among the children it was supplements in ten cases that pushed them over and breakfast cereals in three, with a multivitamin fruit juice and a prescribed liquid feed accounting for the other two.
The original discussions regarding fortification were based on the principle that all these voluntary sources of exposure would be capped. Somewhere along the line that intention was dropped. Folic acid in flour is now being added on top of these exposures.
What fortification does to children
The regulations mandate the fortification of all non-wholemeal flour at 250 micrograms per 100 grams.
| Age group | Upper limit | Above the limit |
| 1 to 3 years | 200 µg | 4.4% |
| 4 to 6 years | 300 µg | 1.4% |
| 7 to 10 years | 400 µg | 1.1% |
| Whole population | 1,000 µg for adults | 0.6% |
Extract from Table A13 of the modelling report. All non-wholemeal wheat flour at 250 micrograms per 100 grams, no capping of any voluntary source. Per cent of each age group whose average intake will exceed their own age-specific upper limit.
The modellers were clear that multiple scenarios could markedly lower toddler exposures and all of them limited the amounts in voluntary sources like cereal and supplements.
Capping cereals and spreads at 30 micrograms per 100 grams and supplements at 200 a day takes toddler exceedance from 4.4 per cent to 0.8 per cent.
| One to three year olds, at 250 µg/100g flour | Above the limit |
| No capping, which is the policy | 4.4% |
| Cereals, spreads and supplements capped | 0.8% |
Extracts from Tables A13 and A16 of the modelling report.
In 2006 SACN recommended mandatory fortification with the one condition that there would be restrictions on voluntary fortification so that the number of people above the upper limit would be limited. The calls for that condition were repeated in 2009 and again in 2017. The regulations from 2024 ignored that advice.
Breakfast cereals supply 27 micrograms a day on average of folic acid to one to three year olds, against a recommended intake of 70 and a ceiling of 200. A single 30 gram serving of the heavily fortified brands carries 50 to 100 micrograms and a real bowl can be nearer 45 grams which would give 75 to 150 micrograms. For those children who eat cereal daily it contributes two or three times the daily cereal average the model assumes.
About one toddler in twenty-three breaches the limit on average. If the question was phrased as how many will breach the limit on some days of the year the percentage would be much higher. By contrast one in a hundred and sixty of the adult population exceeds this arbitrary limit. Children are the only group the report shows exceeding 1 per cent. They have the lowest limits and they eat plenty of flour. SACN’s 2017 report recommended further research be done on outlier groups with higher consumption and more risk of significant exposure. The regulations were made without it.
What is exposure like in reality?
All those figures rely on a model of flour intake that is too low. The survey even measured how much it under-recorded finding the difference between reported energy intake and measured energy expenditure. It was about 14 per cent in young children and about 37 per cent across the sample as a whole. Despite going to the effort of measuring it, this correction was never used in the models.
The modellers did model for different concentrations and this data can be used because using a higher dose would have the same effect as a lower dose which was consumed at higher quantity. In the end the amount of folic acid taken in is the same. To adjust for the 14 per cent extra exposure in children the equivalent dosing would be 285 micrograms per 100 grams. That would mean 6 per cent of one to three year olds would exceed their limit.
| What the flour intake is corrected by | Equivalent level | One to three year olds above the limit |
| Nothing, as the model stands | 250 µg/100g | 4.4% |
| Under-recording measured in young children | 285 µg/100g | 6% |
Per cent of one to three year olds whose average intake exceeds their 200 microgram limit, read from Table A13 of the modelling report.
The survey had its own biases. It recorded four days of eating, only a snapshot. This is too short to describe what a child habitually eats and the proportion exceeding the limit may be lower (or indeed higher) if measured over a longer period.
It does not even reach the at-risk women
Women of childbearing age eat less flour than average so fortifying flour with folic acid has the least effect on them. The women with the lowest intake of flour are also the group least likely to take supplements. Only seven per cent of their folate comes from metabolising folic acid compared to half in the highest-intake group.
| Flour fortification | Mean total folate | Still below the recommended intake |
| None, as now | 109 µg/d | 100% |
| 250 µg/100g, the chosen level | 183 µg/d | 59.5% |
Extract from Table 15 of the modelling report. Women of childbearing age in the lowest fifth of folate intake, all non-wholemeal wheat flour, supplements capped.
All of the women the policy is aimed at are below the recommended intake levels prior to fortification. Three in five remain below after fortification. The report also modelled adding 450 micrograms of folic acid per 100 grams of flour and found that even then a third of these women would remain below the target level.
How precise is the projected benefit?
In the report’s own data, dietary intake explains less than a fifth of the variation in red cell folate. More than 80 per cent of the variation in levels is due to other factors. Some of the unexplained variation could be due to red cell folate levels reflecting months of intake but the food diary only reported a four-day window that was eight weeks earlier. However, differences in individual physiology will also contribute. Increasing folate consumption shows sharply diminishing returns in terms of red cell folate stores.
Applied to current blood folate, the prediction equations give an expected neural tube defect rate of 2.4 per 1,000 pregnancies. In reality the rate is 1.2 to 1.3 per 1,000. The report focuses on percentage reductions instead of absolute rates and ignores the discrepancy between the modelled rates and reality. The model substantially overestimates the present rates yet it is used to claim that it could predict a relative reduction thanks to the intervention.
Ultimately, this modelling has been used to claim a small reduction in affected pregnancies and the same model has shown that those most at risk of over exposure are small children who cannot possibly benefit. The simple measure of reducing voluntary fortification could have reduced toddler exceedance almost six-fold and was ignored by a policy that was pushed through without a House of Commons debate.
