MRC Elsie Widdowson Laboratory

Revised blood folate status for the UK has been published as part of the National Diet and Nutrition Survey Rolling Programme (NDNS RP)

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Leafy green vegetables are high in folate. Credit: Samantha Forsberg Flickr

In November 2017, Public Health England published a revised report: blood folate results for the UK as a whole, Scotland, Northern Ireland (Years 1 to 4 combined: 2008/09 – 2011/12) and Wales (Years 2 to 5 combined 2009/10 – 2012/13). The report presents results for the UK overall, and separately for Scotland, Northern Ireland and Wales for red blood cell (RBC) folate, serum total folate and unmetabolised (free) folic acid concentrations for adults and children aged 1.5 years and over and women of childbearing age (16 to 49 years).

MRC EWL provides the scientific lead for the NDNS RP; the survey is carried out in collaboration with NatCen Social Research and, for this period (2008-2012), the University College London Medical School.

The report, first published in March 2015, has been updated in 3 ways:

  • changes to the criteria used to assess the extent of population folate deficiency in the light of publication of revised thresholds and uncertainty about the applicability of the biochemical threshold to the NDNS RP data
  • incorporation of the new World Health Organization (WHO) recommended threshold (assay-specific) for folate concentration delineating relative risk of fetal folate-sensitive neural tube defects (NTDs), and
  • correction of a calibration error which had led to a bias in the assay used in the NDNS RP for quantitation of serum unmetabolised (free) folic acid.

Key findings of the report for the UK overall

Two measures of blood folate are reported: red blood cell folate, which reflects longer term body stores and is generally considered the better measure of long term status and serum total folate, which reflects recent dietary intake.

Red blood cell (RBC) folate

The percentage of girls aged 11 to 18 years with RBC folate concentration below the clinical threshold indicating risk of anaemia (305nmol/L) was 13%; it was 5% or less in the other age/sex groups.

Among women of childbearing age (16 to 49 years), 75% of participants had a RBC folate concentration lower than the threshold for optimal avoidance of folate-sensitive fetal NTDs (748nmol/L). Mean RBC folate was significantly lower for women aged 16 to 24 years than for those aged 35 to 49 years.

The overall proportion of women of childbearing age with a RBC folate concentration below the clinical threshold indicating risk of anaemia (305nmol/L) was 7%, with the highest proportion being those aged 16 to 24 years (12%).

Serum folate

The percentage of adults and children with serum folate below the WHO clinical threshold for folate deficiency (7nmol/L) was no more than 5% in any age group. The percentage with serum folate concentration below the WHO threshold for possible deficiency (13nmol/L) was 31% for adults aged 19 to 64 years, 27% for adults aged 65 years and over, 41% for older children and 6% for children aged 4 to 10 years.

For women of childbearing age (16 to 49 years), the proportion with a serum folate concentration below the WHO clinical threshold for folate deficiency (7nmol/L) was 3%. There is no recommended serum folate threshold for minimising folate-sensitive NTDs.

Biochemical folate insufficiency

Substantial proportions of all age/sex groups had blood folate levels indicating risk of biochemical insufficiency. In the UK population between a fifth and a half of most age/sex groups (excluding children aged 4 to 10 years) had RBC folate levels below the estimated threshold range indicating biochemical folate insufficiency (450 to 550nmol/L).

The full revised report is available on the UK Government website.

The adjusted results for folate status will be available in the UK Data Archive after the publication of the Years 7 and 8 NDNS RP combined report later in 2018, and will include a further 4 years (2012/13 – 2015/16) of blood folate status for the NDNS RP.