1. ¹Cardiovascular Sciences Research Group, Wales Heart Research Institute, University of Wales College of Medicine, Cardiff, Wales, UK
2. ²Department of Epidemiology, Statistics and Public Health, University of Wales College of Medicine, Cardiff, Wales, UK

Correspondence: Dr I F W McDowell, Department of Medical Biochemistry, University of Wales College of Medicine, Cardiff, Wales CF14 4XN, UK. E-mail: ian.mcdowell@cardiffandvale.wales.nhs.uk

^†Current address: Strangeways Research Laboratory, Wort's Causeway, The University of Cambridge CB1 8RN, UK.

^*Guarantor: Dr IFW McDowell.

^‡Contributors: PALA-W, MLB, IFWMcD, RGN designed the study. PALA-W and JMW collected the data presented here. ZEC and SJM were responsible for the genotyping and biochemical assessments. RGN analysed the data. PALA-W wrote the first draft of the paper and the other authors commented on this and subsequent drafts.

Received 18 June 2001; Revised 27 May 2002; Accepted 28 May 2002.

Abstract

Objective: To assess and compare the effects of natural folate (100 g) with those of folic acid from fortified sources (100 g/day) on plasma folate and homocysteine.

Design: Randomized controlled trial (parallel groups).

Setting: Men and women living in South Wales, UK.

Subjects: A total of 135 healthy individuals recruited from the local workforce and blood donor sessions. All subjects possessed the 'wild-type' CC genotype for C677T polymorphism in methylenetetrahydrofolate reductase (MTHFR).

Interventions: Subjects underwent one of the following dietary interventions for 4 months: (1) fortified diet—usual diet plus 100 g/day folic acid from fortified foods; (2) natural folate diet—usual diet plus 100 g/day folate from natural sources; (3) control—usual diet.

Results: The fortified group increased reported intake of folic acid from fortified foods compared to other groups (P<0.001) achieving an extra 98 g/day (95% CI 88–108). The natural folate group increased reported intake of natural source folates compared with the other two groups (P<0.001), but achieved a mean increase of only 50 g/day (95% CI 34–66). Plasma folate increased (P<0.01) by a similar amount in both intervention groups compared to controls (fortified group 2.97, 95% CI 0.8–5.1; natural group 2.76, 95% CI 0.6–4.9. Plasma homocysteine, vitamins B₆ and B₁₂ were not significantly changed.

Conclusions: Subjects achieved increases in folate intake using fortified foods more easily than by folate-rich foods, however both sources increased plasma folate by a similar amount. These levels of intake were insufficient to reduce homocysteine concentrations in MTHFR CC homozygotes, but may be more effective in other genotypes.

Sponsorship: This study was supported by the UK Ministry of Agriculture, Fisheries and Foods (latterly UK, Food Standards Agency, Project Reference N05002). The Kellogg Company of Great Britain provided funding for reimbursement of subjects for the cost of fortified foods.