A comparison of the effect of advice to eat either ‘5-a-day’ fruit and vegetables or folic acid-fortified foods on plasma folate and homocysteine

OBJECTIVE:
To assess and compare the effects of natural folate (100 micro g) with those of folic acid from fortified sources (100 micro 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 microg/day folic acid from fortified foods; (2) natural folate diet-usual diet plus 100 microg/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 microg/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 microg/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 B(6) and B(12) 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.