Nutritional advice to increase soluble fibre intake does not change plasma folate or homocysteine in men with angina: a randomised controlled trial

Objective: To study the effect of advice to increase dietary soluble fibre, including fruit and vegetables, on plasma folate and homocysteine in men with angina. Design: Data were collected on a subset of subjects from the Diet and Angina Randomised Trial (DART II). In a randomised (2 x 2) factorial design, subjects received advice on either, neither or both interventions to: (1) increase soluble fibre intake to 8.0 g day(-1) (fruit, vegetables and oats); (2) increase oily fish intake to 2 portions week(-1). Those who received soluble fibre advice were compared with those who did not. Subjects were genotyped for C677T variant 5,10-methylenetetrahydrofolate reductase (MTHFR). Setting/subjects: Seven hundred and fifty-three male angina patients were recruited from general practice. Results: Plasma homocysteine concentrations were at the upper end of the normal range (median 11.5, 25% 9.4, 75% 14.0 mumol l(-1)). Baseline intake of fruit and vegetables was positively correlated with plasma folate (r(s)=0.29, P<0.01). Smokers had lower intakes of fruit and vegetables, lower plasma folate and higher homocysteine (all P<0.01). Homozygotes for variant MTHFR had higher homocysteine concentrations at low plasma folate (P<0.01). Reported intakes of fruit and vegetables and estimated dietary folate increased in the intervention group (ca. +75 g day(-1), P<0.01 and ca. +20 g day(-1), P<0.05, respectively). However, neither plasma folate (baseline/follow-up 4.5 vs. 4.4 mug l(-1), P=0.40) nor homocysteine (baseline/follow-up 11.7 vs. 11.7 mumol l(-1), P=0.31) changed. Conclusions: Plasma homocysteine, a cardiovascular risk factor, is influenced by MTHFR genotype, plasma folate and smoking status. Dietary advice successfully led to changes in fruit and vegetable intake, but not to changes in plasma folate or homocysteine, possibly because the fruits and vegetables that were chosen were not those richest in folate.