Upping levels of dietary fibre may reduce the risk of heart attack in patients with previous heart problems, but the type of fibre may also have a role to play, suggests the results of a study in northern Italy.
The study, performed at the Istituto di Richerche Farmacologiche 'Mario Negri' in Milan, investigated the association between fibre intake - according to type and source of fibre - and risk of heart attack in a Mediterranean country.
Reporting in this month's European Journal of Clinical Nutrition, the researchers found that total fibre intake reduced heart attack risk by 28 per cent , but unexpectedly, cereal fibre registered a positive effect of 11 per cent, increasing the chances of heart attack.
A total of 507 people who had had one non-fatal heart attack and 478 control participants who were in hospital for acute heart conditions were included in the study. The patients were interviewed using a questionnaire that included a validated food frequency section. Fibre was measured as non-starch polysaccharides.
The researchers also adjusted for several recognised heart attack risk factors, such as smoking, diabetes and hypertension.
The results showed evidence of an inverse relationship between the majority of fibre sources and the risk of heart attack, although the results differed according to the source. Fruit and soluble fibre had the greatest and statistically significant effect on heart health, lowering risk of attack by 36 per cent each. Total insoluble fibre and cellulose both reduced the risk by 23 per cent, while insoluble non-cellulosic polysaccharides had a lesser impact at 19 per cent, a similar result to vegetable fibre.
The study revealed that when further adjusted for carotene, vitamin C and vitamin E intake, the fruit fibre showed the strongest inverse relation with the risk of heart attack, although the association was no longer significant. According to the researchers, the protective effect of fibre was more marked in, or restricted to, subjects with the other heart attack risk factors, as mentioned above.
Though an inverse association between fibre intake and risk of heart attack appears established, the researchers said that the causality of this association is still open to debate.
In the study population, cereal fibre is mainly derived from refined grains, and the researchers gave this as a possible explanation for the lack of protection from this type of fibre.