Although studies suggest that the more fibre a person eats, the lower the risk of heart disease, few studies have looked at the relationship between dietary fibre from different sources and the impact on heart health.
The researchers from Harvard University found that for each 10 gram per day increment of total fibre consumed, there was a 14 per cent decrease in risk for coronary heart disease events (such as non-fatal and fatal heart attack) and a 27 per cent decreased risk of dying from coronary heart disease.
In contrast, vegetable fibre was not associated with coronary heart disease incidence or mortality.
The findings confirm the strong evidence supporting the role of fruit and wholegrain consumption on heart health. But the puzzling findings on vegetable fibre may throw some doubt on national health guidelines that promote 'five-a-day' fruit and vegetable intake.
Vegetables do offer a host of other nutrients aside from fibre, including vitamins and minerals. But discussion of health claims may require further research into different types of dietary fibre. In the US, the Food and Drug Administration (FDA) has authorised several health claims referring to the effects of a high fibre, low fat diet in helping to lower the risk of coronary heart disease and cancer. It has also recently approved health claims relating to wholegrain foods and prevention of heart disease and cancers.
The European Union is currently discussing a regulation on health claims, to include a possible nutrient or health claim for fibre content in foods.
For the new study, Mark A. Pereira and colleagues analysed the pooled results of several studies from the United States and Europe, including 91,058 men and 245,186 women, to determine whether the source of dietary fibre from fruit, vegetables or grains had any effect on the reduction in heart disease risk. Each study recorded the food types and how much the participants ate.
Although there was considerable variation in the level of dietary detail across the studies, all studies had some measurement of dietary fibre, they note in this week's issue of The Archives of Internal Medicine(164:370-376).
Among the total participants from the studies, there were 5,249 incident (new) coronary heart disease cases. Just over 2,000 participants died of coronary heart disease in the six to 10 years of follow-up.
The results suggest that dietary fibre intake during adulthood had a strong protective effect against coronary heart disease. Coronary risk was 10 per cent to 30 per cent lower for each 10 gram per day increment of total, cereal, or fruit fibre, reported the authors.
The researchers also found that associations were stronger for coronary deaths than for all events, "with reductions in risk of 25 per cent for cereal fibre and 30 per cent for fruit fibre for each 10 gram per day increment".
"Therefore, the recommendations to consume a diet that includes an abundance of fibre-rich foods to prevent CHD are based on a wealth of consistent scientific evidence," conclude the authors.
Dietary fibre is thought to reduce the risk of heart disease by lowering blood pressure and reducing cholesterol levels. The UK government recommends a daily intake of 18g per day although it is thought that most people only eat 12g daily on average.
Heart disease kills more people around the world than any other disease, according to the World Health Organisation.