US researchers based at the National Cancer Institute in Maryland and the AARP in Washington DC concluded that dietary fibre from grains, but not from other sources, was significantly inversely related to total and cause-specific death in both men and women.
Such fibre intake, they reported, also lowered the risk of death from cardiovascular, infectious, and respiratory diseases by 24 per cent to 56 per cent in men and by 34 per cent to 59 per cent in women.
Moreover, the authors found that inverse association between dietary fibre intake and cancer death was observed in men but not in women.
The researchers argue that while dietary fibre has been hypothesized to lower the risk of coronary heart disease, diabetes, and some cancers little is known of the effect of dietary fibre intake on total death and cause-specific deaths.
Furthermore, they stressed that “previous studies examining the association between dietary fibre and mortality were limited by small sample sizes, narrow ranges of dietary fibre intakes, and inadequate control for confounding, leading to decreased power, intakes without the necessary ranges to observe associations, and residual confounding.”
So the team explained their objective thus was to investigate dietary fibre intake in relation to total and cause-specific mortality in a large prospective cohort of men and women in the US based NIH (National Institutes of Health) -AARP Diet and Health Study, in which more than 30,000 deaths occurred during an average of 9 years of follow-up and a wide range of dietary intakes.
The researchers said that diet was assessed using a food-frequency questionnaire at baseline. Cause of death was identified using the National Death Index Plus. Cox proportional hazard models were used to estimate relative risks and 2-sided 95 per cent confidence intervals (CIs).
“We also collected demographic, anthropometric, and lifestyle information, including history of smoking, physical activity, family history of cancers, menopausal hormone therapy use in women, and some medical conditions at baseline,” they said, adding that they performed sex-specific analysis and reported the results by sex.
Results
The authors concluded that dietary fibre intake was associated with a significantly lowered risk of total death in both men and women.
Comparing the lowest quintile of dietary fibre intake, both men and women in the highest quintile had a 22 per cent lower risk of total death, they reported.
Dietary fibre intake was also significantly inversely related to total death in former and current smokers in both men and women, commented the authors. A significant association with dietary fibre intake was also observed across categories of BMI.
“During an average of 9 years of follow-up, we identified 20,126 deaths in men and 11,330 deaths in women,” they reported. There were 5248 CVD deaths and 8244 cancer deaths in men and 2417 CVD deaths and 4927 cancer deaths in women, noted the team.
Furthermore, the authors said that they examined the association stratified by age at baseline (<60 and >60), self-rated health condition (excellent/good and fair/poor), and menopausal hormone therapy use in women (never and ever) and observed a consistently inverse association between dietary fibre intake and total death across all categories examined.
“We found that dietary fibre from grains was significantly inversely related to the risk of total, CVD, cancer, and respiratory disease deaths in both men and women. Comparing the highest with the lowest intake of fibre from grains, men had a 23 per cent lower risk of total death and women had a 19 per cent lower risk of total death,” they reported.
The researchers said fibre from vegetables and beans was also weakly associated with a lower risk of total death in both men and women. However, fibre from fruits was not related to total and cause-specific deaths in men and women, they said.
Source: Journal of the American Medical Association
Published online ahead of print: doi:10.1001/archinternmed.2011.18
Title: Dietary Fiber Intake and Mortality in the NIH-AARP Diet and Health Study
Authors: Y Park, A. F. Subar, A. Hollenbeck, A. Schatzkin.