"Several prospective cohort studies have observed a protective effect of dietary fiber on risk of type 2 diabetes," write S. Goya Wannamethee, PhD, from University College Medical School in London, United Kingdom, and colleagues. "However, this has not been observed in all studies and the biological mechanisms by which dietary fiber may be beneficial for diabetes are unclear. Several studies have shown inverse associations between dietary fiber and markers of inflammation, insulin sensitivity and hepatic function, factors which have been linked to the development of diabetes in other studies."
The goal of this study was to evaluate the association between dietary fiber and the risk for type 2 diabetes in older men, as well as the role of hepatic and inflammatory markers. The study cohort consisted of 3428 nondiabetic men aged 60 to 79 years who were originally enrolled in the British Regional Heart Study (BRHS). During a 7-year follow-up, there were 162 incident cases of type 2 diabetes.
After adjustment for total energy intake and potential confounding variables, the lowest quartile of total dietary fiber (≤ 20 g/day) was associated with an increased risk for diabetes (relative risk [RR], 1.47; 95% confidence interval [CI], 1.03 – 2.11). Low cereal and low vegetable/fruit fiber intake were each separately associated with increased risk.
Dietary fiber was inversely associated with the inflammatory markers C-reactive protein (CRP) and interleukin-6 (IL-6), as well as with tissue plasminogen activator (t-PA) and gamma glutamyl transferase (GGT). After adjusting for these markers, the increased risk for diabetes seen with low dietary fiber was attenuated (RR, 1.28; 95% CI, 0.89 – 1.86).
"Dietary fiber is associated with reduced diabetes risk which may be partly explained by inflammatory markers and hepatic fat deposition," the study authors write. "We can not establish the nature of the association between fiber intake and hepatic function and the inflammatory process."
Limitations of this study include a predominantly white, European, male population, limiting generalizability of the findings. Further studies are required in women and in other ethnic groups.
The British Heart Foundation Research Group supported this study. The BRHS also received support from Diabetes UK. The study authors have disclosed no relevant financial relationships.
Diabetes Care. Published online July 23, 2009. Abstract