It's no surprise that fiber is an important
part of a healthy diet, but researchers at the National Cancer Institute say
that fiber from whole grains reduces the risk of death.
Getting lots of
dietary fiber appears to reduce the risk of dying — particularly from
cardiovascular, infectious, or respiratory diseases — according to a large
observational study.
The study of more than
500,000 people found those with the highest dietary fiber intake — an average
of 29. grams per day for men and 26 for women — had a 22 percent lower risk of
dying from any cause over nine years of follow-up compared with those with the
lowest fiber, according to Dr. Yikyung Park, of the National Cancer Institute
in Rockville, Md., and colleagues found.
Higher fiber
consumption lowered the risk of death from cardiovascular, infectious, and
respiratory diseases by 24 percent to 56 percent in men and by 34 percent to 59
percent in women, Park and co-authors reported online in the Archives
of Internal Medicine.
"Making
fiber-rich food choices more often may provide significant health benefits," the group wrote in the paper — but
noted that only grain sources of fiber were significantly linked to the
mortality benefit.
U.S. dietary
guidelines recommend eating fiber-rich fruits, vegetables, and whole grains to
get 14 g of fiber per 1,000 calories.
In the study, though,
fiber from beans and vegetables showed only a weak link to mortality, while
fiber from fruit showed no link.
An accompanying
editorial argued that piling on whole grains was the way to go.
"While fiber is
clearly a component of whole grains, the reverse is not true," wrote Dr.
Lawrence de Koning, and Dr. Frank B. Hu, both of Harvard.
"Fiber isolates
probably do not provide the same benefits as intact, whole grains," they
added. "Substituting whole grains for refined grains would provide
benefits not only from fiber but also from other unique health-promoting
components of whole grains."
The study findings
came from analysis of the National Institutes of Health-AARP Diet and Health
Study, a prospective cohort study that assessed diet through a questionnaire at
baseline in 1995-1996.
Among the 567,169
individuals ages 50 to 71 that completed the food-frequency questionnaire,
20,126 men and 11,330 women died during the subsequent nine years.
Each 10-g-per-day
increment of fiber intake was associated with a multivariate-adjusted lower
risk of death.
This relationship
persisted in analyses by smoking status and across body mass index categories.
Correction for measurement error in assessing dietary fiber intake actually
strengthened the associations.
The researchers noted
that these results matched the consistently reduced cardiovascular risk seen in
prior studies with higher fiber intake, which may be due to its effects on
lipids, insulin factors, and blood pressure.
The anti-inflammatory
properties of fiber could be another part of the explanation for reductions in
cardiovascular, respiratory, and infectious disease mortality, they suggested.
However, they
cautioned, while the benefit for lowered respiratory and infectious disease
mortality was "interesting," it requires further confirmation.
The group also warned
that they could not rule out the possibility that dietary fiber was simply a
marker for a healthier diet or healthier lifestyle, which may have
been incompletely controlled for in the study.
The study was
supported by the Intramural Research Program of the National Cancer Institute,
National Institutes of Health.
The researchers
reported having no conflicts of interest to disclose.
Hu and de Koning
reported having no conflicts of interest to disclose.