Research - Dietary Fibre
Fiber consumption and all-cause, cardiovascular, and cancer mortalities: A systematic review and meta-analysis of cohort studies
Lihua Liu1, Shan Wang2 and Jianchao Liu3
1 Institute of Hospital Management, Chinese PLA General Hospital, Beijing, P. R. China
2 Department of Epidemiology and Biostatistics, School of Basic Medical Sciences, Peking Union Medical College/Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences Beijing, P. R. China
3 Office of Hospital Informatization, Institute of Hospital Management, Chinese PLA General Hospital, Beijing, P. R. China
The present meta-analysis aimed to investigate fiber consumption and all-cause mortality, and cause-specific mortality. MEDLINE and web of science database were searched for cohort studies published from inception to August 2014. Studies were included if they provided a hazard ratio (HR) and corresponding 95% CI for mortality in relation to fiber consumption.We found that, compared with those who consumed lowest fiber, for individuals who ate highest fiber, mortality rate was lower by 23% (HR, 0.77; 95% CI, 0.72–0.81) for CVD, by 17% (HR, 0.83; 95% CI, 0.74–0.91) for cancer, by 23% (HR, 0.77; 95% CI, 0.73–0.81) for all-cause mortality. For each 10 g/day increase in fiber intake, the pooled HR was estimated to be 0.89 (95% CI, 0.86–0.93) for all-cause mortality, 0.80 (95% CI, 0.72–0.88) for CHD mortality, and 0.66 (95% CI, 0.40–0.92) for IHD mortality, 0.91 (95% CI, 0.88–0.94) for cancer. Dietary fiber and CVD mortality showed a strong dose–response relation. Apparently, fiber consumption is inversely associated with all-cause mortality and CVD, IHD, cancer mortality.
Source : Molecular Nutrition and Food Research
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Dietary Fiber Intake Is Inversely Associated with Stroke Incidence in Healthy Swedish Adults
Background: Prospective studies of dietary fiber intake in relation to stroke risk have reported inconsistent results.
Objective: This study assessed the association between intake of total fiber and fiber sources and stroke incidence in healthy Swedish adults.
Methods: The analysis was based on 69,677 participants (aged 45–83 y) from the Swedish Mammography Cohort and the Cohort of Swedish Men who were free from cancer, cardiovascular disease, and diabetes at baseline (1 January 1998). Diet was assessed with a food-frequency questionnaire. Cases of stroke were ascertained through linkage to the Swedish Inpatient Register and the Swedish Cause of Death Register. Cox proportional hazards regression model was used to calculate RRs, adjusted for potential confounders.
Results: During 10.3 y of follow-up, 3680 incident stroke cases, including 2722 cerebral infarctions, 363 intracerebral hemorrhages, 160 subarachnoid hemorrhages, and 435 unspecified strokes, were ascertained. High intakes of total fiber and fiber from fruits and vegetables but not from cereals were inversely associated with risk of stroke. After adjustment for other risk factors for stroke, the multivariable RRs of total stroke for the highest vs. lowest quintile of intake were 0.90 (95% CI: 0.81, 0.99) for total fiber, 0.85 (95% CI: 0.77, 0.95) for fruit fiber, 0.90 (95% CI: 0.82, 1.00) for vegetable fiber, and 0.94 (95% CI: 0.84, 1.04) for cereal fiber.
Conclusion: These findings indicate that intake of dietary fiber, especially fruit and vegetable fibers, is inversely associated with risk of stroke.
Source : The Journal of Nutrition
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Dietary Fiber Nibbles Down Stroke Risk
Eating more fiber may modestly reduce the risk of stroke, although details remain uncertain and it might just be a surrogate for other healthy behaviors, a meta-analysis determined.
Each additional 7 g of daily dietary fiber intake was associated with a significant 7% lower risk of hemorrhagic and ischemic stroke combined, Diane Threapleton, MSc, of the University of Leeds, England, and colleagues reported online in Stroke.
"Our study supports current guidelines to increase fiber consumption," the researchers concluded, although they noted that too little data were available to narrow down what sources or types of fiber were most protective.
They called a 7-g per day boost in roughage doable, it being the equivalent of an extra serving of beans or two servings of fruit like apples and oranges.
The average American falls short of the daily recommended fiber intake by more than that, though, getting an average of just 13 g for women and 17 g for men compared with the 21 to 25 g and 30 to 38 g, respectively, called for by guidelines.
Although the observational data couldn't ascribe causality, a role for dietary fiber is plausible, Threapleton's group noted.
"Soluble types of fiber form gels in the stomach and small intestine, slowing the rate of nutrient absorption and slowing gastric emptying, which increases satiety and influences the overall amount of food eaten, resulting in lower levels of overweight," they wrote. "Bacterial fermentation of resistant starch and soluble fibers in the large intestine produces short-chain fatty acids which inhibit cholesterol synthesis by the liver, consequently lowering serum levels."
Prior studies have shown links to stroke risk factors, including hypertension and high cholesterol, as well as insulin resistance.
The literature search turned up eight prospective cohort studies from the U.S., northern Europe, Australia, and Japan reporting on fiber intake in healthy individuals (defined as not recruited based on history of disease or poor health) and incidence of first ever stroke.
Pooled results showed a steadily declining stroke risk with higher total fiber intake, with a relative risk of 0.93 per 7 g per day (95% CI 0.88 to 0.98).
Few individuals had fiber levels above 25 g per day, "so extrapolation of risk at higher intakes should be undertaken with caution," the researchers warned.
There was some evidence of heterogeneity among the studies, with a difference by study size.
Ischemic stroke appeared less common with higher total dietary fiber intake in two of the four studies that reported on this outcome, while a third showed a similar trend but with wide confidence intervals.
Hemorrhagic stroke occurred less often at higher fiber levels in one of the three studies looking at that outcome.
Soluble fiber showed a nonsignificant trend, with 6% lower relative risk of stroke per 4 g/day increase in daily intake across the studies.
The insoluble fiber results couldn't be pooled. One of the three studies reporting on this measure suggested a 38% lower stroke risk, while the others indicated no association.
Fiber from grain sources appeared protective in several studies, as did vegetable fiber, but again results couldn't be pooled.
The reviewers cautioned about the "inherent problem of unadjusted confounding" since fiber may be acting as a surrogate for other healthy behaviors like less smoking and more exercise that also would reduce stroke risk.
"All of the pooled studies did, however, include adjustment for potentially important confounding variables such as age, body mass index, blood pressure or history of hypertension, smoking status, alcohol intake, physical activity, and sex (where applicable), and also a variety of other health and lifestyle variables," Threapleton and colleagues noted.
Source : Medpage Today
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Dietary fiber alters gut bacteria, study finds
University of Illinois study shows that dietary fiber promotes a shift in the gut toward different types of beneficial bacteria. And the microbes that live in the gut, scientists now believe, can support a healthy gastrointestinal tract as well as affect our susceptibility to conditions as varied as type 2 diabetes, obesity, inflammatory bowel disease, colon cancer and autoimmune disorders such as rheumatoid arthritis.
As these microbes ferment fiber in the intestine, short-chain fatty acids and other metabolites are produced, resulting in many health benefits for the host, said Kelly Swanson, a U of I professor of animal sciences.
"When we understand what kinds of fiber best nurture these health-promoting bacteria, we should be able to modify imbalances to support and improve gastrointestinal health," he said.
This research suggests that fiber is good for more than laxation, which means helping food move through the intestines, he added.
"Unfortunately, people eat only about half of the 30 to 35 grams of daily fiber that is recommended. To achieve these health benefits, consumers should read nutrition labels and choose foods that have high fiber content," said Swanson.
In the placebo-controlled, double-blind intervention study, 20 healthy men with an average fiber intake of 14 grams a day were given snack bars to supplement their diet. The control group received bars that contained no fiber; a second group ate bars that contained 21 grams of polydextrose, which is a common fiber food additive; and a third group received bars with 21 grams of soluble corn fiber.
On days 16-21, fecal samples were collected from the participants, and researchers used the microbial DNA they obtained to identify which bacteria were present. DNA was then subjected to 454 pyrosequencing, a "fingerprinting" technique that provides a snapshot of all the bacterial types present.
Both types of fiber affected the abundance of bacteria at the phyla, genus and species level. When soluble corn fiber was consumed, Lactobacillus, often used as a probiotic for its beneficial effects on the gut, increased. Faecalibacterium populations rose in the groups consuming both types of fiber.
According to Swanson, the shifts in bacteria seen in this study--which occurred when more and differing types of fiber were consumed--were the opposite of what you would find in a person who has poor gastrointestinal health. That leads him to believe that there are new possibilities for using pre- and probiotics to promote intestinal health.
"For example, one type of bacteria that thrived as a result of the types of fiber fed in this study is inherently anti-inflammatory, and their growth could be stimulated by using prebiotics, foods that promote the bacteria's growth, or probiotics, foods that contain the live microorganism," he said.
Source : NewHope 360
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