Posts Tagged ‘Dietary fiber’

Benefits of Fiber in Diet

Reporter and Curator: Dr. Sudipta Saha, Ph.D.


UPDATED on 1/15/2019

This is How Much Daily Fiber to Eat for Better Health – More appears better in meta-analysis — as in more than 30 g/day

by Ashley Lyles, Staff Writer, MedPage Today

In the systematic review, observational data showed a 15% to 30% decline in cardiovascular-related death, all-cause mortality, and incidence of stroke, coronary heart disease, type 2 diabetes, and colorectal cancer among people who consumed the most dietary fiber compared to those consuming the lowest amounts.

Whole grain intake yielded similar findings.

Risk reduction associated with a range of critical outcomes was greatest when daily intake of dietary fibre was between 25 g and 29 g. Dose-response curves suggested that higher intakes of dietary fibre could confer even greater benefit to protect against cardiovascular diseases, type 2 diabetes, and colorectal and breast cancer.


Eating more dietary fiber was linked with lower risk of disease and death, a meta-analysis showed.

According to observational studies, risk was reduced most for a range of critical outcomes from all-cause mortality to stroke when daily fiber consumption was between 25 grams and 29 grams, reported Jim Mann, PhD, of University of Otago in Dunedin, New Zealand, and colleagues in The Lancet.

By upping daily intake to 30 grams or more, people had even greater prevention of certain conditions: colorectal and breast cancer, type 2 diabetes, and cardiovascular diseases, according to dose-response curves the authors created.

Quantitative guidelines relating to dietary fiber have not been available, the researchers said. With the GRADE method, they determined that there was moderate and low-to-moderate certainty of evidence for the benefits of dietary fiber consumption and whole grain consumption, respectively.

Included in the systematic review were 58 clinical trials and 185 prospective studies for a total of 4,635 adult participants with 135 million person-years of information (one trial in children was included, but analyzed separately from adults). Trials and prospective studies assessing weight loss, supplement use, and participants with a chronic disease were excluded.


Food is digested by bathing in enzymes that break down its molecules. Those molecular fragments then pass through the gut wall and are absorbed in our intestines. But our bodies make a limited range of enzymes, so that we cannot break down many of the tough compounds in plants. The term “dietary fiber” refers to those indigestible molecules. These dietary fibers are indigestible only to us. The gut is coated with a layer of mucus, on which sits a carpet of hundreds of species of bacteria, part of the human microbiome. Some of these microbes carry the enzymes needed to break down various kinds of dietary fibers.


Scientists at the University of Gothenburg in Sweden are running experiments that are yielding some important new clues about fiber’s role in human health. Their research indicates that fiber doesn’t deliver many of its benefits directly to our bodies. Instead, the fiber we eat feeds billions of bacteria in our guts. Keeping them happy means our intestines and immune systems remain in good working order. The scientists have recently reported that the microbes are involved in the benefits obtained from the fruits-and-vegetables diet. Research proved that low fiber diet decreases the gut bacteria population by tenfold.


Along with changes to the microbiome there were also rapid changes observed in the experimental mice. Their intestines got smaller, and its mucus layer thinner. As a result, bacteria wound up much closer to the intestinal wall, and that encroachment triggered an immune reaction. After a few days on the low-fiber diet, mouse intestines developed chronic inflammation. After a few weeks, they started putting on fat and developing higher blood sugar levels. Inflammation can help fight infections, but if it becomes chronic, it can harm our bodies. Among other things, chronic inflammation may interfere with how the body uses the calories in food, storing more of it as fat rather than burning it for energy.


In a way fiber benefits human health is by giving, indirectly, another source of food. When bacteria finished harvesting the energy in the dietary fiber, they cast off the fragments as waste. That waste — in the form of short-chain fatty acids — is absorbed by intestinal cells, which use it as fuel. But the gut’s microbes do more than just make energy. They also send messages. Intestinal cells rely on chemical signals from the bacteria to work properly. The cells respond to the signals by multiplying and making a healthy supply of mucus. They also release bacteria-killing molecules. By generating these responses, gut bacteria help to maintain a peaceful coexistence with the immune system. They rest on the gut’s mucus layer at a safe distance from the intestinal wall. Any bacteria that wind up too close get wiped out by antimicrobial poisons.


A diet of fiber-rich foods, such as fruits and vegetables, reduces the risk of developing diabetes, heart disease and arthritis. Eating more fiber seems to lower people’s mortality rate, whatever be the cause. Researchers hope that they will learn more about how fiber influences the microbiome to use it as a way to treat disorders. Lowering inflammation with fiber may also help in the treatment of immune disorders such as inflammatory bowel disease. Fiber may also help reverse obesity. They found that fiber supplements helped obese people to lose weight. It’s possible that each type of fiber feeds a particular set of bacteria, which send their own important signals to our bodies.

























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Increased Consumption of Dietary Fiber is associated with a significantly Lower Risk of CVD and CHD

Reporter: Aviva Lev-Ari, PhD, RN

LEEDS, UK — Aside from keeping you “regular,” eating fiber also appears to be good for your heart. A new review has shown that increased consumption of dietary fiber is associated with a significantly lower risk of CVD and CHD.

For every 7 g of dietary fiber eaten daily—which can be achieved by eating two to four servings of fruits and vegetables or a serving of whole grains plus a portion of beans or lentils—the risks of CVD and CHD were each lowered by 9%, according to a new meta-analysis published December 19, 2013 in BMJ [1].

“Lower risk of cardiovascular disease was also seen with greater intakes of insoluble, cereal, fruit, and vegetable fiber,” write Diane Threapleton (University of Leeds, UK), a PhD student, and colleagues. “In addition, reduced risk for CHD was associated with greater intake of insoluble fiber and fiber from cereal or vegetable food.”

A cardioprotective effect of dietary fiber was first suggested in the 1970s, and numerous studies have attempted to investigate the link, including the effects of fiber on CV risk factors.

In the present meta-analysis, Threapleton et al analyzed 22 cohort studies that reported total dietary-fiber intake, fiber subtypes, and fiber from food sources and CVD or CHD events. CVD events included CHD along with fatal and incident stroke. Five studies suggested that each 7-g/day increase in insoluble fiber lowered the risk of CVD and CHD by 18%, respectively. Fiber consumption from cereals lowered the risk of CVD and CHD, as did fiber from vegetables. Fiber sourced from fruit lowered the risk of CVD only.

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Putting these results in perspective, Dr Robert Baron(University of California, San Francisco) gets straight to the point in his editorial, “Eat More Fiber”[2]. Although the study is limited by the potential for confounding—there is the possibility of an association between high fiber intake and other healthy behaviors—”clinicians should enthusiastically and skilfully recommend that patients consume more dietary fiber,” writes Baron. This includes a mix of soluble and insoluble fiber and fiber from multiple food sources, he adds.

Although the evidence for recommending higher fiber intake comes from “imperfect evidence,” including observational studies and expert opinion, the updated meta-analysis by Threapleton et al increases confidence in the recommendation, writes Baron.

The study was funded by the UK Department of Health. Threapleton reports that her PhD studentship receives funding from Kellogg’s. Baron reported no relevant financial disclosures.


  1. Threapleton DE, Greenwood DC, Evans CE, et al. Dietary fiber intake and risk of cardiovascular disease: systematic review and meta-analysis. BMJ 2013; 347:f6879. Available at: http://www.bmj.com.
  2. Baron RB. Eat more fiber. BMJ 2013; 347:f7401. Available at: http://www.bmj.com.




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