Health Benefits of Fiber: Overall Health

Seven servings of whole grains a day keep the doctor away

Eating three more portions of dietary fiber a day--say, two pieces of whole grain bread and a bowl of whole grain breakfast cereal--is associated with a lower risk for all cardiovascular diseases and for dying of cancer, diabetes, and respiratory and infectious diseases, a study just published in the BMJ has shown. The study is strong proof that consuming lots of whole grains is good for our health, says first author Dagfinn Aune, a PhD candidate at the Norwegian University of Science and Technology who is currently working at Imperial College, London.

The meta-analysis isn't the first study that links whole grains to positive health effects, but it is the first one to look at how much whole grain one should eat to minimize health risks and that has examined the connection with various causes of death. In general, the study showed that the higher the consumption, the better protected you are.

"We saw the lowest risk among people who ate between seven and seven and a half servings of whole grain products a day, which was the highest intake across all the studies. This corresponds to 210-225 grams of whole grain products in fresh weight and about 70-75 grams of whole grains in dry weight, and is about the same as the health authorities in Norway and other Nordic countries recommend as the minimum daily allowance," says Aune.

Applies only to whole grain products

The researchers' analyses showed fewer risk factors for people who consumed more bread and cereal with whole grains, as well as foods with added bran. On the other hand, people who ate a lot of white bread, rice or cereals with refined grains did not show reduced risk.

"A lot of folks eat plenty of grains, but they choose refined breads instead of varieties with more dietary fiber. Our study suggests that you can reduce the risk of premature death by replacing a big part of the white flour in your diet with whole grain products," said Aune.

Some of the beneficial health effects of eating whole grains may lie in their high fiber content. A high intake of dietary fiber can stabilize blood sugar levels, lower blood pressure, cholesterol, and levels of inflammatory markers in the blood, and can positively affect the gut environment. All of this can contribute to a reduced risk of diabetes, cardiovascular disease and cancer.

Whole grain products also contain several other biologically active substances, such as antioxidants, B vitamins, iron, magnesium, and zinc. It is probably the whole package of favorable components that contribute to the positive effect on the risk of chronic disease and mortality.

Something is much better than nothing

Aune and an international group of researchers collected data from 45 different population studies that investigated whole grain intake in relation to risk of future illness or death due to specific causes.

To be included, the scientists required risk estimates in the studies to be adjusted for other factors that could affect the relationship between dietary fiber intake and health. The findings are now being published in The BMJ, one of the highest ranked medical journals, and reviewed in an editorial in the same issue.

In the editorial, Cecilie Kyrø and Anne Tjønneland from the research centre of the Danish Cancer Society, wrote, "Today, the Nordic countries have the most specific recommendations in the world for how much dietary fiber you should eat: 70-90 grams a day in dry weight, which corresponds to about 210-270 grams of product.

In Denmark, the intake of whole grains has doubled over the last ten years, thanks to the food and health authorities ensuring that food may not be labeled as whole grain if it does not meet strict content requirements. But even in Denmark, no more than 6% of the population follow the recommendations to eat seven or more servings of whole grains a day.

Nevertheless, the researchers believe it is possible to get more people to eat that much whole grain, both in Scandinavia and other countries.

"It may seem ambitious, but effective campaigns and product development can lead to much greater consumption of whole grains. When the health authorities implement measures to increase the population's dietary fibre intake, it is important not to promote whole grain products with a high sugar and salt content," write the Danish researchers, and they point out that greatest health impact at the population level can be achieved by getting more people to eat some whole grains instead of none.

This idea is also supported by the meta-analysis findings.

"We found the greatest risk reduction in people who consumed 0 grams up to those who ate 50 grams of whole grain products a day. The risk continued to decrease - but to a lesser extent - up to an intake of 225 grams a day," said Aune.

Reduced mortality risk for many diseases

Nine studies with a total of more than 700,000 participants examined the risk for all types of cardiovascular disease and correlated cardiovascular deaths. The half of the study subjects who ate the most whole grains had a 16% lower risk than those who consumed less, and every third portion more of whole grain a day reduced the risk by 22%.

The seven studies that looked at coronary heart disease (heart attack and angina) showed similar risk estimates, whereas the reduced risk of stroke was slightly lower in the combined analyses of the six studies that examined this. Analyses of whole grains and mortality from stroke showed a statistically significant 14% reduction in risk.

The risk of dying prematurely from all causes was 18% lower for individuals who consumed a lot of whole grains compared to those who consumed lesser amounts, while three additional servings each day were associated with a 17% reduction in mortality. The risk for deaths associated with cancer (15%), respiratory diseases (22%), diabetes (51%) and infectious diseases (26%) was also lower the more whole grains individuals consumed.

Still need more research

The researchers acknowledge the limitations in measuring how much grain was eaten via self-reported data and that the various studies may have had different definitions for what was regarded as whole grain products. The researchers also cannot rule out that the results may be influenced by people who eat lots of whole grains also living healthier in other ways, but point out that they got the same results when they only analysed studies that adjusted for smoking, alcohol consumption, BMI, physical activity and consumption of other foods such as red meat, sugary drinks and fruits and vegetables.

"Future studies need to improve the way grain intake is measured, and more research that looks at whether the different types of whole grains can have different effects on health is also needed. For example, some studies indicate that oats and rye are better whole grain sources than wheat in terms of reducing the risk of cardiovascular disease," the Danish researchers Kyrø and Tjønneland write.

And a lot of research is still missing on the relationship between dietary fibre intake and relatively rare causes of death.

Aune says that much of the research on whole grains so far has been focused on the most widespread illnesses such as cardiovascular diseases, cancers (mainly colorectal cancer) and type 2 diabetes. "However, our results suggest that consuming whole grain products may have beneficial effects on several other diseases, like mortality from respiratory diseases and infections, and the literature suggests that whole grains may even protect against rare cancers.

Now several very large population-based studies have been established, allowing us to examine less common diseases in more detail than previously. So we'll continue to examine the relationship between whole grains and diseases that have only been studied minimally or not at all," he says.

Eating more whole grains linked with lower mortality rates

Eating more whole grains may reduce the risk of premature death, according to a new meta-analysis by researchers from Harvard T.H. Chan School of Public Health. The study found that people who ate the most whole grains (70 grams/day, about 4 servings), compared with those who ate little or no whole grains, had a lower risk of dying during the study period.

"These findings further support current dietary guidelines that recommend at least 3 daily servings (or 48 grams) of whole grains to improve long-term health and prevent premature death," said Qi Sun, assistant professor in the Department of Nutrition and senior author of the study.

The study will appear online June 13, 2016 in Circulation.

Previous studies have found that whole grains may reduce risk of cardiovascular disease (CVD), diabetes, and poor gut health, among other conditions.

The meta-analysis combined results from 12 published studies, in addition to unpublished results from the National Health and Nutrition Examination Survey (NHANES) III and NHANES 1999-2004. The studies were conducted in the United States, the United Kingdom, or in Scandinavian countries between 1970 and 2010. Health information from 786,076 participants was included in the analysis.

The results showed that people who ate 70 grams/day of whole grains, compared with those who ate little or no whole grains, had a 22% lower risk of total mortality, a 23% lower risk of CVD mortality, and a 20% lower risk of cancer mortality.

Mortality rate is a measure of the number of deaths in a particular population for a specific period of time.

The researchers note that multiple bioactive compounds in whole grains could contribute to their health benefits, and that high fiber content may lower cholesterol production and glucose response and increase satiety.

The researchers recommend that people choose foods that are high in whole grain ingredients--such as bran, oatmeal, and quinoa--that have at least 16 grams per serving, while reducing consumption of unhealthy refined carbohydrates.

One limitation of the meta-analysis was that some of the studies used were carried out before a more consistent definition of whole grains became available; therefore, lists of whole grain foods varied substantially among individual studies. In addition, as most of the studies were from the U.S. and Scandinavian countries, it is not known whether these findings can be generalized to other populations.

Fiber intake associated with reduced risk of death

Dietary fiber may be associated with a reduced risk of death from cardiovascular, infectious and respiratory diseases, as well as a reduced risk of death from any cause over a nine-year period, according to a report posted online today that will be published in the June 14, 2011 print issue of Archives of Internal Medicine, one of the JAMA/Archives journals.

Fiber, the edible part of plants that resist digestion, has been hypothesized to lower risks of heart disease, some cancers, diabetes and obesity, according to background information in the article. It is known to assist with bowel movements, reduce blood cholesterol levels, improve blood glucose levels, lower blood pressure, promote weight loss and reduce inflammation and bind to potential cancer-causing agents to increase the likelihood they will be excreted by the body.

Yikyung Park, Sc.D., of the National Cancer Institute, Rockville, Md., and colleagues analyzed data from 219,123 men and 168,999 women in the National Institutes of Health-AARP Diet and Health Study. Participants completed a food frequency questionnaire at the beginning of the study in 1995 and 1996. Causes of death were determined by linking study records to national registries.

Participants' fiber intake ranged from 13 to 29 grams per day in men and from 11 to 26 grams per day in women. Over an average of nine years of follow-up, 20,126 men and 11,330 women died. Fiber intake was associated with a significantly decreased risk of total death in both men and women—the one-fifth of men and women consuming the most fiber (29.4 grams per day for men and 25.8 grams for women) were 22 percent less likely to die than those consuming the least (12.6 grams per day for men and 10.8 grams for women).

The risk of cardiovascular, infectious and respiratory diseases was reduced by 24 percent to 56 percent in men and 34 percent to 59 percent in women with high fiber intakes. Dietary fiber from grains, but not from other sources such as fruits, was associated with reduced risks of total, cardiovascular, cancer and respiratory disease deaths in men and women.

"The findings remained robust when we corrected for dietary intake measurement error using calibration study data; in fact, the association was even stronger with measurement error correction," the authors write.

"The current Dietary Guidelines for Americans recommend choosing fiber-rich fruits, vegetables and whole grains frequently and consuming 14 grams per 1,000 calories of dietary fiber," the authors conclude. "A diet rich in dietary fiber from whole plant foods may provide significant health benefits."

 

Increase dietary fiber, decrease disease

We should all be eating more dietary fiber to improve our health - that's the message from a health review by scientists in India. The team has looked at research conducted into dietary fiber during the last few decades across the globe and now suggests that to avoid initial problems, such as intestinal gas and loose stool, it is best to increase intake gradually and to spread high-fiber foods out throughout the day, at meals and snacks. Writing in the International Journal of Food Safety, Nutrition and Public Health, the team offers fruit, vegetables, whole-grain foods, such as muesli and porridge, beans and pulses, as readily available foods rich in dietary fiber.

Dietary fiber, also known as roughage, is the general term of the non-digestible parts of the fruit and vegetable products we eat. There are two forms soluble and insoluble. Soluble (prebiotic, viscous) fiber that is readily broken down or fermented in the colon into physiologically active byproducts and gases. The second form is insoluble fiber, which is metabolically inert, but absorbs water as it passes through the digestive system, providing bulk for the intestinal muscles to work against and easing defecation.

Vikas Rana of the Rain Forest Research Institute, in Assam, India, and colleagues point out that research has shown that modern food habits have, it seems, led to an increase in the incidence of obesity, cardiovascular diseases, and type 2 diabetes. These are growing more common even in developing nations where a "western" diet of highly processed foods, high in sugars and saturated fats, beef and dairy products and low in dietary fiber is displacing more traditional options. The team suggests that evidence points to a loss of dietary fiber in the diet as being a major risk factor for health problems but one of the simplest to remedy without recourse to major changes in diet or the addition of supplements or so-called functional foods and nutraceuticals to the diet.

Given that dietary fiber has physiological actions such as reducing cholesterol and attenuating blood glucose, maintaining gastrointestinal health, and positively affecting calcium bioavailability and immune function, it is important for the current generation and future generations that this component of our diets be reasserted through education and information.

"Consuming adequate quantities of DF can lead to improvements in gastrointestinal health, and reduction in susceptibility to diseases such as diverticular disease, heart disease, colon cancer, and diabetes. Increased consumption has also been associated with increased satiety and weight loss," the team concludes. Given the ready availability particularly in the West and in the relatively richer parts of the developing world of vegetables, fruit and other foods high in dietary fiber it is a matter of recommending that people eat more dietary fiber rather than consistently taking the unhealthy low-fiber option throughout their lives.

Soluble fiber, exercise reduce belly fat

All fat is not created equal. Unsightly as it is, subcutaneous fat, the fat right under the skin, is not as dangerous to overall health as visceral fat, the fat deep in the belly surrounding vital organs.

According to a new study by researchers at Wake Forest Baptist Medical Center, the way to zero in and reduce visceral fat is simple: eat more soluble fiber from vegetables, fruit and beans, and engage in moderate activity.

The study found that for every 10-gram increase in soluble fiber eaten per day, visceral fat was reduced by 3.7 percent over five years. In addition, increased moderate activity resulted in a 7.4 percent decrease in the rate of visceral fat accumulation over the same time period.

"We know that a higher rate of visceral fat is associated with high blood pressure, diabetes and fatty liver disease," said Kristen Hairston, M.D., assistant professor of internal medicine at Wake Forest Baptist and lead researcher on the study. "Our study found that making a few simple changes can have a big health impact."

Ten grams of soluble fiber can be achieved by eating two small apples, one cup of green peas and one-half cup of pinto beans; moderate activity means exercising vigorously for 30 minutes, two to four times a week, Hairston added.

In the longitudinal study, published in the June 16, 20111 online issue of the journal Obesity, researchers examined whether lifestyle factors, such as diet and frequency of exercise, were associated with a five-year change in abdominal fat of African Americans and Hispanic Americans, populations at a disproportionally higher risk for developing high blood pressure and diabetes and accumulating visceral fat.

At the beginning of the study, which involved 1,114 people, the participants were given a physical exam, an extensive questionnaire on lifestyle issues, and a CT scan, the only accurate way to measure how much subcutaneous and visceral fat the participants had. Five years later, the exact same process was repeated.

Researchers found that increased soluble fiber intake was associated with a decreased rate of accumulated visceral fat, but not subcutaneous fat.

"There is mounting evidence that eating more soluble fiber and increasing exercise reduces visceral or belly fat, although we still don't know how it works," Hairston said. "Although the fiber-obesity relationship has been extensively studied, the relationship between fiber and specific fat deposits has not. Our study is valuable because it provides specific information on how dietary fiber, especially soluble fiber, may affect weight accumulation through abdominal fat deposits."

Study shows soluble fiber boosts immune system

A new University of Illinois study touts the benefits of soluble fiber—found in oats, apples, and nuts, for starters—saying that it reduces the inflammation associated with obesity-related diseases and strengthens the immune system.

"Soluble fiber changes the personality of immune cells—they go from being pro-inflammatory, angry cells to anti-inflammatory, healing cells that help us recover faster from infection," said Gregory Freund, a professor in the U of I's College of Medicine and a faculty member in the College of Agriculture, Consumer and Environmental Sciences' Division of Nutritional Sciences.

This happens because soluble fiber causes increased production of an anti-inflammatory protein called interleukin-4, he said.

The study appeared in the May 2010 issue of Brain, Behavior, and Immunity.

In the experiment, laboratory mice consumed low-fat diets that were identical except that they contained either soluble or insoluble fiber. After six weeks on the diet, the animals had distinctly different responses when the scientists induced illness by introducing a substance (lipopolysaccharide) that causes the body to mimic a bacterial infection.

"Two hours after lipopolysaccharide injection, the mice fed soluble fiber were only half as sick as the other group, and they recovered 50 percent sooner. And the differences between the groups continued to be pronounced all the way out to 24 hours," said Christina Sherry, who also worked on the study.

"In only six weeks, these animals had profound, positive changes in their immune systems," she said.

Now Freund has a new question: Could soluble fiber offset some of the negative effects of a high-fat diet, essentially immunizing obese persons against the harmful effects of fat?

Scientists have long known that obesity is linked to inflammatory conditions, such as diabetes and heart disease.

Yet, in a recent study, the U of I scientists demonstrated that fat tissue produces hormones that appear to compensate for this inflammation. "There are significant anti-inflammatory components in fat tissue and, if they were strategically unleashed, they could potentially protect obese people from further inflammatory insults, such as a heart attack or stroke. In obese animals, you can see the body compensating in an effort to protect itself," he said.

Not all fat is bad, the researcher noted. The Mediterranean diet, which receives high marks for its health benefits, includes such foods as olive oil; salmon, tuna, sardines, and trout, which contain important omega-3 and -6 fatty acids; and plant sources of fat, such as flaxseed.

"Now we'd like to find a way to keep some of the anti-inflammatory, positive effects that develop over time with a high-fat diet while reducing that diet's negative effects, such as high blood glucose and high triglycerides. It's possible that supplementing a high-fat diet with soluble fiber could do that, even delaying the onset of diabetes," he said.

This study is one of the first to provide two valuable lessons, said Sherry. The first, already noted, is that soluble fiber has direct anti-inflammatory effects and builds up the immune system. The second is that the amount of soluble fiber necessary to achieve these health benefits is a reasonable, not a pharmacological, amount.

The recommended daily dietary recommendation is 28 to 35 grams of total fiber, but most of the FDA's health claims are for insoluble fiber, and that's where things get a bit complicated, she said.

"Not all fiber is created equal, although you wouldn't know that by reading nutrition labels," said Sherry. "Most manufacturers don't tell you how much of each type of fiber a food contains, and we think it's important that this information be included on a product's packaging."

Good sources of soluble fiber are oat bran, barley, nuts, seeds, lentils, citrus fruits, apples, strawberries, and carrots. "We used a citrus-based pectin in our study," Sherry said.

Insoluble fiber, found in whole wheat and whole-grain products, wheat bran, and green, leafy vegetables, is also valuable for providing bulk and helping food move through the digestive system, but it doesn't provide the boost to the immune system that soluble fiber provides.

 Apple fiber offers many benefits

A report, in the journal Comprehensive Reviews in Food Science and Food Safety March 2010 finds that apple fiber, a soluble type of fiber, is rich in pectin. Soluble or gel-forming fibers absorb water from the digestive tract. This helps to increase the size of the stool and normalize its transit time through the bowel. Soluble fiber can be beneficial in cases of constipation and diarrhea. Having adequate fiber in the diet may also have a protective effect against diverticulosis, colon cancer, hemorrhoids, and varicose veins. Studies have shown that apple fiber, when used as part of a calorie-controlled diet, can enhance weight loss.

Similarly, a study conducted to visualize the effect of apple fiber on lowering of increased plasma and liver cholesterol, it was found that apple fiber or pectin substantially reduces the same when fed at 2.5% or 5% in the diet (Wells and Ershoff 1961).

Apple fiber has a mild appetite suppressing effect by producing a sense of fullness; it also improves the process of digestion and elimination by stimulating healthy bowel functioning.

The pectin in apple fiber helps to normalize the levels of fats in the blood stream. Research has shown that apple fiber taken each day can have the effect of reducing total cholesterol up to 10% in people with elevated cholesterol levels (http://au.health.yahoo.com/041101.)