This review of research on the health benefits of fiber is divided into the following sections:
Cancer, Diabetes, Heart Disease, Overall Health
Consumption Of Resistant Starch May Protect Against Bowel Cancer
Western diets are typically low in fibre and have been linked with a higher incidence of bowel cancer. Even though Australians eat more dietary fibre than many other western countries, bowel cancer is still the second most commonly reported cancer in Australia with 30 new cases diagnosed every day.
Dr David Topping, from CSIRO's Food Futures Flagship, said this is referred to as 'the Australian paradox'.
"We have been trying to find out why Australians aren't showing a reduction in bowel cancer rates and we think the answer is that we don't eat enough resistant starch, which is one of the major components of dietary fibre," Dr Topping said.
Resistant starch is a component of dietary fibre that resists digestion in the small intestine and instead passes through to the bowel where it has positive effects on bowel health. Resistant starch is sometimes called the third type of dietary fibre (in addition to soluble and insoluble fibre) and is found in legumes, some wholegrain breads and cereals, firm bananas and cooked and cooled potatoes, pasta and rice.
These findings, published in the April, 2012 issue of The Journal of Nutrition, reinforce the fact that dietary fibre is beneficial for human health, but go further to show that fibre rich in resistant starch is even better.
"It's not just the amount of fibre that we eat that's important, but the diversity of fibre in our diet," Dr Topping said.
"We studied various sources of resistant starch, including corn and wheat, and the results suggest they could all protect against DNA damage in the colon, which is what can cause cancer."
Dr Trevor Lockett, colorectal cancer researcher with CSIRO's Preventative Health Flagship, said Australia has one of the highest incidence rates of bowel cancer in the world.
"Research suggests that improving our diets could go a long way to reducing our personal risk of developing this disease, which would also have the follow-on benefit of reducing healthcare costs associated with bowel cancer.
"These new studies suggest that increasing the amount of resistant starch in our diets may be one important step along the path to reducing the burden of bowel cancer. It takes about 15 years from the time of the first bowel cancer-initiating DNA damage to the development of full-blown bowel cancer, so the earlier we improve our diets the better," Dr Lockett said.
The recommended intake of resistant starch is around 20 grams a day, which is almost four times greater than a typical western diet provides. Twenty grams is equivalent to eating three cups of cooked lentils.
"Currently, it is difficult for Australians to get this much from a typical diet," Dr Topping said.
"We have already had success in developing barley with high levels of resistant starch, and now our focus is on increasing the levels of resistant starch in commonly consumed grains like wheat. These grains could then be used in breads and cereals to make it easier for Australians to get enough resistant starch from their diet."
High Fiber Diet Prevents Prostate Cancer Progression, Study Shows
A high-fiber diet may have the clinical potential to control the progression of prostate cancer in patients diagnosed in early stages of the disease.
The rate of prostate cancer occurrence in Asian cultures is similar to the rate in Western cultures, but in the West, prostate cancer tends to progress, whereas in Asian cultures it does not. Why? A University of Colorado Cancer Center study published in the January 2013 issue of the journal Cancer Prevention Research shows that the answer may be a high-fiber diet.
The study compared mice fed with of inositol hexaphosphate (IP6), a major component of high-fiber diets, to control mice that were not. Then the study used MRI to monitor the progression of prostate cancer in these models.
"The study's results were really rather profound. We saw dramatically reduced tumor volumes, primarily due to the anti-angiogenic effects of IP6," says Komal Raina, PhD, research instructor at the Skaggs School of Pharmacy and Pharmaceutical Sciences, working in the lab of CU Cancer Center investigator and School of Pharmacy faculty member, Rajesh Agarwal, PhD.
Basically, feeding with the active ingredient of a high-fiber diet kept prostate tumors from making the new blood vessels they needed to supply themselves with energy. Without this energy, prostate cancer couldn't grow. Likewise, treatment with IP6 slowed the rate at which prostate cancers metabolized glucose.
Possible mechanisms for the effect of IP6 against metabolism include a reduction in a protein called GLUT-4, which is instrumental in transporting glucose.
"Researchers have long been looking for genetic variations between Asian and Western peoples that could explain the difference in prostate cancer progression rates, but now it seems as if the difference may not be genetic but dietary. Asian cultures get IP6 whereas Western cultures generally do not," Raina says.
How fiber prevents diabetes and obesity
Most sweet fruit and many vegetables such as salsify, cabbage or beans, as well as
berries and other fresh fruit, vegetables, whole grains, seeds and nuts are rich in so-called fermentable fibers. Such fibers cannot be digested directly by the intestine but are instead fermented by intestinal bacteria into short-chain fatty acids such as propionate and butyrate, which can in fact be assimilated by our bodies. The protective effect of these fibers is well known to researchers: animals fed a fiber-rich diet become less fat and are less likely to develop diabetes than animals fed a fiber-free diet.
Whilw scientists have known for the past twenty years that a fiber-rich diet protects the organism against obesity and diabetes but the mechanisms involved have so far eluded them. A French-Swedish team including researchers from CNRS, Inserm and the Université Claude Bernard Lyon 1 (Unité Inserm 855 “Nutrition et Cerveau”) has succeeded in elucidating this mechanism, which involves the intestinal flora and the ability of the intestine to produce glucose between meals. These results, published in the journal Cell on 9 January 2014, also clarify the role of the intestine and its associated microorganisms in maintaining glycaemia. They will give rise to new dietary recommendations to prevent diabetes and obesity.
Fiber protects against cardiovascular disease -- especially in women
Foods high in fibre provide good protection against cardiovascular disease, and the effect is particularly marked in women. This is shown in a new study from Lund University in Sweden.
The study, which was recently published in the scientific journal PLOS One, involved the study of the eating habits of over 20 000 residents of the Swedish city of Malmö, with a focus on the risk of cardiovascular disease. The importance of 13 different nutrient variables (aspects of fibre, fats, proteins and carbohydrates) was analysed.
"Women who ate a diet high in fibre had an almost 25 per cent lower risk of suffering from cardiovascular disease compared with women who ate a low-fibre diet. In men the effect was less pronounced. However, the results confirmed that a high-fibre diet does at least protect men from stroke", says Peter Wallström, a researcher at Lund University and the primary author of the article.
The exact reason for the difference between the sexes is unclear. However, a probable explanation is that women consume fibre from healthier food sources than men do. Women ate a lot of fibre in the form of fruit and vegetables, whereas the most important source of fibre for men was bread.
"The difference in the results for men and women shows that we need to pay more attention to gender when we conduct research on diet", says Peter Wallström.
However, the researchers did not identify any definite links between the other nutrients in the study and cardiovascular disease, for example the proportion of saturated fat or sugar in the diet.
"These results should be interpreted with a certain amount of caution. Almost everyone eats more saturated fat than recommended, including the participants in many other population studies. It is therefore difficult to compare recommended and high fat intake. Other types of study that have been carried out have shown that those who limit their fat and sugar intake are at lower risk of cardiovascular disease", says Peter Wallström.
Peter Wallström is sceptical of 'extreme' diets and says that the dietary recommendations from the National Food Administration are good, despite having received criticism:
"The National Food Administration's dietary advice, which is based on extensive research, is well balanced. In the short term, most weight-loss diets achieve their aim as long as you follow them. However, we know too little about the long-term effects to be able to recommend more drastic changes to one's diet", says Peter Wallström.
Data for the study has been taken from the Malmö Diet and Cancer population study, which has involved 30 000 Malmö residents since the start of the 1990s. The participants have given blood samples and detailed information about their diet.
Fiber-Rich Foods May Cut Your Risk of Heart Disease
Boosting the amount of fiber in your diet may lower your risk for heart disease, a new study finds.
"With so much controversy causing many to avoid carbohydrates and grains, this trial reassures us of the importance of fiber in the prevention of cardiovascular disease," said one expert not connected to the study, Dr. Suzanne Steinbaum, a preventive cardiologist at Lenox Hill Hospital, in New York City.
In the study, researchers led by Diane Threapleton, of the School of Food Science and Nutrition at the University of Leeds, in England, analyzed data from the United States, Australia, Europe and Japan to assess different kinds of fiber intake.
Her team looked at total fiber; insoluble fiber (such as that found in whole grains, potato skins) soluble fiber (found in legumes, nuts, oats, barley); cereal; fruits and vegetables and other sources.
The study also looked at two categories of heart disease. One, "coronary heart disease" refers to plaque buildup in the heart's arteries that could lead to a heart attack, according to the American Heart Association. The second type of heart trouble is called "cardiovascular disease" -- an umbrella term for heart and blood vessel conditions that include heart attack, stroke, heart failure and other problems, the AHA explains.
The more total, insoluble, and fruit and vegetable fiber that people consumed, the lower their risk of both types of heart disease, the study found. Increased consumption of soluble fiber led to a greater reduction in cardiovascular disease risk than coronary heart disease risk. Meanwhile, cereal fiber reduced the risk of coronary heart disease more than the risk of cardiovascular disease, researchers found.
For every additional 7 grams per day of fiber consumed, there was a significantly lower risk of both types of disease, according to the study published online Dec. 19 in BMJ.
Sports dietitian Dana Angelo White said the findings are in line with what nutritionists have long known about the importance of a high-fiber diet.
"The tricky part is finding ways to get Americans to eat more [fiber]," said White, who is also an assistant clinical professor at Quinnipiac University in Hamden, Conn. "The daily recommendation ranges from 20 to 38 grams per day. This may seem like a tall order for most folks, but can be achieved by making some small dietary changes."
The British study found that adding just 7 grams per day of fiber to the diet boosts heart health. According to White, people can get that amount of fiber from the following:
* 1 1/2 cups of cooked oatmeal (7 grams)
* 1 1/4 cups of shredded wheat cereal (8 grams)
* Two slices of whole-wheat bread (6 to 7 grams)
* One large pear (8 grams)
* 1 cup raspberries (8 grams)
* 1/2 cup black beans (7.5 grams)
The study authors said their findings support current recommendations for increased fiber intake and that the reduced heart disease risk associated with consuming more fiber could potentially benefit "many thousands" of people, according to a journal news release.
Steinbaum added that "it's critical that people understand that whole grains -- such as barley, bulgur, millet, quinoa, brown rice, rye, oats and whole wheat, along with fruits, vegetables, nuts and seeds -- are part of a heart-healthy diet."
Study strengthens link between low dietary fiber intake and increased cardiovascular risk
A new study published in the December, 2013 issue of The American Journal of Medicine shows a significant association between low dietary fiber intake and cardiometabolic risks including metabolic syndrome, cardiovascular inflammation, and obesity. Surveillance data from 23,168 subjects in the National Health and Nutrition Examination Survey (NHANES) 1999-2010 was used to examine the role dietary fiber plays in heart health.
In the current study investigators have taken a closer look at possible sex, age, racial/ethnic, and socioeconomic disparities in dietary fiber consumption, as well as examined the association between dietary fiber intake and various cardiometabolic risk factors.
Dietary fiber, which previous studies have shown may assist in lowering blood pressure, cholesterol levels, and inflammation, is thought to play an important role in reducing cardiovascular risk. Despite this knowledge, investigators found that dietary fiber intake was consistently below recommended intake levels for NHANES participants.
The Institute of Medicine defines recommended intake levels according to age and sex: 38g per day for men aged 19-50 years, 30g per day for men 50 and over, 25g for women aged 19-50 years, and 21g per day for women over 50. Using data from NHANES 1999-2010, the study reveals that the mean dietary fiber intake was only 16.2g per day across all demographics during that time period.
"Our findings indicate that, among a nationally representative sample of nonpregnant US adults in NHANES 1999-2010, the consumption of dietary fiber was consistently below the recommended total adequate intake levels across survey years," says senior investigator Cheryl R. Clark, MD, ScD, Center for Community Health and Health Equity, Brigham and Women's Hospital and Harvard Medical School, Boston. "Our study also confirms persistent differences in dietary fiber intake among socioeconomic status and racial/ethnic subpopulations over time."
The research team found variations according to race and ethnicity, with Mexican-Americans consuming higher amounts of dietary fiber and non-Hispanic blacks consuming lower amounts of dietary fiber compared with non-Hispanic whites.
The study highlights the importance of increasing dietary fiber intake for US adults by showing a correlation between low dietary fiber and an increased risk for cardiovascular risk. Participants with the highest prevalence of metabolic syndrome, inflammation, and obesity were in the lowest quintile of dietary fiber intake.
"Overall, the prevalence of the metabolic syndrome, inflammation, and obesity each decreased with increasing quintiles of dietary fiber intake," comments Clark. "Compared with participants in the lowest quintile of dietary fiber intake, participants in the highest quintile of dietary fiber intake had a statistically significant lower risk of having the metabolic syndrome, inflammation, and obesity."
This new data analysis emphasizes the importance of getting adults across diverse ethnicities to increase their dietary fiber intake in order to try and mitigate the risk for cardiovascular damage.
"Low dietary fiber intake from 1999-2010 in the US and associations between higher dietary fiber and a lower prevalence of cardiometabolic risks suggest the need to develop new strategies and policies to increase dietary fiber intake," adds Clark. "Additional research is needed to determine effective clinical and population-based strategies for improving fiber intake trends in diverse groups."
Eating more fiber may lower risk of first-time stroke
- Eating foods with more fiber was linked to a lower risk of first-time stroke.
- Every seven-gram increase in total dietary fiber was associated with a 7 percent lower risk of first-time stroke.
- The results reinforce the importance of a diet that includes at least 25 grams of fiber daily.
Eating more fiber may decrease your risk of first-time stroke, according to new research in the American Heart Association journal Stroke.
Dietary fiber is the part of the plant that the body doesn’t absorb during digestion. Fiber can be soluble, which means it dissolves in water, or insoluble.
Previous research has shown that dietary fiber may help reduce risk factors for stroke, including high blood pressure and high blood levels of low-density lipoprotein (LDL) “bad” cholesterol.
In the new study, researchers found that each seven-gram increase in total daily fiber intake was associated with a 7 percent decrease in first-time stroke risk. One serving of whole wheat pasta, plus two servings of fruits or vegetables, provides about 7 grams of fiber, researchers said.
“Greater intake of fiber-rich foods – such as whole-grains, fruits, vegetables and nuts – are important for everyone, and especially for those with stroke risk factors like being overweight, smoking and having high blood pressure,” Diane Threapleton, M.Sc., and Ph.D. candidate at the University of Leeds’ School of Food Science & Nutrition in Leeds, United Kingdom.
Researchers analyzed eight studies published between 1990-2012. Studies reported on all types of stroke with four specifically examining the risk of ischemic stroke, which occurs when a clot blocks a blood vessel to the brain. Three assessed hemorrhagic stroke, which occurs when a blood vessel bleeds into the brain or on its surface.
Findings from the observational studies were combined and accounted for other stroke risk factors like age and smoking.
The results were based on total dietary fiber. Researchers did not find an association with soluble fiber and stroke risk, and lacked enough data on insoluble fiber to make any conclusions.
The average daily fiber intake among U.S. adults is lower than the American Heart Association’s recommendation of at least 25 grams per day. Six to eight servings of grains and eight to 10 servings of fruits and vegetables can provide the recommended amount.
Most people do not get the recommended level of fiber, and increasing fiber may contribute to lower risk for strokes,” Threapleton said. “We must educate consumers on the continued importance of increasing fiber intake and help them learn how to increase fiber in their diet.”
In the United States, stroke is the fourth leading cause of death, killing more than 137,000 people annually. Among survivors, the disease is a leading cause of disability.
In addition to following a nutritious diet, the American Heart Association recommends being physically active and avoiding tobacco to help prevent stroke and other heart and blood vessel diseases.\\
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.
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."
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."
Hairston's next study, expected to be in clinical trials later this summer, will examine whether increasing soluble fiber with a widely available fiber supplement will produce similar results to those obtained in this study using soluble fiber from food.
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 will appear in the May 2010 issue of Brain, Behavior, and Immunity and is available online.
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.)