Fiber

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Fiber became a household word back in 1970s when Dr. Denis Burkitt, a man nicknamed the Fiber Man, and his colleagues made “the fiber hypothesis” that states that fiber can prevent certain diseases. Through their work in Africa, they discovered that diseases that were common in the Western cultures were not common there. These included heart attacks and high blood pressure (cardiovascular diseases), obesity and diabetes (metabolic disorders), intestinal problems (constipation, diverticulosis, diverticulitis, gallstones, appendicitis, hemorrhoids, polyps, and colon cancer), varicose veins and blood clots (deep vein thrombosis). The primary dietary difference was the high intake of fiber and low intake of refined carbohydrates in the African population. Burkitt also noted the emergence of these diseases in the United States and England after 1890 following the introduction of a new milling technique that removed fiber from whole grain flour to produce white flour.

While the exact mechanism by which fiber might prevent these diseases remained unknown, Burkitt made a discovery about the beneficial impact that fiber had on bowel movements and how that related to certain diseases. Burkitt noted that he was able to predict the number of a patient’s hospital visits from the size and frequency of their bowel movements. Those with high intakes of fiber had more frequent and bulky stools and had less illness. Burkitt proposed that fiber’s health benefits stemmed from its ability to increase stool bulk and speed up how quickly stool moves through the colon. Since these findings, controversy remains. A great deal of research has both supported and disputed what Burkitt had discovered.

What is fiber?

Fiber is a substance in plants. Dietary fiber is the kind you eat. It is in fruits, vegetables and grains. It is the part of the plant that your body can’t digest. Yet it is an important part of a healthy diet. It adds bulk to your diet and makes you feel full faster, helping you control your weight. Fiber helps digestion and helps prevent constipation.

You can get fiber from whole grains, beans, nuts, fruits and vegetables. You should add fiber to your diet slowly. Increasing dietary fiber too quickly can lead to gas, bloating and cramps.

A variety of definitions of fiber exist. In an attempt to develop one definition of fiber that everyone can use, the Food and Nutrition Board assembled a panel that came up with the following definitions:

* Dietary fiber consists of nondigestible carbohydrates and lignin that are intrinsic and intact in plants. This includes plant nonstarch polysaccharides (for example, cellulose, pectin, gums, hemicellulose, and fibers contained in oat and wheat bran), oligosaccharides, lignin, and some resistant starch.

* Functional fiber consists of isolated, nondigestible carbohydrates that have beneficial physiological effects in humans. This includes nondigestible plant (for example, resistant starch, pectin, and gums), chitin, chitosan, or commercially produced (for example, resistant starch, polydextrose, inulin, and indigestible dextrins) carbohydrates.

* Total fiber is the sum of dietary fiber and functional fiber. It’s not important to differentiate between which forms of each of these fibers you are getting in your diet. Your total fiber is what matters.

You may also hear fiber referred to as bulk or roughage. Call it what you want, but always remember that fiber is an essential part of everyone’s diet. While fiber does fall under the category of carbohydrates, in comparison, it does not provide the same number of calories, nor is it processed the way that other sources of carbohydrates are.

This difference can be seen among the two categories that fiber is divided into: soluble and insoluble.

* Soluble fiber dissolves in water to form a gel-like substance. Sources of soluble fiber are oats, legumes (beans, peas, and soybeans), apples, bananas, berries, barely, some vegetables, and psylluim.

* Insoluble fiber increases the movement of material through your digestive tract and increases your stool bulk. Sources of insoluble fiber are whole wheat foods, bran, nuts, seeds, and the skin of some fruits and vegetables.

Fiber for weight control

There is some evidence that “bulking up” could lead to slimming down. In a recent study of more than 1700 overweight and obese men and women, those with the highest fiber intake had the greatest weight loss over 24 months. Results from the Continuing Survey of Food Intakes by Individuals (CSFII) from 1994 -1996 also supported the relationship between a high-fiber intake and lower body weight. One of the reasons that fiber may have an impact on body weight is its ability to slow the movement of food through the intestines. The gel-like substance that soluble fibers form when they dissolve in water causes things to swell and move slower in the intestines. This increase in time that foods stay in the intestines has been shown to reduce hunger feelings and overall food intake. It has also been shown to decrease the number of calories that are actually absorbed from the ingested food. One study showed an increase in the number of calories that were excreted in the stools when high-fiber psyllium gum-based crackers were given in comparison to low-fiber crackers. Whenever fewer calories are taken in, or more are excreted, weight loss will generally occur

Fiber for controlling diabetes

A high-fiber diet may be just what the doctor ordered to get your blood sugars under control. Keeping our blood sugars stable is a goal that we would all benefit from. If you don’t have type 2 diabetes, this could be the way to prevent it. If you do have it, this could be the way to keep it under control. The best time to address type 2 diabetes is before it has developed. Research has shown that high-fiber diets can help prevent this form of diabetes. The most recent study on done on overweight and obese men and women without diabetes showed reductions in blood sugar and insulin with the use of a high soluble fiber supplement. A German clinical trial reported that eating fiber-enriched bread for only three days improved insulin sensitivity in overweight and obese women by 8%. If a diet intervention this small can have that great of an impact, you can imagine what years of following a high-fiber diet, filled with vegetables, fruits and whole grains would do. The good news for those with diabetes is that increasing your fiber now can also prevent long-term complications from diabetes. Soluble fiber has been found to produce significant reductions in blood sugar in 33 of 50 studies testing it. In clinical intervention trials ranging from two to 17 weeks, consumption of fiber was shown to decrease insulin requirements in people with type 2 diabetes. If you have ever had to inject yourself with insulin, you can appreciate how much easier and less painful it would be to increase your fiber intake to avoid the need for insulin injections.

Fiber for preventing heart disease

If we were to sit down and have a “heart to heart,” I would tell you that one of the best things that you could do on your own to protect your heart is to follow a high-fiber diet. Numerous studies have produced compelling evidence to support this. In a Harvard study of over 40,000 male health professionals, researchers found that a high total dietary fiber intake was linked to a 40% lower risk of coronary heart disease, compared to a low-fiber intake. Another study of over 31,000 California Seventh-day Adventists found a 44% reduced risk of nonfatal coronary heart disease and an 11% reduced risk of fatal coronary heart disease for those who ate whole wheat bread compared with those who ate white bread. One minor change in their diets provided a protective effect that could save their lives.

Another strong predictor of heart disease is abnormal blood cholesterol, LDL, and/or HDL levels. It appears that soluble fiber reduces the absorption of cholesterol in your intestines by binding with bile (which contains cholesterol) and dietary cholesterol so that the body excretes it. The oat bran and bean fiber intervention trials where dietary fiber supplementation was combined with a low-fat diet shows that reductions in total cholesterol levels ranged from 8-26%. Other studies have shown that 5 to 10 grams of soluble fiber a day decreases LDL cholesterol by about 5%. All of these benefits will occur regardless of changes in dietary fat. In a trial with low fat and low fat plus high fiber groups, the group consuming high fiber exhibited a greater average reduction (13%) in total cholesterol concentration than the low fat (9%) and the usual diet (7%) groups. It seems that you don’t have to change everything to gain something.

Fiber for bowel disorders

“Roughing” up your diet can be the key to healthier bowels. With the introduction of white flour came an increased prevalence of bowel disorders such as diverticulosis, diverticulitis, hemorrhoids, polyps, colon cancer, and irritable bowel syndrome (IBS). In Burkitt’s early research into this phenomenon, he made reference to the fact that the typical African stool specimen was large and soft, and that stool transit times were rapid, compared to the puny hard fecal deposits and slow transit times of Europeans. In one of his studies, they conducted elaborate experiments in which volunteers in England, India, and Africa had their bowel movements timed and their stools weighed. Among the results of the study: People living under primitive conditions, on diets high in insoluble fibers, passed from 2½ to 4½ times as much feces as sailors in the Royal Navy, and were relatively free of many of the diseases studied. Current research supports the early findings. Studies have shown that a high-fiber diet (particularly fruit and vegetable fiber) help to prevent diverticulosis and will decrease the risk of complications if you have it. Although the mechanism by which fiber may be protective against diverticulosis is unknown, several hypotheses have been proposed.

For example, some scientists report that fiber helps by decreasing transit time, increasing stool weight, and decreasing pressure within the colon. The same has been found for irritable bowel syndrome (IBS). The current guidelines for the treatment of IBS include following a high fiber diet. The bulk that fiber provides is thought to help prevent the painful spasms often associated with IBS and aid in comfortable regularity. There is still a great deal of debate about the role of fiber in preventing colon cancer. The studies that look for connections with people’s diets and their health have seen a trend in low-fiber diets and people with colon cancer. The studies that tried to intervene by putting people on high-fiber diets in order to prevent colon cancer or polyps did not find the same protective relationship. Burkitt’s work and a more recent study showed that a daily stool weight greater than 150 grams needs to be achieved for the protective affect against colon cancer. This was not taken into account in many of the studies and may be the reason the protective effect was not found.

Fiber for preventing or treating constipation

Fiber may just be the way to go when constipation is the problem. Although what constitutes constipation is not well established, diets that increase the number of bowel movements per day, improve the ease with which a stool is passed, or increase stool bulk are considered beneficial. Both soluble and insoluble fibers are necessary for regular bowel movements. Oftentimes, people use over-the-counter supplements to assist with regularity. Unfortunately, these supplements only provide soluble fiber. Studies support the benefits of the combination of soluble and insoluble fiber in alleviating constipation, but only with the consumption of an adequate fluid intake. High amounts of fiber, without fluids, can aggravate, rather then alleviate constipation. The way to go is to eat foods high in both soluble and insoluble fibers and drink lots of water to flush it down.

A high-fiber diet has many benefits, which include:

* Helps maintain bowel integrity and health. A high-fiber diet may lower your risk of developing hemorrhoids, and small pouches in your colon (diverticular disease). Some fiber is fermented in the colon. Researchers are looking at how this may play a role in preventing diseases of the colon.
* Lowers blood cholesterol levels. Soluble fiber found in beans, oats, flaxseed and oat bran may help lower total blood cholesterol levels by lowering low-density lipoprotein, or “bad,” cholesterol levels. Epidemiologic studies have shown that increased fiber in the diet can reduce blood pressure and inflammation, which is also protective to heart health.
* Helps control blood sugar levels. Fiber, particularly soluble fiber, can slow the absorption of sugar, which for people with diabetes can help improve blood sugar levels. A diet that includes insoluble fiber has been associated with a reduced risk of developing type 2 diabetes.
* Aids in weight loss. High-fiber foods generally require more chewing time, which gives your body time to register when you’re no longer hungry, so you’re less likely to overeat. Also, a high-fiber diet tends to make a meal feel larger and linger longer, so you stay full for a greater amount of time. And high-fiber diets also tend to be less “energy dense,” which means they have fewer calories for the same volume of food.
* Uncertain effect on colorectal cancer. Evidence that dietary fiber reduces colorectal cancer is mixed — some studies show benefit, some show nothing and some suggest increased risk. If you’re concerned about preventing colorectal cancer, adopt or stick with a colon cancer screening regimen. Regular testing for and removal of colon polyps can prevent colon cancer.

How Much Fiber?

The average American consumes 14 grams of dietary fiber a day, which is considerably less than the recommended level. The 2005 Dietary Guidelines for Americans recommends 14 grams of fiber per 1000 calories consumed. So, if you consume a 2,500 calorie diet, you should eat approximately 35 grams of fiber per day. Also, fiber intake may vary depending on age and gender.

While the 2005 Dietary Guidelines for Americans serves as a general guide to healthy eating, the Dietary Reference Intakes (DRIs) provide standard recommended amounts for nutrients. In 2002, the Food and Nutrition Board of the National Academy of Sciences Research Council issued DRIs for fiber (see Table 1). Previously, no national standardized recommendation existed. The new DRIs represent desirable intake levels established using the most recent scientific evidence available.
Table 2: Dietary Reference Intakes (DRI) for Fiber.

Age g/day Fiber

Children
1-3 years 19
4-8 years 25

Males
9-13 years 31
14-18 years 38
19-50 years 38
51+ years 30

Females
9-13 years 26
14-18 years 26
19-50 years 25
51+ years 21

Pregnancy
<18 years 28 18+ years 28 Lactation <18 years 29 18+ years 29 For many people, meeting the DRI for fiber may require changes in their eating habits. Eating several servings of whole grains, fruits, vegetables and dried beans each day is good way to boost fiber intake. Anyone with a chronic disease should consult a physician before greatly altering a diet. If you are not used to eating high fiber foods regularly, these changes should be made gradually to avoid problems with gas and diarrhea. Also, drink plenty of water to minimize intestinal gas. If problems with gas continue to be an issue, gas-reducing over-the-counter and prescription drugs are available. How can I get more fiber in my diet? The amount of fiber you should get from your diet each day depends on your age and sex. Men 50 years of age and younger should consume at least 38 grams of fiber per day, while men older than 50 years of age should aim for at least 30 grams of fiber daily. Women 50 years of age and younger should consume at least 25 grams of fiber per day, while women older than 50 years of age should aim for at least 21 grams of fiber daily. Try the following ideas to increase the fiber in your diet: * Eat at least 2 cups of fruits and 2 1/2 cups of vegetables each day. Fruits and vegetables that are high in fiber include: o Beans such as: + navy (1/2 cup = 9.5 grams), + kidney (1/2 cup = 8.2 grams), + pinto (1/2 cup = 7.7 grams), + black (1/2 cup = 7.5), + lima (1/2 = 6.6 grams), + white (1/2 cup = 6.3 grams) + great northern (1/2 cup = 6.2 grams). o Artichokes (1 artichoke = 6.5 grams) o Sweet potatoes (1 medium sweet potato = 4.8 grams) o Pears (I small pear = 4.4 grams) o Green peas (1/2 cup = 4.4 grams) o Berries such as raspberries (1/2 cup = 4.0 grams) and blackberries (1/2 cup = 3.8 grams) o Prunes (1/2 cup = 3.8 grams) o Figs and dates (1/4 cup = 3.6 grams) o Spinach (1/2 cup = 3.5 grams) o Apples (1 medium apple = 3.3 grams) o Oranges (I medium orange = 3.1 grams) * Replace refined white bread with whole-grain breads and cereals. Eat brown rice instead of white rice. Eat more of the following foods: o Bran muffins o Oatmeal o Bran or multiple-grain cereals, cooked or dry o Brown rice o Popcorn o 100% whole-wheat bread * When eating store-bought foods, check the nutrition information labels for the amounts of dietary fiber in each product. Aim for 5 grams of fiber per serving. o Add 1/4 cup of wheat bran (miller's bran) to foods such as cooked cereal, applesauce or meat loaf. o Eat beans each week. Start slowly When you first add fiber to your diet you may notice bloating, cramping or gas. But you can prevent this by making smaller changes in your diet over a period of time. Start with one of the changes listed above, then wait several days to a week before making another. If one change doesn't seem to work for you, try a different one. Be sure to drink more fluids when you increase the amount of fiber you eat. Liquids help your body digest fiber. Try to drink 8 glasses of no- or low-calorie beverages, such as water, unsweetened tea or diet soda each day. thank you and references http://www.ext.colostate.edu http://www.mayoclinic.com http://www.nlm.nih.gov http://www.medicinenet.com http://familydoctor.org http://www.whfoods.com http://www.webmd.com

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