Dietary Fiber

Insoluble fiber

Insoluble fiber acts like a sponge and absorbs water as it's digested, so it adds bulk and softness to bowel movements. This not only prevents constipation, but also speeds the rate at which food passes through your system—leaving less time for certain foods to deposit impurities and cancer promoting compounds on the intestinal wall. This may be one reason why diets high in fiber are associated with low rates of bowel and colon cancer. Recent results from one of the largest studies ever conducted into the link between diet and cancer—the EPIC (European Prospective Investigation of Cancer and Nutrition) Study—involving more than 500,000 people from 10 countries for nearly five years, found that the people eating the most fiber had a 40 percent lower risk of colon cancer than those people eating the least.

Soluble fiber

Soluble fiber works differently from insoluble fiber because it's broken down by the action of bacteria in the digestive tract and some of the healthy by-products of this process are absorbed into the blood stream. Once in the blood stream these healthy by-products have been found to bind with bile acids (compounds originally derived from cholesterol stores in the liver) and escort them out of the body. This draws cholesterol from the blood, and in turn lowers cholesterol levels. In one study of men with high cholesterol levels, adding half a cup of cooked dried beans (rich in soluble fiber) to their normal diet reduced their blood cholesterol levels by 13 percent in 21 days. Soluble fiber also slows the release of glucose into the bloodstream, which helps regulate blood sugar levels.

Both soluble and insoluble fiber have also been shown to protect against heart disease and breast cancer. In a study of over 43,000 U.S. male health professionals conducted by Harvard University, it was found that over a six-year period those who ate the most fiber had a 55 percent lower chance of coronary death than those who ate the least. And a recent study of more than 1000 Australian women (half had been diagnosed with breast cancer, half were free of the disease) found that those who ate more than 28 grams of fiber per day had the lowest risk of the disease, while those who ate less than 14 grams per day faced the highest risk.

The weight loss bonus

Fiber not only promotes good health and keeps you regular, it can also help control your weight. Here's why. Firstly, fiber is nature's best appetite suppressant because it fills the stomach and satisfies your appetite much earlier than fiber depleted foods. And fiber isn't only bulky and filling, it also can't be digested like normal foods (it basically passes right through you) so it adds virtually no calories to your diet.

The chewiness of high-fiber foods also prolongs eating time which, in turn, gives your body time to tell your brain that your stomach is full.
And a high-fiber diet may actually cut the number of calories you ingest by blocking your body's ability to digest the fat and protein consumed along with it. In a recent study by the U.S. Department of Agriculture, researchers set a certain number of calories for subject groups and altered the fiber content. Results demonstrated that fewer calories were absorbed with increased fiber intake. It was found that people who consumed up to 36 grams of fiber a day absorbed 130 fewer daily calories. Over a year, that adds up to over 47,000 calories!

Are you getting enough?

The importance of fiber as part of a healthy diet is beyond question. Unfortunately most people in Western countries like the U.S., the U.K. and Australia consume very little dietary fiber—only around 10-15 grams a day. While this is better than none, it's too little for any appreciable benefits. Throughout the Mediterranean and Asia fiber intake is traditionally between 30-40 grams a day. This is the level to strive for. Luckily by following a MediterrAsian style of eating—which includes lots of fiber-rich whole grains, fruits, vegetables, nuts and legumes—you'll naturally be eating this level of fiber without even having to think about it.