Although research is preliminary, there is evidence to suggest that a high fiber intake may offer protection from breast cancer. Toronto researchers found that 20 grams of fiber per day was associated with a modest effect that was statistically significant.10
Fiber may help lower your risk of breast cancer by binding to estrogen in the intestine and causing it to be excreted in the stool. Every day, your intestine reabsorbs estrogen from bile, the compound that’s released into your intestine from your gallbladder to help digest fat. If dietary fiber can attach to estrogen and facilitate its removal from the body, your body has to take estrogen out of your bloodstream to make more bile. The net result is a lower level of circulating estrogen. It’s possible that following a high-fiber diet for many years could lower your risk for breast cancer.
High-fiber diets also tend to be higher in antioxidant vitamins and lower in fat, both of which might protect from breast cancer. People who eat plenty of fiber also tend to maintain a healthy weight. There are many possible explanations for fiber’s protective effect. The studies do suggest, however, that dietary fiber works best if you follow a low-fat diet. So adding a little wheat bran to a diet that’s high in fat and low in fruits and vegetables probably won’t do you much good. More and more we are learning that health protection comes from a combination of healthy foods in the diet.
Dietary fiber is actually made up of two types of fiber, soluble and insoluble. Both types are present in varying proportions in different plant foods, but some foods may be rich in one or the other. And both types of fiber function differently in your body to promote health.
Foods like wheat bran, whole grains and some vegetables contain mainly insoluble fibers. Like their name suggests, these fibers do not dissolve in water, but they do have a significant capacity for retaining water. In this way they act to increase stool bulk and promote regularity. And it’s wheat bran (insoluble fiber) that’s been studied the most in relation to breast cancer risk.
Soluble fibers do dissolve in water. Dried peas, beans and lentils, oats, barley, psyllium husks, apples and citrus fruits are good sources of soluble fiber. When you consume these foods, the soluble fibers form a gel in your stomach and slow the rate of digestion and absorption.
It’s estimated that North Americans are getting 11 to 14 grams of fiber each day, only half of what is recommended. Health authorities agree that a daily intake of 25 grams of total dietary fiber is needed to reap its health benefits. To learn what foods are higher in fiber, see the table on page 29 in chapter 1. To boost your intake of insoluble fiber and wheat bran, try the following:
• Strive for at least five servings of fruits and vegetables every day.
• Leave the peel on fruits and vegetables whenever possible.
• Eat at least five servings of whole-grain foods each day.
• Buy high-fiber breakfast cereals. Aim for at least 4 to 5 grams of fiber per serving (check the nutrition information panel).
• Add 2 tablespoons (30 ml) of natural wheat bran or oat bran to cereals, yogurt, casseroles and soup.
• Add nuts and seeds to salads.
• Reach for high-fiber snacks like popcorn, nuts, dried apricots or dates.
Don’t increase your fiber intake overnight; instead, gradually build up to the daily 25 grams of fiber. Too much fiber too soon can cause bloating, gas and diarrhea. And don’t forget that fiber needs water to work. Drink 8 ounces of fluid with every high-fiber meal and snack.