Why you should have fiber in your diet

August 30, 2013

By Brian Higginson, RD, CD
Clinical Nutrition Specialist

Fiber is a general term for the various plant cells that give plants their structure – it helps trees stand up tall, and is what makes fruits and vegetables crunch when you bite into them. No fiber naturally exists in meats or dairy products; fiber is found only in plants. Fruits, vegetables, nuts and seeds, along with other foods such as whole grains, are good sources of fiber.

Benefits and Types of Fiber

High fiber foods help to “bulk the stool”, meaning that they help you have more regular bowel movements. This is important throughout our lifecycle, but especially as we age. The added benefit of this “bulking of the stool” is that the intestinal tract gets scrubbed clean because fiber acts as a “scrub brush”. Clean intestines are associated with a lower risk of colon cancer, irritable bowel syndrome, and other bowel problems.

Fiber also helps us feel full when we are done eating a meal or snack. High fiber foods make the stomach empty more slowly, which helps us feel fuller for a longer period of time. Plus, we have to chew high fiber foods more, and some studies suggest that this action makes our brains think we are eating more, helping us feel fuller.

There are two main types of fiber, soluble and insoluble. The term relates to the ability of the fiber to mix with water or not. Insoluble fiber (or “roughage” like the skins on fruits and vegetables, leaves such as spinach or kale, seeds, and the bran component of whole grains) is important for bowel regularity and improving the overall health of the intestines. Look for “100% whole grain” products, eat fruits and vegetables with their skins still on them, and don’t overcook your vegetables because this breaks down the fiber and you might not get as much benefit from them!

Soluble fiber is the type that mixes with water. Think about a bowl of oatmeal - if it sits, then it gets goopy. This is the good stuff in action! This gelatinous goop also forms in our intestines and gets digested slowly. This can help keep our blood sugar levels steady by slowing down the overall speed of digestion and absorption. Also, this type of fiber can help lower our cholesterol by trapping up the globs of fat and cholesterol in the intestine and causing them to pass through in a bowel movement instead of being absorbed into the body.

The gelatinous goop from soluble fiber also traps and clears bile from the intestines. Bile is used in the digestion of fat, and bile itself is made from cholesterol. Without the bile being reabsorbed by the intestines, the body then has to use cholesterol from the “pool” in the body, thus helping to lower overall cholesterol levels. Major sources of soluble fiber include oats and oat bran, barley, beans and legumes, ground flax seeds, citrus fruits, apples, plums and prunes, sweet potatoes, broccoli, carrots, onions, and winter squash.

Working Fiber Into Your Diet

If you’re already eating high fiber foods on a regular basis, that’s great! If not, try working one new high fiber food into your diet for a few days, then add in another one, and then another. If you start eating a lot of fiber and your body isn’t used to it, then you will likely get an upset stomach. Cooking foods will help make them easier to digest, but don’t cook them into mush - you lose most of the benefits! Drinking plenty of water is important as well. Fiber needs fluid to help move it easily through the intestines. If you eat a lot of fiber (especially from grains) but don’t drink enough fluid, then you can become constipated.

Fresh raw fruits and vegetables are generally the best sources of fiber, but frozen ones are OK too. Look for frozen foods that don’t have added sauces or other ingredients. Canned foods almost always have added salt or sugar, so rinse them with cold water to get the most benefit.

Bonus Tip

Cooking high fiber foods (especially vegetables) will help make them more appealing to most family members. Try tossing raw or cooked vegetables in a little olive oil and vinegar, maybe a splash of soy sauce, sautéed garlic, top them with some parmesan cheese, just a small pinch of salt and pepper, or a small amount of salad dressing. The important thing is to be sure to include them regularly. Ideally, every meal that we eat will have some form of fruit, vegetable, and/or whole grain. The more fiber we eat, the healthier our intestines will be!