7 Fiber Myths and Facts

By now, you've probably heard that fiber is good for you, and maybe you've even made an effort to get your daily recommended amount. Fiber is the indigestible part of edible plants like fruits, vegetables, and grains that has been linked to numerous health benefits, including normal bowel function, lower cholesterol, balanced blood sugar levels, and even weight loss.

Here we examine seven common misconceptions about fiber—along with some key truths—to help you increase your fiber IQ.

Myth #1: All fiber is created equal.

Fact: There are two different types of fiber: soluble, which dissolves partially in water, and insoluble, which does not dissolve. Soluble fiber is plentiful in apples, oranges, dry beans, legumes, barley, and oats. Good sources of insoluble fiber include whole-wheat pasta, bulgur wheat, bran, rolled oats, and brown rice.

Soluble and insoluble fiber play different roles, and for best results, you need both. "Soluble fiber helps lower blood cholesterol levels, while insoluble fibers help food move through the digestive track, which helps prevent constipation and promotes digestive regularity," says Alison Massey MS, RD, LDN, CDE, Director of Diabetes Education at Mercy Medical Center in Baltimore. Although there’s no hard and fast formula, some experts recommend that one quarter of your fiber intake be soluble fiber, and the rest, insoluble.

Myth #2: Most people get enough fiber naturally in their diet.

Fact: How much fiber you consume in your diet depends on how healthful your eating choices are. Unsurprisingly, "Individuals who live on processed fast foods and eat few fruits, vegetables, and whole grains often lack fiber in their diet," Massey says. "It is important to look at food labels on packaged food products to assess the fiber content per serving and also to eat plenty of foods that are naturally high in fiber like beans, lentils, oatmeal, nuts, and berries." FYI: Fiber-rich foods contain five or more grams of fiber per serving.

Myth #3: Everyone’s fiber needs are equal.

Fact: A good rule of thumb is to aim for about 25-35 grams of fiber daily, Massey says. But exact dietary fiber needs can vary by gender and age. She offers the Institute of Medicine’s following list of daily recommendations for most healthy adults:

  • Men 50 years and younger: 38 grams (g) fiber per day.
  • Men 51 years and older: 30 g fiber per day.
  • Women 50 years and younger: 25 g fiber per day.
  • Women 51 years and older: 21 g fiber per day.

If you’re unsure of exactly how much fiber you personally need, ask your doctor or nutritionist for guidance. Since raw fruits and vegetables don’t always come with nutrition labels, you can look up the fiber content in the United States Department of Agriculture (USDA)’s National Nutrient Database—where we learned that a large pear has about 7 grams of fiber.

Myth #4: If your diet is lacking in fiber, you’ll probably experience some obvious health symptoms.

Fact: While many people today don’t consume enough fiber, some of them may not have any direct obvious signs that they need to up their intake. The biggest clues are frequent constipation or changes in bowel habits. These symptoms should alert you to review your fiber consumption and see if you should be adding more to your diet. Adopt a diet rich in fruits, vegetables, whole grains, beans/lentils, and nuts to help keep your bowel function regular, Massey suggests.

Myth #5: Foods that are labeled whole-grain are always high in fiber.

Fact: Not all whole grain foods are actually rich in fiber, according to Massey. Take whole grain cereal. Often the grains are refined, which strips them of fiber and takes away the health benefits. They can also contain high amounts of sugar and hydrogenated oils—oils that are solid at room temperature, and have been linked to high cholesterol levels and heart disease. So don’t just assume whole grain foods are good for you: Always read the ingredient list and check the fiber count.

Myth #6: Foods that have been artificially fortified with fiber are just as beneficial as foods in which fibers occurs naturally.

Fact: There has been much controversy in the medical community about the benefits of adding fiber (often referred to as "isolated" fiber) to foods. Isolated fiber, often listed on nutrition labels as oligofructose, polydextrose, or inulin, is sometimes added to foods like ice cream and cereals. But many experts believe that adding fiber does not provide the same health benefits you get when it occurs naturally. So it’s always best to go for foods that are naturally rich in fiber (again, look for five or more grams of fiber per serving), Massey says.

What are some excellent sources of natural fiber? Raspberries, kidney beans, and garbanzos (chick peas) are a few good ones. "Other good natural fiber choices include oats, whole grains, lentils, nuts, and pears," Massey adds.

Myth #7: If a little fiber is good, a lot of fiber is even better.

Fact: "Too much fiber in the diet may cause some digestive distress and loose stools," Massey says. This is why it’s always best to start slowly if you want to increase your fiber intake; let your body adjust before you increase the amounts up the recommended levels. To aim for optimal fiber intake, some nutritionists recommend working up to eating at least five servings of fruits and vegetables (good sources of fiber) each day, and including one whole grain serving at each meal.

Alison Massey, MS, RD, LDN, CDE, Director of Diabetes Education, Mercy Medical Center, reviewed this article.


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"National Nutrient Database for Standard Reference Release 27." United States Department of Agriculture Agricultural Research Service. Accessed May 7, 2015.

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