What’s the Skinny on Fiber?

Getting enough fiber in your diet is an important component in helping stabilize and regulate blood sugars, maintain a healthy body weight and optimize our over-all health. Besides helping regulate and stabilize blood sugars by shielding carbohydrates and delaying the absorption of glucose it also increases food volume which helps provide a satiating effect by slowing the emptying of the stomach helping you feel full longer without increasing calories.

In scientific terms fiber is a non-digestible polysaccharide (poly = many; saccharide = sugar), which means it’s a complex form of carbohydrate. In a more simplistic manner, what this means is that fiber is a type of carbohydrate that the body is unable to digest, therefore accounting for zero calories.

Fiber is traditionally divided into two general categories based on its solubility in water and how it reacts within the body:

Soluble fiber is viscous, fermentable and dissolves in water. This type of fiber-acting as a prebiotic- is metabolized by probiotics, the beneficial microorganisms living in our digestive tract. This fiber source comes from fruits, vegetables, oats, beans, peas, lentils, barley, nuts, and seeds. When mixed with liquid, it forms a gel in our body, which helps control blood sugar and helps reduce cholesterol. (1, 2, 3, 4)

Insoluble fiber does not dissolve in water and passes through the body relatively intact helping to bulk up stool volume and improve motility. This type of fiber comes from fruits, grains, and vegetables. It adds bulk to food and acts like a brush to clean out the colon. It helps food pass through the digestive tract more quickly and prevents constipation. (5, 6)

The fact is 85% of the fiber in our diet comes from things like grains, vegetables, legumes, fruits and nuts. These same food sources also provide a lot of other important nutrients. However, due to the fact that we live in an industrialized world of refined and fortified foods, there are now functional dietary fibers. These are the isolated, non-digestible carbohydrates that fortify foods not usually containing fiber. This allows the processed food industry to make label touting health claims on a host of unhealthy products. (7)

Why fiber is so important

Throughout the 1970’s, British researchers, Denis Burkitt and Hugh Trowell, became leaders in the field proposing the “dietary fiber hypothesis”. Within it suggests that common GI diseases like colon cancer, diverticulosis and appendicitis are due, in part, to lack of dietary fiber in our diet. (8, 9, 10)

It’s not hard to understand why when we take a closer look at the facts:

  • Americans consume about 15 grams of fiber per/day, on average (17 grams for males and 13 grams for females).
  • Refined sugars, oils, dairy products and alcohol contain no fiber and accounts for nearly 50% of the calories in the average U.S. diet.
  • Nearly 75% of individuals with a fiber intake below 20 grams/day think that the amount of fiber they take in is sufficient, while the Institute of Medicine (IOM) recommends 19 to 38 grams/day (varying based on age and gender).
  • Refined flours provide the majority of fiber in our standard Western diet. This notable fact is not because foods made from these products contain a lot of fiber, but rather that a majority of our diet is made up of foods made from these products.

Bottom Line:  People eating a standard Western diet aren’t getting anywhere near the amount of fiber that they should be getting.

A low fiber diet is associated with many health risk factors, including:

  • Excess body fat – fiber contributes to satiety and dilutes caloric density helping reduce overeating and weight gain.
  • Diabetes – fiber helps controls blood sugar, insulin and body fat, reducing the risk for metabolic abnormalities such as insulin resistance and type II diabetes.
  • Cardiovascular disease – fiber helps bind and reduce blood cholesterol and fat in the blood known as triglycerides.
  • GI disorders, cancers and poor bowel function – fiber helps keep the GI tract clean and can ease constipation while reducing the risk for diverticular disease.
  • High blood pressure – fiber helps to reduce inflammation caused by high blood sugars.

Studies conducted in 10 European countries with over 500,000 people showed that people who ate 30 grams of fiber or more per/day had approximately half the risk of colon cancer than those who ate 15 grams or less per/day. (11, 12)

Fiber and Body Weight

Fiber increases dietary bulk, decreases caloric density and reduces caloric intake. This is helpful for the 75% of Americans who are now overweight. However, because fiber increases satiety, eating too much fiber may not be advantageous for those seeking to increase body weight. (13)

Fiber and Type II Diabetes

Consuming more fiber seems to help prevent type II diabetes. This is likely due to the moderation of blood sugar and insulin release. (14, 15)

Fiber and Mineral Absorption

More fiber means more fecal energy losses, since GI transit time speeds up. Rapid GI transit leads to less time for digestion and absorption of nutrients. This could be somewhat problematic if mineral intake is lacking due to an unhealthy diet. Consuming up to 35 grams of fiber each day doesn’t seem to diminish mineral balance in adults, while 25 grams seem to be the upper register for children. (16)

Fiber and Cardiovascular Disease

In one study, researchers followed more than 16,000 middle-aged men from around the world for 25 years. The study concluded that a higher consumption of fiber consummated a lower risk of death from heart disease by as much as up to 82%. (17, 18)

Fiber and Blood Lipids

In randomized controlled trials, compared to baseline values, higher fiber diets were associated with a 20% decrease in total cholesterol and a 35% decrease in LDL cholesterol known as the bad cholesterol. (19, 20, 21)

Fiber and GI Function

Fiber can stimulate bacterial fermentation in the large intestine or pass through the GI tract unfermented. Since GI health is synonymous with immune function, fiber seems to play an important role in immunity. (22, 23, 24)

Fiber and Diet

Plant based foods contain lots of fiber. The best sources are vegetables, legumes, whole grains, fruits and nuts/seeds.

Diets combined with higher amounts of vegetables and plant based foods tend to be much higher in fiber. People incorporating these types of foods in their diet tend to have lower rates of cardiovascular disease, cancer, lower blood fat, lower blood pressure, and lower over-all body weight.

Remember that whole grain means the “whole grain” and not whole grain flour, whole grain pasta, whole grain nutrition bars, or cereals with whole grains added to it.

What should you look for?

Check the label and make sure that the first ingredient on the products you choose is one of the whole grain ingredients listed below, and that they have a minimum of 3 grams of fiber per/serving.

  • brown rice
  • buckwheat
  • bulgur
  • millet
  • quinoa
  • rolled oats
  • steel cut oats
  • sprouted grain
  • wheat berries
  • whole-grain barley
  • whole oats
  • whole rye
  • whole wheat
  • wild rice

Fiber and Kids

Adequate fiber during youth can reduce the risk of cardiovascular disease, cancer and diabetes from early on.

The 2005 U.S. Dietary Guidelines recommend a fiber intake of 14 grams per 1,000 calories. (25)

  • All children 1 to 3 years, 19 g/day
  • All children 4 to 8 years, 25 g/day
  • Boys 9 to 13 years, 31 g/day
  • Girls 9 to 13 years, 26 g/day

However, too much fiber in a child’s diet can reduce overall food intake due to its satiating effect, increase fecal energy loss, and decrease mineral absorption. Although in children consuming a standard Western diet, this is rarely a problem.

Also notable is grain and legume intolerance in children. These are most commonly tied to wheat, soy, and peanuts. Parents may want to choose alternative sources such as vegetables, fruit, other seeds/nuts, and other beans/legumes if necessary.

Can you take in too much fiber?

Too much fiber can actually reduce the absorption of calories and some attached nutrients. Although this may seem like a negative response especially where food supplies are scarce, In the U.S., this might actually be quite positive.

Fermentation of fiber by bacteria in the colon can produce gases. This may lead to bloating, internal pressure and gas.

A small percent of people can become intolerant to a form of fiber. There is evidence that the lectins (carbohydrate binding proteins) in some grains and legumes can cause health problems for susceptible people, because they affect the lining of the gut. However, there is also evidence that prebiotic fiber sources such as inulin help create healthy intestinal micro-flora aiding in and elevating inflammatory bowel disorders. (26, 27)

How much fiber do we need?

Getting enough fiber is important for overall health and disease prevention. And it keeps your plumbing in good working order.

If you build your diet around vegetables, fruits, legumes, whole grains, nuts and seeds, you’re probably getting enough fiber.

If you want a goal:

  • Women should aim for at least 25 to 30 grams of fiber per day.
  • Men should aim for at least 30 to 35 grams of fiber per day.

You should get your fiber from whole foods. Fiber supplements or fiber-supplemented foods do not provide the micronutrients, phytochemicals and water the body needs which are found in whole plant foods. If you are currently relying on a fiber supplement because you fail to get enough fiber from the foods you are eating, you need to re-evaluate your current diet and incorporate whole foods that will increase your fiber intake naturally.

Best High-Fiber Quick List

Vegetables
  • Artichokes — Fiber: 10 grams per medium vegetable, cooked.
  • Peas — Fiber: 9 grams per cup, cooked.
  • Broccoli — Fiber: 5 grams per cup, boiled.
  • Brussels Sprouts — Fiber: 4 grams per cup, boiled.
Fruit
  • Avocado — Fiber: 10 grams per medium fruit, raw.
  • Blackberries — Fiber: 8 grams per cup, raw.
  • Raspberries — Fiber: 8 grams per cup, raw.
  • Pear — Fiber: 6 grams per medium fruit, raw.
Nuts
  • Almonds — Fiber: 4 grams per 1 oz.
  • Pistachios — Fiber: 3 grams per 1 oz.
  • Macadamia — Fiber: 3 grams per 1 oz.
  • Pecans — Fiber: 3 grams per 1 oz.
Legumes
  • Split Peas — Fiber: 16 grams per cup, cooked.
  • Lentils — Fiber: 15 grams per cup, cooked.
  • Black Beans — Fiber: 15 grams per cup, cooked.
  • Lima Beans — Fiber: 13 grams per cup, cooked.
Grains
  • Bran Flakes — Fiber: 7 grams per cup, raw.
  • Pearled barley — Fiber: 6 grams per cup, cooked.
  • Quinoa — Fiber: 5 grams per cup, cooked.
  • Oatmeal (old fashioned, slow cooked) — Fiber: 4 grams per cup, cooked.

Tips to Add More Fiber to Any Meal

  • Add flaxseed meal to oats, smoothies, yogurt and baked goods — you can even try breading chicken or fish with it. A two-tablespoon serving contains 3.8 grams of fiber and a dose of omega-3 fatty acids to boot.
  • Chia seeds have a whopping 5.5 grams of fiber per table­spoon. When they meet with water, they form a goopy gel that is great for thickening smoothies or making healthy puddings.
  • Veggies can easily be sliced or grated and snuck into many dishes without much hassle. Try adding some to shakes, omelets, salads, soups or other homemade dishes.
  • Food processors are fiber’s best friend. Purée some cooked vegetables and add them to sauces and stews, or swap out rice for chopped-up cauliflower.
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