Dietary Fiber: Why do we need it?

Fiber is one of the most overlooked nutrients in our diet. The majority of Americans do not even consume half the recommended daily amount. Where do we find it? Plant foods, of course! Fiber can be found in fruits, vegetables, whole grains, nuts, and seeds. Fiber is an undigested carbohydrate that moves into your colon to feed the trillions of friendly gut bacteria residing there, stimulating their growth with its nutrients. These beneficial bacteria promote healthful effects like prevention of intestinal inflammation, weight regulation, and improved insulin sensitivity, and ultimately reduce the risk of metabolic diseases like heart disease and type 2 diabetes. So, it’s a great idea to feed the gut bacteria lots of fiber. Eating many diverse sources of fiber may be the best way to do this. If we are feeding trillions of different bacteria, it makes sense that they would thrive on a diet sourced from many different strains of fiber.

Classification of dietary fiber is determined through their ability to dissolve in water, or their solubility. Insoluble fibers, like wheat bran, vegetables, and whole grains, do not add bulk to stool and allow food to pass more quickly through the stomach and intestines. This is the fiber that keeps you regular and may help prevent colorectal cancer in the future. Soluble fiber attracts water, slowing digestion and decreasing fat absorption as it takes on liquid and forms a gel-like substance. It’s great for your heart by lowering cholesterol, regulating blood sugar, and providing a sense of fullness from your meal. Examples can be found in oat bran, seeds, beans, lentils, and some fruits.

Nutrition Label

How can we interpret the fiber quality and quantity from a nutrition label? Check out the dietary fiber on the nutrition facts label on the back of your favorite snack or grain product. A good source of fiber is one that contains 3g of fiber or more per serving, or at least 10% of the Daily Value (DV). An excellent source of fiber is one that contains 5g of fiber or more per serving, or at least 20% of the DV.

There are so many varieties of bread and pasta on grocery shelves these days! Products labeled as “stone-ground”, “7-grain”, “multigrain”, etc. often appear to be whole grain products, but they aren’t always. To further complicate things, the packaging on grain products often states something along the lines of “11 grams of whole grains per serving”; but this does not necessarily mean that it is entirely whole grain.

So how can we find a high-quality and fiber-rich source of whole grains? Look for the word whole at the beginning of the ingredients list. If you see the words enriched or refined, that means it is not a whole grain choice. Enriched grains are stripped of some of the fiber and nutrients naturally present in the grain. Many refined grain products are also high in added sugars and sodium, which can easily be overlooked if the product is not inherently sweet or salty.

How to fit it into your meals

The general recommendations are around 25g/day for women and 38g/day for men. You may need more fiber depending on your calorie needs. Here are some things you can do to ensure you are consuming adequate fiber:

  • Eat a variety of fruits, vegetables, legumes, nuts, and seeds.
  • Make half of your grains whole grain.
  • Eat your fruits and veggies as opposed to drinking them.

A helpful guide to boosting fiber in your diet can be found on Fill half of your plate with fruits and non-starchy veggies such as broccoli, spinach, kale, cauliflower, carrots, tomato, and eggplant. Keep the skins of your fruits and veggies intact (if edible), as these are rich in fiber. Fill the remainder of the plate with grains (prioritizing whole grain sources), and your favorite protein. Legumes are a great source of fiber and protein!

When increasing or beginning to incorporate fiber into your diet, do it gradually and with plenty of water. Fiber absorbs water in the digestive system, so keeping hydrated will help prevent constipation and nausea.

Fiber Jargon

Prebiotics - Fibers that aren't digestible by your body, and therefore, can move into the gut undigested and feed the good bacteria that grow there.

Examples - Inulin, fructo-oligosaccharides (FOS), and galacto-oligosaccharides (GOS), all found naturally in plant foods.

Probiotics - Live microbes in your gut that move food by affecting nerves that control gut movement. They help balance your body, preventing diarrhea and easing the symptoms of irritable bowel disease. They can help create vitamins, support the cells that line the gut, and break down and absorb medications. To be considered a probiotic, a microbe must have a proven benefit, survive in the intestine after being eaten, and be safe to consume. They can also be found in the mouth, vagina, urinary tract, skin, or even lungs.

Examples – Lactobacillus (yogurt, fermented foods), Bifidobacterium (dairy products), saccharomyces boulardii (yeast)

Microbiome - the genetic material of the 10-100 trillion friendly microbial cells that are harbored by each individual person, living on and inside their bodies.

Microbiota - all the microorganisms found in an environment, including bacteria, viruses, and fungi.