Research Information

Taylor Morgan, PA-C, RDN, LD, IFNCP
Physician Assistant, Registered Dietitian Nutritionist 

What is Fiber?

Fiber is one of the most beneficial things you can consume for your health. It has the ability to help with digestive issues (including IBS, constipation, and diarrhea), weight management, cholesterol reduction and overall inflammation.

But what exactly is it?

Fiber is a type of carbohydrate from plant-derived foods, like beans, grains, vegetables and fruits that cannot be fully broken down by human digestive enzymes. While most carbohydrates are broken down by the body into sugar, fiber passes through the body undigested. In fact, most dietary fiber doesn’t get absorbed either. Instead, it stays within the intestine where it modifies digestion of other foods and affects the consistency of the stool.

While you should seek to increase your overall fiber intake, it’s important to know that there are two kinds of fiber: soluble and insoluble, each with its own unique benefits. The biggest differentiator and where each kind of fiber gets its name is from the ability to dissolve in water, or solubility. So soluble fiber can be dissolved in water, while insoluble fiber cannot.

The chart below has some more differences, the health benefits and what foods are good sources of each type. As you seek to add more fiber to your diet, vegetables are great starting point. Many of them contain both types of fiber and will provide you with benefits from each category. Another great option is adding a fiber supplement to your daily regimen.

Dissolves in water
Does not dissolve in water
Example Food Sources
Oats, nuts, seeds, beans, lentils, fruits such as citrus fruits, apples, berries, and avocados, and many vegetables such as brussels sprouts, artichokes, asparagus, broccoli, dark leafy greens, peppers, squash, carrots
Whole grain products, flaxseeds, rice, legumes (ie. beans, peas and lentils), nuts, and many vegetables such as cauliflower, carrots and green beans
Health Benefits
-Slows digestion and makes you feel fuller longer -Lowers cholesterol -Helps with weight loss & weight management -Improves blood sugar levels -Reduces diarrhea -Increases healthy gut bacteria (which can lower inflammation and aid digestion)
-Eases and prevents constipation -Good for colon health -Helps your body process & eliminate waste -Reduces your risk for some colorectal conditions, such as diverticulitis and hemorrhoids
How It Works
Attracts water and turns into gel which slows digestion
Speeds food through the digestive tract and adds bulk to prevent constipation
Consists of a group of substances that is made of carbohydrates
Comes from plant cell walls


Fiber Benefits

Eating a high fiber diet has many health benefits including decreased risk of type 2 diabetes, heart disease, stroke, obesity, and many types of cancer (colorectal, oral, larynx, breast). Additionally, a diet rich in fiber is a commonly recommended to treat many digestive problems, like hemorrhoids, constipation, and diarrhea.

Because of the way our bodies process fiber and its varying characteristics, fiber has many benefits, as listed below:

Characteristics of Fiber
Benefits of Fiber
Reduces overall inflammatory markers
Prevents and treats diarrhea
Improves satiety and reduces hunger
Prevents and treats constipation
Slows absorption of glucose
Improves detoxification and elimination of toxins
Stimulates healthy bacterial overgrowth
Optimizes your gut microbiome
Binds materials and organic substances
Maintains healthy blood sugar levels, even those with among type 1 and type 2 diabetics
Increases stool bulk
Maintains healthy body weight and decreases risk of obesity
Slows transit of digested food through the intestine
Decreases levels of systemic inflammation and can reduce risk of coronary artery disease

There are two kinds of fiber, insoluble and soluble, that produce different positive results when consumed regularly.

Insoluble fiber comes from whole grain products, rice, legumes, vegetables, nuts and seeds. It is recommended to treat digestive disorders to include constipation, hemorrhoids, and fecal incontinence.  This type of fiber helps to bulk the stool, making it softer and easier to pass.

Soluble fiber comes from oats, nuts, seeds, psyllium, legumes, fruits and vegetables. It slows digestion which can help to treat diarrhea, improve blood sugar, lower cholesterol and thus, reduce the risk of cardiovascular disease and type 2 diabetes.

Studies show that a high fiber diet can reduce the risk of coronary artery disease and stroke by 40 to 50 percent (compared to a low fiber diet). Also, in those that already have diabetes (type 1 or type 2), soluble fiber can help control blood sugar levels. Since soluble fiber helps you to stay fuller longer, it can aid with weight loss and weight management.

Additionally, soluble fiber can stimulate short chain fatty acid production. These acids are naturally produced by the gut microbiome. They promote gastrointestinal health, metabolism, heart health and support a healthy immune system. Beyond those benefits, studies have shown that improving the gut microbiome can decrease overall levels of inflammation throughout the body.

How Much Fiber Do We Need Daily?

Fiber is a type of carbohydrate that comes from certain plant-derived foods like beans, grains, fruit and vegetables that cannot be fully broken down and digested by the human body. While that sounds like a bad thing, it’s actually beneficial! Some of fiber’s benefits include helping reduce constipation, assisting with healthy weight management, lowering cholesterol and reducing inflammation. While the benefits of fiber are vast, most people don’t consume as much fiber as recommended on a daily basis.

The recommended fiber intake is 25-35g/daily, but most people in the United States only consume about 8-15g/daily. So, how can we add more fiber to our diet to reach the recommended daily intake?

While many different foods can provide fiber, some foods actually have higher fiber content and can more easily help you to consume adequate amounts of fiber every day. Some of these higher fiber foods include: 

  • Vegetables*
  • Fruits*
  • Beans & Lentils
  • High-Fiber Breakfast Cereals
  • Wheat bran
  • Fiber Supplements, like those
  • that contain psyllium

*In order to reap the full benefits of fiber, plant foods must be eaten in their whole form (most, including their skin). Fruit and vegetable juices do not contain the beneficial fiber found in their whole food form.

Here’s a chart that includes the fiber content of some fiber-rich foods:

2 Tbsp Flax Seeds
2.5 g
1 Oz Almonds
3.5 g
1 Oz Pumpkin Seeds
5.2 g
1/2 Cup Quinoa (cooked)
2.6 g
1/2 Cup Artichoke
7.2 g
1/2 Cup Lentils (cooked)
7.8 g
1/2 Cup Navy Beans (cooked)
9.3 g
1/2 Cup Raspberries
4 g
1 Cup Oatmeal (Cooked)
3.4 g
1 Small Apple (Including skin)
3.6 g
1 Medium Banana
3.1 g
1 Medium Avocado
13 g
1 Medium Pear (Including skin)
6 g
1 Medium Sweet Potato (Including skin)
3.6 g


As you can see, there are many foods that are rich in fiber that can easily be added into your diet. Here are some other tips on how to increase your daily fiber intake:

  • Aim to consume 5-10 servings of fresh vegetables per day
  • Incorporate fresh, whole fruits and vegetables into every meal or snack
  • Choose whole grain rice, breads and pastas over products made with refined or white flour
  • Swap juices for smoothies, using the same ingredients
  • Add in a fiber supplement such as -  Nature’s Fiber

    As you add more fiber to your diet, you might notice some side effects like abdominal bloating or gas. You can minimize these side effects by starting with a small amount of fiber and slowly increasing, as your body tolerates it.

    Some other practical tips on reducing negative side effects from increased fiber intake are:

    • Fiber supplement dosing should be increased slowly to prevent gas and cramping
    • Ensure adequate fluid per day (at least 64 ounces of water per day)
    • And, always take fiber supplements with adequate fluids

      Ultimately, as you increase your fiber intake, listen to your body and increase slowly as tolerated. There are some people like those with irritable bowel syndrome that cannot tolerate fiber supplements. If you are one of those people, consult a medical professional for additional guidance before adding in fiber supplements.