Fiber 101

By Danielle McAvoy, MSPH, RD
May 9, 2022

When people talk about what they eat they tend to focus on macronutrients, always looking for the perfect balance of protein, fats, and carbs. What you don’t hear a lot about is fiber, arguably the most important nutrient of all. It’s best known for its role in digestion, but fiber impacts many aspects of physical and mental health, and it may even extend your life.  

What the heck is fiber anyway? 

Fiber is a type of indigestible carbohydrate found in many plant foods. There are two main types: soluble and insoluble.


Soluble fiber dissolves in water and forms a gel in your GI tract. This gel slows digestion and the absorption of nutrients. It also slows the rate that carbs are converted into sugars, which helps keep blood sugar levels steady. Slower digestion means you feel full longer, which can help you maintain healthy body weight. Soluble fiber also clears bad cholesterol from the bloodstream, protecting cardiovascular health.  

Insoluble fiber sometimes called bulk or roughage, doesn’t dissolve in water. Its job is to help move food through the digestive tract. By keeping things moving, insoluble fiber helps prevent toxins from building up in the intestines. 

While fiber is indigestible for us, it’s a feast for the billions of microbes that live in our gut. Prebiotic fiber is a soluble fiber that fuels healthy gut bacteria. Those bacteria improve the health and diversity of the gut microbiome, boost immunity, improve mood, and ensure the healthy production of nutrients like Vitamin K made by gut bacteria. A diverse gut microbiome is essential for energy and for getting quality sleep. It can help decrease cravings for sugary and fatty foods, and for special populations like new moms, a diverse, healthy gut improves milk supply and lowers the risk of postpartum depression. 

What does fiber do for me? 

1. Helps regulate blood sugar: Because fiber slows digestion, it helps keep blood sugar levels from spiking. High blood sugar levels can increase the risk of heart disease and stroke, kidney disease, poor vision, and nerve damage.

2. Lowers cholesterol: Soluble fiber helps reduce bad cholesterol levels by binding to cholesterol particles in the small intestine and keeping them from entering the bloodstream and traveling to other parts of the body. This may help reduce the risk of heart disease.

3. May prevent intestinal cancer: Insoluble fiber increases the bulk and speed of food moving through the intestinal tract, which reduces the time for harmful substances to build up.

4. Can add years to your life: There is some evidence that increasing the amount of fiber in your diet, especially whole-grain cereal fiber may reduce your risk of dying from cardiovascular disease and all cancers.

What are the best sources of fiber? 

The good news is that many foods like fruits, vegetables, legumes, whole grains, and nuts are loaded with fiber. There are countless delicious ways to increase the amount of fiber in your diet. From artichokes and apples to chickpeas, walnuts, and quinoa, many plant foods are excellent sources of fiber

So how much fiber do I need? 

It’s recommended that most women should eat between 21 and 25 grams of fiber per day, while men should consume between 30 to 38 grams of fiber per day. Water increases the effectiveness of fiber, another good reason to stay hydrated and drink plenty of water throughout the day.

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