Why Is Fiber Important?

You’ve probably heard of fiber by now, but have you ever wondered what it does and why it’s so beneficial for our overall health? Fiber is the non-digestible carbohydrate found in various foods; it helps keep us full, keeps our digestive system working optimally, and helps keep our blood sugar levels within the normal range. Our gut microbiome, the trillions of gut bacteria in our large intestines, love fiber and reap its benefits each and every day. Keep reading to learn the ins and outs of fiber, discover some fiber friendly foods, and learn why it’s not actually necessary to know net carbohydrates in order to reach your fiber intake goal. 

What is Fiber? 

Simply put, fiber is the portion of whole, plant-derived food that cannot be broken down by human digestive enzymes. It’s split into two broad categories, based on its solubility (how easily it dissolves) in water. 

• Soluble Fiber: Soluble fiber dissolves in water and can be metabolized by the “good” gut bacteria. This type of fiber creates a gel-like substance with food as it is digested, making us feel more full and slowing down the passage of waste in the digestive tract–think S for soluble, S for “slow”. 

• Insoluble Fiber: Insoluble fiber does not dissolve in water. Instead, it adds bulk to the stool, speeding up our digestion: think Insoluble, “Go”. It’s most beneficial for those who experience constipation. 

While fiber can be split into these two categories, there is a lot of overlap when it comes to nutrition and food. Most foods contain both soluble and insoluble fibers; the difference is the ratio in which these fibers are present. Dietitians recommend eating at least 28 grams of total fiber per day to maintain overall and digestive health and wellbeing. 

How is Fiber Used in Our Body?

The gut microbiome, primarily the bacteria that live in our large intestine, plays a crucial role in our digestive health. From digesting and breaking down our foods, producing waste, and excreting waste, digestion is one of the human body’s most important functions. Therefore, there is a mutually beneficial relationship between you and the “good” bacteria that live in our digestive system: our body provides food and shelter, while the bacteria take care of processes that the human body cannot do on its own. 

After we eat a meal, our body works hard to break down and absorb all of the nutrients we have given it. The carbohydrates, protein, and fat in the meal are mostly already absorbed into the bloodstream for other uses; however, fiber remains unchanged, because our cells do not have the enzymes needed to digest fiber. Even so, intestinal bacteria love fiber, and fiber helps to promote the growth of these good bacteria; it’s a win-win! Fermenting these fibers helps our bacteria to feed the cells of the large intestine, leading to reduced inflammation and a decrease in bloating. 

Fiber also plays an important role in the maintenance of our blood sugar levels. Because the body is unable to absorb and break down fiber, it won’t cause a spike in blood sugar like other carbohydrates can. Think about it like this: have you ever had a simple carbohydrate alone, like a baked good, and felt that ‘sugar high’ and then felt tired after? That’s because the glucose (or sugar) in our blood spikes rapidly as our body works to process these simple carbohydrates. However, when we eat foods higher in fiber, OR the simple carbohydrates alongside some protein, fat and fiber rich foods,  we don’t feel that sugar rush; instead, we feel satisfied and full, and often more energized after eating. The fiber present in these foods helps to mitigate our blood sugar response, and therefore it will stay closer to baseline instead of sharply increasing and decreasing. But, that’s not to say there isn’t a time and place for all foods! All foods fit, it’s just a matter of our body’s response to them. When we’re eating a balanced diet by following our body’s cues, our body will know what to do. 

How Much Fiber is Too Much Fiber? 

Now that we’ve covered how beneficial fiber can be, it’s important to realize that too much of a good thing can be a bad thing, fiber included. Recent media has recognized and popularized fiber for its various health-helping benefits; however, too much fiber can actually have a reverse effect. When taken to an extreme, too much fiber can have unwelcome effects, such as: 

• Bloating 

• Abdominal pain

• Flatulence (the passage of gas)

• Loose stools or diarrhea 

• Constipation 

Dietitians, including us at HSH, actually consider 35 grams to be a high fiber diet. This is not to say that tracking food should become a norm. Stick to a variety of foods that make you feel good in your body, and your fiber amount will most likely be at its sweet spot. If you are having unpleasant side effects, and feel it could be realted to too much or too little fiber intake, an RD can help you determine what's going on! 

What Foods Have Fiber? 

Fiber from food sources will always be better than fiber from a supplement. High-fiber foods contain various vitamins and minerals that the body needs to maintain optimal health. 

Soluble Fiber Foods: 

• Oats 

• Brussels sprouts 

• Beans 

• Peas 

• Apples 

• Oranges 

• Nuts 

• Flaxseed, chia seed, and other seeds 

Insoluble Fiber Foods: 

• Wheat bran 

• Vegetables, including dark leafy greens 

• Root vegetables, like carrots and beets 

• Fruit skins 

• Intact whole grains, like barley and rice 

Net Carbs are Unnecessary

Net carbohydrates are sometimes used within dietetics, especially within the diabetes population. They are found by subtracting the amount of fiber from the total carbohydrate amount. However, numbers are not part of a true intuitive eating pattern. Instead, focusing on incorporating different types of carbs –like fruits, vegetables, and whole grains– will ensure that our body is getting the fiber it wants and needs. When we follow external cues, such as numbers and beliefs promoted by diet culture, we end up making decisions that may not serve our bodies in the best way. This can hinder progress and blind us to what truly feels good for our bodies. Calculating net carbohydrates can actually cause a lot of confusion. Intuitive eating allows us to choose different foods each day, all while following our body’s internal signals. One day’s dinner can be a pasta and pizza night, while the next day’s dinner can consist of roasted veggies and whole grains. Trust that your body will tell you what it needs, and your fiber intake will be right where it should be. 

*Disclaimer: This information is not meant as a substitution for medical information. If you are experiencing a gut-related illness, please consult with a Registered Dietitian before making any changes to your current eating patterns.*

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Written by Serena Pratt

Hi, I’m Serena! I’m a first year grad student at Columbia University studying Nutrition. I’m a former figure skater for Team USA, and because of that, I’ve had my own struggles relating to my complex relationship with food. Learning about nutrition has helped me to understand more about my personal journey, but has also led me to wanting to help others who may feel the same way! I’ve since learned how to listen to my body, can enjoy foods again, and am excited to share with and guide others in doing the same. 

Learn more about me and the HSH offerings here.