What is fiber?
Dietary fiber consists of non-digestible carbohydrates present in the cell wall of all plant foods. Fiber is not broken down by the body’s digestive enzymes and remains unchanged throughout the digestive tract until it reaches the large intestine, where the majority of the microbes in our microbiome reside. In the large intestine, our microbes are responsible for processing fiber and producing the main health benefits of fiber consumption (more on this later).
What are the different types of fiber?
There are millions, if not billions, of different types of fiber. Fiber is classified in a variety of different ways, but let’s break it down into two main categories:
- Soluble fiber attracts and binds to water to form a gel as it moves through the digestive tract. It slows the movement of food through your system, softens stool, and can delay the absorption of carbohydrates, fats, and proteins. This delayed absorption of nutrients is why soluble fiber can be particularly beneficial for blood sugar regulation and heart health. Key sources of soluble fiber include beans, oats, psyllium, prunes, pears, leafy greens, cauliflower, flaxseed, acorn squash, and potatoes.
- Insoluble fiber does not dissolve in water and can help bulk the stool as it moves through the digestive tract. This type of fiber can increase the rate that food moves through your system, which can have a laxative effect, helping to relieve constipation. Key sources of insoluble fiber include whole grains, nuts, seeds, and the skins of fruits & vegetables.
What about the role of fiber for gut health?
The role of fiber in the digestive tract is dependent on the type of fiber consumed + the composition of microbes within your gut. Outside of the soluble and insoluble fiber classification, fiber can also be classified based on its ability to be fermented by the microbiome when it reaches the large intestine. This type of fiber is known as fermentable or prebiotic fiber.
When our microbes ferment prebiotic fiber, they produce anti-inflammatory molecules known as short-chain fatty acids (SCFAs). The three main SCFAs produced are acetate, propionate, and butyrate. These molecules not only support the gut microbiome but are also essential for optimal health and disease prevention.
Let’s look at all the different health benefits of SCFAs:
- Enhance immune function
- Repair and strengthen the lining within the gut
- Inhibit the growth of pathogenic bacteria & enhance the growth of beneficial bacteria within the gut
- Provide energy for the cells of the large intestine
- Regulate blood sugar & improve insulin sensitivity
- Inhibit abnormal cell & tumor growth
- Support brain health
- Activate satiety hormones to help control weight
- Lower cholesterol levels & improve overall heart health
- And MANY more!
Main sources of prebiotic fiber:
- Sprouted wheat, barley, rye
- Green bananas
- Cooked then cooled rice & potatoes
- Green & black tea
- Herbs & spices
How much fiber should I be getting in my diet?
The Institute of Medicine (IOM) recommends that men aged 50 and younger consume 30 grams of fiber per day, and those over 50 consume 30 grams. Women aged 50 and younger should consume 25 grams per day, and those over 50 should consume 21 grams per day.
Due to the typical consumption of a Western-style diet, high in processed foods, fat, and animal products, individuals in the United States tend to fall short of this recommendation. It is estimated that only about 3% of the population currently meets the IOM’s recommendations, averaging only 15 grams of fiber per day.
If you think you may fall into the group of individuals outside of the current fiber recommendation, start to make small changes over time to increase fiber consumption. Research shows that individuals who consume a diverse diet with 30+ plants per week have a more diverse microbiome and tend to have more SCFA producing bacteria than those who consume a less diverse diet. Aim to include a variety of plants (fruits, vegetables, whole grains, nuts, seeds, and legumes) in your diet to keep your gut microbes happy and healthy!
Maybe you’re thinking, “okay, fiber is important, but I feel terrible when I eat more fiber.”
Although fiber is an essential nutrient for optimal health, some individuals may struggle to process fiber, leading to various adverse symptoms such as bloating, gas, abdominal pain, diarrhea, or constipation. There are multiple reasons someone may not be tolerating a higher fiber intake. These include dehydration, an underlying condition or imbalance in the gut, increasing fiber too quickly, an inadequate balance of the various types of fiber, poor meal hygiene (aka eating too fast), or stress.
While your solution to resolving symptoms associated with a higher fiber intake could be as simple as increasing water intake or taking time to chew your food adequately at mealtime, there could be underlying issues that need to be addressed. Our gut microbiome contains all the necessary enzymes to digest fiber(humans can’t digest fiber without our microbes). Therefore, an imbalanced gut microbiome (known as dysbiosis) could impair your ability to digest fiber properly.
Steps to take if you are not tolerating fiber:
- Go slow! Your gut is a muscle, and it can take time to adapt to a higher fiber intake. Slowly increase your fiber intake over time.
- As you increase your fiber intake, you will also need to increase your water intake to keep things moving smoothly throughout your system. Aim for half your body weight in ounces as a starting point.
- Slow down at mealtime and adequately chew your food. Try to take a few deep breaths before starting your meal to activate the “rest and digest” nervous system.
- Eat a variety of different plant foods to ensure you are getting a good balance of the different types of fiber in your diet.
Suppose you are still struggling after trying out steps 1-4. In that case, you may need to reach out to a qualified practitioner to rule out underlying GI conditions or imbalances in the gut that could be contributing to symptoms.
- Work with a qualified practitioner to rule out underlying GI conditions such as constipation, irritable bowel syndrome, inflammatory bowel disease, celiac disease, or small intestinal bacterial overgrowth.
- In my practice, I run the GI Map stool test to assess the health of the gut microbiome along with intestinal health markers to provide personalized nutrition to reduce symptoms and improve gut health. Click hereto schedule a call to see if we would be a good fit to work together!
- I also offer a guide called “Rewire your gut,” full of gut-loving recipes and education on all things gut health to help you feel your best. Click here to check it out.
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