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3 Best Fiber Supplements + When and How to Take Them

Written by Dr. Michael Ruscio, DC on December 10, 2024

Written by Dr. Michael Ruscio, DC on December 10, 2024 — Reviewed by Aimee Gallo

• When to Take Fiber Supplements|
• Choosing a Supplement|
• How Much Fiber|
• When to Avoid|
• Specialized Diets|

If you’ve been struggling with constipation, diarrhea, or both, fiber supplements may seem like a miracle cure. But research clearly shows supplemental fiber can be a double-edged sword—some people do well, others not so much.

Let’s break down when to take fiber supplements, the potential benefits and risks, and the best option if a fiber dietary supplement is the right course of action. And since it’s usually best to get fiber from your diet, I’ll share how to meet fiber goals with food.

When Should You Take Fiber Supplements?

In the clinic, we tend to recommend supplemental fiber only after implementing other foundational approaches (e.g., diet, lifestyle, and probiotics).

Fiber supplements may seem like a simple solution, but I encourage my clients to avoid thinking of them as a first-line option for digestive troubles.

Skipping a holistic approach and going straight to supplemental fiber can further stress a struggling digestive system. This can result in side effects such as diarrhea, constipation, cramping, and bloating 1 2.

Before starting a fiber supplement, we want to prepare the gut to handle more fiber. So, I encourage laying a foundation with gut-supportive fundamentals first. As I discuss in Healthy Gut, Healthy You, this means implementing:

• A whole-foods, anti-inflammatory diet
• Restorative sleep
• Mindful movement
• Stress management
• Time in nature
• Probiotics

If these strategies don’t get someone across the finish line, we may add digestive enzymes and gut rebuild nutrients (e.g., vitamin A, zinc, l-glutamine, aloe vera, N-acetyl-D-glucosamine).

For most of our clients, this roadmap works very well—they’re able to increase their dietary fiber intake back to a healthy level and there’s no need for fiber supplements.

But there are times when we may want to use fiber supplements strategically to help feed the healthy gut bacteria.

How Do You Choose a Fiber Supplement?

There are a couple of things to consider when choosing a fiber supplement:

• Solubility, or how well the fiber dissolves in water
• Fermentability, or how much the fiber will feed the gut bacteria

This table details the differences between soluble and insoluble fiber:

No one fiber will be right for all people. Let me share how to choose and when to take fiber supplements.

What is the Best Fiber Supplement?

I’ll go through a few fiber supplement options below, but use the following tips for all of them:

• Use 1–2 tablespoons, 1–2 times a day
• Slowly build to the full dose over a two-week period (start with a low dose, pay attention to symptoms, and increase as able)
• Take the supplement with a full glass of water
• Take on an empty stomach or with food

Fiber #1—General Fiber for All-Around Support

Biota-Fiber contains 3 grams of soluble fiber and 1 gram of insoluble fiber derived from natural sources (mostly fruits and vegetables). I have found this fiber works best for a variety of conditions, so it’s the first fiber to try.

If Biota-Fiber isn’t tolerated, move on to the next option.

Fiber #2—Low Fermentability and Low FODMAP, Mostly Soluble

For people who experience gas or bloating easily, or if they’re very FODMAP sensitive, consider trying:

• Heather’s Tummy Fiber, a natural fiber made from acacia that contains only low FODMAP soluble fiber.
• Citrucel, a synthetic fiber that contains only non-fermentable soluble fiber. It comes in both powder and pill form. Citrucel powder does contain artificial sweeteners; the capsules do not. 

Fiber #3—Low Fermentability and Low FODMAP, Partially Soluble

The final fiber supplement worth trying, should the others not work, is psyllium. 

Psyllium husk has a 2:1 ratio of soluble to insoluble fiber. It’s important to look for psyllium products with only psyllium, like Metamucil. Avoid fiber blends.

Psyllium is a functional fiber that‘s been shown to lower cholesterol levels, lower blood sugar levels, and relieve constipation and diarrhea 3 4 5. 

Psyllium husk may have a wider range of positive benefits for cholesterol, blood glucose, and stool regularity than other well-researched fiber supplements with health benefits (such as large-particle wheat bran, guar gum, and beta-glucan from oats) 3.

In contrast, some types of fiber supplements, including wheat dextrin (Benefiber), inulin (usually from chicory), and methylcellulose (Citrucel), have not shown any of these benefits 3.

That said, the health benefits of eating fiber-rich foods far outweigh those of simply taking a dose of Metamucil. In fact, some studies show very little clinical benefit of taking fiber supplements when compared to a high-fiber diet 4 6 7.

What Time of Day Should You Take Fiber Supplements?

If you’re wondering if you should add fiber in the morning or at night, you get to choose! It doesn’t matter what time of day you take fiber supplements.

How Much Fiber You Need

Fiber is a type of indigestible carbohydrate found in plant foods. When we eat fibrous foods, our gut bacteria digest and assimilate these fibers. We benefit from this process more when the fiber comes from foods rather than supplements 3.

Roughly 95% of Americans fail to eat the recommended amount of fiber each day, which, according to the Institute of Medicine, is 8:

• Men: 30–38 grams of fiber per day
• Women: 21–26 grams of fiber per day
• Children: 19–25 grams of fiber per day

When consumed in adequate or higher amounts, dietary fiber may be associated with a reduced risk of 8 9 10:

• Stroke
• Heart attack
• Heart disease
• High blood pressure
• Colorectal, gastric, and breast cancers
• Obesity
• Depression
• Metabolic dysfunction, including prediabetes and Type 2 diabetes
• Gastrointestinal disorders such as hemorrhoids and diverticular disease

Some researchers believe adults should consume 50 grams of dietary fiber each day for longer lifespans, better quality of life, and lower healthcare costs 11.

That being said, dietary guidelines around how much fiber is too much aren‘t consistent across individuals. 

Health status (especially gut health) greatly determines how much fiber can be tolerated in a meal or in a day. So, there’s no need to force yourself to reach 50 grams of fiber a day if it doesn’t work for your body.

As you can see, a wide swath of healthy foods contain fiber. But if you’re in a position that prevents you from eating enough of them, functional (supplemental) fiber may be a decent substitute in the short term. 

When to Avoid Fiber Supplements

Fiber supplements may seem like an obvious, simple solution. And for many people, fiber supplements are generally safe with few side effects. But it’s possible to experience mild disturbances such as 1 12 13:

• Diarrhea
• Constipation
• Nausea and vomiting
• Difficulty swallowing
• Back pain
• Fatigue
• Flatulence
• Heartburn
• Pelvic pain
• Joint pain
• Bloating
• Feeling too full

Preparing the gut to handle more fiber with the foundational strategies I shared earlier can mitigate some of these effects.

While supplemental fiber is generally safe, there are certain groups who may want to avoid taking fiber supplements altogether, including 14:

● Malnourished or ill people

● Very young or very old people

● People with impacted bowels

● People who take fiber supplements for constipation, but end up with diarrhea

Fiber Supplements for Specialized Diets

Special diets geared toward addressing gut challenges like SIBO (small intestinal bacterial overgrowth), IBS (irritable bowel syndrome), IBD (inflammatory bowel disease), or diverticulitis tend to restrict carbs (i.e., fiber sources) and focus on proteins and fats. 

Some of these diets allow for adequate dietary fiber. But it’s easy to fall into a habit of not eating enough fiber when following these meal plans.

When to Take Fiber Supplements on the Ketogenic Diet

The ketogenic diet aims to replace most of the calories generally taken in from carbohydrates with calories from fat. As a result of this swap, people on a keto diet are likely to dramatically reduce their total intake of high-fiber foods.

While the keto diet has swept the internet with promises of dramatic weight loss and endless energy, research doesn’t support this way of eating in the long term, especially when it comes to digestive health.

A lack of high-fiber foods while on the keto diet may contribute to: 15 16 17:

• Reduced microbial diversity
• Increased the risk of leaky gut
• Reduced nutrient levels (of fiber, vitamins, minerals, and iron)
• Reduced short-chain fatty acid production

Without adequate dietary fiber intake, people following a keto diet may be at risk for gut health disturbances that are associated with poor immunity, inflammatory diseases, and a host of other systemic problems.

Getting adequate fiber from the diet is optimal 3 4 5. So, here’s a list of foods that can provide dietary fiber while on a ketogenic diet 18:

• Leafy greens (kale, chard, collards, spinach, bok choi, lettuce)
• Cauliflower
• Broccoli
• Brussels sprouts
• Asparagus
• Bell peppers
• Onions
• Garlic
• Mushrooms
• Cucumber
• Celery
• Summer squashes
• Berries 
• Avocado
• Nuts (macadamia, walnuts, almonds, pecans)
• Seeds (sunflower, pumpkin, sesame, hemp, flax)
• Firm tofu

Since the ketogenic diet is very high in fat and moderate in protein, it can be very satiating. If eating enough fiber is a struggle, then fiber supplements may be a helpful addition for diarrhea or constipation temporarily. 

When to Take Fiber Supplements on a Low FODMAP Diet 

A low FODMAP diet is designed to starve out bacteria living in the small intestine by limiting the fiber those bacteria like to eat. 

In doing so, people with digestive issues such as IBS and SIBO can significantly reduce gut inflammation, improve the balance of gut microbes, and give the digestive tract a chance to heal 19 20 21 22 23.

While getting fiber through your diet is the best course of action, research suggests people with IBS on a low FODMAP diet may benefit from psyllium, a type of soluble fiber 24.

Psyllium helps to regulate constipation and diarrhea and may even help the gut better handle other types of fiber, like prebiotics 25.

Research also shows supplemental soluble fiber, especially psyllium, can improve global IBS symptoms 14 26 27 28. But, it may be best used as a temporary measure until dietary fiber can be increased to an adequate level 25.

The following table provides a list of some high-fiber, low-FODMAP-friendly foods 29:

When to Take Fiber Supplements on the Specific Carbohydrate Diet

The specific carbohydrate diet (SCD) was designed to help people with celiac disease avoid gluten and other irritants found in cereal grains and other hard-to-digest fibers found in starchy vegetables and fructooligosaccharides (prebiotic plant sugar).

But this diet is also used for people with inflammatory bowel diseases (IBD), including microscopic colitis, Crohn’s disease, and ulcerative colitis.

Even though grains, starchy vegetables, and added fructooligosaccharides are restricted, the SCD includes many good sources of dietary fiber, such as:

• Certain legumes (navy beans, lima beans, lentils, raw peanuts, peas, and split peas)
• Raw cashews
• Raw peanut butter with no additives
• Most fresh, frozen, raw, or cooked veggies (but not starchy tubers, like potatoes, sweet potatoes, or turnips)
• Fresh, raw, frozen, cooked, or dried fruits with no added sugar
• Most nuts and nut flours

If it’s not possible to obtain adequate amounts of dietary fiber, then supplemental dietary fiber may be helpful in the short term on the SCD 24.

When To Take a Break From Fiber

I want to reiterate that therapeutic diets are meant to be a temporary solution. They’re designed to address a specific issue that may require a short-term reduction in dietary fiber intake 30. And they’re best guided by a healthcare professional such as a registered dietitian.

Reducing fiber intake takes the pressure off of the gut, similar to how avoiding activity helps heal a sprained ankle. We rest to allow the ankle to heal, and then start slowly adding activity until we’re back to normal.

The same applies to fiber—we rest the gut with a therapeutic diet, as it heals we slowly add back restricted foods (including fibrous ones) until we can tolerate an overall healthy diet with adequate fiber 7.

A fiber supplement may be a good temporary solution if following one of these diets causes diarrhea or constipation. 

Food First, But Supplement When Needed

Fiber supplements can be a helpful addition but they have the potential to tax the digestive system unnecessarily if not used strategically. 

We prefer to help our clients create a healthy foundation with diet, lifestyle, and probiotics before adding supplemental fiber.

If fiber supplements are needed, we recommend starting with Biota-Fiber first, slowly working toward the goal of 1–2 tablespoons one to two times per day, and drinking plenty of water.

Navigating digestive challenges can be stressful and time-consuming. But we’re here to help—contact us at the Ruscio Institute for Functional Health to schedule an appointment.

The Ruscio Institute has developed a range of high-quality formulations to help our clients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you. The information on DrRuscio.com is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment.