Probiotics vs. fiber: What’s the difference?

In an era where everyone is taking the plunge into wellness and personal well-being, two hot topics have been dominating the health discussions: probiotics vs fiber. Providing distinct nutritional and health benefits, these two dietary substances — available widely in many natural foods, but also in supplement form — are often favored in the path towards establishing a more well-rounded diet. 

Both probiotics and fiber play roles in improving the composition of your gut by increasing the diversity and quality of its microbiota. Fiber is of the utmost importance because it not only feeds your already naturally-present “good bacteria,” but in the process it enhances nutrient uptake, lowers bad cholesterol, reduces risk of colon cancer, boosts the immune system, and improves digestive and metabolic health, among other health benefits. Probiotics help certain individuals find symptom relief from the discomfort of specific gastrointestinal disorders, and they can also ameliorate certain allergies and various infections; however, the potential for probiotics to provide benefits to healthy people and help prevent disease and disorders is still an ongoing area of research. Most clinicians recommend that the majority of us would benefit most from combining prebiotics (the type of fiber associated with the most health benefits) with probiotics at most meals. (Learn more: Can you take prebiotics and probiotics together?) 

What are probiotics?

Probiotics are essentially live bacteria and yeasts that confer certain health benefits, especially for the digestive system. While most people assume (and not incorrectly) that bacteria can cause diseases, your body is actually full of both beneficial as well as bad bacteria. Probiotics are considered the "good" or the "friendly" bacteria because they help keep your gut healthy.

These beneficial microorganisms can be found in various food sources such as yogurt, kefir, sauerkraut, and other fermented foods. Or, various probiotic strains can be obtained in dietary supplement forms. They work by balancing the natural gut flora, which in turn supports digestion and boosts the immune system. 

Probiotics can help alleviate symptoms of certain gastrointestinal (GI) conditions, such as irritable bowel syndrome (IBS). Research has also shown that probiotics may have a positive impact on mental health, although much remains to be studied in this realm. The gut-brain axis, a bidirectional communication system between the gut and the brain, is influenced by the gut microbiota. By maintaining a healthy balance of bacteria in the gut, probiotics can potentially improve mood and reduce symptoms of anxiety and depression.

How probiotics work

Probiotics work by balancing the good and the bad bacteria in your body. Having the correct balance of bacteria can help keep your body functioning optimally. When you consume probiotics, they travel through your digestive system and reach your gut. Once there, they adhere to the lining of your intestines, forming a protective barrier. This barrier helps prevent harmful bacteria from attaching to your intestinal walls and causing infections. Furthermore, probiotics produce antimicrobial substances that can inhibit the growth of pathogens, such as harmful bacteria and viruses. By doing so, they help maintain a healthy gut environment and support your immune system's ability to fight off infections.

In addition to their role in balancing gut bacteria and supporting immune function, probiotics also play a crucial role in digestion. They help break down food and extract nutrients, making them more easily absorbable by your body. This can enhance your overall nutrient absorption and contribute to better overall health.

Health benefits of probiotics

Probiotics boast a range of health benefits. Let's explore some of these benefits in more detail.

Managing irritable bowel syndrome (IBS): Studies have shown that certain strains of probiotics can help alleviate symptoms of IBS, such as bloating, abdominal pain, and irregular bowel movements. They work by restoring the balance of gut bacteria and reducing inflammation in the digestive tract. (However, as we detail in our report, Can probiotics cause gas?, certain individuals may find that probiotics — at least when initially introduced into the diet — are associated with the very side effects they seem to relieve in other individuals. Then again, so can fiber initially cause GI distress when consumption is suddenly increased.) 

Benefits of probiotics for those with inflammatory bowel disease (IBD), a group of disorders including Crohn’s disease (CD) and ulcerative colitis (UC), are still debatable. A 2021 systematic analysis of the efficacy of probiotics in CD and UC found that probiotics can induce remission during the active period of UC, but have no obvious therapeutic advantage in maintaining CD and UC remission. Similarly, a 2022 review opines that while probiotics (and other dietary changes) have not been shown to have enough effects on their own to be used as sole treatment for IBD, these strategies were found helpful in supplementation to medical treatment, mainly to improve a patient’s quality of life.

Improving skin conditions: The health of your gut and skin are closely linked. Probiotics can help improve various skin conditions, including acne, eczema, and rosacea. They do this by reducing inflammation, strengthening the skin's barrier function, and inhibiting the growth of harmful bacteria on the skin's surface.

Boosting immune function: Probiotics support immune function by maintaining a healthy gut environment and inhibiting the growth of pathogens. By doing so, they help strengthen your immune system's ability to defend against infections and diseases.

While the research on other areas is still young, the intake of probiotic-rich foods and supplements is linked to therapeutic support for:

• Insulin resistance and improved glucose control, suggesting the potential for reducing risks for (and better managing) type 2 diabetes.
  
  
• Blood lipid management: Certain probiotic strains have been linked to a notable reduction in triglyceride levels in individuals with mild to moderately elevated levels, suggesting the potential for reduced risks for cardiovascular diseases.
  
  
• Stress management: The gut-brain connection is a fascinating area of research, and probiotics appear to play a role in this connection. Studies have shown that certain probiotics can help reduce symptoms of anxiety and depression, improve mood, and enhance overall mental well-being. This is believed to be due to the communication between the gut and the brain through the gut-brain axis.

Potential side effects of probiotics

While probiotics are generally safe for most people, they can cause side effects, primarily digestive ones like gas, bloating, and diarrhea. Most of these are mild and go away as your body adjusts. Certain individuals with serious illnesses or compromised immune systems should avoid probiotics or take them under medical guidance.

Remember that food tolerance is highly individualized. Since most natural fermented (and probiotic) foods contain more than just probiotics, it may well be other ingredients in the particular foods (e.g., gluten, lactose, sugar alcohols) that are causing GI distress, and not the probiotics. It’s important to work with your medical provider or nutritionist and to aim for assessing which foods work best for you. 

Best sources of probiotics

As mentioned previously, natural food sources of probiotics include the following fermented foods easily found in supermarkets:

• Yogurt
• Kimchi (fermented Korean vegetables)
• Kombucha
• Kefir
• Sauerkraut
• Miso
• Tempeh
• Apple cider vinegar
• Certain unpasteurized cheeses
• Non-heated salami, pepperoni
• Cottage cheese (not all brands, so look for those that state “fermented with live active cultures”)

Some of the above listed foods, such as kefir, have been well-studied for their role in GI health — but further investigation is warranted for most of the foods on the list. Of those fermented foods that are also considered dairy foods (such as yogurt and cheese), a 2022 JAMA systematic review of 28 meta-analyses concluded that the only dairy product associated with protective abilities against diabetes is yogurt. 

Bear in mind, too, that certain fermented foods contain both probiotics and fiber, which may contribute to their potential to increase gut microbiome diversity, potentially upping positive downstream health benefits.

If you are not a fan of fermented foods (or they don’t agree with you), but you still want to safely support the health of your gut microbiome, there are a bevy of different probiotic supplements sold in supermarkets and pharmacies. However, before trying a supplement, speak to your medical professional; supplements containing probiotics may not be suitable for those with compromised immune systems, certain medical conditions, or those undergoing specific medical treatments. Furthermore, the functional benefits differ amongst probiotic species, and many clinicians caution that further research is necessary to determine which strains and at what dose will provide specific benefits to most individuals. If you are a good candidate for dietary supplementation, be an informed consumer and utilize resources available to you when shopping for the supplement that’s best for you: See our 3-Step guide: How to buy supplements. Dietary supplements are not regulated by the Food & Drug Administration (FDA), so it’s important to find a supplement from a reputable brand backed by scientific rigor. 

Eden’s Synbiotic Superblend contains both probiotics and prebiotic fibers, along with several polyphenols that were carefully selected by Eden’s team of physicians and scientists — and the supplement has been proven to be very well-tolerated. This unique combination has been formulated to promote metabolic, cardiovascular, immune, and gut health. 

3-in-1 Synbiotic Superblend

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What is fiber?

Defined simply, fibers are those carbohydrates that the body can't digest. But there are different kinds of fiber, and frankly the ways that fiber can be categorized do not always correlate well with their health benefits. Traditionally, dietary fiber has been classified according to its solubility:

• Soluble fiber (found in foods such as oats, fruits, and legumes) dissolves in water and forms a gel-like substance in the digestive tract. This gel-like substance helps slow down digestion, allowing for better nutrient absorption. Soluble fibers can also be more easily accessed and metabolized by fiber-degrading microorganisms in the intestine and produce a series of beneficial and functional metabolites, in which case they are “prebiotic” fibers (see discussion below).
  

• Insoluble fiber (found in foods like whole grains, nuts, and vegetables), on the other hand, does not dissolve in water and adds bulk to the stool. Insoluble fiber helps prevent constipation by promoting regular bowel movements and maintaining healthy gut transit time. Most insoluble fibers are not (or are just slowly) utilized by gut bacteria, and yet some may have certain prebiotic properties.

While the above division of soluble and insoluble fiber is still used in nutrition labeling, recent scientific research into the health benefits of various types of fiber draws into question the utility of this categorization split. It is of perhaps of much greater importance to distinguish which fibers are “prebiotic”: If a fiber gets fermented in the colon and then promotes specific changes in the composition and/or activity of your GI microflora, conferring benefits, that’s a prebiotic fiber. 

Put simply, prebiotics improve the gut microbiome by “feeding” the beneficial bacteria or microorganisms that reside there. Some of the most important end-products of prebiotics, which result from feeding the beneficial bacteria in your gut, are short-chain fatty acids (SCFAs) — including lactic acid, butyric acid, and propionic acid. SCFAs have wide-ranging beneficial impacts on host physiology, from helping to maintain gut and immune health to aiding in preventing certain diseases. 

While it’s true that most prebiotics are also soluble, not all soluble fibers confer the same benefits: for example, some confer cholesterol-lowering benefits, while some do not. Some soluble fibers aid in glucose balance, while others do not. By the same token, the effect of insoluble fiber on stool weight is highly variable; and, in fact, some partly soluble fiber foods (such as oat bran) may still enlarge stool weight. In addition, some insoluble fibers may well be fermented, too — and so have prebiotic characteristics! 

Bear in mind also that there are many foods which contain both soluble and insoluble fibers. Furthermore, many foods that are high in fiber (like whole grains, vegetables, fruits, and legumes) contain more than just fiber! In some foods, it may be these co-passengers with fiber that provide the protective health properties of fiber, rather than the fiber itself. Also, additional properties of fiber, such as viscosity, affect the physiological benefits. (Viscous fibers are those that have gel-forming properties in the intestinal tract.) While soluble fibers typically have a higher viscosity than insoluble fibers, not all soluble fibers are viscous.

Health benefits of fiber

Summing up the major health benefits of fibers, and especially prebiotic fibers, they:

• Support gastrointestinal (GI) health by protecting the lining of intestinal walls and preventing chronic inflammation caused by the contamination of particles across gut walls or lining
  
  
• Improve digestive health and certain gut conditions (such as IBS) by promoting regularity while improving the quality of stool and reducing the body’s digestive transit time
  
  
• Improve blood glucose control and encourage better insulin response, lowering risks of developing type 2 diabetes (and helping to better manage the disorder)
  
  
• Play a role in reducing risks for colorectal cancer
  
  
• Support brain health through an upregulating effect on general cognition, learning, and mood
  
  
• Modulate energy metabolism and satiety
  
  
• Strengthen bone health and density by improving mineral absorption including calcium
  
  
• Support heart health by defending gut health and downregulating cholesterol and triglyceride levels

Fiber has another trick up its sleeve: consuming fiber may contribute to weight loss. Especially when you eat foods rich in soluble fiber, like oats or beans, they form a gel-like substance in your stomach. This gel slows down the digestion process, making you feel full quicker and keeping you satisfied for a more extended period. As a result, you're less likely to indulge in unnecessary snacking and consume fewer calories overall.

Potential side effects of fiber

Fiber ultimately helps better regulate your digestion; and yet, for some individuals, especially if they up their intake of fiber dramatically in a short period of time, just the opposite (GI distress) may occur. Experts agree that fiber alone may not be enough for regular bowel movements, especially in those who are already constipated. In fact, for some who suffer from IBS or IBD, clinicians may resort to prescribing a “low-FODMAP” diet, which is one that selectively restricts certain high-fiber foods that may be GI irritants when consumed in high quantities for particular individuals. Examples of FODMAPS (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) include beans and legumes, simple sugars, artificial sweeteners, and garlic and onions; see a more comprehensive list in our report, How to manage your IBS symptoms. 

As we iterated with probiotics, food tolerance is highly individualized. Since most natural foods contain more than just fiber, it may well be other ingredients in the particular foods (e.g., gluten or lactose) that are causing GI distress, and not the fiber. It’s important to work with your medical provider or nutritionist and to aim for assessing which foods work best for you. 

Best sources and recommended daily amounts of fiber

The USDA 2020-2025 Dietary Guidelines for Americans and the American Diabetes Association recommend 14g of dietary fiber for every 1,000 calories per day, which is typically between 30-40 grams of fiber per day. (Learn how the amounts vary by gender and age in our report, How much fiber do you need in a day?) Unfortunately, more than 90% of women and 97% of men fall short of the recommended intakes for dietary fiber. 

Because nutrition labels fail to break out the various types of dietary fiber (e.g., soluble vs. insoluble, fermentable or non-fermentable), eating an extensive variety of high-fiber foods (such as fruits, vegetables, whole grains, and nuts and seeds) is the best way to capture as many sources of necessary fibers as possible.

Prebiotic fibers are found in many vegetables, fruits, and whole grains, including:

• Grains: Oats, wheat bran, barley
• Vegetables: Jerusalem artichokes, garlic, asparagus, leeks, onions, chicory, dandelion greens, burdock root, jicama, mushrooms, seaweed, beets, broccoli, Brussels sprouts, fennel, kale
• Fruits: Bananas, blueberries, citrus, apples, pears, nectarines, watermelon, cherries, grapes, raspberries, avocados, kiwi
• Legumes/nuts/seeds: soybeans, chickpeas, lentils, flaxseeds, kidney beans, almonds, pistachios

If you’re concerned about not getting enough fiber in through your diet, consider a supplement. Eden’s Synbiotic Superblend contains 8g of fiber per serving — a high percentage of your recommended daily intake. Eden’s five carefully selected fibers provide a precise ratio of soluble and insoluble fibers in order to optimally fuel the growth of specific gut bacteria responsible for increasing the production of beneficial secondary metabolites. In addition, Eden’s contains four probiotics and five polyphenols. The overall blend of ingredients in Eden’s has been formulated to give your good gut microbes everything they need to thrive.

The similarities between probiotics and fiber

While probiotics and fiber are completely different substances, and work in different ways, both contribute to a healthier digestive system and a healthier gut microbiome for most individuals. (With either, however, certain individuals may experience unpleasant side effects — such as bloating, gas, even constipation or diarrhea — especially when first increasing their consumption of either or both food or supplement types.) They also both contribute to weight management, heart health, metabolic health, immune health, and mental health. 

Probiotics vs. fiber: What's the difference?

While they both directly impact the digestive system and the gut microbiome, and contribute to some of the same “downstream effects” (relief from gastrointestinal distress symptoms, mitigation of blood glucose swings, modification of bad cholesterol levels, immune system enhancements, mood and cognition elevation), the properties and mechanisms of actions of probiotics are completely different from those of fibers. Probiotics are friendly bacteria that work by crowding out the bad bacteria so that the latter can’t produce as many of the endotoxins associated with chronic inflammation and disruptions to barrier integrity. Good gut bacteria, on the other hand, produce health-promoting compounds. Fibers are nondigestible carbohydrates, some of which “feed” those good probiotic bacteria in your gut. Other types of fiber add bulk to your stool, which can help relieve constipation and make bowel movements more regular.

Which is better for your health?

If you could only choose either fiber or probiotics in your diet, the importance of fiber is overwhelming. Fiber feeds “the good bacteria” that is already in your gut, such as bifidobacteria and lactobacilli. By promoting the growth and activity of those beneficial microorganisms, prebiotic fibers help to create a balanced and diverse microbiome, which is crucial for a healthy digestive system. In turn, the abundant good bacteria produce metabolites, including short chain fatty acids (SCFAs,) which play a vital role in the maintenance of gut, metabolic, cardiovascular, immune, and cognitive health. 

While probiotics also play a role in restoring microbial balance and maintaining a healthy bacterial population, many scientists and clinicians argue that if you’re healthy, probiotics may not improve your health status or significantly reduce your risks for major chronic disorders. However, as an “adjunct therapy” to provide relief from certain existing gastrointestinal disorders, infections and other ailments, probiotics do have demonstrated efficacy for certain populations. Further research may clarify potential downstream benefits in such areas as cardiovascular and metabolic health.

But why choose between them, when most health professionals agree that a balanced diet including both probiotics and fiber is a key to a healthy digestive system? The best decision would appear to be adherence to a diet that integrates both of them, rather than choosing one over the other: the Mediterranean, MIND and DASH diets are the three most recommended diets for overall health, and it’s no surprise that both fiber and probiotics are important food sources in all three of these diets.