When it comes to nutrition, few topics are as foundational (and as overlooked) as fiber. While it’s long been associated with digestive regularity, fiber does much more than keep things moving. It plays a central role in gut health, immune function, and even metabolic balance.
But not all dietary fiber is created equal. There are two main types—soluble and insoluble—and both offer unique benefits. Understanding their differences (and how to get enough of each) is a simple but powerful step toward better health, especially when paired with targeted gut and immune support.
What Is Fiber, Really?
Dietary fiber is a type of carbohydrate found in plant-based foods that the body can’t digest. Unlike other carbs that are broken down into sugar, fiber passes through the digestive tract mostly intact.
Fiber doesn’t just passively move through the system, though—it actively supports health along the way. From feeding beneficial gut bacteria to promoting smooth digestion and even helping regulate immune responses, fiber is one of the most versatile tools in your wellness toolkit.
Soluble Fiber: The Gel-Former
Soluble fiber dissolves in water to form a viscous, gel-like substance, slowing digestion. This slowing of digestive processes can help with blood sugar regulation, cholesterol reduction, and satiety (feeling full).
In the gut, soluble fiber acts as a prebiotic, feeding beneficial bacteria that live in your gut.
Common sources of soluble fiber include:
· Whole grains like oats and barley
· Fruits like apples, bananas, citrus fruits, and pears
· Legumes like beans, lentils, and peas
· Nuts and seeds like chia seeds, almonds, and flaxseeds
· Vegetables like broccoli, carrots, and sweet potatoes
· Psyllium, a common fiber supplement
Insoluble Fiber: The Broom of the Gut
Insoluble fiber, on the other hand, does not dissolve in water. Instead, it adds bulk to the stool and helps food pass more efficiently through the digestive system. This is the kind of fiber most associated with regularity and colon health.
Insoluble fiber also plays a mechanical role in keeping the digestive tract clean, potentially reducing the risk of constipation, diverticulitis, and other gut-related discomforts.
Common sources of insoluble fiber include:
· Whole grains like whole wheat flour, wheat bran, barley, brown rice, and whole wheat pasta
· Nuts and seeds like almonds, walnuts, sunflower seeds, and flaxseeds
· Vegetables like green beans, cauliflower, potatoes, and leafy greens
· Legumes like beans and lentils
· Fruits with edible skins, such as apples and pears
Why You Need Both
Your digestive system thrives when it has a balanced intake of both soluble and insoluble fiber. Both types offer different benefits that work in tandem with each other for optimal health and well-being.
Soluble fiber feeds the gut microbiome and helps regulate internal processes like inflammation, cholesterol metabolism, and blood sugar regulation. Insoluble fiber supports mechanical digestion and overall motility, helping to prevent constipation by keeping waste moving efficiently. Together, they support a healthy, diverse gut microbiome—something science increasingly recognizes as a cornerstone of long-term wellness. In fact, a large-scale analysis of almost 250 studies has confirmed that a high-fiber diet can decrease your risk of dying due to heart disease, stroke, type 2 diabetes, and colorectal cancer.
Since most high-fiber plant foods contain both soluble and insoluble fiber, you can ensure you get enough of both types by having a varied diet of fruits, vegetables, and whole grains.
Fiber, the Gut, and Immune Health
It’s estimated that 70%–80% of the immune system resides in the gut. So, it makes sense that what we eat significantly impacts how well our immune system functions.
When gut bacteria ferment soluble fiber, they create short-chain fatty acids like butyrate, propionate, and acetate. These important compounds:
· Strengthen the gut barrier, preventing “leaky gut,” a condition in which harmful toxins or bacteria from the gut enter your bloodstream, causing widespread inflammation and other issues
· Regulate the activity of many different types of immune cells
· Reduce systemic inflammation, in turn reducing the risk of chronic disease
A balanced fiber intake, then, does more than support digestion—it actively contributes to a more resilient, balanced immune system.
Getting Enough: Daily Fiber Recommendations
The recommended daily intake of fiber for adults is approximately:
· 25 grams for women
· 38 grams for men
Most people only get about half of that. One way to close the gap is to make a conscious effort to include fiber-rich foods at every meal—and to aim for a mix of soluble and insoluble sources.
Tips to increase fiber:
· Start your day with oatmeal topped with berries and flaxseed
· Swap white rice for quinoa or brown rice
· Add a handful of beans to salads or soups
· Snack on raw veggies, nuts, or air-popped popcorn
· Leave the skin on fruits and vegetables when possible
When increasing fiber, do so gradually—and drink plenty of water to help it move smoothly through your system.
When Fiber Needs a Boost
While fiber is foundational, there are times when the gut needs extra support—especially during times of stress, immune challenge, or gut imbalance.
This is where a metabiotic supplement can complement your fiber intake. Metabiotics are non-living bacterial cell fragments that help regulate immune activity and support gut resilience—without the need for live probiotics.
Stellar Biotics’ del-IMMUNE V®, for instance, is a metabiotic derived from probiotic bacteria Lactobacillus rhamnosus that has been shown to regulate immune responses and support gut balance. It works in tandem with a high-fiber diet to promote a robust gut ecosystem. And because it acts quickly and doesn’t require refrigeration, del-IMMUNE V® is a simple, all-natural, science-backed addition to a gut-supportive lifestyle.
In Summary: Fiber First, Always
Fiber may not be the flashiest nutrient, but it’s one of the most important—especially for gut, immune, and overall health. Check out our other blog posts to better understand how your gut health affects your cognitive and mental well-being, cardiovascular health, and immune system.
By incorporating various foods with soluble and insoluble fibers into your daily meals, you’re giving your body the tools it needs to thrive. And when paired with targeted, evidence-based support like del-IMMUNE V®, you can further strengthen your gut health—and, in turn, your entire being.
