The Fiber That Feeds Us - What You Don't See

What is fiber — and why it's different from everything else

Dietary fiber is the fraction of plant-based carbohydrates that our digestive system cannot digest. Unlike proteins, fats, and simple sugars, fiber reaches the large intestine virtually intact. That's where the real work begins.

There are two main types: soluble fiber (which dissolves in water and forms a gel — found in oats, legumes, fruit) and insoluble fiber (which does not dissolve and speeds up intestinal transit — found in whole grains, vegetables, seeds). The ideal? Consume both types regularly.

Did you know? The EFSA (European Food Safety Authority) recommendation is at least 25 g of fiber per day for adults. Most Europeans consume less than 20 g.

Your gut will thank you — and return the favor

When we eat fiber, we are literally feeding our microbiome — the billions of bacteria that live in the gut and regulate everything from immunity to mood. Beneficial bacteria ferment fiber and produce short-chain fatty acids (SCFAs), such as butyrate, propionate, and acetate.

These compounds have anti-inflammatory properties, strengthen the intestinal barrier, and regulate immune responses. A randomized controlled study published in Microorganisms (2025) showed that those who consumed more fermentable fiber for 4 weeks had significant improvements in intestinal well-being and an increase in beneficial bacterial genera such as Bifidobacterium and Anaerostipes.

A fiber-poor diet reduces microbiome diversity — and this loss has been associated with obesity, diabetes, cardiovascular disease, and chronic inflammatory diseases.

The numbers science can't ignore

A review published in Clinical Nutrition (2025), which analyzed 33 meta-analyses covering over 17 million people, found convincing evidence that higher fiber intake is inversely associated with mortality from cardiovascular disease, pancreatic cancer, and diverticular disease.

• −13% in the risk of all-cause mortality
• −13% in the risk of cardiovascular mortality
• 76% of meta-analyses confirm inverse association with chronic diseases

A meta-analysis in Frontiers in Nutrition (2023), with 2.6 million participants, confirmed a linear relationship between fiber intake and reduced cardiovascular mortality. The protective effect remains stable above 15 g/day and increases from 25–29 g/day.

Diabetes, cholesterol, and weight — the fiber that balances everything

Soluble fiber slows down the absorption of sugar into the bloodstream — which stabilizes blood sugar and reduces insulin spikes after meals. A systematic review in PLOS Medicine demonstrated that higher fiber intake in people with pre-diabetes or diabetes is associated with lower cardiovascular mortality and better glycemic control (HbA1c).

Regarding cholesterol, soluble fiber binds to bile acids in the intestine and promotes their excretion, leading the liver to use circulating cholesterol to produce more bile acids — which results in reduced LDL. And when it comes to weight, a study from the POUNDS Lost program (J. Nutr., 2019) showed that fiber intake was the best predictor of weight loss and dietary adherence in adults on calorie-restricted diets.

Where does all this fiber come from?

The good news: fiber is everywhere — as long as you're not eating ultra-processed foods. The best natural sources are:

• Whole oats
• Legumes (lentils, chickpeas, beans)
• Nuts and chia seeds
• Fruit with skin (apple, pear, berries)
• Broccoli, cabbage, and carrots
• Figs and dates
• Rye bread and whole grains
• Peanuts and sweet potatoes

The trick is not to eat a "superfood" — it's to diversify. The more varied the fiber source, the more diverse (and healthy) your gut microbiome will be.

How to increase consumption without complicating your life

It's not necessary to turn your diet upside down. Small adjustments make a real difference:

Breakfast: Swap refined cereals for oatmeal or granola with real ingredients. You start the day with 5–8g of fiber at once — and you won't be hungry by mid-morning. CORIAL Protein Oatmeal is made with whole oats, rich in beta-glucan (the soluble fiber in oats), protein, and no added sugar — the breakfast that truly sustains you. CORIAL Gut Granola is another excellent option: just add to yogurt or eat by the spoon.

Lunch and dinner: Always add a portion of legumes or vegetables. A serving of lentils has about 8g of fiber — and fits into any dish.

Snack: This is where most people fail. CORIAL Gut Granola was specifically formulated for gut health, with ingredients that feed the microbiome. A high-fiber snack makes the difference between 15g and 25g/day — without resorting to ultra-processed foods.

Hydration: Fiber needs water to work. Increasing fiber intake without increasing fluid intake can cause intestinal discomfort. Drink at least 1.5–2L per day.

At CORIAL, fiber is not an extra — it's a principle

Our products are formulated with real ingredients — oats, figs, dates, peanuts, seeds — because we believe that functional nutrition doesn't have to come in capsules. Zero pills. Zero complications. Just food that works.

• CORIAL Protein Oatmeal — whole oats as a base, rich in soluble beta-glucan fiber, protein, and no added sugar.
• CORIAL Gut Granola — formulated for gut health, with ingredients that feed the microbiome and provide the fiber your gut needs to function well.

Scientific references

1. Yao F. et al. (2023). "Dietary intake of total vegetable, fruit, cereal, soluble and insoluble fiber and risk of all-cause, cardiovascular, and cancer mortality." Frontiers in Nutrition, 10:1153165. doi: 10.3389/fnut.2023.1153165
2. Veronese N. et al. (2025). "The impact of dietary fiber consumption on human health: An umbrella review of evidence from 17,155,277 individuals." Clinical Nutrition. doi: 10.1016/j.clnu.2025.06.021
3. Feng J. et al. (2023). "Dietary Fiber Intake and Gut Microbiota in Human Health." Nutrients, 15(5), 1154. doi: 10.3390/microorganisms10122507
4. Bacha AA et al. (2024). "Role of dietary fiber and lifestyle modification in gut health and sleep quality." Frontiers in Nutrition, 11:1324793. doi: 10.3389/fnut.2024.1324793
5. Miyazaki M. et al. (2025). "Effects of Dietary Fiber Supplementation on Gut Microbiota and Bowel Function in Healthy Adults: A Randomized Controlled Trial." Microorganisms, 13(9):2068. doi: 10.3390/microorganisms13092068
6. Reynolds A. et al. (2020). "Dietary fibre and whole grains in diabetes management: Systematic review and meta-analyses." PLOS Medicine. doi: 10.1371/journal.pmed.1003053
7. Al-Mssallem M. (2024). "Dietary fiber influence on overall health, with an emphasis on CVD, diabetes, obesity, colon cancer, and inflammation." Frontiers in Nutrition, 11:1510564. doi: 10.3389/fnut.2024.1324793
8. Miketinas D.C. et al. (2019). "Fiber intake predicts weight loss and dietary adherence in adults consuming calorie-restricted diets: The POUNDS Lost study." Journal of Nutrition, 149(10), 1742–1748.