On social media, it's called fibermaxxing, or fibermaxxing, and it involves maximizing your daily fiber intake. Meanwhile, the word fiber has popped up everywhere on supermarket shelves: bread, bars, high-fiber yogurt. But when people ask why fiber is good for them, the answer almost always stops at the same point: it helps the intestines.
It's a real answer, and it's far below what fiber does for the body. In the first episode of "Feed the mind", the podcast of the Faculty of Science and Biotechnology of theUniversità Campus Bio-Medico di Roma, Chiara Spiezia, a nutritional biologist who graduated here, proposed to tackle it in another way: "Let's try to look at it as a woman would look at it
scientist, or rather, how four female scientists would look at him."
The four are her; the prof Laura Dugo, professor of Food Chemistry and Nutrient Metabolism; Ilaria and Irene, from the team that won Ecotrophelia Italia with the Food Science, Technology, and Food Design course. Clinical nutrition, food chemistry, and food design: three skills that coexist in the same Faculty.
In summary:
- Dietary fiber is not a single substance: it is a family of molecules with different behaviors.
- The reference for an adult is about 25 grams per day, achievable with diet and without supplements.
- The fermentation of fiber produces butyrate, the fuel for the cells lining the intestine.
- Oat and barley beta-glucans help lower LDL cholesterol: EFSA has approved a claim regarding this effect.
- More fiber does not mean better: during weaning, growth, and in some clinical conditions, the amount should be personalized.
- Without water, fiber doesn't work.
What is dietary fiber?
Dietary fiber is a family of molecules, almost all carbohydrates, that the human body cannot digest. "Fiber is not a simple nutrient, but a family of molecules that we refer to as dietary fiber, composed of many molecules that are actually part of carbohydrates.", explains Laura Dugo, professor of Food Chemistry and Nutrient Metabolism at theUniversità Campus Bio-Medico di RomaWe can't digest them. "because some enzymes that are useful for breaking the bonds of these complex molecules are missing."
Fiber in the singular, therefore, is an imprecision. Cellulose, pectin, beta-glucans, inulin, and resistant starch have different chemical structures and behaviors: some of these, like inulin or resistant starch, interact with water and form a gel in the intestine and can be fermented by the bacteria that make up the gut microbiota. Others pass through the digestive tract mechanically, without being transformed. This is why the advice "eat more fiber" is half-baked: it also matters what type of fiber you eat, that is, how varied your diet is.
What is butyrate and what is it used for?
Butyrate is a short-chain fatty acid produced by intestinal bacteria when they ferment fiber, and it nourishes the cells lining the colon wall. Some of the fiber reaches the colon virtually intact, where it becomes food for the microbiota.
The next question in the episode is a straightforward one: what does butyrate do? Simply put, it's literally the fuel for the cells lining our intestines: it nourishes them, helps keep the intestinal barrier sealed, and keeps local inflammation at bay.
This is where the chain closes: those who eat fiber feed their own bacteria before themselves, and it is the bacteria that produce what the intestinal wall needs. This benefit is passed on through a living intermediary, and therefore sensitive to dietary variation. With a caveat that comes immediately afterward in the episode: not all fibers ferment. It is primarily the soluble ones that form gels and are fermented.
Does fiber lower blood sugar and cholesterol? How does it work?
Yes, and both effects arise from the same mechanism: the gel that soluble fiber forms in the intestine. This gel makes the intestinal contents more viscous and slows the absorption of carbohydrates and sugars. With the same amount of food, blood sugar rises gradually, with a lower peak, and the pancreas doesn't have to respond by producing large amounts of insulin all at once.
The path to cholesterol is longer, and it's worth pursuing to the end. The beta-glucans in oats and barley increase intestinal viscosity and promote the elimination of a portion of bile acids. To regenerate those bile acids, the body must consume cholesterol. Over time, this translates into lower LDL cholesterol levels.
The effect is documented to the point that the European Food Safety Authority, EFSA, as Dugo recalls, "it approved a claim relating to the efficacy of these molecules in stabilizing LDL cholesterol levels"This is one of the few cases where a health claim of this type can legitimately be included on a label.
How much fiber do you need per day?
The nutritional reference for an adult is about 25 grams of fiber per day, and this can be achieved through diet, without supplements. The number alone says little, and in fact Spiezia adds: "But what does this mean, without getting too hung up on the numerical value? Eating a balanced diet that includes at least five servings of fruits and vegetables, preferably whole grains, and legumes at least two or three times a week allows us to reach this amount."
No counting, and no powder to dissolve.
Can you overdo it with fiber? When fibermaxing becomes a problem.
Yes. Fiber doesn't work according to the "more, the better" logic, and in some stages of life and certain clinical conditions, the amount should be reduced or adjusted. This is the part that trends don't cover, and it's the one a nutritionist focuses on the most: customization.
During weaning, excess intake increases the child's feeling of satiety, which consequently reduces caloric intake precisely at the stage when they need it. In growing children, excess intake slows the absorption of micronutrients important for growth, such as calcium and iron. In clinical conditions such as irritable bowel syndrome, inflammatory bowel disease, or post-surgery, the amount should be adjusted on a case-by-case basis. The conclusion of Spiezia distinguishes two things that social media confuses: "Here too, the key is not to eliminate the amount of fiber from the diet, but to follow the advice of a nutritionist and personalize the intake."Reducing isn't eliminating, and personalizing isn't something you do alone.
Why you need to drink more with fiber
Because it's water that allows the fiber to form the gel: increasing fiber intake without drinking enough produces the opposite effect to the desired one. This is the practical condition that is most often forgotten, and that Dugo he would like to add: "fiber intake goes hand in hand with hydration."
Fiber as a material: the case of the EdlyQ edible straw
The same molecules that nourish the microbiota can serve as the building blocks for a food. So far, fiber on the plate. But in this episode, there's a second way to look at it, and it comes from two students. "We started with an object that no one ever looks at: the straw. You use it for two minutes and it becomes waste.", he says Irene. It's small, seemingly harmless, but it's one of the symbols of single-use. Plastic weighs heavily on the environment. Paper seems like the solution, until it wilts in your drink and ruins your drink. So we asked ourselves: what if you ate the straw instead of throwing it away?. He then continues: "From disposable to use and enjoy. It's called EdlyQ and it's an edible straw made with plant-based ingredients like rice cream, pea protein, and corn starch. And here we return to our theme because it contains fibers like inulin and resistant starch."
They are the same molecules we have been talking about so far, and here they do two jobs together. Dugo He specifies: inulin and resistant starch have not only a nutritional function but in this case also perform a technological function, because they give structure to the product and hold it together.
The straw must remain upright in the glass and resist the liquid without immediately melting, without altering the flavor of the drink, and still be tasty and crunchy to eat. The formula developed lasts about 25 minutes in cold drinks. This isn't just an aesthetic gimmick: it's food technology applied to an everyday gesture.
In terms of sustainability, the dyes are sourced from plant sources—turmeric, spinach, spirulina, purple carrot, and charcoal—and the process is zero-waste: waste from the production line is then reintroduced into other stages of the process. With this project, the team won the Ecotrophelia Italia final in May, and the next step is the European competition.
EdlyQ is a prototype developed within the Faculty as part of an industry competition, not a commercial product.
And above all, as Spiezia is keen to clarify immediately after the presentation, it is not a functional food in disguise: a straw certainly isn't a substitute for fruit, vegetables, whole grains, and legumes. The point of the project lies in what it demonstrates: fiber can be used in products designed to reduce waste, while remaining fiber in every respect.
Fibers carry polyphenols: the little-talked-about effect
Many phenolic compounds, the bioactive molecules in fruits, vegetables, and whole grains, travel attached to the fibrous part of the food, and the fiber transports them to the colon. It's a function that, says Dugo, "is actually very little discussed": "So the fiber carries these bioactive molecules into our body, which then perform important protective functions not only for our intestine but for the entire organism."This is why the benefit of a vegetable almost never coincides with a single nutrient that can be isolated and replicated in a tablet.
Is fiber only good for the intestines?
No: they act on the glycemic response, on cholesterol levels and on the microbiota, and through the microbiota they communicate with the entire organism. "For me they are much more", he replies Spiezia. "They are a real metabolic modulator, therefore they act on the glycemic response, positively impacting cholesterol levels." Bowel function is only part of what they do. Dugo adds the other half: the fiber "It's not just a molecule we receive in our diet on our plates, but as we've seen, it can be the ingredient of a technologically innovative product. Even a straw."
Nutrition, food chemistry, and food design approached the same topic from three different directions and converged on a hand-held object. Bringing these three fields together within a single Faculty is what makes science usable, and it's the essence of the University's self-declared motto: "The University of Science for Humanity."
FAQ
Are soluble fiber and insoluble fiber the same thing? No. Soluble fibers interact with water, forming a gel in the intestines, and are fermented by the microbiota. Insoluble fibers pass through the digestive tract while remaining mechanical. The effects on blood sugar and cholesterol levels depend primarily on the former.
Is it better to get fiber from foods or supplements? From food. The 25 grams per day reference is achieved with five servings of fruits and vegetables, preferably whole grains, and legumes 2-3 times a week, without the need for supplements.
Does FiberMaxxing Work? The principle of increasing fiber is correct for those who consume little, but the logic of maximum does not hold: the useful amount depends on age and health conditions, and in some situations an excess is counterproductive.
Who should limit or calibrate fibers? Children who are weaning and growing, and those living with irritable bowel syndrome, inflammatory bowel disease, or post-surgery. In these cases, the amount should be personalized with a nutritionist, not reduced to zero on your own.
