Good stuff to know about Fiber, not Skincare (at least not directly)

According to The Economist (1), fiber is about to replace protein as this year’s TikTok nutrition obsession. Fiber-maxxing, like a lot of these trends, is old news to the experts but an epiphany to the Tik Tok Docs…. That doesn’t make it useless; if anything, it’s one of the few fads that’s actually grounded in solid science. But there’s no need to make it complicated.

What is Fiber?

Fiber is a type of carbohydrate found in plant foods that your body can’t fully digest and it’s essential for gut health and a healthy metabolism. What makes them non-digestible is that humans just don’t have the chemical machinery, the right enzymes, to break them down into smaller bits we can absorb. Sugar and starch are carbohydrates our enzymes handle just fine but fiber is the one they mostly can’t.

Unless your gut microbiome gets involved then, fiber passes through most of your digestive system largely intact. That doesn’t mean “it does nothing.” Quite the opposite, it changes how fast you absorb nutrients, how your gut bacteria behave, and what ends up in your bloodstream, all good and really important stuff.

Soluble vs Insoluble Fiber

There are two main types of fiber:

• Soluble fiber: dissolves in water and forms a gel.

• Insoluble fiber: big surprise, doesn’t dissolve, the classic “roughage.”

Note: Soluble / insoluble has nothing to do with “digestible vs indigestible” for humans. Whether it dissolves or not, as above, we don’t digest any fiber because we don’t make the enzymes that break it down. 

Soluble fiber

You find soluble fiber in foods like oats, apples, citrus fruits, beans, lentils, and grains like barley. In the gut, the gel that soluble fiber forms:

• Slows digestion and slows absorption of glucose, which blunts blood sugar spikes (which is a really good thing).

• Binds some dietary cholesterol and reduces how much you absorb. (Worth remembering: most of the cholesterol in your blood is made by your liver, not just imported from your food.)

• In some cases, serves as food for certain gut bacteria, which convert it into short-chain fatty acids (SCFAs) and other metabolites that we depend on. See prebiotics below.  

Insoluble fiber

Insoluble fiber doesn’t dissolve; it adds bulk to poop and helps move material through the GI tract. Think whole wheat, nuts, seeds, and the skins of many fruits and vegetables.

Most whole plant foods contain both soluble and insoluble fiber. That’s one of several reasons a mixed, plant-forward diet is ideal instead of depending on a single fiber ingredient or one “magic” fiber supplement.

Prebiotic Fiber

“Prebiotic” is just a way of saying, “this is something your microbes can use in a way that benefits you.” All prebiotic fibers are fermentable fibers, but not all fiber is prebiotic. By fermentable, we mean fibers that your gut bacteria can break down and “eat,” turning them into useful compounds we need (2). Short-chain fatty acids (SCFAs) such as acetate, propionate, and butyrate are the main ones.
Those SCFAs:

• Help dampen low-grade inflammation

• Support immune function

• Help maintain the integrity of the gut lining

Foods naturally rich in prebiotic fibers include garlic, onions, leeks, asparagus, bananas, and chicory root. You don’t have to memorize the list; the point is that different fibers do different things, and some are more microbiome-active than others.

Fiber Supplements

Most people undershoot the recommended 25-38 grams of fiber per day, so supplements are sometimes useful. They’re fine as tools but they shouldn’t be a substitute for eating actual plants, which also provide vitamins, minerals, and a long list of bioactive compounds you don’t get from a jar of powder. Some common supplemental fibers are:

A Word on Skin

Why is this on a skin-care site at all? Because what happens in the gut doesn’t stay in the gut.
A reasonably balanced gut microbiome and an intact gut barrier are increasingly linked to lower systemic inflammation and better control of inflammatory skin conditions like acne, rosacea, eczema flare patterns, etc. Fiber is not a topical treatment and it won’t “cure” your skin, but the gut-skin axis (the gut to skin connection) is real enough that ignoring it while chasing serums is probably a bad idea.

Bottom Line

Most people need more fiber, from actual plants, and more often. Soluble, fermentable, prebiotic fibers are the workhorses for the microbiome; insoluble fiber keeps things moving. Supplements are useful when the diet is clearly lacking, but they’re backup, not the main act.

1. https://www.economist.com/science-and-technology/2026/02/20/should-you-be-fibremaxxing 

2. https://pmc.ncbi.nlm.nih.gov/articles/PMC10196242/