The main fiber in Fiber Shield is called NatureKnit®. Unlike processed fibers like inulin or psyllium which are found in many fiber supplements, NatureKnit is a complex fiber from a blend of organic upcycled fruits and vegetables. It has the plant's natural polyphenols still attached, which gives you more than fiber alone.
The short answer
A polyphenol-bound fiber is plant fiber that still carries the polyphenols it grew with. In a whole fruit or vegetable, some of these protective plant compounds are attached to the fiber of the cell wall. Processed single-source fibers leave those compounds behind, and a polyphenol-bound fiber keeps them.
Most of us eat too little fiber
According to the 2020 to 2025 Dietary Guidelines for Americans, more than 90 percent of women and 97 percent of men do not meet the recommended intake for fiber.
Many people turn to a fiber supplement, but most contain just one type of processed fiber from a single source. Inulin comes from chicory root, and psyllium comes from the husk of a seed. Both have been separated from the rest of the plant.
The part that usually gets left behind
Polyphenols are naturally occurring plant compounds that contain potent anti-inflammatory and antioxidant properties. Plants make these compounds to protect themselves from predators. They are found in fruits and vegetables such as berries, grapes, apples, spinach and carrots. They can also be found in dark chocolate, coffee, green tea and olive oil. More than 8,000 naturally occurring polyphenols have been identified in plants. They can help protect cells from oxidative stress and support brain and heart health, a healthy inflammatory response, blood sugar regulation and a balanced gut microbiome.
More isn't always better
A larger dose doesn't automatically make a fiber supplement more effective or easier on your stomach. In fact, a low dose of a multi-source, polyphenol-bound fiber may out-perform a larger dose of a single-source purified fiber. This is due to the complexity of the fiber matrix, leading to a more diverse microbiome and a slower fermentation period.
Some fibers, such as single-source purified ones, break down quickly, and taking too much at once can lead to gas, bloating or cramping. A single-source fiber offers one kind of food and only feeds certain species of the microbiome. This is known as prebiotic monoculture.
In contrast, NatureKnit, the main fiber in Fiber Shield, brings together a more complex mix of fruit and vegetable fibers. NatureKnit also keeps the plant's natural polyphenols bound to the fiber. They travel together to the colon, where gut bacteria help release the polyphenols and break down the fiber. This gives bacteria access not only to the fiber but to all of the plant compounds.
This complex fiber matrix leads to microbial diversity and richness. The fiber blend breaks down slowly, supporting steady production of beneficial short-chain fatty acids (SCFAs), including acetate, propionate and butyrate. These are the reasons a smaller dose is able to significantly increase overall microbial diversity and richness more than a larger dose of a single source fiber.
Our goal is to give your gut a varied mix of plant fibers and polyphenols it can put to use. A bigger scoop alone doesn't tell the whole story.
What NatureKnit is
NatureKnit is a blend of organic upcycled fruit and vegetable fibers, including apple, grape, blueberry, carrot, and spinach. Its fruit fibers come from the pulp left over when juice is pressed. The organic blend contains at least 40 percent dietary fiber. Each serving of Fiber Shield contains 2,500 milligrams of NatureKnit.
In September 2026, NatureKnit won the Microbiome Support category of WholeFoods Magazine's 2026 Ingredient Choice Awards. Supplement companies submit their ingredients for the awards, and members of the industry vote.
What the studies found
Two studies have tested NatureKnit. Both were run in a laboratory model of the human colon, seeded with gut bacteria from healthy donors. The first used the original blend and bacteria from three donors. The second used an organic blend and nine donors, at an amount scaled to stand for a 2.5 gram serving. That is the weight of NatureKnit in a serving of Fiber Shield. The figures below are from the second.
| Over 48 hours | NatureKnit | Inulin | Psyllium | No fiber |
|---|---|---|---|---|
| Rise in short-chain fatty acids | 48.2 mM | 42.7 mM | 38.8 mM | 31.4 mM |
| Kinds of bacteria counted at the end | 619 | 475 | 569 | 549 |
| Acidity kept rising for the full 48 hours | Yes | No | No | n/a |
The rise in short-chain fatty acids from NatureKnit was significantly larger than that of inulin or psyllium. Against no fiber, the count of kinds of bacteria was higher for NatureKnit only.
Slower fermentation, and what it does not show
Rising acidity is a sign that bacteria are fermenting. With NatureKnit it rose through all 48 hours, while with inulin and psyllium it rose early and then eased. The authors describe this as a slower, more gradual fermentation and suggest it may be easier on the gut. They did not test comfort in people.