Why is Fiber Good For You? For Starters, It Can Save Your Knees

Why is Fiber Good For You? For Starters, It Can Save Your Knees

The Latest in Microbiome Research Involving Prebiotic Fiber

Your grandmother may have called it “roughage.”

When you think of fiber, an image of the “sticks and twigs”-like cereal and dry bran muffins you were forced to choke down as a kid might spring to mind.

But there is a lot more to fiber than that.  There is a whole world of soluble fibers, many of which are also prebiotic. Now more than ever, we can answer the question, “Why is fiber good for you?”

While there are all manner of mechanisms through which fiber consumption can confer health benefits, our focus at Microbiome Bulletin is of course, the microbiome and microbiota.  And as it turns out, those soluble prebiotic fibers feed the microorganisms in your gut, the ones that make up your gut microbiota.

And depending on the prebiotic fiber you consume, it increasingly appears that we can effectively target large classes of microorganisms generally considered to be beneficial.

By feeding those beneficial microorganisms, we can increase their numbers, and presumably, increase their benefit.

Of course, you need to take this all with a handful of salt. The research that follows is promising, to be sure, and is based in large part on our general understanding of the way the microbiota modulates immune function and through it, systemic inflammation. Skepticism and caution is warranted. In fact, we’ve noted that here in the past. (See, “Are Probiotics Bad For You?”)


There is almost no disputing the important role fiber plays in your gut health and through it, your overall health. This truly is an exciting area of research, and not too long in the future, we might be placing dietary fiber right alongside exercise as a nearly universal tonic for your health.

Speaking of which…


Protective effect of prebiotic and exercise intervention on knee health in a rat model of diet-induced obesity


Nature – Scientific Reports


Animal study using Sprague Dawley rats.


The consumption of prebiotic fiber and the addition of aerobic exercise, each separately, and both together, prevented the development of knee osteoarthritis (knee OA) in rats with induced obesity.


Rats are not humans, of course, however you cannot ethically conduct a study in which you induce obesity in humans and also effectively and precisely control diet and behavior. Further to that point, the fact that the obesity in the rats was induced through a high-fat, high-sugar (HFHS) diet raises other questions as human obesity has many causes, not all of which are well understood. Human population studies will be needed to help confirm these findings.

Important Takeaways

Knee osteoarthritis (OA) is a very common malady among those suffering from obesity and metabolic syndrome. It has been established that rats with induced obesity suffer from the same malady.

The notion that relatively simple, low-cost interventions, such as the introduction of prebiotic fibers to the diet and regular aerobic exercise, either each alone, or both together, can alleviate much of this suffering and the associated expenses on health care systems and society at large is worthy of further exploration.

Actionable Information

The consumption of prebiotic fiber, specifically the oligofructose used in this study, can help prevent knee OA in people suffering from obesity. While not cited in the study, we would surmise it can potentially be helpful for people who are simply overweight and who might be suffering less severe damage to their knee joints.

While outside the purview of Microbiome Bulletin, it is important to note that aerobic exercise, too, can help prevent knee OA. While one might be tempted to note that exercise can affect the microbiota in positive ways that was not necessarily the mechanism at work here as there is some evidence suggesting that such alterations do not occur in obese individuals.


Gut bacteria selectively promoted by dietary fibers alleviate type-2 diabetes




Humans in a randomized clinical study.


Dietary fiber can alleviate symptoms of type-2 diabetes mellitus


This was an open-label, parallel-group randomized study. Open-label means that both the participants, and the individuals conducting the study, knew whether or not they were part of the test group or placebo group. This introduces the possibility of confirmation bias and other affects that could contaminate the results vs. a single or double-blind placebo study in which one or both do not know which group they are a part of.

Important Takeaways

Patients suffering from type-2 diabetes mellitus (T2DM) often suffer from a deficiency in the production of short chain fatty acids (SCFAs). This study was designed to test the hypothesis that targeting the microbes associated with producing SFCAs with a variety of non-digestible carbohydrates (fiber) could increase their numbers, and in so doing, increase the production of SFCA which in turn could theoretically alleviate symptoms.

The study found that the group fed the prebiotic fiber, resulted in a select group of microbes associated with the production of SFCAs being favored, while others were either disfavored or remained unchanged.

These microbes then increased production of SFCAs resulting in a measurable increase in levels of glucagon-like peptide-1, and the establishment of adequate glycemic control.

While none of this means that patients with T2DM can down some fiber and be symptom free, the study helped support a number of contentions.

First, it is in fact possible to increase the numbers of certain SFCA-producing bacteria in the gut simply by consuming prebiotic fiber.

My own testing up to this point also supports this. One of the more efficient SFCA-producing bacterium identified in the study as being favored by the additional fiber consumption was Bifidobacterium pseudocatenulatum.

While my testing does not get granular enough to confirm that specific species, I have seen the Bifdobacterium genera skyrocket when I’ve added prebiotics to my diet.

Second, the study supported the notion that SFCA production can potentially improve blood glucose regulation of those suffering from T2DM

Actionable Information

The introduction of a variety of prebiotic fibers can help alleviate type-2 diabetes mellitus. Anyone suffering from T2DM should of course consult with their physician.

For the rest of us, it’s interesting to note that adding prebiotic fiber to your diet can result in an increase in SFCAs, which is generally believed to confer many health benefits.


Resistant Starch Reduces Systemic Inflammation


Wiley Online Library


Human, end-stage renal patients


Patients with end-stage renal disease who had amylose resistant starch added to their diets experienced a measurable reduction in inflammation.


Study focused on end-stage renal patients only.

Important Takeaways

Resistant starch is a relative newcomer to the world of fiber, at least in terms of it being recognized as a fiber at all, and as a prebiotic one at that.

This study was focused on patients seriously ill with end-stage renal disease. It is believed that many of the symptoms and discomfort these patients experience is the result of systemic inflammation resulting from a dysfunctional microbiota.

In an attempt to alleviate this suffering, patients were provided with amylose resistant starch. A similar control group received a placebo. This was a double-blind study in which neither the patients nor the individuals providing the supplement knew whether or not it was the resistant starch or a placebo.

The study found that the resistant starch resulted in an increase in Faecalibacteria, and a decrease in systemic inflammation.

This is something I have observed with my own testing. When I introduced prebiotic fibers to my diet (including a form of resistant starch) my levels of Faecalibacteria also increased materially.

It is early yet, and this is no panacea for patients suffering from renal disease, however, as with so much in this field, it is very promising, not the least of which because it adds to the evidence that dietary intervention can result in material impacts in gut health, and beyond.

Actionable Information

Specifically, patients with end-stage renal disease might find some relief adding amylose resistant starch to their diet. This would have to be in consultation with their doctor.

Generally, resistant starch appears to favor certain residents of your microbiota and their increased activity can potentially reduce systemic (body-wide) inflammation. While more research on this is needed, I have added green banana flour to my diet for its resistant starch component.

Thank You

As big a fan as I am of fiber (just take a look at the MicrobioME Project), it’s ability to make such dramatic, real-world impacts on people’s health and well-being surprises even me.

However, the more we learn about how the microbiota functions, and the far-reaching affect it can have on our human bodies, the more respect this “indigestible” carbohydrate earns.

Thanks for reading.  Please feel free to leave comments, observations, and questions below.

And let me know if you’re thinking of adding a little bit more fiber to your own diet.  Just make sure at least some of it is truly “prebiotic” by reading “What Is A Prebiotic?

It shouldn’t all be bran muffins!

Take care!