PROS AND CONS OF FIBER

What Is Fiber?

Fiber is a mostly non-digestible carbohydrate found in plant foods like vegetables, grains, legumes, and nuts. A majority of fiber is never absorbed into the body and therefore comes out in the feces. Fiber provides very little to no Calories or nutrients. (1, 2) However it does have some other functions that will be discussed below.

Mainstream nutrition praises fiber and recommends you eat lots of it for colon health, weight loss, microbiome health, and regular bowel movements. While some of these are true to some extent, that’s far from the whole picture. Moderation is key when it comes to fiber consumption as you will see when we dig into the pros and cons of fiber.

Pros:

1) Rids The Body Of Old Recirculating Fats

When you eat fat, bile (a fluid made primarily of cholesterol) is released from the gall bladder into the intestines to aid in the digestion of fat. After digestion, in the absence of fiber, about 95% of the bile is reabsorbed into the blood stream and travels back to the gall bladder waiting to be used again. (1) Due to the efficiency of this recycling process, fats can be reused many many times and may go rancid with time. Fiber however binds to bile in the intestines, preventing reabsorption. This forces the body to make new bile from new cholesterol. (1) Thus fiber helps rid the body of old (possibly rancid) fats.

2) Aids The Gut Microbiome

Soluble fiber, a type of fiber that dissolves in water, feeds the good bacteria in your gut and promotes a healthy microbiome. (2) Most of the food we eat has already been broken down and absorbed into the blood stream before it can reach the large intestine. This leaves very little food for the good bacteria in our large intestines and that’s where fiber comes in. Since we can’t digest fiber, it reaches the large intestine relatively intact and is then used as food for our gut bacteria. This is called a prebiotic. (2)

But why should we care about feeding our gut bacteria?

Our gut is a complex ecosystem that effects many aspects of our health including digestion, the majority of serotonin production, our mood, biochemical signaling between the GI tract and central nervous system (this is known as the gut brain axis), our weight, our food cravings, immunity, and much more. It’s important that we fed the good bacteria to aid in these functions as well as to fight off bad bacteria. If we don’t feed the good bacteria, the bad bacteria may get too numerous which can lead to candida over growth, yeast infections, UTIs, bacterial infections, compromised immunity, and more. (2, 3, 4, 5, 6)

3) Detoxifies The Gut Of Environmental Toxins

Fiber helps pull environmental toxins, xenoestrogens, and endotoxins out of the gut, binding to them and bringing them out through the feces. Mushrooms and raw carrots are particularly effective for this. (7) In modern society we are exposed to so many toxins which can cause many health problems such as hormonal imbalance, fertility and reproductive issues, headaches, cancer, fatigue, anxiety, and more. (7, 8) This makes both reducing our exposure and finding ways to detox and remove these toxins extremely important. More info on this can be found in this article.

4) Reduces Blood Sugar Spike

Fiber, particularly soluble fiber, has been shown to slow down the absorption of sugar due to it’s viscosity and therefore decrease the blood sugar spike associated with eating carbohydrates. (1, 2) It’s important to avoid frequent blood sugar spikes because over time they may lead to metabolic dysfunction, insulin resistance, and diabetes. If fiber is causing problems for you, fat and protein can also help lower the blood sugar spike when consumed with carbs.

Cons:

1) Can Worsen Constipation And Gut Issues

Contrary to popular belief, too much fiber has been found to worsen constipation and gut issues such as bloating, anal bleeding, abdominal pain, and strain in having bowel movements. Fiber appears to be more damaging in those with idiopathic constipation, IBS, Chrohn’s Disease, Ulcerative Colitis, Diverticulitis, leaky gut, and autoimmune diseases. (9)

One study of 63 people with idiopathic constipation (constipation with an unknown cause) looked at the effects of no fiber and low fiber diets on bowel movement frequency and common symptoms associated with constipation. For the first two weeks the participants went on a no fiber diet, then for the remainder of the 6 month testing period they were able to choose the amount of fiber they wanted.(9)

“Forty one patients who completely stopped fiber intake had their bowel frequency increased from one motion in 3.75 d (± 1.59 d) to one motion in 1.0 d (± 0.00 d) (P < 0.001). Of 16 patients who reduced their dietary fiber intake, 12 patients had daily bowel movement, 3 had one bowel movement every 2 to 3 d and one had a bowel movement every 4 to 6 d, giving one motion per 1.9 d (± 1.21 d) on a reduced fiber diet compared with 1 motion per 4.19 d (± 2.09 d) on a high fiber diet (P < 0.001). There was no change in the frequency of bowel movement for patients who continued with high dietary fiber intake, with one motion per 6.83 d (± 1.03 d) before and after consultation (P = 1.00).” (9)

There was also a complete elimination of anal bleeding, constipation, bloatedness, strain in bowel opening, and abdominal pain in the no fiber group. These symptoms were reduced in the low fiber group and remained almost unchanged in the high fiber group. The results can be seen in the table below. (9)

In addition to this study, many people have tried this on their own and found reducing fiber to be extremely helpful. I myself found heavily reducing fiber to help me overcome bloating, painful intestinal cramps, loss of appetite, chronic idiopathic constipation (After being constipated most of my life, I now have a bowel movement nearly every day), and strain in bowel movements. Many other people have reported similar experiences, a few can be found on this testimonial page.

So why does decreasing fiber help cure constipation and its associated symptoms?

“The role of dietary fiber in constipation is analogous to cars in traffic congestion. The only way to alleviate slow traffic would be to decrease the number of cars and to evacuate the remaining cars quickly. Should we add more cars, the congestion would only be worsened. Similarly, in patients with idiopathic constipation and a colon packed with feces, reduction in dietary fiber would reduce fecal bulk and volume and make evacuation of the smaller and thinner feces easier. Adding dietary fiber would only add to the bulk and volume and thus make evacuation even more difficult.” (9)

2) Can Cause Gas And Bloating

As seen in the study we just talked about, higher fiber intake is associated with bloating. (9) This is because when we eat fiber it sits in our gut and ferments creating hydrogen, carbon dioxide, and methane as a byproduct. These gases are trapped by peristaltic colon and therefore exert pressure on the walls, causing abdominal pain and gas. (9)

3) Can Damage The Gut Lining

Fiber, especially insoluble fibers like cellulose, can scrape the gut lining making it fragile and allowing things like endotoxins (and food particles in severe cases like Leaky Gut) to enter the blood stream. In a healthy gut some fiber is fine, however with a damaged gut in cases like leaky gut, Chrohn’s Disease, Ulcerative Colitis, and autoimmune diseases, fiber can do a lot of damage. (10)

In these conditions think of your gut lining like a fresh scab. You have to be careful with the scab and what rubs on it until it is fully healed. Since fiber can scrape against the gut lining, it’s best to avoid it until your gut is healed and can tolerate it again. (10)

How Much Fiber Should You Consume?

It really depends. If you have chronic constipation, IBS, leaky gut, Chrohn’s Disease, Ulcerative Colitis, or an autoimmune disease then little to no fiber for a period of time would likely be ideal. The more severe the condition, the more restrictive of fiber you’ll need to be and the longer you’ll need to restrict fiber in order to heal your gut and condition.

If you have a healthy gut, then you can likely tolerate a small to moderate amount of fiber just fine. I still wouldn’t recommend going hog wild on the fiber though, especially insoluble fiber which seems to do more damage. Insoluble fiber is in things like brown rice, wheat, rye, vegetables (especially the peels/skins), and other plants. (1)

I would opt for more soluble fiber instead, which is found primarily in oats and fruit. (1) The optimal amount of fiber ultimately varies a lot based on the individual. Therefore I recommend you experiment with it to see what works best for you.

Works Cited

1. Dr. Lauren Housley, Ph.D., R.D. “Carbohydrates.” Human Nutrition Class. January- May 2020, Chico State University, Chico, CA. Power Point.

2. Gunnars, Kris. “Why Is Fiber Good for You? The Crunchy Truth.” Healthline. 23 May 2018. https://www.healthline.com/nutrition/why-is-fiber-good-for-you#TOC_TITLE_HDR_3

3. Hills, Ronald D Jr et al. “Gut Microbiome: Profound Implications for Diet and Disease.” Nutrients vol. 11,7 1613. 16 Jul. 2019, doi:10.3390/nu11071613

4. University of Utah Health. “These gut bacteria prevent mice from becoming obese — what could that mean for us?” Science Daily. 25 July 2019. www.sciencedaily.com/releases/2019/07/190725150401.htm.

5. Cryan, J.F. and O’Mahony, S.M. (2011), The microbiome-gut-brain axis: from bowel to behavior. Neurogastroenterology & Motility, 23: 187-192. https://doi.org/10.1111/j.1365-2982.2010.01664.x

6. Bonaz, Bruno et al. “The Vagus Nerve at the Interface of the Microbiota-Gut-Brain Axis.” Frontiers in neuroscience vol. 12 49. 7 Feb. 2018, doi:10.3389/fnins.2018.00049

7. Julia. “Endocrine Disruptors Damage Your Hormonal Balance.” Julia’s Wellness Tips. 25 April 2020. https://juliaswellnesstips.com/2020/04/25/endocrine-disruptors-damage-your-hormonal-balance/

8. O’Brien, Kayley. “Health Consequences of Xenoestrogens.” Heart to Kitchen. 19 February 2021. https://www.hearttokitchen.com/health-consequences-of-xenoestrogens/

9. Ho, Kok-Sun et al. “Stopping or reducing dietary fiber intake reduces constipation and its associated symptoms.” World journal of gastroenterology vol. 18,33 (2012): 4593-6. doi:10.3748/wjg.v18.i33.4593

10. “Don’t Think That Fiber Is Perfectly Harmless…” YouTube, uploaded by Healthy With Nicole, 13 March 2021. https://www.youtube.com/watch?v=mQP2CDUOC-k