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Fiber – The Favourite Food of Our Gut Bacteria

What is fiber?

Dietary fiber (also called roughage) is a part of plant foods that cannot be digested by gastrointestinal enzymes. It consists mainly of non-starch polysaccharides, is a carbohydrate, and soluble (dissolves in water) or insoluble. Most high-fiber foods have both soluble and insoluble components. They move indigested through our digestive system, absorb water, ease bowel movements, and can be fermented by beneficial colon bacteria to butyrate. Butyrate is a short-chain fatty acid that provides energy to our gut bacteria.

What is fiber good for?

There are several well-known benefits from both types of roughage: prevention of constipation, hemorrhoids, colitis, and colon cancer. Furthermore, it ensures regulation of pH in the intestines, reduction of (bad) cholesterol, and promotion of bowel movements. Plus, it provides improvement of immune health, elimination of waste through the colon such as bile acid, and regulation of sugar intake. Consuming high levels of dietary fiber may be protective against several chronic conditions: chronic bowel disease, heart disease, colon cancer, and diabetes. There is a lot of evidence that eating dietary fiber may lower the risk of cardiovascular diseases.

People consuming roughage appear to have lower weight because of the feeling of fullness without absorbing the calories. They are not absorbed by our bodies due to their indigestibility. There is a lot of evidence that high fiber intake is associated with the prevention of weight gain.
Among women, a higher intake of it was linked to a significantly 62-85% reduced risk of breast cancer. Every 20 g of fiber a day was linked to a drop of 15% of the risk to suffer from breast cancer.

The daily recommendation is a minimum of 30 g/day – people having a „normal“ western diet eat about 15 g/day, vegetarians 20 g/day, and only vegans eat 47-68,7 g/day. Several experts even recommend 80 g/day.

Where can I find fiber?

Whole, unprocessed plant whole foods are the only source of fiber and of basal importance in our diet. You can find it in fruits, vegetables, nuts, cereals, roots, tubers, whole grains, and legumes. Eating this plant-based food, you also get healthy proteins, lipids, antioxidants, minerals, and – of course – vitamins. Processed food such as white bread, white rice, or pasta lack in roughage. Fiber-rich foods are mainly whole grain products, oats, barley, flax and psyllium seeds, raw vegetables and fruits, as well as dried beans and peas.

Fiber – your gut bacteria would love you for eating this :)
Fiber – your gut bacteria would love you for eating this 🙂

How does fiber work?

While eating roughage, we feed the good bacteria in our gut. Butyrate is a bacterial metabolite that is produced by our healthy gut flora. Butyrate feeds the cells that line our colon to make sure that there is a good balance of old and new cells. Furthermore, it has an anti-inflammatory effect on our whole health system. Anti-inflammatory effects can reduce oxidative stress and free radical damage.
Beneficial bacteria protect the host by maintaining gut homeostasis. This ensures their own survival.

Our immune system must constantly maintain a balance between good and bad bacteria. Butyrate-levels may be a signal to inform the host immune system that the levels of butyrate-producing bacteria are within the needed range.

What if we don’t eat enough fiber?

Our good bacteria use fiber to create butyrate. If we don’t eat enough fiber, we can have lots of good bacteria still they can’t make enough butyrate. Noticing such low levels of butyrate our body wrongly thinks our gut is filled with bad bacteria. Our body does not know about processed food for millions of years. It evolved by getting mainly food rich in roughage. Detecting low levels of butyrate our body doesn’t think of low fiber but of bad bacteria: A signal to go on the inflammatory offensive.

That’s the reason why fiber can be so anti-inflammatory: Not supplements but whole plant foods are one of the critical factors for optimal health. Eating high amounts of sugar and fat from processed food lacking fiber may lead to arteriosclerosis, fatty liver disease, and tumor growth. Plus, our good bacteria will decrease which can lead to inflammation, Crohn’s disease, colorectal cancer or ulcerative colitis.

If you have eaten low roughage food for a long time, you have to know that your body needs to adapt to your new diet. Just as little as a person being quite a sluggard can run a marathon without exercising, your good bacteria need to grow step by step to manage all the fiber coming in.

What about you? Do you eat enough fiber? I avoid white bread, rice, and pasta because after eating it, I’m still hungry.

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Sources for this blog post

Baron, R. B. 2013: Eat more fibre – The likely benefits include a lower risk of cardiovascular disease, pass it on, in BMJ: Vol. 347, 2013.

Eastwood, M./Kritchevsky, D. 2005: Dietary Fiber: How Did We Get Where We Are?, in: Annual Review of Nutrition, Vol. 25, 2005, pp. 1-8.

Chang, P. V./Hao, L./Offermanns, S./Medzhitov, R. 2014: The microbial metabolite butyrate regulates intestinal macrophage function via histone deacetylase inhibition, in: Proceedings of the National Academy of Sciences of the United States of America, Vol. 111, 2014, No. 6, pp. 2247-2252.

Chitchumroonchokochai, C. 1995: Dietary Fiber and Phytate Intake of Strict Vegetarian Thai Adults, in: Asia Pacific Journal of Public Health, Vol. 8, 1995, No. 1, pp. 10-13.

Dewell, A./Weidner, G./Sumner, M. D./Chi, C. S./Ornish, D. 2008: A Very-Low-Fat Vegan Diet Increases Intake of Protective Dietary Factors and Decreases Intake of Pathogenic Dietary Factors, in: Journal of the Academy of Nutrition and Dietetics, Vol. 108, 2008, No. 2, pp. 347-356.

Kuo, S.-M. 2013: The Interplay Between Fiber and the Intestinal Mircobiome in the Inflammatory Response, in: Advanced Nutrition, Vol. 4, 2013, pp. 16-28.

Li, Q./Holford, T. R./Zhang, Y./Boyle, P./Mayne, S. T./Dai, M./Zheng, T. 2013: Dietary fiber intake and risk of breast cancer by menopausal and estrogen receptor status, in: European Journal of Nutrition, Vol. 52, 2013, No. 1, pp. 217-223.

Satija, A./Hu, F. B. 2012: Cardiovascular Benefits of Dietary Fiber, in: Current Atherosclerosis Reports, Vol. 14, 2012, No. 6, pp. 505-514.

Tan, J./McKenzie, C./Potamitis, M./Thorburn, A. N./Mackay, C. R./Macia, L. 2014: The Role of Short-Chain Fatty Acids in Health and Disease, in: Advances in Immunology, Vol. 121, 2014, pp. 91-119.

Threapleton, D. E./Greenwood, D. C./Evans, C. E. L./Cleghorn, C. L./Nykjaer, C./ Woodhead, C./Cade, J. E./Gale, C. P./Burley, V. J. 2013: Dietary fibre intake and risk of cardiovascular disease: systematic review and meta-analysis, in: BMJ, Vol. 347, 2013.

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