Chemotherapy Linked to Gut Imbalance

Anyone who has undergone chemotherapy treatment knows how terrible its side effects can be.  Flu-like symptoms, mouth sores, changes in taste and smell, fatigue, hair loss, pain, weight gain – these are just a handful of common after-effects.

One of the most common and overwhelming side effects of chemotherapy is digestive impairment, characterized by diarrhea, constipation, loss of appetite, nausea and / or vomiting.

Now, current research published in Alimentary Pharmacology & Therapeutics demonstrates why chemotherapy impacts the gut so dramatically.

In this study, researchers studied the fecal samples of 28 patients with non-Hodgkin’s lymphoma before and after chemotherapy (with no other therapies used, such as antibiotics) and discovered that following chemotherapy, the microbial makeup of each sample were highly imbalanced. All subjects’ samples contained higher elevations of some microbes and a marked reduction of others.

This study suggests that chemotherapy dramatically changes the make-up of the gut’s vital yet delicate microbiome. The effects of this change are potentially catastrophic on the body’s health as a whole, especially if you consider the multiple rounds of chemotherapy that many patients are prescribed to take.

To fully comprehend why chemotherapy kills gut bacteria, though, we need to truly understand what this therapy is.

Most common chemotherapeutic agents are cytotoxic – they work by killing cells that divide rapidly. Cancer cells divide quickly, but so do many other cells in the body, including those important cells in the bone marrow, digestive tract and hair follicles. Because of this, immunosuppression, hair loss and intestinal inflammation result.

But chemotherapy doesn’t only kill cancer cells and healthy body cells. The fecal study above clearly shows that bacteria is also a target.

This is because many types of chemotherapy are also antimicrobial in nature: they can kill bacteria, viruses and fungi. Topotcan (TPT), for instance, which is a chemotherapeutic agent commonly used in the treatment of ovarian and lung cancer, has also been shown to impede the growth of viruses like HIV–1.

The fact that chemotherapy does not just target cancer cells but also viruses, fungi and bacteria forces us to contend with three questions:

  1. How can you sustain the gut bacteria needed to support a healthy body and mind if you choose to go on chemotherapy?
  2. Is chemotherapy effective for some people because it kills cancer cells or because it kills an underlying infection (virus, bacteria or fungi) that is at the heart of their disease? We know that infection can cause cancer. Human papilloma viruses (HPVs), Epstein-Barr virus (EBV), Hepatitis B virus (HBV) and hepatitis C virus (HCV) are just a few of the viruses that been shown to be closely linked to this insidious disease. In fact, it is estimated that viral infections contribute to 15–20% of all human cancers. There is also a growing body of research showing that fungal infections, too, are a cause. So, does chemotherapy work for some because is kills the cancer or a hidden infection that causes it?
  3. If it is effective because it targets an underlying infection, is there not a safer, more holistic approach to fighting it while still supporting the essential functioning of one’s gut microbiome?

Chemotherapy is not effective for everyone. In fact, a study published in Clinical Oncology found that the contribution of chemotherapy to 5-year survival in adults was only 2.3% in Australia and only 2.1% in the US – revealing that chemotherapy actually does very little to boost cancer survival rates. Knowing that it is also detrimental to our gut health (which is so vital in sustaining overall health and fighting infection), it becomes clear that people really need to weigh their options before deciding if chemotherapy is right for them.

Whatever a person decides, treating an underlying infection and cutting off its food supply are paramount to stopping disease. Avoiding GMO’s, pesticides, processed carbs and sugars, additives and preservatives and choosing foods that are high in organic, non-starchy vegetables, organic non-GMO fed poultry and beef, wild fish and good fats will help weaken the infection in the body by cutting off its food supply. And a weaker infection will be more easily knocked back by therapies and be less likely to gain strength in the body over time.

It is also important to reduce your exposure to radiation and environmental pollutants which can speed the rate at which infections multiply and spread.

For those that choose chemotherapy, it is vital that gut balance is restored to the best of their ability by regularly consuming probiotics and fermented vegetables. For who simply cannot restore balance, studies are now showing that fecal transplants can help replenish the gut’s microbes quickly and dramatically. If you are considering this option, first consult your family doctor to discuss whether it is right for you.


“Biomarkers of chemotherapy-induced diarrhoea: a clinical study of intestinal microbiome alterations, inflammation and circulating matrix metalloproteinases.” Supportive Care in Cancer. July 2013, Vol 21, Issue 7, pp 1843-1852


“Topotecan Inhibits Human Immunodeficiency Virus Type 1 Infection through a Topoisomerase-Independent Mechanism in a Cell Line with Altered Topoisomerase I.” ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, May 1997, p. 977–981 Vol. 41, No. 5 

“Viruses Associated With Human Cancer.” Biochimica et Biophysica Acta (BBA) – Molecular Basis of Disease Vol 1782, Issue 3, March 2008, P 127–150.

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