Antibiotic use has been linked to a number of different cancers, not just colorectal cancer, and antibiotics are now known to cause long-term damage to the gut microbiome and the immune system. Over 70 billion doses of antibiotics were prescribed in 2010 worldwide and it is estimated that at least half were given for conditions they could not treat. Millions of people suffered damage more than a decade ago.
Breast cancer and antibiotic use
The Journal of the American Medical Association (Feb 18, 2004; 291:827-35) reported a study of 10,000 women. Those who took antibiotics for more than 500 days in a 17 year period held more than twice the risk of breast cancer as women who had taken none. Women who had taken just one dose of antibiotics statistically increased their risk by 1.5 times.
The likely explanation might involve the action of antibiotics in destroying good bacteria in the gut and causing dysbiosis in the microbiome. This could lead to a lowered immune system, to the loss of important compounds that commensal bacteria make (B vitamins, melatonin, serotonin etc.), inflammation and the uncontrolled growth of certain 'bad' bacteria such as E.coli.
The researchers argued that it could also be simply a case of women who get more infections have weaker immune systems and may be more prone to cancer. But they knew little about the importance of the microbiome to your health at that time.
The study followed up on original findings in Finland in 2000 where the first connection was made.
Lung cancer and antibiotics
A review of cases (1) of lung cancer showed "an increased risk of lung cancer associated with prescription antibiotics". The researchers do state that more antibiotics are prescribed for people who have more chest infections. But their conclusion is clear.
There is also now known to be a Gut-Lung axis. If you damage the gut microbiome, you will damage the lung microbiome.
Go to: Gut-lung axis crucial in fighting lung cancer
Antibiotics and Colorectal cancer
A disturbed microbiome (dysbiosis) is most likely to affect conditions in the GI tract. We know it leads to IBS, Crohn's, colitis and diverticulitis.
Not only does antibiotic use seem to be linked to more cases of colorectal cancer, but the type of antibiotic and the location of the cancer - bowel, anal etc. - seem to be linked (2).
An overgrowth of yeasts/fungi after antibiotic use is common. Normally your healthy bacteria consume such yeasts at night time while you sleep. Candida albicans is known to colonise the gut and even areas of the body and it can reduce oxygen in those local areas as it is an anaerobe. Cancer thrives in low oxygen conditions.
Go to: Three studies show antibiotics increase Colorectal cancer risk
Go to: Colorectal cancer cases increasing in the young
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References
- https://cebp.aacrjournals.org/content/17/6/1308
- https://gut.bmj.com/content/68/11/1971