Bayer's probably best-known drug, aspirin, has been found to be associated with a reduction in the risks of developing several cancers of the digestive tract.
A large and probably the most comprehensive analysis to date of the link between aspirin and digestive tract cancers was published in the leading cancer journal Annals of Oncology in April 2020. Researchers reported reductions in the risk of these cancers of between 22% and 38%.
Aspirin has been linked to a reduction in the risk of bowel cancer for some time, and other, smaller analyses have found associations with cancers of the oesophagus and stomach.
This analysis looked at evidence from 113 observational studies investigating cancers in the general population published up to 2019. It as found that regular use of aspirin, defined as taking at least one or two tablets a week, was associated with a significant reduction in the risk of developing cancers of the digestive tract.
High aspirin doses were associated with a larger reduction in risk of the disease. However, the choice of dose should also take into consideration the potential risk of stomach bleeds, which increases with higher aspirin doses. In addition to stomach bleeds, the side effects of aspirin include bleeding in other parts of the body.
Please note: As the study is based on observational studies and funded by Bayer, results might be slightly biased. Several confounding factors may partly explain its results.
So, to answer our original question ”Is an aspirin a day keeping the cancer away”, we must say: we don't know for sure.
Aspirin and the risk of colorectal and other digestive tract cancers: an updated meta-analysis up to 2019, by C. Bosetti et al. Annals of Oncology. doi: https://doi.org/10.1016/j.annonc.2020.02.012