Research on glucosamine, one of the most popular dietary supplements, shows anti-inflammatory and anti-cancer benefits with minimal adverse effects. An international team of researchers aimed to explore the relationship between the use of glucosamine and the risk of lung cancer and lung cancer mortality based on data from the large-scale nationwide prospective UK Biobank cohort study.
Participants were enrolled between the years 2006 and 2010 and followed up to 2020. The Cox proportion hazards model was used to assess the relationship between glucosamine use and the risk of lung cancer and lung cancer mortality. Subgroup analyses and sensitivity analyses were performed to explore the potential effect modifications and the robustness of the main findings.
A total of 439,393 participants (mean age: 56 years; 53% females) with a mean follow-up of 11 years were included for analyses. There were 82,603 (18.80%) participants reporting regular use of glucosamine at baseline. During follow-up, there were 1,971 (0.45%) lung cancer events documented. Glucosamine use was significantly associated with a decreased risk of lung cancer (hazard ratio=0.84, 95% CI: 0.75-0.92, p<0.001) and lung cancer mortality (hazard ratio=0.88, 95% CI: 0.81-0.96, p=0.002) in fully adjusted models. A stronger association between glucosamine use and decreased lung cancer risk was observed in participants with a family history of lung cancer when compared to those without a family history.
The authors concluded that regular use of glucosamine was significantly related with decreased risk of lung cancer and lung cancer mortality, based on data from this nationwide prospective cohort study.
A previous analysis of the same data concluded that regular glucosamine supplementation was associated with lower mortality due to all causes, cancer, CVD, respiratory and digestive diseases. The new analysis shows a strong association with lung cancer.
This is certainly interesting, but does it prove a causal relationship?
The answer is no.
Correlation is not causation!
What would be helpful in testing whether we are dealing with a cause-effect relationship?
- We need data from other studies. Several other epidemiological investigations indicated that glucosamine use might play a role in the prevention of cancer.
- We require to know the strength of the association. The new analysis suggests that it is indeed strong.
- We need a mode of action. Might the anti-inflammatory action of glucosamine explain the effect?
- We should ask whether there is a dose-response relationship. As far as I know, this has not been addressed as yet.
- Ideally, we would require a randomized trial to test the hypothesis. But I fear that such a study might be too difficult to conduct and will thus not be forthcoming.
And what if glucosamine should one day be proven to reduce the cancer risk? Would it become the first ALTERNATIVE measure to prevent cancer?
It would automatically become a conventional method of cancer prevention. All the research into the subject has been entirely conventional and is unrelated to the alternative medicine movement. Or, to put it bluntly, alternative cancer prevention is a contradiction in terms. Either it works in which case it is conventional medicine, or it doesn’t in which case it is not even an alternative but at best so-called alternative medicine.
I agree with you that observational studies of this nature can only be hypothesis-generating due the bias inherent in their design. But I disagree that it would be too difficult to conduct a randomised and blinded cancer-prevention study. There have been a number of cancer-prevention studies, including some ongoing, using cheap and readily-available drugs (vitamin E, selenium, aspirin, metformin…), not to mention many other studies looking at such things as secondary prevention after myocardial infarction (beta blockers, aspirin), statins, antihypertensives etc. Given that an apparently sizeable effect was seen after only 11 years of follow-up I would have thought that there would be considerable interesting in such a trial.
I am delighted that you are more optimistic than I; fingers crossed then!