Just published in the British Medical Journal (BMJ), a meta-analysis of glucosamine and chondroitin for osteoarthritis involving 10 trials and 3803 subjects – showing no benefit for either, separately or in combination. These supplements, like so many that have gone before them, are little more than expensive placebos.

Glucosamine and chondroitin are among the most popular supplements, and the most popular for osteoarthritis. The theory is that these substances, which are made naturally in the body, are used to build cartilage, the smooth substance that lines joints and breaks down with age and wear and tear. This theory, however, has always been weak. It suffers from the same faulty assumptions of many supplements – that if little is good, more is better; that dietary sources of these substances are inadequate and that the biological processes that use them are limited by availability of this raw material. None of these assumptions are likely valid.

First, for many substances in the body (vitamins, minerals, etc.) there is likely an optimal range of intake, not a linear relationship where more is always better. This is generally what we find when we examine biological systems. So taking supplements to increase the amount of a nutrient is as likely to cause harm as good. This point may not be as relevant to building block nutrients like glucosamine and chondroitin as to cofactors like most vitamins, however.

More relevant, likely, are the latter two points, which both must be true in order for such a supplement to be helpful. In other words – in order for chondroitin or glucosamine to work as claimed – by providing more raw material for the repair of cartilage, then it must both be true that not enough of these materials is derived from the diet and the limiting factor to cartilage health and repair is the availability of these building blocks. But neither of these assumptions is proven, or perhaps even likely.

In developed nations these nutrients are unlikely to be lacking in the diet. Again – more is not necessarily better, and once as adequate supply is obtained from the diet supplementing would have no benefit. Further, break down of cartilage occurs with use. The ability to repair cartilage at a sufficient rate to balance wear and tear may not be limited by the availability of raw material. It may be limited by other biological factors. So supplements would not even be addressing the problem.

However, the supplement industry has built its market on the rather simplistic assumptions above. They are sometimes true, but such determinations should be based upon evidence, not assumptions. Salt is fortified with iodine and milk with calcium to address common nutrient insufficiencies. We may be facing a relative insufficiency of vitamin D that needs to be addressed. And there are many specific situations in which specific supplements are beneficial, like folate for pregnancy. But this should not lead to the casual assumption that supplements are always good, or that they can address any specific problem.

Getting back to this study, the authors found no statistical difference between glucosamine and chondroitin alone or in combination and placebo, either with subjective improvement or with objective findings, such as joint space narrowing. They also noted that supplement industry-sponsored studies showed a greater trend toward a positive result than did independent studies (the same effect has been found for pharmaceutical company-sponsored studies, so this should be no surprise).

They also found that there was no direct harm from the supplements, and so while they concluded that the NHS should not fund the supplement, they also said that if patients want to give it a try that was reasonable. I found that soft approach to be wanting, however. There may be no direct medical harm, but there is certainly financial harm and possible indirect harm from neglecting other interventions that may be more effective. The BBC notes that these supplements were a £1.3bn market in 2008. That is a lot of wasted resources. That is money that cannot be spent on other health care interventions that may be actually effective. People with limited resources who are deciding where to spend their limited health care dollars (or pounds) will be harmed if they are wasting their money on useless supplements.

Conclusion

The data has been coming back negative on glucosamine and chondroitin for years – this meta-analysis is just the capper. For example, the recent GAIT trial of glucosamine and chondroitin for knee arthritis found no benefit.

As a clinician, what to do with this evidence is clear. There is no benefit from these supplements, so I would recommend not to take them. Don’t waste your money and effort. But as a society the question is a bit trickier. What we largely have now is a situation where supplements can be marketed with implied health claims prior to evidence of actual efficacy. Over and over the public wastes billions of dollars on useless supplements, until the evidence comes in showing that they are ineffective, then the markets shrink but do not go away. Meanwhile, the supplement industry is on to the next miracle supplement. This does not seem like an effective system of regulation to me.

If the public wishes to err on the side of freedom vs quality control and consumer protection, so be it. But I don’t think this is a common popular choice. The public mostly believes that health products are regulated, and claims cannot be made without evidence, but in most countries this is simply not true. The supplement industry has successfully lobbied for relaxed regulations – to benefit them. Consumer protection advocates seem to be asleep at the switch.

Perhaps as we enter an era of greater attention to the cost of health care, more attention will be paid to this issue. We’ll have to wait and see.