The supplement industry is huge. Truly enormous. By 2025, the global market for dietary supplements is projected to be worth nearly $200 billion, and it’s growing at an amazing rate. Even now, the industry is worth tens of billions of dollars, with some individual supplements being worth vast sums to the companies that produce them.
This is all a bit odd, because as I’ve written before, supplements mostly don’t work. There are certain specific supplements that work for certain specific conditions, like iron for menstruating women who are feeling tired*, but in general for most supplements we either know they don’t work or don’t have any evidence that they do.
So why do we have so many pills on the supermarket shelves that gently hint that they can improve health? Why can you find tablets to “improve liver function” in any pharmacy the world over, even if your liver is operating perfectly anyway?
Let’s take a look at the genesis of these supplements, and the shaky scientific foundation that they’re built on.
We start with an example. A recently published study has been widely reported as being proof-positive that fenugreek pills can enhance women’s libidos. Specifically, a pill called Libicare, which contains fenugreek and a few other spices. According to news sources from around the world, a pill taken daily will spice up your sex life with curry-flavored arousal.
At this point, I usually go into detail about the research, looking carefully to see exactly how and why it probably doesn’t quite match the headlines. Maybe explain a complex statistical phenomenon that makes it a bit useless for predicting health in general. In this case, there’s really no need to do that.
You see, this study was almost entirely useless.
It was a tiny study, with only 29 women, no control group, poor statistical analytic techniques, a flawed trial design, no blinding, massive conflicts of interest — it was funded by Procare, who make the supplement in question — and barely found any improvements anyway. Going over the study in detail is a waste of time, because there’s not a single point that could provide useful information about fenugreek and people’s sex lives.
If you give a pill to a group of people who are having sexual issues, tell them that it will improve their sexual function, and then find two months later that they think it did by a tiny bit, you’ve basically got a classic case of regression to the mean. Well-conducted clinical trials are built to protect against this, but this piece of research broke pretty much every rule of good trial design. There’s really nothing you can take away from the study except that the scientists should probably do a better study.
And this is pretty much the only research on fenugreek and the pills that you can find**. There’s some evidence that it’s been used as a libido-enhancer traditionally, but even then there’s little evidential support for the theory. On the other hand, while fenugreek is mostly harmless, there’s some evidence it does cause issues and it does have the potential to be toxic.
Given the complete lack of data, you’d expect the company involved to be extremely careful with their claims. Remember, if this was a drug it would need years of careful testing to ascertain efficacy and make sure it wasn’t harming people.
Unfortunately, we find the exact opposite. You can buy Libicare pills from many online pharmacies, with the proposed indication that they can double sexual desire for women.
And there, we have a largely unevidenced supplement being born.
Isn’t it wonderful.
You can see this trend repeated over and over. There’s no real incentive for large, well-conducted trials of supplements — you don’t need to prove that they work to sell them, and good trials are often less likely to be positive anyway— so most of the trials aren’t very good. And since there’s very little regulation about what you need to prove to sell a supplement, the evidence generally is very similar to this study.
And based on science like this, we have an industry that will soon be worth $200 billion. Depressing, that.
This isn’t to say that some supplements don’t have benefits. As I mentioned, there is evidence for a rare few, mostly for very specific conditions. But the reality is that most supplements don’t improve your health in any measurable way, and they are marketed and sold on science that doesn’t really show much of anything at all.
People are going to keep taking supplements. The gigantic industry isn’t just going to disappear. But next time you’re at a supermarket going past the supplement aisle, it might be worth walking on instead of stopping.
If you’re worried about your health, see a doctor, not a bottle of spice pills.
You can now listen to Gid on the Sensationalist Science podcast for your weekly dose of scientific shenanigans and media muddling:
*Note: While unsurprising, this is very well-supported by evidence. If you’re worried about your iron levels, always worth having a chat with your doctor.
**Note: There is one fairly good trial showing some modest benefits for fenugreek in menopause symptoms, but it’s not quite the same focus and definitely not what most of these pills are being sold for!