Absence of evidence is …

    A vital concept for understanding health.

    ( Absence of evidence ) is not ( evidence of absence )

    Fully understanding the above phrase is absolutely critical for understanding evidence-based health.

    On the surface, the concept seems simple: just because there haven’t been studies on something doesn’t mean it’s not true. But that’s not the whole story.

    Question of the week:

    If you had to pick, is it more important that Examine …

    A. Covers every topic out there (no matter how obscure), but doesn’t update pages as quickly

    B. Updates the most noteworthy topics (e.g., fish oil, creatine) very often, but covers fewer topics in general

    Click on a link above or Contact us and let us know!

    What types of things don’t have much evidence?

    Lots and lots of things!

    Primarily individual responses.

    You know how creatine works for most people, yet some people are creatine “non-responders” and don’t experience much, if any, benefit?

    Well, creatine is one of the most researched supplements of all time, so creatine non-response has actually been studied. Think about all the hundreds of other popular supplements with way less evidence. Their response rates and the possible mechanisms explaining who they work for and who might not experience an effect haven’t been studied.

    Now consider how little side effect data is collected, compared to efficacy data. Or the scarcity of evidence on interactions between different supplements, or supplements interacting with foods, drugs, genetics, or the microbiome.

    But that all pales in comparison with the biggest evidence gap: interactions between a treatment and a health condition.

    People with health conditions are explicitly excluded from trials

    If you want to find out if a supplement works, you’d test it in the simplest population group possible.

    For example, if you’re testing fish oil’s effects on high blood pressure, you’d recruit a group of participants with high blood pressure. Not people with high blood pressure plus a couple of other chronic health conditions, because those health conditions could affect the treatment’s efficacy.

    One big problem though: 27% of Americans have more than one of the 10 most common chronic conditions. And that’s excluding the hundreds of less common chronic conditions!

    Surprisingly little is known about the molecular mechanisms behind chronic conditions, or how they interact with other conditions. The body can respond in unpredictable ways when it’s not well.

    So it’s not surprising that the results of a trial may not apply to you if you’re not totally healthy. Or you may experience a reaction that your healthcare provider doesn’t believe, because it’s not in the evidence they’ve seen.

    This has happened to me several times. Here’s one example:

    I once had a lidocaine injection into a joint, and it didn’t numb the area very well. The surgeon said that it should have, and maybe my mind was playing tricks on me. Years later, I found studies showing that people with Ehlers-Danlos Syndrome like me are more often resistant to local anesthesia.

    Don’t go all conspiracy theory now!

    Please don’t take all this to mean that healthcare providers don’t know what they’re talking about, or that evidence doesn’t matter.

    Rather, just know that healthcare providers are fallible (as is everyone!), and evidence is hugely important but also fallible and incomplete. Four years of medical school and several years of residency exposes physicians to vast amounts of knowledge and many patients, but health is insanely complex and nobody can be perfect.

    This is complicated by the thousands of important health studies published each month. No healthcare provider or lay person has the time or expertise to read through all of them.

    If any of you Examine readers are secret billionaires and volunteer to give us an unrestricted grant, we can use that money to analyze many more studies than we currently do. We could even expand outside of nutrition and supplementation into exercise, medications, surgeries, and other topics. I’m pretty sure it would help humanity. Plus you might be able to get a tax deduction?

    Whether you’re a secret billionaire or not, just keep in mind that humility is key to both assessing your own knowledge of health, and when choosing a healthcare provider. It’s great when you can find a doctor who can say “I’m not sure — I’ll look into it.” And sometimes even looking into it isn’t enough, because the evidence only covers so much!


    Kamal Patel
    Co-founder, Examine