Why Doctors Are Sceptical of Supplements (a Surgeon's View)

Written by Dr Jatin Joshi, co-founder and Chief Medical and Scientific Officer of Personally, and a researcher at the University of Oxford's Centre for Evidence-Based Medicine. I have a financial stake in this company, and you should weigh what follows with that in mind.

You mentioned a supplement to your doctor and got a shrug, or a raised eyebrow, or a polite change of subject. It is a common experience, and it is easy to read it as your doctor being dismissive, or behind the times, or simply not interested in prevention.

I want to give you a more useful answer, which is that in most cases your doctor is right, and I say that as one of them. I trained as a surgeon and I spent years reading trial data to decide whether to change what I did in theatre. When I look at how most of the supplement industry behaves, I share the profession's scepticism almost entirely. So rather than tell you the scepticism is unfair, I want to walk you through why it exists, honestly, and apply every bit of it to my own company as I go. Then I will tell you about the narrow set of cases where a supplement genuinely is worth taking, and what would make a sceptical doctor change their mind.

This is the big one. Walk down the supplement aisle and read the fronts of the bottles: boosts immunity, supports focus, balances hormones, promotes healthy ageing. Then go looking for the evidence behind any given one, and most of the time you find a thin trail: a small study, often in the wrong people, sometimes measuring a marker in the blood rather than whether anyone actually felt or fared better. The marketing is written as though the question were settled. The science underneath it usually is not.

A doctor is trained to want the evidence before the claim, not after it. When the claim arrives first and the evidence is left to catch up, their instinct is to distrust the whole thing, and that instinct is sound. It applies to us too. The honest position for any supplement company is to say plainly where the evidence is strong and where it is thin, in the same breath, and most of the industry does the opposite.

Supplements in most markets are not held to the standard medicines are. A medicine has to prove it is safe and that it works before it can be sold. A supplement, broadly, does not: it can go on sale first and be challenged later only if something goes wrong. That regulatory gap is not a conspiracy, it is simply how the category is written into law, but it means the quality control sits with the manufacturer rather than with a regulator checking before release.

The consequence is real. Independent testing has repeatedly found products that do not match their label claims, containing less of an active than they state, more, or occasionally something not on the label at all. A doctor who has seen this cannot assume the number on the tub is the dose in the capsule, and neither should you. This is exactly why we disclose every active ingredient and its dose in a Personally formula, and why the manufacturing controls matter as much as the recipe, because a disclosed dose is one you can actually hold us to.

Look at the back of many supplements and you will see a proprietary blend: a list of ingredients with one combined weight, so you cannot tell how much of each you are getting. There are occasionally legitimate formulation reasons for this. Far more often it is a way to include a fashionable ingredient in a quantity too small to do anything, while still printing its name on the label. A clinician cannot assess a dose they are not allowed to see, so they discount the product, and again they are right to. Every active dose in a Personally formula is stated, because a dose you cannot see is one you are being asked to take on trust.

The strongest reason for a doctor's caution is that "natural" does not mean "safe", and the evidence for that is not hypothetical. Fat-soluble vitamins can accumulate to toxic levels because the body cannot easily clear the excess. In large trials, beta-carotene given to smokers increased their risk of lung cancer rather than lowering it. Some botanicals interact with prescription medicines in ways that matter, changing how a drug is cleared from the body. A doctor carries these cases in their head, and it makes them cautious about waving through anything a patient wants to add, particularly alongside medication. That caution is not obstruction. It is the job.

When routine multivitamins have been tested properly, in large trials of generally well-nourished people, they have mostly failed to show the benefits people hope for on the outcomes that matter, like living longer or avoiding major disease. That does not mean no supplement ever helps anyone. It means that topping up someone who is already replete is a much weaker proposition than the marketing implies, and a doctor who has read those trials knows it. I have read them too, and they are a large part of why I think most people, eating reasonably, do not need most of what is sold to them.

Here is the turn. Your doctor is not against supplements as a category. Ask an obstetrician about folic acid for a woman trying to conceive and you will get an immediate, unhesitating recommendation, because the evidence that it lowers the risk of certain birth defects is about as strong as evidence in medicine gets. The scepticism is not reflexive. It is aimed at the claims that have not earned it, and it lifts the moment the evidence is real.

A supplement genuinely earns its place in a narrow set of cases. The clearest is correcting a real, measured deficiency: a documented low vitamin D, a low B12, a low ferritin. There the logic is simple and the evidence is good, because the body was short of something it needs and now it is not. The important word is measured. Do not start taking iron because an article told you to. Correcting a genuine deficiency needs a diagnosis, a sensible dose, and someone watching how you respond. Test first, then treat, and have your bloods checked rather than guessing.

The other case is a body whose needs have genuinely changed faster than an ordinary diet can keep up. Someone whose appetite has dropped sharply on a GLP-1 medication is eating far less, so what they do eat, and supplement, has to work harder. Someone going through perimenopause has shifting needs across several systems. These are real physiological changes, not marketing categories, and this is where thoughtful nutrition has something honest to offer, alongside medical care rather than instead of it. If a symptom is persistent or new, that is a reason to see your doctor, not to reach for a supplement first.

The scepticism lifts under specific conditions, and they are worth knowing because they are the same conditions that tell a good supplement from a bad one. A doctor starts to pay attention when the evidence is in people who actually resemble you, not in a cell culture or a different population entirely. When the thing is correcting something you are genuinely short of, rather than topping up a level that is already fine. When every active ingredient and its exact dose are visible, not buried in a blend. When the company takes account of the medicines you already take, because some of them interact. And when someone is willing to tell you which parts of the case are thin, instead of delivering every claim with the same manufactured confidence.

That last one is the standard I wanted to build a company around, and it is the one we have tried to build ours around. Personally exists because I thought the discipline the profession applies to medicines could be brought closer to supplements: disclosed doses, attention to what you already take, correcting real gaps rather than inventing them, and being straight about where the evidence is strong and where it is not. Whether we live up to that is fair for you to judge, using exactly the scepticism your doctor showed you, and to hold against us if we fall short.

Your doctor's shrug was not laziness. It was a filter, built from watching an industry overclaim for decades. The right response is not to ignore the filter, it is to find the few things that pass it.

If applying that filter is the kind of thing you want help with rather than more marketing, that is genuinely what we try to publish. When we assess an ingredient or change our mind about one, we write up the reasoning in plain terms, and you are welcome to have those sent to you. There is nothing to buy attached to it.

Two pieces sit alongside this one if you want to keep going. How we assess the evidence sets out the standard itself, step by step, and why am I always tired, even with enough sleep is that same standard applied to a real symptom, showing where nutrition fits and, more often, where it does not.