Which supplements actually do anything?

Transcript

Welcome to the sofidex Health Drive podcast series. Today we are talking about supplements, and about the shelf in the kitchen that fills up one bottle at a time without anybody ever really deciding what it is for. Maybe yours has a multivitamin on it, some fish oil, something for colds, and something a friend swore by. You might have added up what it costs one evening and felt slightly sick, and then realised you could not say what most of it was actually doing for you.

And the advice out there comes in two unhelpful kinds. Either it is all expensive nonsense and you should bin the lot, or every bottle is essential and you should probably be buying more. You are far from alone in this. In the United States, about half of adults say they have taken at least one supplement in the past month, and the most common reason they give is their overall health.

So we want to ask a better question than whether supplements work. The question is what gap each bottle is meant to fill, and whether you actually have that gap. We will go through one shelf, bottle by bottle, and look at what the large trials and reviews found for each. We will get to the vitamin the official advice says to take every winter, and the one it says not to take at all. And we will find the bottle that was missing from the shelf, which has more behind it than any of them.

Nothing here is a reason to stop anything a doctor has prescribed you, and if a blood test has shown you are short of something, that is a different conversation from this one. One thing before we start. This is health information, not medical advice, and nothing in it is a substitute for talking to your own doctor about your own treatment. What we can tell you is where all of it came from — 9 published sources, all listed with the episode. I want to do this one through a single person again. Not a real patient — somebody we've made up, so we can follow her all the way through. Call her Priya. She's thirty-six. She and her partner want to start trying for a baby in the new year. And on the shelf above her kettle there are five bottles. Last week she added up what they cost. It came to about forty pounds a month. And then she realised she couldn't say what a single one of them was doing.

And that's a better question than most people ever ask about that shelf. Because the shelf usually builds itself. One bottle because a friend swore by it. One because of a headline. One because it was on offer by the till. Nobody sits down and designs it. So I'd like to go through Priya's bottles one at a time. What each one is for. What the evidence says it does. And by the end, which ones stay, which ones go, and the one she's missing. Because she's missing one. And it's the one that matters most for her.

Hold that thought, because I want to get there properly. But start with the shelf itself. Five bottles, forty pounds a month. Is Priya unusual?

Not remotely. Not even slightly. The best figures on this come from America, so take them as a sense of scale rather than a British number. The recommendation from the United States Preventive Services Task Force cites survey data showing 52 per cent of adults had used at least one supplement in the previous month, and 31 per cent had used a multivitamin. So she's in the majority. And the reason people give is the interesting part. The most commonly cited reason, it says, is overall health and wellness, and filling nutrient gaps in the diet. Hold on to that phrase. Filling gaps. It turns out to be the key to the whole episode.

Filling gaps. Okay. So bottle one is the multivitamin. Which is the one most people would call obviously harmless and probably useful.

Harmless, mostly. Useful is harder. Much harder. The Task Force looked at exactly this question for heart disease and cancer. And it concluded the evidence is insufficient to say whether multivitamins help or harm. Not that they don't work. That nobody can tell. Then there's the evidence review underneath it, which found something small. A small benefit for cancer incidence with multivitamin use. But the reviewers also said the evidence for multivitamins had important limitations. So the fair summary is short. Not nothing. Not much. Not certain. Which is a strange thing to pay for every month. But it isn't a reason to panic and throw it away either.

Why is it so hard to tell, though? Millions of people take them. You'd think somebody would have just checked by now.

They have. Over and over. Big trials. And here's the thing that changes how you read every result in this episode. Look at who goes into these trials. The evidence review only included adults with no known vitamin or mineral deficiency. And that's the right design for the question being asked. Does topping up a healthy person prevent disease? But think about what that means. You're pouring petrol into a tank that's already full. And then you're measuring whether the car goes any faster. It doesn't. Of course it doesn't. But that's not a finding about petrol. It's a finding about full tanks.

So the question for Priya isn't really whether multivitamins work. It's whether her tank's empty to begin with.

Exactly that. Is the tank empty? And that's the frame for every bottle on the shelf. A supplement is a fix for a gap. If you've got the gap, it can matter a great deal. If you haven't, it's mostly buying nothing. So the question I'd want Priya asking of each bottle isn't "is this good for me". It's "what gap is this filling, and do I actually have it". For the multivitamin, she can't really answer that. She eats reasonably well. Nobody's told her she's short of anything. So it's a broad insurance policy against a gap nobody's found. Some people think that's worth the money. Fine. Some don't. Also fine. But there's one exception to all of that, and it comes up when we get to the baby.

And how would she even know if she had a gap? Because I think most people buy these on a feeling. Tired. Run down. Getting every cold going.

And that's the trouble with feelings. They lie. Tiredness is about the least specific symptom going. It's poor sleep. It's a busy job. It's winter. It's a toddler, for plenty of people. Occasionally it's a real deficiency. But you can't tell which from the inside. And a bottle off the shelf won't tell you either, because if you feel better you'll credit the bottle. Whatever the real reason was. So if Priya genuinely thinks she's short of something, the move isn't a guess at the pharmacy. It's a conversation with her GP, and possibly a blood test. That turns a feeling into a number. Then a supplement is treating something, rather than hoping.

Right. Bottle two. Fish oil. And this one's personal. Her dad had a heart attack at sixty-one. She started the capsules the month after.

Which is a completely understandable reason to buy it. Of course. And it's also the bottle where the evidence is biggest and clearest. There's a Cochrane review that pulled together eighty-six randomised trials. Big ones. Most trials assessed omega-three supplementation with capsules. So, exactly what Priya's taking. And what it found was little or no effect on dying from any cause, and it rates that as high-certainty evidence. Little or no effect on cardiovascular events either. So the thing she bought it for — protecting her heart the way her dad's wasn't protected — isn't what the big picture shows.

That's going to be hard for her to hear. Her dad's the whole reason the bottle's there. Is there really nothing in it?

There's a little, and I'd want her to have it straight rather than rounded down to zero. The same review found omega-three may slightly reduce deaths from coronary heart disease, and coronary events, though it calls that low-certainty evidence. And the size is small. Really small. For coronary events, the number needed to treat was 167. So roughly 167 people taking it, for one of them to avoid an event. Not zero. Just nowhere near what the bottle implies. And the review found little or no effect on serious adverse events, so as far as anyone measured, it isn't hurting her either. It's just not doing the job she hired it for.

Is there anything fish oil does do, then? Because I've seen it on blood test results. Something about fats in the blood.

Triglycerides. Yes. That one's real. And this one's worth understanding, because it catches people out. The Cochrane review found that increasing omega-three reduced triglycerides by about fifteen per cent, rated high-certainty evidence. So it does move a number. A real number, on a real blood test. But here's the trap. A number moving isn't the same as fewer heart attacks. Heart events are what the trials were actually counting. And on that, as we said, the effect was little or nothing. So a blood result can improve while the outcome you care about barely shifts. It happens all over medicine. It's worth knowing it happens here too.

Then what should she do with it? Because "the evidence is weak" doesn't feel like enough when it's your dad.

No, and I don't think the bottle's really the point. There's a better question hiding inside her dad's story. Does Priya know her own blood pressure? Her cholesterol? Does her GP know her father had a heart attack at sixty-one? Those are things somebody can measure. And if they're high, things somebody can actually do something about. A capsule feels like doing something. It's quiet, it's daily, it's under her control. But it's the weakest part of the plan. So keep it if she likes it. Just don't let it stand in for the appointment. And because she's planning a pregnancy, fish oil in pregnancy is its own conversation, with a midwife or a pharmacist. We didn't source that one, so we're not going to guess at it.

Bottle three is vitamin C. She takes it every day from October to March. Because she gets every cold going, and she's convinced it helps.

This one's been argued about for a very long time. The Cochrane review on it says it's been a subject of controversy for seventy years. And the answer's quite precise now. For ordinary people, taking it every day doesn't stop you catching colds. In the general community trials, the risk of getting a cold barely moved. But there was one group where it did. Marathon runners, skiers, and soldiers on subarctic exercises. People under brief, extreme physical stress. Their risk of a cold roughly halved. Which is fascinating. But Priya isn't on subarctic exercises. She's on the Northern line.

So for her it's useless. That's the verdict. Thirty-odd pounds a winter on fizzy tablets, and they don't stop a single cold.

Not quite. Not useless. And this is the part I find interesting. The same review found that regular vitamin C did shorten colds. In adults the duration of colds was reduced by about eight per cent. That's real. It's also small. On a cold that drags on for a week, you're talking hours, not days. And here's the catch for how Priya uses it. The benefit showed up in people taking it every single day, before they got ill. When people started it at the first sniffle, there was no consistent effect. So if she keeps it, the only version that makes sense is the every-day one. And she should know what she's buying. A slightly shorter cold. Not fewer of them.

But she'd swear it works. She takes it, and the cold goes. Every time.

And every cold goes. Every one. That's the trouble. A cold gets better on its own, almost always. So whatever you took last gets the credit. If Priya starts the tablets on day two and feels better on day six, the tablets look brilliant. But she'd probably have felt better on day six anyway. It's the same reason people swear by honey, or a hot toddy, or a particular brand of soup. It's not that they're lying. It's that a cold is a story that always has a happy ending. And whatever you were doing near the end gets written in as the hero. Trials exist precisely to get round that.

Okay. Bottle four. And this is the one I suspect you've been waiting for. Vitamin E. She bought it because the label says antioxidant.

This is the one I'd take off the shelf first. Straight away. And I want to say why carefully. The Task Force is about as cautious a body as exists. Most of what it says about supplements is some version of "we can't tell". But on vitamin E it goes further. It recommends against taking vitamin E to prevent heart disease or cancer. It concludes with moderate certainty there's no net benefit. And it says the same about beta carotene, only stronger. On beta carotene it says the harms outweigh the benefits. So this isn't the usual shrug. It's one of the few places this body says, plainly, don't.

Harms. From a vitamin. That's the bit people won't believe. Because the whole appeal of a vitamin is that it's natural, and natural feels safe.

It sounds absurd. I know. But it came out of trials, not theory. In the evidence review, beta carotene was associated with an increased risk of lung cancer. And that was in people already at high risk of lung cancer. Then the review found limited evidence of other harms too. Vitamin E, and a kind of bleeding stroke. Vitamin A, and hip fracture. Vitamin C and calcium, and kidney stones. Now, I want to be careful, because limited evidence means exactly that. Nobody should be frightened of their orange juice. But it kills off the idea that the worst a supplement can do is nothing. A pill that can do something can do the wrong something.

Does Priya's multivitamin have any of this in it? Because now I'm worried about the harmless one.

It might, and that's worth her turning the bottle round for. Some multivitamins carry beta carotene. Some carry vitamin E. The point isn't that a small amount in a multivitamin is dangerous. We don't have evidence either way on that, so I'm not going to claim it. The point is that she should know what's in it, rather than assume a vitamin is a vitamin. Read the back, not the front. The front is marketing. The back is the list. And for the vitamin E capsule on its own, I'd just stop. There's a recommendation against it, from the most cautious body in the business, for the very job its label hints at.

Right. So that's three bottles doing very little, and one she should stop. Bottle five. Vitamin D. And I'll admit, I take this one.

So do a lot of people. Plenty. And this is where the story turns. Because vitamin D is the bottle with the most contradictory headlines, and both sides are right about different things. Start with the big trial. It's called VITAL. Tens of thousands of people took part, men over fifty and women over fifty-five. They were given two thousand units of vitamin D a day, or a dummy pill. And they were followed for a median of just over five years. The question was cancer and heart disease. And vitamin D didn't result in a lower rate of invasive cancer or cardiovascular events than the dummy pill. So if Priya's taking it to prevent cancer, a very large trial says it won't. And it isn't one trial on its own. The evidence review found vitamin D use wasn't significantly associated with death, heart disease or cancer either.

Then why is anyone told to take it at all? Because I didn't start it for cancer. I started it because somebody told me to.

Because preventing cancer was never the reason it's recommended. And this is the bit the headlines keep missing. The UK advice is about running short, not about preventing disease. Vitamin D helps regulate calcium and phosphate, which keep bones, teeth and muscles healthy. The body creates vitamin D from direct sunlight on the skin. And here's the problem with living where Priya lives. Between October and early March, we don't make enough vitamin D from sunlight. The sun isn't strong enough. So the government advice is that everyone should consider a daily supplement containing ten micrograms of vitamin D during the autumn and winter. That's not insurance against a gap nobody's found. That's a gap we know about, every winter, for most people in the country.

So it's the gap thing again. Vitamin D isn't a booster. It's a refill.

That's it exactly. A refill. And it changes how you read the trial. The people in that American trial were being tested on whether extra vitamin D prevents cancer and heart disease. Not on whether running short does you harm. Those are completely different questions. You can be right that topping up a full tank does nothing, and right that running on empty is a problem. And the UK advice doesn't claim the first thing. It only claims the second. So Priya should keep this bottle. But there's a catch, and it's printed on her label. She bought the high-strength one. A hundred micrograms a tablet. And her multivitamin has another ten in it.

Is that a problem, though? It's a vitamin. If ten is good, surely a hundred is just more of the good thing.

This is the one place on the shelf where more can genuinely hurt. Taking too much over a long time can cause too much calcium to build up in the body. And that can weaken the bones and damage the kidneys and the heart. So the NHS is explicit about a ceiling. Don't take more than a hundred micrograms a day, as it could be harmful. Which means Priya's tablet on its own sits right on the line. Add the multivitamin and she's over it. Every day she takes both. And for what? The advice says ten micrograms a day will be enough for most people. She's taking eleven times that, to stand on the wrong side of a safety limit.

And how's she supposed to check that? Because half the labels I've seen say units, not micrograms. And the numbers are enormous.

That's a genuine trap. A big one. And the NHS spells it out. One microgram of vitamin D is forty units. So ten micrograms is the same as four hundred units. And the ceiling of a hundred micrograms is four thousand units. Which means if Priya's tablet says four thousand on the front, it's the same tablet. Same dose. Different number. And a bigger number looks like more. So the rule for her is simple. If it says micrograms, she wants ten. If it says units, she wants four hundred. Anything with a thousand in it, she should stop and ask why.

So swap the big one for a ten microgram one, and that's the problem solved.

Swap it, yes. And there's one more thing in that advice she should know, because it changes her answer specifically. It's not only autumn and winter for everyone. If you have dark skin, for example an African, African-Caribbean or south Asian background, you may not make enough from sunlight. And the advice is to consider ten micrograms throughout the year. It's the same if you're not often outdoors, or you usually cover most of your skin. Priya's family is from Gujarat. So for her, that moves the answer from "October to March" to "every day". Which makes it the one bottle she should take more consistently, not less. Just at a sensible dose.

Couldn't she just eat more oily fish instead, though? That feels more natural than another tablet on the shelf.

It helps. A bit. And the NHS lists the foods. Oily fish, like salmon, sardines or mackerel. Red meat. Egg yolks. Some fortified spreads and cereals. But it's blunt about the limit too. It says it's difficult for people to get enough vitamin D from food alone. And there's a British detail people don't expect. In the UK, cows' milk generally isn't a good source, because it isn't fortified, unlike in some other countries. So food's a good start. But for most people through a British winter, food on its own won't close the gap. That's why the advice lands on a tablet.

Every day, ten micrograms, and lose the big one. Okay. Which leaves the bottle you said she was missing.

Folic acid. That's the one. And this is the one where the evidence is about as strong as health advice gets. The Task Force says that for people planning to or who could become pregnant, there's high certainty folic acid supplementation has a substantial net benefit to prevent neural tube defects. That's conditions like spina bifida, where the baby's brain, skull and spinal cord don't develop properly. And it recommends a daily supplement containing four hundred to eight hundred micrograms of folic acid. It's graded A. Not a maybe. Not "evidence is insufficient". A clear yes. So of everything we've talked about, this is the bottle with the most behind it.

Why before, though? That's the part that sounds odd to me. If she's not pregnant yet, what's it actually doing?

Because the timing is the whole point. Folate matters most very early. The part of the baby it protects forms very early, often before anyone knows there's a pregnancy to protect. So by the time a test turns positive, the moment it mattered most can already be passing. And the Task Force notes that many neural tube defects are caused by low folate levels in the body. That's the gap again. Only this time it's a gap with a deadline on it. So the NHS says you should start taking it before you get pregnant, ideally three months before. And then keep going. If you're pregnant, you should take a folic acid supplement for the first twelve weeks.

Doesn't her multivitamin have folic acid in it, though? Most of them seem to.

It might. Plenty do. Not all. But "has some" and "has enough" aren't the same thing. She needs to turn the bottle round, find the folic acid line, and check whether it reaches four hundred micrograms. A general multivitamin may or may not. And there are two more things in the NHS advice worth her hearing. Some women who are pregnant, or planning a pregnancy, need a higher dose than others, and it says to check with a pharmacist, midwife or doctor. And if she's pregnant, she should check before taking a multivitamin that contains folic acid. So this is exactly the conversation to have now, before the new year. Not in the second month of a pregnancy.

And this is the one that wasn't on the shelf at all. That's the bit that got me when you said it.

It's the bit I keep coming back to. Five bottles. Forty pounds a month, and the single supplement with the strongest evidence for someone in her exact situation wasn't one of them. And not because she's careless. She's clearly the opposite of careless. She's spending money every month trying to look after herself. It's because nobody's marketing folic acid to her. It's dull. It doesn't promise glowing skin, or immunity, or energy. It doesn't come in a pretty jar. So the shelf got built by what was being sold to her. Not by what she needed. And I think that's true of most shelves. They're a record of adverts and recommendations, not of gaps.

Can I ask what everybody's thinking at this point? How can any of these be sold, if the evidence is this thin?

Because legally a supplement isn't a medicine. The clearest statement of that comes from the American regulator, the FDA. It says it doesn't have the authority to approve dietary supplements for safety and effectiveness before they're sold to the public. Under that law, it's the responsibility of the companies to make sure their products meet the safety standards. That's the American rule, and we haven't checked every country's, so I won't claim they're all identical. But it's a useful reminder of what you're holding. A medicine had to show somebody it worked. A supplement mostly had to show somebody it would sell.

So next month, when something new turns up in her feed promising energy or immunity or whatever the word is that week, how should she judge it? Because there'll always be another bottle.

Three questions, and they take about ten seconds. What gap does this fill? Do I actually have that gap, and how do I know? And who says it works — a trial, a guideline, or the people selling it? If she can't answer the first, it's probably not for her. If the answer to the last one is only the seller, she's reading an advert. That's not a crime. Adverts are allowed. But it's worth knowing which one you're reading. And notice it's the same test we've used all episode. Bottle by bottle. It's just the shelf, run in advance.

It's all a bit bleak, though, isn't it? Is there anything genuinely reassuring in all this for her?

Quite a lot, actually. Genuinely a lot. Because the news for Priya is mostly good. Nothing on the shelf is a disaster. The vitamin E is unnecessary. The vitamin D dose is simply too high. Both easy to fix. And the one thing that genuinely matters for her — folic acid — is one small tablet a day. She doesn't have to become an expert in nutrition. She needs three changes and one appointment. That's a far better place to be than where she started, staring at forty pounds of bottles with no idea what any of them did.

So bring it back to her. It's Monday morning. What does she actually do with the shelf?

First thing, she buys folic acid. Today. Not next month. Four hundred micrograms a day, and she asks a pharmacist whether she's one of the women who needs more. Second, she bins the high-strength vitamin D and buys a ten microgram one. And because of her family background, she takes it every day of the year. Third, the vitamin E goes. Fourth, the vitamin C is her choice. But it's either every day through winter, for a slightly shorter cold, or not at all. Taking it at the first sniffle is the version with nothing behind it. And then the multivitamin and the fish oil. She reads the back of the multivitamin. And she books the GP appointment her dad's heart attack ought to have prompted already. Blood pressure, cholesterol, family history. That's the real heart plan. The fish oil can stay or go. It's not the thing that matters.

And the forty pounds a month? Because that's where she started.

Probably it drops. I won't put a number on it, because prices vary and I'd only be guessing. But the shape of the shelf changes. The vitamin E goes. The folic acid comes in. The vitamin D gets smaller. And the vitamin C and the fish oil become choices she's making on purpose, rather than bottles she's scared to stop. And the bigger change isn't the money at all. It's that she can now say what each bottle is for. Which was the question that started all this. She looked at the shelf and couldn't name a single job. Now every bottle has a job, and the ones without a job have gone.

Before we finish — what don't we know? Because you've been careful about that line all episode, and I want you to draw it.

Three things. Three big ones. First, who was in the trials. The vitamin D trial took men over fifty and women over fifty-five. Priya's thirty-six. So when we say vitamin D didn't prevent cancer or heart disease, that's a finding about older adults. It probably carries over. But it wasn't measured in her. Second, everything we've said about prevention was tested in people without a known deficiency. If a blood test shows she's short of something, iron or anything else, that's a different question entirely, and the answer comes from her doctor rather than from this. And third, the long tail. Turmeric. Collagen. The powders. The mushroom blends. We haven't sourced any of those for this episode, so we're not going to tell you anything about them. And I'd gently point out that "nobody's tested it" isn't the same as "it works". It's just the absence of an answer. Nothing more. And I'd rather say that plainly than fill the gap with a guess, because a guess said confidently on a podcast is exactly how most of those bottles got onto the shelf.

If Priya takes one thing from all this, one sentence she can say to herself in the aisle next time, what is it?

That a supplement is a refill, not an upgrade. If there's a gap, it can matter enormously. Folic acid before a pregnancy is the clearest example of that. Vitamin D through a British winter is another. If there's no gap, you're mostly pouring petrol into a full tank. So the question to ask of every bottle isn't "is this healthy". It's "what's it filling, and do I actually have that gap". Ask that, and most shelves shrink. And the one thing they were missing tends to show up.

And three things to take to her doctor. Because she's going to be there anyway, with the folic acid question.

First. I'm planning a pregnancy. What dose of folic acid should I take, and am I someone who needs a higher one? That's the most important question on the list. Second. My father had a heart attack at sixty-one. Can we check my blood pressure and my cholesterol? Because that's what her fish oil was really trying to answer, and it's a question the capsule can't answer. And third. Should I be taking vitamin D all year, given my background, and at what dose? She'll probably hear ten micrograms. Which is less than she was taking, and safer. Which is the nicest kind of answer a doctor can give you. And also the least exciting one. Which is usually how it goes.