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Simon Parrott – Vitacuity Ltd
Health headlines often use “relative risk” to describe supplement dangers, which can be misleading without the actual numbers. For example, “doubles your risk” sounds terrifying but might mean going from a 1 in 100 chance to a 2 in 100 chance. The most famous alarming findings, like beta-carotene causing lung cancer in smokers or vitamin E raising death risk, become far less dramatic when you look at absolute risk and the specific populations studied.
Many of these studies also show that the same supplement helps some people while harming others. For instance, vitamin E reduced pneumonia risk by 69% in light smokers but increased it by 68% in heavy smokers, so the average effect appeared neutral. Geographic and lifestyle factors often matter enormously, but headlines strip away this crucial context.
On the positive side, vitamin D supplementation showed a consistent 13% reduction in cancer mortality across over 81,000 people in multiple large trials, suggesting a genuine benefit. Water-soluble vitamins like B vitamins and vitamin C are safe at standard doses since excess is simply excreted. The key lesson is asking “relative or absolute?” whenever you see a supplement statistic.
Verdict: Most alarming supplement headlines are technically accurate but practically misleading because they use relative risk figures and ignore population-specific context, while genuine benefits like vitamin D’s effect on cancer mortality often go underreported.
What if the most frightening health statistic you’ve ever read was technically accurate, but practically meaningless? What if “doubles your risk” could mean the difference between a 1-in-100 chance and a 2-in-100 chance, a change so small it would barely register in a room of a thousand people? And what if the supplement industry, the media, and even some academic papers were all, sometimes inadvertently, sometimes not, exploiting this confusion to make you more scared, more hopeful, or more likely to buy something?
Welcome to the world of relative risk versus absolute risk. It’s one of the most important ideas in all of health science, and almost nobody explains it clearly. At Vitacuity, we’ve sifted through over 1.77 million research papers to bring you the ones that matter most. On this topic, we found something striking: some of the most alarming supplement headlines of the last two decades, “beta-carotene causes lung cancer!”, “vitamin E raises mortality!”, turn out to tell a far more complicated, far more nuanced story once you understand how the numbers actually work. Let’s dig in.
Before we look at any specific research, you need two definitions. They’re simple, but they change everything.
Absolute risk is your actual probability of something happening. If 2 people in 100 develop a disease, your absolute risk is 2%.
Relative risk is how much a factor changes that probability, expressed as a ratio. If an intervention raises your risk from 2% to 3%, the relative risk increase is 50%, because 3 is 50% more than 2. But the absolute risk increase is just 1 percentage point.
Here’s why this matters so much: “50% increased risk” sounds catastrophic. “1 in 100 extra people affected” sounds manageable. They describe *exactly the same thing*. Headlines almost always use relative risk because it sounds more dramatic. Researchers, to be fair, often use it too, because it’s a legitimate statistical tool for comparing across populations with different baseline rates. But without the absolute numbers alongside it, relative risk can be deeply misleading.
This isn’t a niche statistical quibble. It sits at the heart of how we interpret supplement research, including some of the most famous studies ever conducted.
Few findings in nutrition science caused more alarm than the discovery that beta-carotene supplements appeared to increase lung cancer risk in smokers. The story is real, but the way it’s usually told strips out almost all of the context that makes it useful.
The Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study is probably the most cited, and most misunderstood, supplement trial ever run. It studied Finnish male smokers aged 50–69, and it found that beta-carotene supplementation was associated with increased lung cancer incidence in this population [7].
What’s rarely discussed is the nuance embedded in the data. A 2019 analysis published in *Cancer Epidemiology, Biomarkers & Prevention* found that the increased risk associated with beta-carotene supplementation in smokers actually varied significantly depending on the tar and nicotine content of the cigarettes smoked [7]. In other words, even within a high-risk population of smokers, the effect wasn’t uniform. The headline “beta-carotene causes lung cancer” glosses over a more specific finding: high-dose beta-carotene supplementation, in heavy smokers of high-tar cigarettes, was associated with elevated risk.
Evidence grade: Promising (in the sense that a real signal exists), but the specific conditions matter enormously.
The VITAL cohort study (Washington State, 2009) extended this picture. Among 77,126 participants aged 50–76, long-term use of individual beta-carotene supplements was associated with a hazard ratio of 3.22 (95% CI: 1.29–8.07) for small-cell lung cancer compared to non-use, but this was over more than four years of use, and the absolute number of small-cell lung cancer cases in the cohort was 521 out of 77,126 [4]. That’s a baseline rate of about 0.67%. Even a tripling of relative risk in a sub-group still involves very small absolute numbers, though that is not a reason to dismiss the finding, especially for smokers.
The practical message here is important: high-dose individual beta-carotene supplements are genuinely not recommended, particularly for smokers. The signal is real. But the framing matters enormously. “Beta-carotene is dangerous” and “high-dose beta-carotene supplements are not recommended for smokers” are very different statements, one triggers generalised fear, the other gives you actionable, specific information [4] [7].
Perhaps the clearest illustration of how statistical methods shape, and can distort, health conclusions involves vitamin E. In the early 2000s, a series of meta-analyses concluded that vitamin E supplements were associated with increased all-cause mortality. The headlines were alarming. The research, it turned out, was more complicated.
A 2017 analysis published in *Nutrition Research* examined the Cochrane Systematic Review (CD007176, 2012) that had concluded alpha-tocopherol forms of vitamin E had a statistically significant effect on mortality [3]. The paper identified a serious methodological problem.
The ATBC Study, the Finnish smoker trial mentioned above, accounted for a massive 42.6% of the statistical weighting in the Cochrane meta-analysis. And the way the ATBC data was analysed introduced a significant error: the Cochrane Review used a three-cell analytical method, comparing all vitamin E groups (vitamin E alone plus vitamin E combined with beta-carotene) against the placebo-only group. The problem? This approach failed to properly account for the independent mortality contribution of beta-carotene, thereby inflating the apparent mortality risk of vitamin E [3].
When the ATBC data was re-analysed using the more standard two-cell method (vitamin E versus placebo) or the four-cell method (all vitamin E versus all non-vitamin E), the result became statistically non-significant. In other words, once you correctly account for what beta-carotene was doing independently, the vitamin E mortality signal in the most heavily weighted study largely disappears [3].
This isn’t a minor technical footnote. A 42.6% weighted study with a flawed analytical method can swing the conclusion of an entire meta-analysis, and did. The lesson here isn’t that vitamin E is perfectly safe in all doses for all populations. It’s that a headline reading “Vitamin E Raises Death Risk” can be generated from a meta-analysis with a significant methodological flaw, get picked up globally, influence regulatory decisions, and frighten millions of people, on the basis of numbers that, when properly calculated, were not statistically significant.
Evidence grade: Conflicted, the original alarm was based partly on a methodological error, but this doesn’t mean high-dose vitamin E is without risk in all contexts. The weight of evidence does not support routine high-dose vitamin E supplementation in the general population, but the mortality scare was significantly overstated.
Here’s another layer of complexity the headlines rarely capture: even when a supplement shows no average effect, it may be genuinely helping some people and genuinely harming others, and these effects cancel out in the overall data.
A 2016 paper in the *British Journal of Nutrition* used the ATBC Study data to examine vitamin E’s effect on pneumonia risk using the I² statistic, a tool that measures how much variation between study results is real versus due to chance [5]. The finding was striking. The I² value for heterogeneity in vitamin E’s effect on pneumonia was 89–92%, meaning almost all the variation in outcomes was genuine, not random noise.
Vitamin E supplementation decreased pneumonia risk by 69% in participants who smoked the least and exercised during leisure time (about 7.6% of the ATBC cohort). But it increased pneumonia risk by 68% in those with the highest smoking exposure who did not exercise (about 22% of the cohort) [5].
Think about what happens when you average those two effects together. You get… roughly nothing. A null result. A study that appears to show “vitamin E doesn’t affect pneumonia risk” is actually hiding the fact that it dramatically helped one group and dramatically harmed another. The absolute numbers matter here too, but the point stands: average effects can be deeply misleading when the underlying biology is heterogeneous.
This is a fundamental challenge in nutritional research that relative risk statistics, reported without subgroup context, systematically obscure. Evidence grade: Promising for the subgroup heterogeneity finding specifically, this is solid methodology applied to a large RCT dataset.
Now let’s look at an example where the absolute risk numbers, when you actually read them, tell a more reassuring story than the relative risk figures might suggest, and where the conclusion is more positive than many headlines imply.
A 2019 meta-analysis published in *Bioscience Reports* pooled data from 10 randomised controlled trials involving 81,362 participants to examine vitamin D supplementation and cancer outcomes [10]. On cancer incidence, vitamin D showed no significant benefit (RR = 0.99; 95% CI: 0.94–1.03). So far, so uninspiring. But here’s where the absolute numbers become interesting: cancer mortality was 2.11% in the vitamin D group versus 2.43% in the placebo group, a statistically significant reduction (RR = 0.87; 95% CI: 0.79–0.95; P = 0.003) [10].
That relative risk reduction of 13% in cancer mortality sounds modest. But in a population-level study of over 81,000 people, a 0.32 percentage point absolute reduction in cancer mortality is real and meaningful. It suggests vitamin D may not prevent cancers from developing, but may influence how they progress.
A second 2019 meta-analysis in *Annals of Oncology* (10 trials, 6,537 cancer cases, follow-up of 3–10 years) confirmed this pattern: no significant effect on cancer incidence (RR = 0.98; 95% CI: 0.93–1.03), but a significant 13% reduction in cancer mortality (RR = 0.87; 95% CI: 0.79–0.96; P = 0.005) [13]. Crucially, this mortality benefit was driven by daily dosing protocols, infrequent bolus doses did not show the same effect [13].
Evidence grade: Strong for the cancer mortality finding specifically, multiple large RCTs, consistent direction of effect, no significant heterogeneity.
Neither headline, “Vitamin D prevents cancer!” nor “Vitamin D useless for cancer!”, captures what the evidence actually shows. The truth requires the absolute numbers, the distinction between incidence and mortality, and an understanding of how dosing frequency affects the outcome.
The story of vitamin E and prostate cancer is another case study in how the same data generates opposite-sounding conclusions depending on how it’s framed.
A 2022 meta-analysis in a peer-reviewed journal pooled observational and interventional studies examining vitamin E intake and prostate cancer risk [12]. Overall, the association between dietary vitamin E (RR = 0.97; 95% CI: 0.92–1.02) and supplemental vitamin E (RR = 0.99; 95% CI: 0.94–1.04) and prostate cancer risk was statistically non-significant. In plain English: across the whole population studied, vitamin E intake didn’t meaningfully change prostate cancer risk in either direction [12].
But in the subgroup analysis of European studies, supplemental vitamin E was associated with a statistically significant reduced risk (RR = 0.81; 95% CI: 0.69–0.97). A 19% relative risk reduction sounds significant, but what does it mean in absolute terms? Prostate cancer risk over a lifetime is roughly 1 in 8 men. A 19% relative risk reduction would shift that to approximately 1 in 9.5. Meaningful, but much less dramatic than the relative figure implies [12].
Evidence grade: Conflicted, population-level null effect with a potentially real signal in specific European populations. The reasons for geographic variation remain unclear, and absolute effect sizes are modest. This does not support routine high-dose supplementation for prostate cancer prevention, but neither does it support alarm.
Being honest about the gaps is central to how Vitacuity operates. Here’s what the research above genuinely cannot tell us:
We don’t fully understand why the same supplement helps some people and harms others. The ATBC pneumonia finding, vitamin E helping light exercisers and hurting heavy smokers by roughly equal amounts, points to profound individual variability [5]. We don’t yet have reliable clinical tools to predict which category any given person falls into.
We don’t know the optimal doses for most of these effects. The vitamin D cancer mortality finding was significant in studies using daily dosing, but not in bolus dosing trials [13]. Whether different daily doses would produce different effect sizes remains unclear.
Most of the alarming supplement findings come from specific, high-risk populations. The ATBC Study was conducted on Finnish male smokers in their 50s and 60s, a very specific cohort [3] [5] [7]. Applying those findings universally, as headlines typically do, is not scientifically justified. At the same time, the signals in high-risk populations deserve to be taken seriously.
The distinction between dietary and supplemental intake matters more than it’s usually discussed. The bladder cancer meta-analysis found different signals for dietary vitamin E versus supplemental vitamin E, with dietary alpha-tocopherol showing a significant protective association (RR = 0.83; 95% CI: 0.72–0.95) while supplemental vitamin E alone did not [11]. This may reflect dose, form, or simply the fact that dietary vitamin E comes packaged with other protective food compounds.
Meta-analyses are only as good as the studies they include, and the methods they use. The vitamin E mortality story is a sobering reminder that even Cochrane-level systematic reviews can produce misleading conclusions when methodological choices are flawed [3]. This isn’t an argument to distrust research, it’s an argument to understand it, which is exactly what we’re trying to help you do.
So what should an intelligent, health-conscious person actually do with all of this?
First: train yourself to ask “relative or absolute?” whenever you see a health statistic. “Doubles your risk” means almost nothing without knowing the baseline. A doubling from 0.5% to 1% is very different from a doubling from 10% to 20%. If a news article or a supplement company doesn’t give you both numbers, treat the claim with scepticism, not because it’s wrong, but because it’s incomplete.
Second: context collapses important distinctions. Almost every alarming supplement finding in the research above comes from a specific population (heavy smokers, people with particular health histories) at a specific dose (often high-dose individual supplements rather than standard multivitamin levels). If you’re a non-smoker taking a standard supplement formulation, the beta-carotene lung cancer finding is not particularly relevant to you [4] [7]. If you’re a smoker, it very much is.
Third: the vitamin D cancer mortality finding is genuinely encouraging, and actionable. Across more than 81,000 participants in multiple RCTs, daily vitamin D supplementation was associated with a consistent 13% reduction in cancer mortality [10] [13]. This isn’t a cure or a guarantee, but it’s a real effect at a population scale, from a supplement that is safe, cheap, and addresses one of the most common nutrient deficiencies in the UK. Vitamin D is fat-soluble, but genuinely difficult to overdose at standard supplement doses (1,000–4,000 IU daily). The risk of deficiency, which is extremely common in the UK, especially through winter, almost certainly outweighs the risk of supplementing at normal doses. Supplement daily with confidence.
Fourth: don’t let “conflicted” mean “doesn’t work.” The vitamin E story is genuinely conflicted, there are real signals in some populations, null results in others, and methodological problems in some of the most alarming meta-analyses [3] [5] [12]. “Conflicted” means “we don’t fully understand this yet”, not “dangerous” and not “useless.” The honest answer is: standard dietary doses of vitamin E appear safe and potentially beneficial; high-dose supplementation remains less clear, particularly for smokers.
Fifth: for water-soluble vitamins (B complex, vitamin C) the calculation is simple. Excess is excreted. Deficiency is common and harmful. Supplement daily, it’s the safe, practical default.
The bigger picture: most alarming supplement headlines are technically accurate and practically misleading at the same time. They choose relative risk over absolute risk, they collapse heterogeneous populations into single averages, and they strip away the context that makes a finding actually useful. Understanding this doesn’t mean ignoring risk, it means understanding it properly, which is the only way to make genuinely informed decisions about your health.
At Vitacuity, this is what we’re here for. Not to tell you everything is safe. Not to tell you everything is dangerous. But to read the research, all 1.77 million papers and counting, and give you the honest, nuanced picture that the headlines almost never do.
[1] Food supplements and fortified foods: benefits, risks and approaches to consumer protection (2025). DOI: 10.1007/s00103-025-04134-1 | https://pubmed.ncbi.nlm.nih.gov/41071248/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12583368/
[2] Dietary supplements and cancer prevention: balancing potential benefits against proven harms (2012). DOI: 10.1093/jnci/djs195 | https://pubmed.ncbi.nlm.nih.gov/22534785/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3352833/
[3] Validity of a Cochrane Systematic Review and meta-analysis for determining the safety of vitamin E (2017). https://pubmed.ncbi.nlm.nih.gov/28814337/
[4] Long-term use of beta-carotene, retinol, lycopene, and lutein supplements and lung cancer risk: results from the VITamins And Lifestyle (VITAL) study (2009). https://pubmed.ncbi.nlm.nih.gov/19208726/
[5] Vitamin E and the risk of pneumonia: using the I² statistic to quantify heterogeneity within a controlled trial (2016). https://pubmed.ncbi.nlm.nih.gov/27780487/
[6] Vitamin D and omega-3 fatty acid supplementation does not reduce the cancer and cardiovascular risk (2019). DOI: 10.1007/s00066-019-01455-4 | https://pubmed.ncbi.nlm.nih.gov/31001644/
[7] β-Carotene Supplementation and Lung Cancer Incidence in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study: The Role of Tar and Nicotine (2019). https://pubmed.ncbi.nlm.nih.gov/29889248/
[8] Dietary Supplements, For Whom? The Current State of Knowledge about the Health Effects of Selected Supplement Use. DOI: 10.3390/ijerph18178897 | https://pubmed.ncbi.nlm.nih.gov/34501487/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8431076/
[10] Meta-analysis of randomized controlled trials on vitamin D supplement and cancer incidence and mortality (2019). DOI: 10.1042/BSR20190369 | https://pubmed.ncbi.nlm.nih.gov/31696224/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6851517/
[11] Association of vitamin C, vitamin D, vitamin E and risk of bladder cancer: a dose-response meta-analysis (2015). https://pubmed.ncbi.nlm.nih.gov/25905583/
[12] Vitamin E Intake and Risk of Prostate Cancer: A Meta-Analysis (2022). https://pubmed.ncbi.nlm.nih.gov/36615673/
[13] Vitamin D supplementation and total cancer incidence and mortality: a meta-analysis of randomized controlled trials (2019). DOI: 10.1093/annonc/mdz059 | https://pubmed.ncbi.nlm.nih.gov/30796437/ | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6821324/
This article is for informational purposes only and does not constitute medical advice. Food supplements should not be used as a substitute for a varied and balanced diet and healthy lifestyle. If you are pregnant, breastfeeding, taking medication or have a medical condition, consult your doctor before taking any supplement. These statements have not been evaluated by the Food and Drug Administration (FDA) or the Medicines and Healthcare products Regulatory Agency (MHRA). This product is not intended to diagnose, treat, cure, or prevent any disease.
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