It’s official. Vitamins don’t do much for your health

This transcript has been edited for clarity.

welcome to Impact factor, your weekly dose of commentary on a new medical study. I am Dr. F. Perry Wilson from the Yale School of Medicine.

Vitamins. If you are like majority of American adults, you have taken a vitamin or supplement recently. Non-prescription sales of these products in this country amount to more than 30 billion dollars per year. It’s more than the statin market — and vitamins are not covered by insurance.

For there to be a $30 billion market, there has to be pretty compelling evidence that vitamin supplements improve health, right?

Well, in the most in-depth meta-analysis to date, Kaiser-Permanente researchers crunched the numbers from virtually every randomized trial of vitamin supplements in adults to conclude that basically they don’t do anything.

Or, as they say in nephrology: vitamins make pee expensive.

As many of you know, the US Task Force on Preventive Services (USPSTF) makes evidence-based recommendations to the American people on a wide variety of health behaviors, aspirin in primary prevention at lung cancer screening.

The USPSTF has commissioned researchers to update data on vitamin supplementation with two important outcomes in mind: cancer and cardiovascular death. Why vitamins? Because the observational data is clear and convincing. People with vitamin deficiencies are at higher risk for these poor outcomes.

Even people with lower levels of certain vitamins, which are not in the deficiency range, are at higher risk for cancer and cardiovascular disease. It stands to reason that if lower levels are associated with poor results and supplements prevent you from having lower vitamin levels, then supplements could improve those results.

The researchers identified 87 randomized controlled trials of adults where at least one vitamin or multivitamin was being evaluated. Caution: These were studies in the general population, not studies in people with known vitamin deficiencies. The results should not necessarily be generalized to those with known deficiencies or disease states that promote deficiency.

There are a lot of vitamins, so there’s a lot to cover, but I’ll touch on some of the highlights.

Of all the multiple potential links between vitamins and outcomes, only one – the link between multivitamin use and cancer – showed any sign of benefit.


It’s a little frustrating because “multivitamins” can mean a lot of things. There were nine randomized trials evaluating “multivitamins” that when combined show this effect, but the specific types of multivitamins were diverse, ranging from a personalized antioxidant cocktail to Centrum Silver. So no, I don’t know which multivitamin you should take.

To be honest, the effect isn’t even that impressive: a 7% relative reduction in cancer incidence. And relative risks really tend to exaggerate the size of the effect. In absolute terms, multivitamins reduced cancer incidence by about 0.2%. This means that 500 people would have to be treated with a multivitamin to prevent one case of cancer.

And while these studies did not specifically recruit patients with vitamin deficiencies, some of those who participated in them may have had them. What we might see is a small population effect based on the benefit accrued by a small number of people who were truly vitamin deficient.

And it really is the best finding of the whole study if you’re a vitamin lover.

No analysis of individual vitamins — beta-carotene, vitamin A, Vitamin E., Vitamin D (with an impressive 32 randomized trials) and calcium supplements – have shown significant benefits in terms of cardiovascular disease or cancer. They don’t seem to do much.

So what makes taking a vitamin so compelling? Why do so many of us, even knowing that the data doesn’t really back it up, continue to take a pill daily? I think there are several reasons.

First, we have to recognize the fact that vitamins are generally quite cheap and have a very low rate of side effects. They don’t make you dizzy or nauseous, tachycardic or tired. They don’t want much.

Given the low risk, something of a Pascal gamble develops here. Sure, vitamins may not help, but they don’t seem to hurt, so why not take them, just in case.

Well, the truth is, they might actually hurt a little. The authors also analyzed adverse events in all of these vitamin trials, although to assess the harm they too included observational studies. This may seem unfair – assess the benefits only with randomized trials, but the harms via randomized trials and observational studies. But I think that’s actually correct, given that the direction of bias in observational studies tends to favor vitamins given the “healthy user effect”. It’s the idea that people who choose to take vitamins tend to make other healthy lifestyle choices, so if you see any harm in taking a vitamin as part of the observation, you’ll probably want to lend a hand. Warning.

Notable findings from the harm analysis included evidence that vitamin A use may increase the risk of hip fracturethat the use of vitamin E could increase the risk of hemorrhagic strokeand that the use of vitamin C or calcium could increase the risk of kidney stones.

Why are observational data showing lower vitamin levels linked to poorer outcomes so powerful, and randomized trial data on supplementation so weak? This is classic confusion. Basically, healthy people have higher vitamin levels and healthy people have less cardiovascular disease and cancers. Vitamin levels are a marker of overall health, not a driver of overall health.

But to be fair, there’s probably not too much harm in taking this daily vitamin. We must not discount here the ineffable value of the ritual. Taking a vitamin, even if it’s a small gesture, is nonetheless an act of self-care — a time taken for yourself and for yourself alone — a commitment to try to to be in a good health. A brief moment of positivity in the morning may not reduce heart attacks or cancer rates, but it may still have benefits.

F. Perry Wilson, MD, MSCE, is Associate Professor of Medicine and Director of the Yale Clinical and Translational Research Accelerator. His science communication work can be found in the Huffington Post, on NPR, and here on Medscape. He tweets @fperrywilson and hosts a repository of its communications work on www.methodsman.com.

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