One of the most common questions I get as an advocate of SBM is – should I take a multivitamin? On the one hand it makes superficial sense. Vitamins and minerals are micronutrients necessary for optimal health, we may not be getting all we need from our Western Industrialized diet, so supplementing is just nutritional insurance. On the other hand, there is a huge marketing campaign selling vitamins, they are mostly pushed by gurus, and the claims for them seem overblown. Where does the truth lie?
We have been answering this question since at least 2008 – multivitamins are mostly useless. This conclusion is now supported by the US Preventive Services Task Force (USPSTF) final recommendation statement, discussed in a recent editorial in JAMA. The USPSTF makes three basic recommendations:
- The USPSTF recommends against the use of beta carotene or vitamin E supplements for the prevention of cardiovascular disease or cancer.
- The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the use of multivitamin supplements for the prevention of cardiovascular disease or cancer.
- The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the use of single or paired nutrient supplements (other than beta carotene and vitamin E) for the prevention of cardiovascular disease or cancer.
These recommendations are for non-pregnant healthy adults. Pregnant women should take folic acid and iron, and should be under the care of their OB. Individuals may also have specific nutritional needs, need to treat a nutritional deficiency, or may have an illness which can benefit from specific supplementation. Targeted supplementation in these situations should be based on measurements of blood levels of the specific nutrients and occur under the guidance of a physician.
But for healthy non-pregnant adults, there is essentially no convincing evidence that routine supplementation, of individual vitamins or multivitamins, is of any health benefit. The USPSTF specifically recommends against beta carotene and vitamin E supplementation because there is evidence that such supplementation increases the risk of overall mortality, cardiovascular mortality, or lung cancer.
This brings up a very important point – vitamins are not necessarily benign. The supplement industry spend about $900 million a year (to support a $50 billion industry). Vitamins are marketed as “natural” and harmless, but they not harmless. Every vitamin is associated with toxicity if the dose is too high. Further, vitamin use, especially beta carotene and vitamin E, may actually increase the risk of major disease, like cancer. While we don’t know the precise mechanism, one theory is that vitamins can feed the metabolically-demanding cancer cells. Regardless, it is an easy recommendation to make to avoid high doses or “megadoses” of any vitamins or supplements, as the potential for harm increases dramatically.
For multivitamins and vitamins other than beta carotene or vitamin E the USPSTF simply says that there is “insufficient evidence” to recommend their routine use, but let’s dive into the details. This does not mean that we don’t have studies – there are multiple large studies. The problem is essentially two-fold. First, it is difficult to do large, controlled studies with vitamins. This does occasionally happen, but most of the data is ecologically, correlating vitamin use with health outcomes. The problem with ecological data is that it is correlational only, with many possible confounding factors.
For example, there are potentially both healthy user and sick user effects. People who take vitamins may also do other things to support their health, such as exercise and eat well. If they have better outcomes, what is causing it, the vitamins or the exercise? On the other hand, people who are sick may be more likely to take vitamins because they think they will help, causing an association between negative health outcomes and vitamins. It’s like the association between dieting and being overweight – dieting results from, and does not cause, being overweight. How do these two opposing confounding factors sort out? We don’t know.
But there is a second and important cause of the insufficient evidence to know what the net health effect of supplementation is – there is likely no large effect. If there were a large benefit from vitamins, we would be able to see it in the data. The signal would be strong. While proving a negative (a lack of an association) is impossible with outcome data, even high-quality data, the evidence can set statistical limits on the possible size of any remaining effect. So while we can’t say there is zero benefit, or zero harm, for that matter, we can say that any possible effect is extremely small. We can chase that tiny effect with increasingly powerful and rigorous studies, but as a public health measure it’s likely to be insignificant.
And this brings us to an important conclusion of the USPSTF and JAMA editorial recommendations – routine vitamin supplementation is not an effective public health intervention. Even worse, it is likely a costly distraction from more effective measures. More than half of Americans take routine supplementation, for no demonstrable benefit (and in some cases possible harm). This accomplishes nothing but feeding supplement industry profits.
Rather, the evidence clearly shows that there are health benefits to having a well-balanced diet with plenty of fruits and vegetables. Taking a supplement as “insurance” may result in a false sense of security, giving people permission to not spend as much effort on their diet. This will have negative health outcomes. Exercise is also a proven lifestyle intervention with a host of health benefits. Good sleep, not smoking, and using alcohol with moderation are other proven lifestyle choices with health benefits, and there is generally no need to complicate things beyond this basic advice.
These are the big five – diet, exercise, sleep, and avoiding smoking and excessive alcohol use. These factors all have big signals in the evidence, they have proven substantial benefit. Yet many people focus on the margins, on possible tiny benefits that may not even be there. Multivitamins are also just part of a much larger problem – a self-help and “wellness” industry that focuses people’s attention mostly on the wrong things. They may pay lip service to the proven lifestyle factors above (that’s low hanging fruit), but for them their real “value added” is being “experts” (sorry for the excessive scare quotes use) in natural medicine, bogus nutritional advice, and pushing fashionable trends like organic food, avoiding GMOs, and “processed” foods.
The wellness industry is really an industry of expensive distraction. This is because the answer to a healthful lifestyle is already out there, and already part of mainstream medicine – diet, exercise, good sleep, avoid smoking and drinking. For most healthy adults, that’s all they need. The info can fit on a pamphlet. That’s the 95%.
In terms of public health, we need to focus on making healthy choices easier and more affordable. Healthy food tends to be more expensive, and many people live in “food deserts” where fresh produce is not available. Meanwhile bad food choices are cheap and abundant. Cities can also be redesigned to facilitate walking and riding bikes. Workplaces can encourage movement and exercise, rather than sitting at a desk all day. Public education can help improve overall sleep hygiene.
These measures can have a large proven health benefit. Multivitamins are an expensive and largely worthless distraction.