Preventive Medicine Column
Dr. David L. Katz
You have likely heard about a recent study, involving roughly 40,000 women over the age of 60, in which daily use of a multivitamin- and several other nutrient supplements- was associated with a higher rate of death. Along with the mix of shock, consternation, and disappointment is the very practical question: could a multivitamin kill you?
Almost certainly not! The current study- like others before it that have hinted at much the same association- is absolutely NOT cause for panic. For each such study, there is another showing no real harm. That vial of (now menacing) multivitamins in your medicine cabinet doesn’t mean you need to fast track the preparation of your will & testament.
For starters, the study now making headlines, and the similar studies preceding it, are observational. A large group of people is simply followed and assessed over time, and the associations between what they do, and what happens to them, are analyzed.
In the current case, routine use of a multivitamin was associated with roughly a 2% greater chance of dying over a 20-year span for women over age 60. So, for starters, a 2% increased risk of dying over 20 years is not exactly cause for panic- especially when one considers that dying in our early 80s is not entirely unexpected or untimely.
But even more important, these women were not assigned to a multivitamin or placebo; they made up their own minds. Some chose to take nutrient supplements, some did not. How did these two groups differ? Like all good observational studies, this one attempted to account for obvious differences- in education, income, smoking status, general dietary pattern, and so on- but the only honest answer is: we don’t know! We can’t possibly know all the ways women who opt to take nutrient supplements differ from those who don’t. (That, by the way, is why randomized trials can be so important; they reliably correct for this limitation of observational studies.)
So, for instance: what if women more concerned about a family history of chronic disease were the ones to take supplements? What if women who were less confident in their ability to eat fruits and vegetables daily were the ones to take supplements? What if women who were just more anxious and pessimistic about their health were the ones to take supplements? Independent of all other factors, pessimism increases mortality, and optimism decreases it.
We don’t know that any of these ‘what ifs’ was true; but if any one of these, or another like them, was true, it might be the reason for the (minimally) higher death rate among supplement users, rather than the supplements per se.
But, the fact of the matter is that several large studies now suggest possible harm attached to the use of multivitamins and certain other supplements (including some B vitamins, and iron). Since we never had any clear evidence of benefit from multivitamin use, and since the ‘at least it couldn’t hurt’ rationale for using multis as an insurance policy is clearly not valid- the day of the conventional multinutrient supplement is over. I used to take a multi, and no longer do; I used to recommend them to patients, and no longer do.
How could a mix of nutrients known to be essential cause harm? When we extract nutrients from their context in food, we are ‘guessing’ about preparation, dose, and combination. Errors in any of these could lead to trouble.
Imagine, for example, that you had all the essential construction material you needed to build a house- but in the wrong proportion. Too many roofing shingle,s but too little lumber. Or perhaps the beams were too short for the dimensions of the roof. We use nutrients to build cells and proteins and hormones every day, and having the right ‘stuff’ but in the wrong form or supply could make a mess of things.
Or, consider a musical analogy. You love a jazz ensemble; a rock band; and a symphony orchestra. Imagine the sax player from the one, the guitarist from the other, and the cellist from the third each playing her own music, all at the same time. Noise! Lovely on their own, a mess when combined badly.
This could be the case with how we have approached nutrient supplementation. Frankly, I don’t know for sure- nobody does- but the potential for real, if modest, harm is plausible.
So what do we do now?
For one thing, we should recall that all along, the best-case scenario was ‘supplement,’ not substitute. There is no substitute for eating well, and that deserves our dedicated commitment.
At this point, unless you are likely to have a serious deficiency in overall nutrient intake- or unless you have a specific indication for taking a multivitamin, such as pregnancy or the intent of pregnancy- use of a multivitamin seems ill advised. You need a good reason to do it; ‘what the heck’ is no longer sufficient.
Judicious use of select supplements still makes sense. We have convincing evidence of known or likely benefit from supplemental omega-3 oils and vitamin D for most men and women, and calcium for most women. For the most part, other supplements should be used for a specific reason, and with input from someone with genuine expertise. As an example, B12 supplementation is warranted for most vegans, and for all older adults with pernicious anemia. Let’s not toss out the baby with the bathwater!
Another intriguing consideration is the use of whole food based supplements (for example). Such products are ‘humble’ in the sense that they don’t presume to know how to combine nutrients- they let nature do it. They simply compress the nutrients from healthful foods into pill form so that those who don’t eat quite as they should – including children- can fill in the gaps. We need more science to prove the benefits of such supplements, but the approach makes sense to me, and may prove to be the new-age answer to the multivitamin/mineral supplement.
Independent of other factors, a multivitamin is very, very unlikely to kill anyone. If there is risk attached to the use of such supplements, it is very small. But there may be some risk- and there is no reliable indication of benefit.
That’s really all we need to know to conclude it’s probably time for us to kill the multivitamin.
Dr. David L. Katz; www.davidkatzmd.com