You probably already know that what you do know about your medicine could kill you. You may not know that what you don’t know could do so as well. Hold that somber thought — we’ll get back to it.

You, and I, and everyone else has seen those direct-to-patient drug ads that Big Pharma runs on primetime television. Invariably, they feature a person skipping through butterflies and wildflowers, demonstrating the wonders of better living through pharmacotherapy, as an announcer calmly rattles off the ways the drug can destroy your health: It can make your liver explode, and your eyeballs catch fire, and your kidneys fall out, and so on. But you won’t mind — you are too busy skipping through meadows.

Except, of course, that people do mind! In fact, I can’t understand those ads at all, since the purpose of advertising is to talk people into things, not out of them. Overwhelmingly, my patients who have seen such drug ads are scared to death of those medicines, and very much disinclined to take them. I don’t recall the last time a patient said to me: “I want that medicine I saw on TV that can make my eyeballs catch fire … ” Generally, it’s quite the opposite; if I recommend that medication, they tell me I must be crazy. As advertising goes, this really is odd.

Before getting to my point, I have a few things to point out to forestall a rush to judgment about my motivations.

I don’t like taking medications myself — not even when I need them. Most of my patients seem to feel that way, and I respect it. I am not on Big Pharma’s payroll and have no stake in the use of any drug. What’s more, I have worked for nearly a decade and a half in integrative medicine, in a model of my own devising, side by side with naturopathic colleagues, with a focus on natural treatments whenever possible. Even those looking for nasty things to say about me would really be pushing it to call me a pill pusher. I’m the guy patients come to see when they want alternatives to their prescribed drugs. Seriously.

It is in that context I need to point out that it’s not only what you do know about your medications that can hurt you; it’s what you don’t know. What people tend not to know is the side effects of not taking medication when it’s truly warranted.

I am a 50-year-old guy with five kids and a desk job. I take no medications. My blood pressure is that of a very fit 20-year-old, and my cholesterol is under 150, with HDL higher than LDL. There are more good biometrics where those came from, but that will do. I am not boasting. None of this is evidence that I’m a swell guy, or special in any way. This is all merely the result of practicing what I preach, and using lifestyle as my medicine.

Everyone could do the same with the right skill set, and if more people did, the pharmaceutical business would be a whole lot smaller and less profitable. From my perspective, that’s a consummation devoutly to be wished — and I am doing all I can to help people get there from here. I devote my time and energy to developing lifestyle programs for adults and children alike; to developing training programs in lifestyle medicine for clinicians and patients alike; and to writing books on the topic for both health care professionals, and everyone else. I practice lifestyle medicine, I preach it, and I am passionate about its potential to improve the human condition.

But I am also pragmatic. I look around and see a world awash in chronic disease, stealing life from years and years from life. And while lifestyle is best to prevent all that misery, modern medicines are often best for treating it.

Despite all the valid concerns about environmental contaminants, cancer rates and deaths have declined, not risen, over recent decades, due largely to advances in medical technologies and drugs. Stroke rates and stroke death have declined dramatically, due to advances in risk factor identification, and in particular, better pharmacotherapy for high blood pressure. Heart attack occurrence, and mortality, have declined, due overwhelmingly to advances in both technology, and pharmacology- from clot-dissolving agents, to statins. These are facts of epidemiology, not principles of ideology.

Lifestyle could be our best medicine, and I both plan and pledge to keep doing all I can to help make it so. The very best medicine means less time in clinics, because it reverberates through our culture.

But in the interim, we do have widespread diabetes, and heart disease, and hypertension, and dyslipidemia, and insulin resistance, and cancer, and so on. All too many of us have conditions that warrant treatment, and for which, fortunately, we often do have effective pharmacotherapy.

Here, then, is the point. Big Pharma is obligated to rattle off the side effects of their drugs in those ads; there are no corresponding ads to rattle off the side effects of needed drugs that go untaken.

Yes, side effects of medications can kill. But so can the side effects of declining medications we really need. When prescribed judiciously by clinicians who know what they are doing to patients who know what they are getting, drugs are far more likely to help than harm.

So here’s to needing less medication; we could make that happen. But until we get there from here, I advise an open mind and lack of prejudice. Get good information from sources you trust, and then take the path of most likely benefit, least likely harm — knowing it may or may not involve a stop at the pharmacy.

David L. Katz is the founding director, Yale-Griffin Prevention Research Center.