I see the word "natural" all the time on food packaging, where it's supposed to imply that the products therein described as natural must be healthful. And it's not just on food. I've seen "natural" claims on cosmetics, cleaning supplies, clothing and furniture – you name it, it's on it.
Rather than debate the definition, let's simply take the word "natural" to represent a product with a set of ingredients that are all derived directly from nature, where human-made "chemicals" need not apply.
For consumers, it appeals to our belief that if it came from the earth, it must be good for us. I think that belief, also known as the natural fallacy, is not only incredibly ill-informed, it's also incredibly arrogant.
It's ill-informed because there's plenty of "natural" on our planet that simply isn't good for us. Tobacco's natural. So is arsenic. And there are plenty of mushrooms growing in my backyard that I'm pretty sure I ought not eat.
Recently, a study came out that linked the consumption of a centuries-old, heavily used "natural" herbal supplement, aristolochic acid (a substance found in leafy, flowery vines called Aristolochia), to the development of kidney cancers, leading the study's lead researcher to state: "This is a pretty clear story. These plants are very dangerous."
This, of course, isn't the first time an all-natural substance was linked to cancer, and it won't be the last. But unfortunately, we're not nearly as likely to hear about natural products' negative outcomes as those of chemicals because, unlike pharmaceuticals, there is no established mechanisms for health practitioners to report potential adverse effects of natural products, nor is there a requirement for short- or long-term safety studies prior to their sales.
So I've explained why the natural fallacy is ill-informed, but why did I call it arrogant? It's arrogant because it suggests that the entirety of the natural world has been created purely as a service to humankind – that somehow the earth and everything on it grows simply for our pleasure or our consumption.
What's also nonsense is the chemophobic notion that "chemicals" are as inherently "bad" as "natural" products are good. Sure there are incredibly harmful chemicals, but it has been the past 100 or so years of chemicals that have helped to push our quantities and qualities of living to previously unheard of levels of luxury and length.
At the end of the day, what should inform our decisions is not the natural fallacy or chemophobia. We cannot simply assume anything we ingest, natural or chemical, is going to be good or bad for us consequent to its origins, and this holds especially true for those substances we ingest in the name of treating or preventing a medical condition.
[Read: U.S. News: Doctor Finder.]
Instead, we need to be reliant on evidence. While truthiness and thinking with your gut may work for Stephen Colbert; as far as your health goes, actual evidence goes a long, long way. And the only assumption that you should make is that if there isn't any evidence, it's best to tread cautiously.
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Yoni Freedhoff, MD, is an assistant professor of family medicine at the University of Ottawa, where he's the founder and medical director of the Bariatric Medical Institute—dedicated to non-surgical weight management since 2004. Dr. Freedhoff sounds off daily on his award-winning blog, Weighty Matters, and you can follow him on Twitter. Dr. Freedhoff's latest book, The Diet Fix: Why Everything You've Been Taught About Dieting is Wrong and the 10-Day Plan to Fix It, will be published by Random House's Crown/Harmony in 2014.