Dr. Mehmet Oz is one of America's most influential doctors. Just ask him. He has a TV show and everything. And in the past, much of his advice had been practical and mundane, the same advice you might hear from your own (perhaps less charismatic) physician. But lately, he's been giving out frankly bizarre medical opinions. Not all of Oz's recommendations are over-the-top strange, but even some of his less-bizarre stuff is hyperbolic to the point of being---in my opinion---deceptive. Let's explore one example close to my heart, diabetes. As an internist, one of my most important tasks is the prevention and treatment of diabetes. I know something about it. As a heart surgeon, Dr. Oz deals with one of the most serious complications of diabetes, coronary heard disease, so he must know a bit about it as well.
So I was a bit surprised to learn from his website that I've been going after diabetes the wrong way. Unknown to me is the "prevention powerhouse" of coffee and vinegar. He recommends heavy consumption of these miracle foods to prevent diabetes and to help the liver and cholesterol, whatever that means. Reading this, two questions come to mind (a few more, really, but two that we will focus on): is this plausible, and is this true?
There are a few epidemiologic studies that support the idea that coffee consumption is in some way associated with diabetes risk. (For a bit of background on different types of studies, see here and here.) There are a few bits of basic science that could explain this relationship, if it turns out to be causal. But these large studies simply show relationships. They have found that people who drink more coffee (regular or decaf) were less likely to develop diabetes during the study period. Most of these studies tried to control for confounding variables (for example, caloric intake) but none of these truly shows cause and effects.
The two biggest potential problems here are recall bias and confounding variables. Do people reliably report the data we ask them to? We aren't directly measuring it, so this is critical. Do coffee drinkers simply have smaller appetites? Or other habits that reduce the risk of diabetes? These studies give us an interesting starting point. The next step to look for actual cause and effect would be a randomized controlled trial (which obviously could not be double-blind), that takes non-diabetics and randomly has half drink coffee and half abstain, and follows them over a several year period. The idea that coffee can affect blood glucose metabolism and the development of diabetes is not nuts, but the available data don't allow us to go any further than that.
The data support the plausibility of the question of coffee and diabetes, but not the truth of the statement. But let's pretend it is true. The next questions are are how much risk reduction is there, and at what cost?
We know that some drugs and proper diet and regular exercise reduce the risk of diabetes. How do these interventions compare with coffee or vinegar? Is one of them 100 times more potent than the other? One thousand? One fifth? And what are the hazards of caffeine consumption? Not that great in general (and lessened by drinking decaf), but even small amounts of caffeine can cause significant acid reflux, sleep problems, heart palpitations, headaches.
What Dr. Oz is suggesting is using an unproven drug (coffee or dilute acetic acid) that isn't needed. We have safe, effective ways to prevent diabetes. Our biggest failure is in providing people with the education, health care, and other tools to follow through.
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VANDAM, R., & FESKENS, E. (2002). Coffee consumption and risk of type 2 diabetes mellitus The Lancet, 360 (9344), 1477-1478 DOI: 10.1016/S0140-6736(02)11436-X
Tuomilehto, J. (2004). Coffee Consumption and Risk of Type 2 Diabetes Mellitus Among Middle-aged Finnish Men and Women JAMA: The Journal of the American Medical Association, 291 (10), 1213-1219 DOI: 10.1001/jama.291.10.1213
van Dam, R. (2006). Coffee, Caffeine, and Risk of Type 2 Diabetes: A prospective cohort study in younger and middle-aged U.S. women Diabetes Care, 29 (2), 398-403 DOI: 10.2337/diacare.29.02.06.dc05-1512
Pereira MA, Parker ED, & Folsom AR (2006). Coffee consumption and risk of type 2 diabetes mellitus: an 11-year prospective study of 28 812 postmenopausal women. Archives of internal medicine, 166 (12), 1311-6 PMID: 16801515
Dam, R., Dekker, J., Nijpels, G., Stehouwer, C., Bouter, L., & Heine, R. (2004). Coffee consumption and incidence of impaired fasting glucose, impaired glucose tolerance, and type 2 diabetes: the Hoorn Study Diabetologia, 47 (12), 2152-2159 DOI: 10.1007/s00125-004-1573-6