Dr. Oz, you’re not helping diabetics

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.


Salazar-Martinez E, Willett WC, Ascherio A, Manson JE, Leitzmann MF, Stampfer MJ, & Hu FB (2004). Coffee consumption and risk for type 2 diabetes mellitus. Annals of internal medicine, 140 (1), 1-8 PMID: 14706966

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

Posted in: Science and Medicine, Science and the Media

Leave a Comment (32) ↓

32 thoughts on “Dr. Oz, you’re not helping diabetics

  1. mxh says:

    Dr. Oz has been bitten by the Oprah bug and has gotten a full case of the quackery.

  2. WilliamLawrenceUtridge says:

    Not to mention, every fat guy or girl watching that show or reading the website is now doing a bit of mental arithmetic.

    “So…he says diabetes can be treated with diet, exercise, coffee and vinegar. Well, I don’t like to exercise, but I do like to eat. What if I didn’t exercise, but drank a lot of coffee and the occasional bottle of vinegar? That must work, Dr. Oz wouldn’t like to me!”

    Dr. Oz wouldn’t lie, but that doesn’t mean he’s right and it doesn’t mean he should promote unproven interventions at the expense of proven ones.

    How much time does he actually spend talking about the importance of diet and exercise? Is it even close to the amount of time spent on reiki and supplements?

  3. windriven says:

    WilliamLawrenceUtridge said, “Dr. Oz wouldn’t lie, but that doesn’t mean he’s right and it doesn’t mean he should promote unproven interventions at the expense of proven ones. ”

    My Merriam Webster offers a second definition of ‘lie’ as “to create a false or misleading impression.”

    So is Oz a liar or incompetent?

  4. marilynmann says:

    Dr. Yoni Freedhoff has a post up on a different Oz show today — worth reading.

  5. Draal says:

    We know that some drugs and proper diet and regular exercise reduce the risk of diabetes.

    linkie dink is broken.

  6. Draal says:

    The data, from a follow-up prospective cohort study of the of the Pereira et al. (2006) article, “support an inverse association between coffee consumption and diabetes and suggest that the time of drinking coffee plays a distinct role in glucose metabolism.”

    Differential effects of coffee on the risk of type 2 diabetes according to meal consumption in a French cohort of women: the E3N/EPIC cohort study
    Author(s): Sartorelli DS, Fagherazzi G, Balkau B, et al.
    Source: AMERICAN JOURNAL OF CLINICAL NUTRITION Volume: 91 Issue: 4 Pages: 1002-1012 Published: APR 2010

  7. daedalus2u says:

    This is interesting, the effect of coffee drinking on the metabolic syndrome, not the nonsense of Dr Oz, that is sad that he is so delusional and angry making that he is exploiting and harming the gullible with his delusions.

    What I find quite interesting is that decaffeinated coffee works too. The study that Draal linked to is interesting also.

    My hypothesis that links all of these together (and to NO physiology of course ;) ) is that the effect of caffeine on the metabolic syndrome is real, and that it derives from “exercising” the body’s glucose/insulin regulatory system by “whacking” it with a jolt of caffeine. A mild “whacking”, provided there is time to recover from the “whacking”, will compel physiological systems to compensate for the “whacking” and result in more robust regulation of blood glucose and insulin. I think in some ways it is like exercise, which is also a “whacking” of physiology which compels it to compensate. I suspect that the effects of alcohol have a similar mechanism.

    If this hypothesis is correct, then a time varying exposure is important. A constant dose of caffeine as from putting it in drinking water, would not have the same time varying effects which would compel remodeling of physiological pathways to provide time varying compensation.

    I assume that people who drink decaffeinated coffee are former drinkers of caffeinated coffee who switched to decaf because of adverse effects of too much caffeine. They still drink decaf because they have been accustomed to drinking coffee. I suspect that their ANS has become conditioned to respond to drinking coffee (containing caffeine or not) and so drinking decaf does give their glucose/insulin physiology a “whack” too, perhaps not as strong as from drinking caffeinated coffee, but enough to stave off the metabolic syndrome a little bit.

    I speculate that the effects from time of day in the study linked by Draal are due to selection bias. Some people (such as myself) are unable to drink coffee in the evening because it dramatically affects sleep patterns. Sleep is a high NO state, and is triggered by high NO. People who have such a robust sleep inducing system such that they can drink coffee in the evening and still sleep, probably don’t need the “whacking” of caffeine to exercise their physiology because it is already sufficiently robust.

    If these speculations are correct, then the effects of caffeine are not acute, but are chronic and modest and not due to the caffeine per se, but to the body’s response to the “whacking” of physiology by caffeine. It isn’t the “whacking” that causes the benefit, it is the compensatory recovery from the “whacking”, which is just like exercise. It isn’t the acute effects of exercise, it is the compensatory recovery from exercise that provide health effects. If you overdo it by not allowing sufficient time and metabolic resources for the compensatory pathways to do their thing, then it is not helpful.

  8. CarolM says:

    Don’t forget decaf coffee often still has significant caffeine, up to 25% as much as reg.

  9. Draal says:

    I was thinking along the lines of a different mechanism. The polyphenols (e.g. tannins (aka proanthocyanins), flavonoids) are capable of inhibiting beta-glucosidase and alpha-amylase, possibly due to non-specific binding of the enzymes. Tannins are capable of precipitating proteins. In effect, the degradation of carbohydrates is slowed and it may decrease the blood sugar spike following consumption of food or increase the time it takes to digest carbohydrates.

  10. the bug guy says:

    Doh! So it’s the pot of coffee I drink per day that’s controlling my diabetes and not all of that tedious exercise and careful diet control.

  11. ConspicuousCarl says:

    This is going to sound like a joke, and I am not even sure if I am serious or not, but do people absorb a significant amount of caffeine if they are already getting coffee enemas?

  12. LovleAnjel says:


    Do you mean, do they absorb less caffeine from their oral ingestion if they are also getting it through another route?

    I doubt it. I don’t think there is a limit on how much caffeine your body will absorb (other than, say, vomiting it up or dying). From my anectdotal experience, drinking more caffeine will not prevent you from absorbing more caffeine. Those extra No-Doze will make you hallucinate.

  13. ConspicuousCarl says:


    I was just wondering how much caffeine, if any, ends up in one’s blood if they receive a coffee enema.

  14. Jayhox says:

    I’m a dentist, and another one of Dr. Oz’s recommendations is to whiten your own teeth with lemon juice and raisins.

    Now, of course I’m a shill for Big Denta, and merely want to line my pockets with the ill-gotten gains of regular teeth whitening, but advising people to marinate their teeth in a solution that has a pH of around 2.5 is a poor poor recommendation. The damage it could do to one’s enamel is significant.

    How does he get away with his BS?

  15. I think quite a lot of caffeine is absorbed in the large intestine. It was a cause of a good portion of the distress experienced by victims of the Gonzalez regimen trial: people who were very sick were unable to sleep because they were wired on all those detoxifying coffee enemas. It sounds horrible.

    The large intestine does absorb, it’s just that by the time our food gets there most of the active transport part of absorption is complete. Active transport of nutrients though the intestinal wall requires pumping water into the lumen of the small intestine. This water is then reabsorbed by the large intestine and most of the rest is waste. However, the large intestine doesn’t just absorb water: vitamin K is produced in the large intestine by commensal bacteria so that is where we get most of our vitamin K.

  16. Dpeabody says:


    You missed the pun, Shame on you! ; P

    “Dr. Oz has been bitten by the Oprah bug and has gotten a full case of the quackery.”

    Dr. Oz has been bitten by the Oprah bug and has gotten a bad case of the woo.


  17. windriven says:


    “I was just wondering how much caffeine, if any, ends up in one’s blood if they receive a coffee enema.”

    I can’t specifically address caffeine but tobacco suppositories were an early form of anesthesia. Tobacco smoke was also used medicinally and led to the expression about blowing smoke up someone’s backside. I also recall reading that alcohol is readily absorbed in the lower GI. So it seems likely that caffeine would be easily taken up by that route.

    Didn’t Isaac Asimov write a short story “Drinking Coffee with Uranus”?

  18. mxh says:

    The Dpeabody. That sounds better.

  19. WilliamLawrenceUtridge says:


    How does Dr. Oz get away with it? His editor is Oprah and his fact checker is Arianna Huffington.

  20. Artour says:

    My experience says that effects of coffee depend on people’s breathing patterns. When breathing is heavy and this is the case with most people these days (i.e., modern NORMAL subjects breathe about 2 times more air than the medical norm), coffee helps people to function better. They can drink up to 10-20 cups per day.
    When the same person normalizes his automatic breathing (the medical norm is 10-12 breaths per minute. 6 L/min; 40 mm Hg CO2 in the arterial blood, and so on), their desire to drink coffee is gone. If they try, they feel jittery and anxious and can sense their heart palpitations. This is normal since CO2 is probably the most potent known vasodilator. Improved perfusion greatly amplifies stimulatory effects of coffee.

    As about diabetes, consider facts. All studies that tested diabetics found that they are hyperventilators:

    Heavy breathing in diabetics causes systemic hypocapnia. Hypocapnia leads to vasoconstriction and the suppressed Bohr effect. As a result, hypocapnia reduces body and cell oxygen levels, decreases insulin production (due to insufficient perfusion and oxygen delivery to pancreas), reduces insulin efficiency, increases pulse rate, promotes chronic inflammation, free radical generations, and disrupts other CO2-related regulatory mechanisms and biochemical reactions.

    Clinical experience of Russian doctors with hundreds of diabetics (the Buteyko breathing doctors) indicates that normalization of breathing (about 6 L/min for minute ventilation and less than 70 beats/min for the heart rate at rest) leads to normal blood glucose control in type 2 diabetes and no need for insulin.

  21. Peter Lipson says:

    My experience says…

    Three words deadly to science.

  22. My experience says, Russian medicine can be much like Chinese medicine, only with a more medical sounding mythology.

    Check out this list of diagnoses found on Russian (orphan) children’s medical records.

  23. WilliamLawrenceUtridge says:

    Yeah, I’m not a fan of the breathing spam either. Last I checked diabetes was caused by insensitivity to insulin or death of the pancreatic islet cells. Not “improper breathing”. Clinical experience isn’t science, but it’s a great way to confirm your biases.

    Artour, if your interventions are as effective as you claim then it should be trivial to test and report them in the peer reviewed literature, and allow for independent replication by people who aren’t trying to sell books. “I wrote a book about my clinical experience” isn’t science, it’s a profit-generating scheme and is disliked for the same reasons supplements and bioidentical hormones are disliked – the claims outrun the evidence and the promotion outrun the claims. A link to a book you wrote convinces only the credulous. A link to a pubmed-indexed article would be the first step towards convincing.

  24. Anthro says:


    Being overweight, I came down with diabetes by age 57 following years of “borderline” status.

    I have been drinking espresso/latte for 35 years, but mixed reg and decaf for the last 10 years–one reg. latte in the am and then decafs the rest of the day. Hey, I’m from Seattle.

    I lost 45 lbs and have maintained if for four years now.

    I have normal blood sugar now. Also greatly improved cholesterol, HDL, and blood pressure.

    My only exercise is housework, gardening and walking the dog, but I never use elevators if I can find the stairs.

  25. Anthro says:


    I use of lot of vinegar too. A lot meaning daily use in dressings and sauces–mostly balsamic.

  26. norrisL says:


    Association does NOT mean causation. Particularly when we are talking about coffee and vinegar having anything to do with a drop in blood glucose levels.

    That said, if there is anything relevant to your glucose reduction in your post, it is the loss of 45 pounds. In that case association probably does have a part to play in causation.

    Glad to see your glucose levels are normal.


  27. ConspicuousCarl says:

    Artour on 24 Feb 2011 at 11:08 pm

    As about diabetes, consider facts. All studies that tested diabetics found that they are hyperventilators:

    Of the 5 references at the top of that page which supposedly support abnormal breathing as a cause of diabetes:

    1 only had 8 patients, which makes it nearly worthless no matter what the conclusion.

    3 were all from the same lead author (Tantucci), which kind of makes them closer to being 1 source.

    These were also studies which SPECIFICALLY addressed diabetics with “autonomic neuropathy”, not all diabetics in general.

    Those studies also did not all clearly conclude that this was the cause of diabetes, rather than a possible result.

    Also missing is any evidence that altering breathing is a cure. When it comes to that point, you just refer to “russian doctors” using a technique which was developed for a different disease, and not even generally accepted for that. What happened to all the links and names and data?

  28. daedalus2u says:

    The “problem” in diabetes type 2 is high blood sugar (I use quotes because I think that is a symptom and not the primary problem) due to “glucose resistance” (the supposed inability to take up glucose from the blood), and “insulin resistance” (the supposed inability to take up insulin and use that insulin to increase glucose uptake).

    I think the problem is actually not enough glucose inside cells that are too far from a capillary. The way that cells get glucose is from the extravascular fluid flowing past them and not from the blood. Blood is confined to blood vessels, plasma containing glucose perfuses everywhere and it is from that plasma that cells get everything except O2 (which diffuses across the extravascular space from the vessels). Glucose can’t diffuse across and through cells the way that O2 can, so plasma has to carry it to the surface of each cell so the cell can get it. As that plasma passes by cells, the cells take up glucose and insulin and the levels of both go down.

    How can physiology respond if there is acutely not enough glucose getting inside of cells? It can raise blood glucose levels, and it does. It also raises insulin levels to cause cells to express more GLUT transporters to get more glucose into cells. What can physiology do if there still isn’t enough? All it can do is try and raise blood glucose and blood insulin ever higher. If the first cells the plasma encounters consume all the glucose, the cells farther away don’t get enough. Physiology has to institute glucose resistance so the first cells the plasma encounters don’t consume it all. Physiology does that by having the GLUT transporters saturate, so they can’t take in any more glucose no matter how high it gets.

    Physiology regulates the number of GLUT transporters with insulin. If the first cells the plasma encounters take up too much insulin, the cells farther away don’t get enough. Physiology institutes insulin resistance where the insulin take up saturates so the first cells don’t take it up so some insulin is left for the cells farther away.

    Cells don’t only use glucose for energy, they can also use other substrates, such as ketone bodies and acetate. Those substrates are not taken up through the GLUT transporter, so their take-up doesn’t saturate the way glucose take-up does.

    I think that acetate in vinegar substitutes as an energy substrate, reducing the need for higher blood glucose. I think this is analogous to what happens when alcoholics go into alcohol withdrawal. Ethanol is metabolized to acetate. When one gets substantial calories from alcohol for extended periods of time, the liver remodels to produce acetate from alcohol, rather than to do gluconeogenesis. When that alcohol consumption is stopped, the liver no longer has substrate to make acetate, and it takes a while for the liver to remodel metabolic pathways to startup gluconeogenesis again. I think the DTs are in part due to psychosis from energy starvation in the brain due to insufficient substrate from the abrupt loss of acetate.

    Acetate may help with some symptoms of diabetes type 2, but (if this analysis is correct) you need to use it as a food (i.e. get a significant fraction of your calories from it) not as a flavoring. A cup of distilled vinegar has ~29 calories, so if you wan to get ~10% of your daily calories from vinegar (~200) you would need to drink about 1.7 quarts of vinegar every day.

  29. weing says:


    Caffeine can be absorbed via the rectal route. Suppositories are much more popular in Europe compared with the US. Dosages can be tricky here. With a drug that has significant first pass metabolism, such as caffeine, the dose is lowered in suppositories. The absorption in this case, occurs in the rectal mucosa and caffeine enters the middle and inferior rectal veins and enters the systemic venous circulation, bypassing the portal circulation and liver metabolism. With an enema, it would depend on how far you shoved in the tube, but most of the caffeine absorbed would end up in the inferior mesenteric vein and enter the portal circulation to be metabolized by the liver.

  30. WilliamLawrenceUtridge says:

    I use of lot of vinegar too. A lot meaning daily use in dressings and sauces–mostly balsamic.

    If that dressing was on salads, was a substitute for cream-based dressing, and those salads were substitutes for more calorie-dense meals, and those sauces were substitutes for something sugary like barbeque sauce or fatty like a cream sauce…you didn’t lose weight because of vinegar, you lost weight because of calorie reduction.

    Interesting, probably fruitless study – take two groups of people, use one as a control, for the second replace an equal number of calories from fat or sugar with vinegar, see if they lose weight (or if the calories drop because that much acetic acid is frankly inedible).

    I very much doubt there’s an actual magic bullet for weight loss beyond amputation, bariatric, amphetamines, calorie reduction and exercise – with only the last two being low-risk.

  31. The Blind Watchmaker says:

    The protein adiponectin is produced by fat cells and has a wide range of positive effects.

    In type 2 diabetes, adiponectin levels are low, adding to the process of insulin resistance.

    Coffee consumption increases adiponectin levels.

    Coffee consumption may also have an effect on obesity via similar process.

    Adiponectin is likely stimulated more effectively by exercise and regular fat burning in the adipocyte.

    In fact, the drug pioglitazone, works by stimulating receptors on the adipocyte to release adiponectin.

    There is a likely effect here from coffee drinking. However, I doubt that it is a panacea. If you have insulin resistance and you like coffee, go ahead in moderation. Many type 2 diabetics are obese and at risk for acid reflux. Coffee increases this risk, and therefore may increase one’s risk of Barrett’s esophagus and esophageal cancer.

    Bottom line, keep the fat cells healthy by keeping the weight under control through proper eating and regular fat burning through exercise.

    I have to go. Coffee’s ready.

  32. EJ says:

    Dr. Oz is very free with his recommendations of herbal supplements. One show on women’s health had me slapping my forehead and shaking it back and forth in disgust! Coffee has been in the news a lot in the last year, though. Listen to the titles of these articles from Coffee, tea may help prevent brain tumors (Nov ’10); Coffee may reduce the incidence of gout (Sept ‘10); Tea and coffee may protect the heart (Aug ’10); Coffee linked to lower risk of head and neck cancers (Jun ’10); Coffee may reduce diabetes biomarkers (Mar ’10); Coffee linked to lower diabetes risk (Mar ’10); and—I am going to skip a couple articles now—Chronic coffee consumption and [increased] cardiovascular risk (Jun ’05). Coffee certainly is being studied, but there is a lack of conclusive findings. These articles and other information about coffee and its effects are on Natural Standard’s website.

Comments are closed.