Sunday, July 1, 2012

Dr. Oz's Zany Zinc Recommendation

Arguably, given his national stage and reach, Dr. Oz is one of the biggest pill pushers in the United States. In the seven months I’ve been watching his show, I cannot remember a week going by without him promoting one dietary supplement or another. 

His favorite recommendations seem to involve some miracle cure or magic pill to lose weight. This past Friday morning, in a repeated episode which first aired September 28, 2011, he made three such recommendations. Today’s blog will focus on the zaniest of the three—his recommendation to ingest extra zinc to support weight loss. Before, I offer some information about the role of zinc in the human body; please indulge me as I provide some additional context for his recommendations.

The tile of Friday’s show was no less haughty than the “Seven Day Miracle Plan to Boost Your Metabolism.” Don’t even get me started on what one’s repeated offering of miracles suggests about the person, but that was the title and here’s what his “miracle” offering entailed. It all started innocently enough. He recommended that people on day one of his seven day plan use an online calculator to determine the rate of their metabolism (how many calories based on your gender, height, weight, and age). To quote the show’s website, “Your basal metabolism represents the number of calories your body burns when at rest, but awake, over the course of one day. This number is one of the factors that determine your total calorie needs for the day.

On day two, he recommended that people reduce their daily intake by 100 calories. To demonstrate how, he took a bowl of chocolate ice cream (really?) and scooped out about three tablespoons and said that represented about 100 calories. Not exactly the example I would have used, but it could be worse. The problem I had with this example was that he started with a heaping bowl of ice-cream so a mere reduction would not factor in any weight loss diet I know. Also, by using ice-cream and imprecise measurements, he was indirectly advocating that conventional sugar-dense and calorie-rich ice cream is a viable part of a healthy diet, let alone a diet meant to result in weight loss. While I am not a fan of the concept of dieting, I do believe that what and how much you eat do affect both weight and health.

Oz then suggested on day three that you add protein to your diet to lose weight. There is logic to the substitution of protein for carbohydrates in one’s diet (amino acids are essential, while carbs are not) although the source of protein may be contentious. I prefer protein to come from nuts, beans, and wild fish rich in Omegas 3s, but I take no issue with this suggestion.

His day four suggestion is somewhat contentious. He stated that to lose weight you must eat every three hours. He recommended snacking with pistachios and dried apricot. First of all, I don’t agree with the dried apricot suggestion. Although preferable to many processed snacks, I am not a fan of dried fruits due to the increased fructose concentration. Nevertheless, I agreed that people should eat their first meal close to awakening. However, if you wake at 6 or 7 each day, I don’t believe you should snack before lunch.  I do believe in snacking between lunch and dinner with an organic apple, baby carrots, and/or mixed unsalted nuts. But these are my personal preferences and his suggestion to snack every three hours is not completely out of whack.

On day five, he recommended that people drink at least three drinks a day with ice-cubes. Oz claimed that when the body comes in contact with an iced drink, it must consume more calories to warm up the drink. An interesting theory, and one that would suggest that people who live in cold climates burn more calories from daily living, right?  For an interesting review of the subject, please see the article at this link, .

I cannot attest to the accuracy of the calculations presented in the article, but the article, particularly the last sentence, should give one serious pause about following Dr. Oz’s suggestion.

Oz’s suggestion also included using coffee or green teas with the ice to boost your metabolism. That’s a whole topic for another day (although green coffee extract was already repudiated in one of my blogs last week).  However, the question to ask is even if coffee boosts the body’s metabolism, which it probably does in the short-term after consumption, does that increase weight loss? I could not find any studies to support that conclusion. Also, most people don’t drink their coffee black; rather, they add milk or cream and some sweetener so those additions also affect your metabolism and the net effects of coffee and green tea on your weight. Personally, I don’t find coffee drinkers to weigh less than non-coffee drinkers.  Do you?

Up until this point, Oz’s suggestions were harmless enough. He suggested a quick calculation, cutting calories, eating more protein, eating every three hours, and drinking iced coffees and teas. So at this point I was thinking to myself that although these don’t quite represent a miracle, they were reasonable enough suggestions and most importantly, he hadn’t recommended any dietary supplements. I was actually excited and delighted, but it was short-lived.

Oz then made one of the zaniest recommendations I have ever heard him make. To quote his site,
Day 6: Take Zinc
Zinc reduces hunger by increasing your level of leptin, a key hormone that alerts the body when you’re full so you won’t keep eating when you’re no longer hungry. You can buy zinc in 15mg packets or simply get it from your multivitamin, which usually contains about 12mg of this essential mineral.”

I was actually on my elliptical while watching the show and I almost dropped my cellphone on which I was taking notes when he uttered his words on zinc. “What???” I thought to myself. “Is that true? Does Zinc elevate leptin? Does elevating leptin actually reduce weight? Is there any science to support any of these assertions?”

Now leptin, discovered in 1994 by studying obese mice, is a known hormone produced by our bodies that acts as an appetite suppressant by suppressing neuropeptide Y, a known appetite stimulant that then suppresses another stimulant and continues down a full cascade (too complicated for this blog).  At one point, leptin held promise as a means to reduce weight, but suffice it to say that numerous studies have failed to support the conclusion that increasing leptin reduces weight. 

Notwithstanding, Dr. Oz took it one step further. He was actually recommending that taking surplus zinc would somehow raise the body’s leptin levels and help one lose weight. I knew at that point that I had a major research project ahead of me to research the facts and discover the truth. After seven hours of research, I discovered what I believe to be the facts.

Before I discuss the leptin-zinc connection, let’s first review of role of zinc in our health.

The Role of Zinc in Human Health

The human body requires certain nutrients that are required for normal body functioning that either cannot be synthesized by the body at all, or cannot be synthesized in amounts adequate for good health and must therefore be obtained from a dietary source. These ‘essential nutrients’ include vitamins, minerals, fatty acids, amino acids, water, and air. (By the way, carbohydrates are not essential because glucose is a byproduct of protein breakdown.) The last among these alphabetically is Zinc, but its importance to the human health cannot be overstated.

It is believed that zinc plays a role for between 100 to 300 enzymes, biological molecules that facilitate and control the rates of human reactions essential to healthy living. Without sufficient zinc, many of these biological reactions would not take place and many illnesses could ensue ranging from depressed immunity, eye and skin lesions, impaired appetite, altered mental function, and defects in how the body processes carbohydrates, to chronic liver and kidney disease, sickle cell disease, diabetes, cancer and other chronic illnesses.  Zinc is very important to say the least.

At the same time as with some, but not all, essential nutrients, excess consumed amounts of zinc may lead to a host of problems such as gastrointestinal disorders, e.g. nausea, vomiting, unpleasant taste, taste distortion, indigestion, anorexia, abdominal cramping, intestinal bleeding, and diarrhea. It may also be unsafe in patients with coagulation disorders or those taking antiplatelet medication, e.g. aspirin,  or other anticoagulants, as zinc may affect platelet aggregation, and it may be harmful due to accumulation in patients taking potassium-sparing diuretics as they are shown to reduce urinary zinc excretion.

Zinc must be used cautiously in patients using thyroid hormones, as based on human research, zinc supplementation may alter thyroid metabolism. Administration of zinc in the absence of copper may cause a decrease in serum copper and iron levels and in individuals with hyperlipidemia or in those taking some lipid lowering drugs, as long-term, high-dose administration of zinc may result in decreased HDL (the ‘good’) cholesterol levels. In animal research, cholestyramine, a bile acid sequestrant, decreased urinary zinc excretion.

To sum the consequences of low doses of zinc, in a review paper titled Zinc Toxicity published in 1990 in the Journal of American Clinical Nutrition, according to the author’s abstract for the paper, “Even lower levels of zinc supplementation, closer in amount to the RDA [recommended daily allowance], have been suggested to interfere with the utilization of copper and iron and to adversely affect HDL cholesterol concentrations. Individuals using zinc supplements should be aware of the possible complications attendant to their use.”

The Leptin-Zinc Connection

Let’s take a quick look at how leptin works.
The hormone leptin has garnered attention as a possible target in the struggle against obesity and being overweight. Your fat cells produce leptin, which suppresses hunger and increases your metabolic rate. In general, the more body fat you have, the higher your blood leptin level. Zinc may affect leptin production, a factor that has led to interest in whether zinc supplementation may boost leptin levels and promote weight loss.

How Leptin Works

The hypothalamus is the part of the brain that is primarily responsible for appetite regulation. The hypothalamus receives many signals from both the central nervous system and hormones that affect your perception of hunger. In general, your leptin level informs your hypothalamus the degree to which you have stored body fat so that when your hypothalamus recognizes a low leptin level as indication of low stored body fat, this triggers increased appetite. An increase in leptin levels sends the opposite message, which normally leads to decreased hunger. As body fat storage levels change slowly, leptin is considered a long-term regulator of body weight and metabolism.

For a good review of the role leptin, please cut and paste this link.

 The Link to Zink

It took me a while to review the state of the literature on Zinc and its relationship to leptin, and here’s what I found. After reviewing some 900 hundred titles of studies for specific information, I found a handful of studies that speak to the issue.

Here was one of them.

Effect of Zinc Supplementation on Serum Leptin Levels and Insulin Resistance of Obese Women 

by Dilina Do Nascimento Marreiro, Bruno Geloneze, Marcos A Tambascia, Antonio C Lerário, Alfredo Halpern, Silvia Maria Franciscato Cozzolino

The conclusion of the study was that nothing basically changed including weight, other than the more zinc consumed, the more zinc was excreted in the urine.

Here was another study:

Zinc Deficiency Reduces Leptin Gene Expression and Leptin Secretion in Rat Adipocytes

by Elizabeth S. Ott and Neil F. Shay

This study focused, as the title suggests, on zinc deficiency. When you have a deficiency it is completely different than when you have a non-deficient state. To use a car analogy, a four wheeled vehicle will have difficulty navigating with three wheels, but it will drive no better (perhaps worse?) with five wheels versus four. By the way, it was a rat study so it doesn’t deserve close merit. Either way, the study’s results do not support the assertion that adding zinc to your diet produces weight loss.

Here’s yet another study:

Relationship between plasma leptin and zinc levels and the effect of insulin and oxidative stress on leptin levels in obese diabetic patients.

by Konukoglu D, Turhan MS, Ercan M., Serin O.

One of the main conclusions of the study was that there was a significant negative correlation between leptin and zinc in obese subjects.

To be facetious, there was not quite Dr. Oz’s conclusion.

Here are the last two studies worth noting.

Zinc May Regulate Serum Leptin Concentrations in Humans

by Christos S. Mantzoros, MD, Ananda S. Prasad, MD, MACN, Frances W.J. Beck, PhD, Susan Grabowski, PhD, Joseph
Kaplan, MD, Connie Adair, RD, and George J. Brewer, MD, FACN


Zinc May be a Mediator of Leptin Production in Humans

by Ming-Der Chen, Yuh-Min Song, Pi-Yao Lin

As discussed earlier, a zinc deficiency may, in fact, reduce leptin production. So what? In a small study conducted by Dr. Christos Mantzoros and colleagues and published in the "Journal of the American College of Nutrition," experimentally induced zinc deficiency decreased leptin levels. Reversal of the deficiency with supplemental zinc led to a corresponding increase in blood leptin. Again, knowing that zinc plays a critical role in the functioning of at least 100 enzymes, it should come as no surprise that a zinc deficiency would preclude the body from functioning normally, including producing leptin. However, this shows no correlation to a person with normal zinc levels. Dr. Oz made no differentiation between the two nor gave fair warning that his recommendation was geared towards someone with a possible zinc deficiency. The Mantzoros study participants did not experience weight or body fat changes despite varying leptin levels.

In the Chen study, data from animal research supports the existence of the zinc-leptin link. Ming-Der Chen, Ph.D., and colleagues reported in a March 2000 article published in "Hormone and Metabolic Research" that leptin levels increased when a moderate dose of zinc was fed to mice with experimentally induced diabetes. Interestingly, both zinc deficiency and high-dose zinc suppressed leptin production. Now although this was also only an animal study, that last sentence should make you wince. Dr. Oz is recommending that the average person who wants to lose weight should supplement with 12 to 15 mg of additional zinc when it may, in fact, be associated with the opposite intended effect.

Some research speculates that overweight and obese patients develop leptin resistance, which means increasing leptin level may have no affect on the hypothalamus.

One more study for consideration:

"Obesity Research;" Relationship Between Circulating Leptin and Energy Expenditure in Adult Men and Women Aged 18 Years to 81 Years

by Susan B. Roberts, Ph.D., et al.

In her 1997 article," Susan Roberts, Ph.D., and colleagues also found no association between blood leptin levels and energy expenditure, a measure of metabolic rate. These findings again suggest that other factors than just leptin play a role as major regulators of appetite and body weight.

So here’s the only logical conclusion one can reach, as Dr. Oz likes to say, “in case you missed it,” taking zinc to increase your leptin levels in the absence of a zinc deficiency has no expected benefits and potential harmful side effects.

A thorough review of the data and research by Dr. Oz and his, I suspect, substantial staff would have reached the same conclusions if they bothered to do the same level of research.

To add insult to injury, as if the zinc recommendation wasn’t bad enough, Oz went so far as to recommend two additional dietary supplements on Friday’s show as additional ‘metabolic boosters.’ They included, white bean extract and L-arginine, neither of which has conclusive scientific data to support its use for boosting metabolism.

This show was a perfect example of Oz piling fiction on truth to create the impression that he had something unique, what he calls a “miracle,” to offer to his audience. Let's not forget that in his world most things also happen in seven days. (Hmm, miracles and seven days. I wonder what he's trying to tell us?)  

Dr. Oz should stick to giving health advice that doesn’t include dietary supplements because when it comes to such supplements, neither he nor his staff seem able to do meaningful research to ferret out the truth and offer sensible recommendations to his audience.  Perhaps they know the truth, but there may be something more nefarious at play here such as financial consideration and greed. It is hard to know what is in a man’s heart, but what’s on his TV show leaves much to be desired. 

Although zinc deficiencies are rare among Americans, here's are two tables with information on zinc offered for your reference. 

Table 1: Recommended Dietary Allowances (RDAs) for Zinc [2]
Age Male Female Pregnancy Lactation
0–6 months2 mg*2 mg*
7–12 months3 mg3 mg
1–3 years3 mg3 mg
4–8 years5 mg5 mg
9–13 years8 mg8 mg
14–18 years11 mg9 mg12 mg13 mg
19+ years11 mg8 mg11 mg12 mg
* Adequate Intake (AI)

Sources of Zinc

A wide variety of foods contain zinc (Table 2). Oysters contain more zinc per serving than any other food, but red meat and poultry provide the majority of zinc in the American diet. Other good food sources include beans, nuts, certain types of seafood (such as crab and lobster), whole grains, fortified breakfast cereals, and dairy products.
Phytates—which are present in whole-grain breads, cereals, legumes, and other foods—bind zinc and inhibit its absorption. Thus, the bioavailability of zinc from grains and plant foods is lower than that from animal foods, although many grain- and plant-based foods are still good sources of zinc.
Table 2: Selected Food Sources of Zinc 
Food Milligrams (mg)
per serving
Percent DV*
Oysters, cooked, breaded and fried, 3 ounces74.0493
Beef chuck roast, braised, 3 ounces7.047
Crab, Alaska king, cooked, 3 ounces6.543
Beef patty, broiled, 3 ounces5.335
Breakfast cereal, fortified with 25% of the DV for zinc, ¾ cup serving3.825
Lobster, cooked, 3 ounces 3.423
Pork chop, loin, cooked, 3 ounces2.919
Baked beans, canned, plain or vegetarian, ½ cup2.919
Chicken, dark meat, cooked, 3 ounces2.416
Yogurt, fruit, low fat, 8 ounces1.711
Cashews, dry roasted, 1 ounce1.611
Chickpeas, cooked, ½ cup1.39
Cheese, Swiss, 1 ounce1.28
Oatmeal, instant, plain, prepared with water, 1 packet1.17
Milk, low-fat or non fat, 1 cup1.07
Almonds, dry roasted, 1 ounce0.96
Kidney beans, cooked, ½ cup0.96
Chicken breast, roasted, skin removed, ½ breast0.96
Cheese, cheddar or mozzarella, 1 ounce0.96
Peas, green, frozen, cooked, ½ cup0.53
Flounder or sole, cooked, 3 ounces0.32
* DV = Daily Value. DVs were developed by the U.S. Food and Drug Administration to help consumers compare the nutrient contents of products within the context of a total diet. The DV for zinc is 15 mg for adults and children age 4 and older. Food labels, however, are not required to list zinc content unless a food has been fortified with this nutrient. Foods providing 20% or more of the DV are considered to be high sources of a nutrient.

The U.S. Department of Agriculture's Nutrient Database Web site lists the nutrient content of many foods and provides a comprehensive list of foods containing zinc.

If you read this far, you deserve this cute video about Zinc. Just copy and paste in your browser, and enjoy!


  1. I love this research as I was just trying to find something on just this subject - Must be a rerun or we are very far behind in New Zealand. When I googled I also found this article.

    1. As I generally no longer waste my time watching his show, I can only imagine that he has taken to repeating himself. How many miracle cures, magic pills, and quick fixes can he ultimately claim exist anyway?

      Thanks for forwarding the Livestrong article. The more articles I read on that website, the less reliable I find the totality of the information presented. The articles hint at actionable conclusions of studies without indicating the scientific validity of the research (double-blind, randomized, controlled) or its applicability to humans.

      For example, the paragraph on 'Increases Leptin Output" doesn't bother to indicate if deficiency existed before supplementation and if appetite was actually suppressed after supplementation due to the purported increased leptin.

      By the way, credible studies involving leptin supplementation failed to show appetite suppression and so did the study reported.

    2. If you dedicate yourself over the next 21-days and follow The 3 Week Diet as outlined, you will be walking around with 12 to 23 pounds of body fat gone from your waist, hips, thighs, belly and butt. Your clothes will be looser, you’ll look healthier and more attractive…and you’ll have more energy than you’ve ever had in a long, long time.

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  2. excellent research,

    Dr Oz's suggestions would only be relevant if there was an underlying zinc deficiency.

    it is notable however to consider that research indicates that up to 75% of the worlds population has some level zinc deficiency due to mitigating factors such as lifestyle, diet and food production.

    in this instance, benefits relating to weight loss in respect to deficiency could be:

    zinc , being the precursor HCl production in the gut: regulating gastric secretions and improving emulsification thereby increasing nutrients absorption in the small intestine due to more available molecules. argenine , would further benefit this as it aids in protein digestion... explaining the link with the extra protien suggestion, the logical and less miraculous explaination being improved gut motility aiding in the regulation of metabolism... leading to weight loss.

    however, as youve said, he is peddling without substantial information and this should not be allowed.

  3. This is a great post!

    I am a MD as you and today had this coversation with my girlfriend regarding zinc and weight loss. Her dietitian told her she needs to take some miracle zinc supplement (that BTW she sells at nearly US$80 a bottle!) She asked me if that was really necessary and I gave her my opinion... The answer she got from the dietitian was "It is impossible to treat patients when they have more knowledge than the doctor. So this is the last time we have this conversation"

    Thank you for your post!

    Mynor Alvarez MD. MSc

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