Doesn’t it seem like when it comes to nutrition there are more opinions than facts to go around? Every day we hear new theories about diets, and supplements, and the best foods to eat. My role is to take the mystery out of good nutrition, and look at the science. Welcome to the Nutrition Facts Podcast. I’m your host Dr. Michael Greger. And I’m here to bring you an evidence-based approach to the best way to live a healthier longer life.
It’s time for the nutrition facts grab bag, where we look at the latest science on a whole variety of topics. First up, we look at why some experiments show that duct tape is ineffective for treating warts.
In 1978, a new approach for the treatment of warts was described, complete with compelling before-and-after pictures. What was it? The application of adhesive tape. This was put to the test head-to-head in a trial of duct tape versus cryotherapy to resounding success.
Now, though this was a randomized controlled study, it wasn’t a double-blind study. “Patients in the duct tape group were instructed to remove all tape prior to making a return visit,” so that the nurses measuring the wart changes wouldn’t be biased one way or the other. But remember, look, cryotherapy can cause redness, “skin discoloration, crusting” and blisters; so, the nurses may have had an idea which kid was in which group, and maybe that could have biased them. So, ideally, there’d be a double-blind, randomized controlled trial of duct tape for the treatment of common warts, and here we go.
They disguised the duct tape so no one knew who was in each group. They used transparent duct tape applied to the underside of moleskin, which is an opaque adhesive pad, and the control group just got the moleskin without the duct tape underneath. So, on the outside, both treatments looked the same, but half the warts were exposed to duct tape, and the other half were not. So, if there was something special about the duct tape adhesive, the duct tape group would triumph, and the straight moleskin group would fail. If there was nothing special about duct tape, and the remarkable success of that other study was just the act of covering warts with anything sticky, then they would both triumph. But instead, they both failed. They both did like, no better than placebo.
The “first double-blind controlled trial investigating” duct tape for warts, and it failed “for treating common warts in adults.” Hmm, well maybe that was the problem? The subjects in the original duct tape study were mostly kids,average age nine, whereas in this study the average age was 54. And yeah, warts in younger populations may be more amenable to treatment. So, is it possible the reason duct tape worked in the first study, but not the second, is that duct tape only works in kids, but not adults? Well, you’d have to repeat the same kind of study, but this time with children.
About 100 schoolchildren were randomized to having duct tape applied to the wart, or a corn pad around the wart as a placebo. So, they both did something, but only one had duct tape on their warts. They used that same clear duct tape, so they wouldn’t recognize it, and it looks nicer too. Six weeks later and—the duct tape failed.
And that’s where the medical community left it. If you look at recent reviews on whether it’s better to burn them, freeze them, or duct tape them, they dismiss duct tape as totally ineffective, which is totally understandable. No matter how good some original results are, if you put the same thing to the test in a bigger, better study and can’t replicate the results, then you have to assume the first study was just a fluke.
But did they put the same thing to the test? Maybe adults wasn’t the operative word here, and instead it was ”transparent.” “Clear duct tape is not duct tape.” It turns out “clear duct tape and moleskin both contain an acrylic-based adhesive, whereas standard silver duct tape contains a totally different rubber-based adhesive.” “It is likely that the success of traditional duct tape is associated with the adhesive that comes in direct contact with the wart during treatment.” In fact, even more likely after the two clear tape studies came out, showing that indeed it appears to be something unique in duct tape, and not merely the act of occlusion, not just covering it up doesn’t do it. And indeed, the latest addition to the body of evidence found that similar 80 percent versus 60 percent duct tape over cryotherapy, using real duct tape, but in this case sticking it on with some superglue, so the duct tape would stick better. In conclusion, odd as it may sound, duct tape is a legitimate and often effective treatment for common warts.
In our next story –we discover a cheap do-it-yourself solution for washing fruits and vegetables.
How might we reduce our exposure to pesticide residues on fruits and vegetables? What about staying away from imported produce? Turns out domestic produce may be even worse, dispelling this notion that imported fruits and vegetables pose greater potential health threats to consumers.
Buying organic dramatically reduces dietary exposure to pesticides, but does not eliminate the potential risk. Pesticide residues are detectable in about 1 in 10 organic crop samples, due to cross-contamination from neighboring fields, the continued presence of very persistent pesticides like DDT in the soil, or accidental or fraudulent use.
By choosing organic, one hopes to shift exposures from a range of uncertain risk to more of a range of negligible risk, but even if all we had to eat were the most pesticide-laden of conventional produce, there is a clear scientific consensus in the scientific community that the health benefits from consuming fruits and vegetables outweigh any potential risks from pesticide residues. But we can easily reduce whatever risk there is by rinsing our fruits and vegetables under running water.
There are, however, a plethora of products alleged by advertisers to reduce fruit and produce pesticide residues more effectively than water, and touted to concerned consumers. For example, Procter & Gamble introduced a fruit and vegetable wash in the year 2000. As part of the introduction, T.G.I. Fridays jumped on board, bragging on their menus that the cheese and bacon puddles they call potato skins were first washed with the new product. After all, it was proclaimed proven to be 98% more effective than water in removing pesticides. So researchers put it to the test, and it did no better than plain tap water. Shortly thereafter, Procter & Gamble discontinued the product, but numerous others took its place, claiming their vegetable washes are three, four, five, or even ten times more effective than water to which the researcher replied, “That’s mathematically impossible.” If water removes like 50%, you can’t take off ten times more than 50%. They actually found water removes up to 80% of pesticide residues, like the fungicide captan for example, so for other brands of veggie washes to brag three, four, five, or ten times better than water is mathematically impossible indeed.
Other fruit and vegetable washes have since been put to the test. They compared Fruit & Vegetable Wash to FIT, to two I’ve never heard of, OrganiClean, and Vegi-Clean, compared to using dishwashing soap, all compared to just rinsing in plain tap water. 196 samples of lettuce, strawberries, and tomatoes were tested, and they found little or no difference between just rinsing with tap water compared to any of the veggie washes, or the dish soap. They all just seemed like a waste of money. The researchers concluded that just the mechanical action of rubbing the produce under tap water seemed to do it, and that using detergents or fruit and vegetable washes do not enhance the removal of pesticide residues from produce above that of just rinsing with tap water alone.
That may not be saying much though. Captan appears to be the exception. When rinsing with plain water was tried against a half dozen other pesticides, less than half of the residues were removed. Fingernail polish remover works better, but the goal is to end up with a less toxic, not more toxic, tomato. We need a straightforward, plausible, and safe method for enhanced pesticide removal, although the efficacy of pesticide removal from fruits and vegetables has been rarely reported in the medical literature. Anything we can add to the tap water to boost its pesticide-stripping abilities?
If you soak potatoes in water, between about 2% to 13% of the pesticides are removed, but a 5% acetic acid solution removes up to 100%. What’s that? Plain white vinegar. But 5% is full strength. What about diluted vinegar? Diluted vinegar seemed only marginally better than tap water for removing pesticide residues. Using full-strength vinegar would get expensive, though. Thankfully, there’s something cheaper that works even better: salt water. A 10% salt water solution appears to work as good or better than full-strength vinegar. To make a 10% salt solution you just have to mix up 1 part salt and 9 parts water, though make sure to rinse all the salt off before eating.
There’s not much you can do for the pesticides in animal products, though. The top sources of some pesticides are fruits and vegetables; but for others, it’s dairy, eggs, and meat, because the chemicals build up in the fat. So what to do about the pesticides in meat, egg yolks, or egg whites? Hard boiling appears to destroy more pesticides than scrambling, but for the pesticides that build up in the fat in fish or chicken, cooking can sometimes increase pesticide levels that you can’t just wash off. In fact washing meat, poultry, or eggs is considered one of the top ten dangerous food safety mistakes.
Now, the remarkable impact of the structure of food beyond nutritional content or composition.
“Food structure,” not just nutrient composition, may be “critical for optimal health.” It should come as no surprise that cornflakes and Rice Krispies cause a much greater spike in blood sugars than rice or corn-on-the-cob; but it’s not just the added sugar. “Even with identical ingredients, food structure can make a major difference. ” For example, if you compare the absorption of fat from peanuts, compared to the exact same number of peanuts ground into peanut butter, you flush more than twice the amount of fat down the toilet when you eat the peanuts themselves, since no matter how well you chew, small bits of peanuts trapping some of the oil that makes it down to your colon. And, “the physical form of food” not only alters fat absorption, but carbohydrate absorption as well. For example, rolled oats have a significantly lower glycemic index than instant oatmeal, which is just oats, but in thinner flakes. And, oat flakes cause lower blood sugar and insulin spikes than powdered oats. Same single ingredient: oats, but in different forms can have different effects.
Why do we care? Well, the overly “rapid absorption” of carbohydrates after eating a high-glycemic index meal can trigger “a sequence of hormonal and metabolic changes” that may promote excessive eating. They took a dozen obese teen boys and fed them different meals, each with the same number of calories, and just followed them for the next five hours to measure their subsequent food intake. And, those that got the instant oatmeal went on to eat 53 percent more than after eating the same number of calories of steel-cut oatmeal. The instant oatmeal group was snacking within an hour after the meal, and goes on to accumulate significantly more calories throughout the rest of the day. Same food, but different form; different effects.
Instant oatmeal isn’t as bad as some breakfast cereals, though, which can get up into the 80s or 90s—even a cereal with zero sugar like shredded wheat. The “new industrial methods” used to create breakfast cereals, such as extrusion cooking and explosive puffing, accelerate starch digestion and absorption, causing an exaggerated blood sugar response, added sugar or not. Shredded wheat has the same ingredients as spaghetti; just wheat, but has twice the glycemic index.
When you eat spaghetti, you get a gentle rise in blood sugars. If you eat the exact same ingredients made into bread form, though, all the little bubbles in bread allow your body to break it down quicker; so, you get a big spike in blood sugars, which causes our body to overreact with an exaggerated insulin spike. And, that actually ends up driving our blood sugars below fasting levels, and that can trigger hunger. Experimentally, if you infuse someone with insulin so their blood sugars dip, you can cause their hunger to spike, and, in particular, hunger cravings for high-calorie foods. In short, lower-glycemic index foods may “help one to feel fuller longer than equivalent higher-glycemic index foods.”
Researchers randomized individuals into one of three breakfast conditions: oatmeal made from quick oats, the same number of calories of Frosted Flakes, or just plain water, and then measured how much people ate for lunch three hours later. Not only did those who ate the oatmeal feel significantly fuller and less hungry…they indeed then went on to eat significantly less lunch. Overweight participants ate less than half as many calories at lunch after eating the oatmeal for breakfast—hundreds and hundreds of calories less. In fact, if you notice, the breakfast cereal was so unsatiating that the Corn Flakes group ate as much as the breakfast-skipping, water-only group. It’s as if the cereal group hadn’t eaten breakfast at all!
Feed people Honey Nut Cheerios, and hours later they feel significantly less full, less satisfied, and more hungry than those fed the same number of calories of oatmeal. Though both breakfasts were oat-based, the higher glycemic index, reduced intact starch, and reduced intact fiber in the Cheerios seemed to have all conspired to diminish appetite control. “The trial was funded by the Pepsi Corporation,” makers of the Quaker oatmeal, pitted against the Cheerios from rival General Mills. And an exposé on industry-funded study manipulation later revealed that the study originally included another arm, Quaker Oatmeal Squares. “I am sorry that the oat squares did not perform as well as hoped,” the researcher told Pepsi, which “decided to publish only the results about its oatmeal.”
We would love it if you could share with us your stories about reinventing your health through evidence-based nutrition. Go to NutritionFacts.org/testimonials. We may share it on our social media to help inspire others. To see any graphs charts, graphics, images or studies mentioned here, please go to the Nutrition Facts Podcast landing page. There you’ll find all the detailed information you need plus links to all of the sources we cite for each of these topics.
For recipes, check out my “How Not to Die Cookbook.” It’s beautifully designed, with more than 100 recipes for delicious and nutritious meals. And all the proceeds I receive from the sales of all my books goes to charity. NutritionFacts.org is a non-profit, science-based public service, where you can sign up for free daily updates on the latest in nutrition research via bite-sized videos and articles.
Everything on the website is free. There’s no ads, no corporate sponsorship. It’s strictly non-commercial. I’m not selling anything. I just put it up as a public service, as a labor of love – as a tribute to my grandmother, whose own life was saved with evidence-based nutrition. Thanks for listening to Nutrition Facts. I’m your host, Dr. Michael Greger.