Subtitles section Play video Print subtitles Let's say you really need to find reliable information about the best diet for high blood pressure, or heart disease, or diabetes. Where do you go? Do you go to a website sponsored by Big Pharma that wants to sell you pills to fix your problem? Or, do you want to treat the cause? Welcome to the Nutrition Facts Podcast with the latest peer- reviewed research on the best ways to eat healthy and live longer. Today we take a close look at a multi-faceted and often misunderstood root vegetable. And we start with a little trick about lowering their glycemic impact. If you systematically pull together all the best studies on potato consumption and chronic disease risk, an association is found for the risk of type 2 diabetes and hypertension. Yeah, but that was for French fries. Consumption of boiled, baked, or mashed potatoes was not associated with the risk of high blood pressure, but there was still a pesky link with diabetes. Overall, potato consumption is not related to the risk for many chronic diseases, but boiled potatoes could potentially pose a small increase in risk for diabetes. That's one of the reasons some question whether they should be counted as vegetables when you're trying to reach your recommended daily servings of fruits and vegetables. If you look at other whole plant foods—nuts, vegetables, fruits, and legumes (which are beans, split peas, chickpeas, and lentils)— they're associated with living a longer life. Significantly less risk of dying from cancer, dying from cardiovascular diseases like heart attacks, and 25 percent less chance of dying prematurely from all causes put together. But no such protection is gained from potatoes for cancer, heart disease, or overall mortality. So, the fact that potatoes don't seem to affect mortality can be seen as a downside. Now, it's not like meat, which may actually actively shorten your life, but there may be an opportunity cost to eating white potatoes, since every bite of a potato is a lost opportunity to put something even healthier in your mouth— something that may actively make you live longer. So, potatoes are kind of a double-edge sword. The reason that potato consumption may just have a neutral impact on mortality risk is that all the fiber, vitamin C, and potassium in white potatoes might be counterbalanced by the detrimental effects of their high glycemic index. Not only are high glycemic impact diets robustly associated with developing type 2 diabetes, but current evidence suggests that this relationship is cause-and-effect. A front group for the potato industry called the Alliance for Potato Research and Education funded a study that found that intake of non-fried potato does not affect blood sugar markers, but that's compared with the likes of Wonder Bread; so, that isn't really saying very much. Foods with a glycemic index (GI) above 70 are classiﬁed as high-GI foods, high glycemic index foods, and those lower than 55 are low-GI foods. Pure sugar water, for example, is often standardized at 100. White bread and white potatoes are way up there as high glycemic index foods. When you compare them to an intact grain, like barley groats (also known as pot barley), a super-low GI food, you can see how refined grains and potatoes are simply no match. Is there any way we can have our potatoes and eat them too, by somehow lowering their glycemic index? Well, if you boil potatoes and then put them in the fridge to cool, some of the starch crystallizes into a form that can no longer be broken down by the starch-munching enzymes in your gut. However, the amounts of this so-called resistant starch that are formed are relatively small, making it difﬁcult to recommend cold potatoes as the solution. But when put to the test, you actually see a dramatic drop in glycemic index in cold versus hot potatoes. So, by consuming potatoes as potato salad, for instance, you can get nearly a 40 percent lower glycemic impact. The chilling effect might, therefore, also slow the rate at which the starch is broken down and absorbed. So, individuals wishing to minimize dietary glycemic index may be advised to precook potatoes and consume them cold or reheated. The downside of eating potatoes cold is that they might not be as satiating as eating hot potatoes. But you may get the best of both worlds by cooling them then reheating them, which is exactly what was done in that famous study I profiled in my book How Not to Diet. The single most satiating food out of the dozens tested was boiled then cooled then reheated potatoes. There's actually an appetite- suppressing protein in potatoes called potato protease inhibitor II, but the way you prepare your potatoes makes a difference. Both boiled and mashed potatoes are significantly more satiating than French fries. That was for fried French fries, though. What about baked French fries? Folks had a big drop in appetite after eating boiled mashed potatoes, compared to white rice or white pasta, which is right where fried French fries were stuck, as well as baked French fries. So, though they may be your BFF, they're not very satiating. In our next story, broccoli, vinegar, and lemon juice are put to the test to blunt the glycemic index of white potatoes. White potatoes have a high glycemic index, and consumption of high glycemic impact foods may increase the risk of diabetes. Normally after a meal, we'd like our blood sugars to just gently, naturally rise and fall. But with high glycemic foods like potatoes, you get an exaggerated blood sugar spike which leads your body to over-compensate with insulin forcing your blood sugars lower than when you started, which results in negative metabolic consequences such as a rise in triglyceride fats in the blood. However, potatoes are a good source of potassium, vitamin C, and polyphenols, which may counterbalance the glycemic impact. This may explain why potatoes appear to have a neutral effect when it comes to lifespan, unlike other whole plant foods, that have been associated with actively living longer. In my last video, I detailed my nip-and-nuke method, where the act of chilling potatoes can dramatically lower their glycemic index, even if you then reheat them in a microwave. How else might we reduce the glycemic impact of white potatoes? The answer is the same way you make anything better in your nutritional life—add broccoli. The co-consumption of two servings of cooked broccoli with your mashed potatoes would certainly do it, immediately cutting the insulin demand by nearly 40 percent. In contrast, adding chicken breast makes things worse and adding tuna fish makes things even worse still, nearly doubling the amount of insulin your body has to pump out. Why does plant protein make things better, but animal protein make things worse? Because decreased consumption of branched-chain amino acids improves metabolic health. I cover this in my book How Not to Diet as well as my video on the topic. Speaking of How Not to Diet, remember the section on vinegar? Here are the blood sugar and insulin spikes someone with prediabetes can get from eating a bagel. Eat that same bagel with a tablespoon or so of apple cider vinegar diluted in about a quarter cup of water, though, the impact is significantly less. Does it work for potatoes too? Simply chilling potatoes may cut down on the blood sugar and insulin spikes, but to get significant drops in both, you just have to add about a tablespoon of vinegar to drop levels by 30 to 40 percent. And that was just plain white distilled vinegar. Is it the vinegar itself, or would any acidy condiment do? In a test tube, lemon juice appeared to have a remarkable starch-blocking effect, but you can't know if it works in people, until you... put it to the test. And indeed, lemon juice reduces the glycemic responses to bread. And not just by a little, but by like 30 percent. Now, the subjects were drinking a half cup of lemon juice, but that makes it even more remarkable that it helped because that added an extra half teaspoon of sugar, and yet they still had a better blood sugar response. Vinegar is more potent, though. Just one to two tablespoons a day of vinegar diluted in water can significantly improve both short- and long-term blood sugar control in diabetics, which is why clinicians may want to incorporate vinegar consumption as part of their dietary advice for patients with diabetes. Finally today, are yellow- fleshed potatoes healthier than white? Let's find out. The high glycemic impact of potatoes may increase the risk of type 2 diabetes, perhaps by chronically overstimulating the insulin-producing cells in the pancreas.