 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 multifaceted 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. An association 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. And 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, pluppies, 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% 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 eating white potatoes, since every bite of 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-edged 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. Now, there are high-glycemic impact diets robustly associated with developing type 2 diabetes, but current evidence suggests this relationship is cause and effect. Now, 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 Breads, so that isn't really saying very much. Foods with a glycemic index 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, but when you compare them to an intact grain, like barley groats, also known as pop 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 the so-called resistant starch that are formed are relatively small, making it difficult to recommend cold potatoes as a 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% 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 pre-cook potatoes and consume them cold, or reheat it. 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 2, 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 leaves your body to overcommon, say, 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. 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, and 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%. 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. But why does plant protein make things better, but animal protein makes things worse? Because decreased consumption of branched chain amino acids improves metabolic health. I cover this in my book, How Not to Diet. Speaking of how not to diet, remember the section on vinegar? Here's the blood sugar and insulin spikes, some with pre-diabetes can get from eating up bagel. Feed 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 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%. That was just plain white distilled vinegar. Is it the vinegar itself, or would any acid-y condiment do? In a test tube, lemon juice appeared to have a remarkable starts-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, not just by a little, but like 30%. 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, 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 and 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 over-stimulating the insulin-producing cells in the pancreas. In my last two videos I explained that you can decrease the glycemic impact of white potatoes by eating them cold or chilling than reheating them, or adding broccoli, lemon juice, or vinegar. What else can we do? Well, if you remember, I had a video a few years back that showed how the pigments in brightly colored berries can act as starch blockers. So if you're going to eat a high glycemic food, you may be able to moderate its impact by spreading raspberries on your toast, for example, or adding strawberries to your cornflakes or sprinkling blueberries in your pancakes. No, I'm not saying you have to put blackberries in your baked potato, but given that the natural color compounds in fruits can slow down starch digestion, what about pigmented potatoes? Even just yellow potatoes like Yukon Gold may be preferable to white, but the best may be purple potatoes. Not just purple skin potatoes, but purple fleshed potatoes. If you've never seen purple potatoes, they are remarkable. They have almost a neon blue glow, and not only do they look cool, but purple potatoes cause less of an insulin and blood sugar spike compared to even the yellow fleshed potatoes, suggesting that switching from yellow or white to purple could have a large potential public health benefit. How do we know it's the pigments themselves that are responsible rather than other differences between the different potato varieties? Researchers tried adding a control comprised of berries and a potato starch jelly, but that would seem to add even more variables. In a test tube, extracts of purple and red fleshed potatoes can act as starch blockers. So hey, if you can extract and purify out the purple potato pigments, say that five times fast, you could remove any other effects of the different potato varieties by adding the purple pigments to yellow potatoes. And lo and behold, compared to just plain yellow potatoes, you can get a suppression of the blood sugar and insulin spikes. This way you don't get that overshoot reaction where your blood sugar can actually drop below fasting like you might get otherwise, instead you'd get the gentler up and down in blood sugars you'd expect from a lower glycemic food. The authors suggest purple potato extracts could be produced and made into supplements or fancy functional foods, but these health-promoting compounds may be more cost-effectively received from consuming purple potatoes themselves. The Potato Association of America likes to paint potatoes as an anti-inflammatory food, but what they don't tell you is that this benefit may be limited to pigmented potatoes. If you randomize people to eat a small white potato every day for six weeks versus a yellow or purple flesh potato, the purple potato group achieves significantly lower levels of inflammation compared to the white potato group measuring both C-reactive protein and interleukin-6. Pigmented potato consumption also alters oxidative stress. Within hours of eating a large purple potato, you get a nice 60% bump in the antioxidant power of your bloodstream, and this translates into less free radical DNA damage. If you compare the antioxidant activity of white potatoes, yellow potatoes, and purple potatoes, Yukon Gold has about twice the antioxidant power of white, but purple has 20 times the antioxidant, which is comparable to what you might see in berries. Half a purple potato has about the same polyphenol antioxidant complement as half a cup of blueberries. Purple potatoes can increase the antioxidant capacity of our bloodstream, whereas straight white potato starch can act as a pro-oxidant and decrease it. Eat a purple potato and over the next eight hours, the antioxidant capacity of your bloodstream goes up. In contrast, if you eat white potato starch, devoid of any pigment, you can end up worse off than where you started. Okay, but does this translate into different physiological effects? Yes, indeed. Half people eat either purple potatoes or white potatoes for two weeks, and the purple potatoes improved a measure of arterial stiffness, whereas the white potato did not, and this translates into a drop in blood pressure, even in those already taking high blood pressure drugs, suggesting purple potatoes are an effective blood pressure lowering agent. But what about the toxic glycoalkyloid compounds in potatoes? The toxic human dose starts around 2 to 5 milligrams per kilogram of body weight, and the lethal dose is not too far behind. The average amount of total glycoalkyloids in most potatoes, however, is less than 100 milligrams per kilogram, so at the average American weight of 180 pounds, a toxic dose is like 4 to 9 pounds of potatoes. What happens when you're post-that? Possible nausea, vomiting, and diarrhea that could easily be confused with something like gastroenteritis or food poisoning. Some people can start to get sick at just 1.25 milligrams per kilogram of body weight, or even 1 milligram per kilogram. That would only be about 2 pounds of potatoes at the average American weight. It's also possible they could start accumulating if you ate them day in and day out, but what about those people who go on a fad potato diet and eat meows 3 or 4 pounds a day? They can do that without risking getting sick, only if they peel their potatoes, which removes nearly all the glycoalkyloids. We would love it if you could share with us your stories about reinventing your health through evidence-based nutrition. Go to nutritionfacts.org slash 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 the sources we cite for each of these topics. For a timely text on the pathogens that cause pandemics, order the e-book, audiobook, or hard copy of my last book, How to Survive a Pandemic. For recipes, check out my second to last book, My How Not to Diet 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.