 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 turn a laser-like focus to that round tuber we call the potato. Are they good for us? Bad for us? Here's our first story. The trouble for white potatoes began in 2006, when the Harvard Nurses' Health Study, which had followed the diets and diseases of tens of thousands of women for 20 years, found that greater potato intake was associated with the greater likelihood of getting tanked to diabetes. OK, but wait, of the hundreds or so pounds of potatoes Americans eat every year, most are in deep fried form of potato chips and french fries. What happened when they looked specifically at mashed or baked potatoes? They found the same link with diabetes. OK, but what might potato eaters eat more of? I'll give you a hint by rephrasing that as what might meat and potatoes people eat more of. Indeed, people who ate more potatoes ate more meat, and we know that animal protein on its own is associated with increased diabetes risk. But the researchers tried to statistically adjust for that, and still found increased risk with potatoes. Well, what do people put on baked and mashed potatoes—butter, sour cream? Again, the researchers tried to adjust for other dietary factors like these, as well as effectively looking at the ratio between plant and animal fats and whether potato eaters drank more soda or maybe skimped on other vegetables, and there still seemed to be this potato diabetes association. OK, but that was just one study. By 2015, Harvard researchers had also looked into other cohorts, including the all-male health professionals' follow-up study to complement the all-female nurses' studies. And they continued to find a small increased diabetes risk associated with baked, boiled, or mashed potatoes, though french fries do indeed appear nearly five times worse. The authors concluded that potatoes are considered to be a healthy vegetable in dietary guidelines, however, the current findings cast serious doubts on that classification. Walt Willett, the chair of Harvard's Nutrition Department at the time, went a step further, suggesting potatoes should be siloed up there with candy. A meta-analysis of potato consumption and risk of type 2 diabetes, published in 2018, combined all six of the prospective studies that have been done to date, and they found about a 20% increase in diabetes risk associated with each serving of potatoes a day, concluding long-term high consumption of potato may be strongly associated with the increased risk of diabetes. But again, the great majority of this potato consumption was fried, and we know there are all sorts of nasty things like advanced location end products and deep-fried foods, and the researchers were unable to assess french fries versus non-fried potatoes. Even just three servings of fries a week is associated with nearly 20% greater risk of type 2 diabetes, whereas there was only a tiny associated risk with potatoes in general, and that included the fries mixed in. The world's largest manufacturer of frozen french fries took issue with this conclusion. Lange claimed that one in three fries eaten on planet Earth to the tune of billions of dollars. They have the money to fund reviews that cast doubt on the science, but they do have an actual point, an observational state. These can never prove cause and effect, and maybe potato consumption, even baked potato consumption, may just be a marker for an unhealthy diet in general. As much as researchers try to adjust for these other factors, as the Journal of the Potato Association of America is quick to remind us, it's not possible to completely separate the effects of potatoes in french fries from the effects of the overall crappy standard american diet. If only there was a country where potato consumption was associated with a healthy diet. If potato consumption was still associated with diabetes there, then that would be concerning. But here we go, a seventh study, but this time out of Iran, where not only is most of their potato consumption from boiled potatoes, but those sweet potatoes had the healthiest diets, ate the most whole plant fruits, fruits, vegetables, whole grains, and beans, and although the researchers tried to tease out those other dietary factors, eating the most boiled potatoes had only half the odds of developing diabetes. This supports the notion that it may be hard to completely separate out just the potato. The bottom line, this systematic review concluded, is that we really don't have convincing evidence to date that the intake of potatoes in general is linked to type 2 diabetes, but we should still probably hold the fries. In our next story we ask, do potato eaters live longer or shorter lives than non-potato eaters? Potato intake and the incidence of hypertension. Harvard researchers followed the diets and diseases of more than 100,000 men and women for decades and found that those who ate potatoes on most days, even just baked, boiled, or mashed, not just french fries and potato chips, appeared to be at a higher risk of developing high blood pressure. Okay, but why do people put on potatoes? Salt, not to mention butter. So maybe the potatoes are just innocent bystanders, maybe, but the researchers made attempts to tease out the effects of salt and saturated fat, and there still seemed to be a link between potato consumption and high blood pressure. Maybe potato eaters are just meat and potatoes, people? After all, the same Harvard researchers had found that meat, including poultry, alone appeared to be associated with increased risk of hypertension, and same with even moderate amount of canned tuna. So when the potato study, they were careful to try to factor out any effects from the consumption of all types of animal flesh, yet they still found increased potato risk and got concerned that the association of potato intake with hypertension could be a critical public health problem. We'd assumed potatoes might actually decrease high blood pressure, given their high potassium content, but they found evidence of the opposite effect. Two similar studies performed in Mediterranean Europe did not find any association between potato consumption and high blood pressure, though. Perhaps this is because they don't smother their potatoes in butter and sour cream in that neck of the woods, and instead eat potatoes with other vegetables. Now, the Harvard folks tried to control for the bad, salty, and fatty dietary components associated with eating potatoes in the West, just like these researchers tried to factor out all the extra vegetables, but you can't control for everything. The primary reason we care about blood pressure is because we care about the consequences. In two studies done in Sweden where they primarily eat their potatoes boiled, no evidence was found that potato consumption was associated with the risk of major cardiovascular disease, and no relationship was found between potato consumption and risk of premature death found in southern Italy either. In the US, however, potato consumption was associated with increased mortality, a whopping 65% increased risk of dying from heart disease, a 26% increased fatal stroke risk, a 50% increased risk of dying from cancer, and increased risk of dying from all causes put together. This all disappeared after adjustment for confounding factors. In other words, it wasn't the potatoes at all. Potatoe-eaters must just smoke or drink more or eat more saturated fat or something. Once you control for all these other factors, the link between potatoes and death disappears. This was confirmed in the NIHARP study, the largest such study of dying health in human history. If we just separate out the potatoes, researchers find that they are not associated with increased risk of death, with the possible exception of French fries, which are associated with increased risk of dying from cancer. Put all the studies together, 20 in all, and no significant association has been found between potato consumption and mortality, though again, fried potatoes may be the exception. Even just twice a week, fries may double once risk of dying prematurely, independently of other factors, but the consumption of unfried potatoes seemed to be neutral. You know it's funny, I've done a bunch of videos on how all plant foods are not created equal, talking about healthy versus unhealthy plant-based diets. To this end, researchers created not just an overall plant-based diet index, just scoring plant versus animal foods, but also a healthy plant-based diet index and an unhealthy plant-based diet index. The healthy index puts a greater emphasis on whole plant foods, whereas the unhealthy index scores how much low-quality plant foods you're eating, grouping potatoes along with soda and cake and wonder bread. Then when you run the numbers, the more plant-based you eat the longer you live, the lower your risk of cardiovascular disease. In other words, more plant foods and less animal foods are associated with a significantly lower risk of dying prematurely. This benefit was limited, though, to those eating the healthier plant-food diets, but they were surprised that those eating all that processed plant-based crap didn't live significantly shorter lives. Now maybe that's just because they were eating fewer animal products, and that's really the primary determinant of lifespan here, or maybe the lack of an association between less healthy plant-based diets and mortality outcomes is because potatoes were kind of coming to the rescue. And indeed, higher intake of potatoes did appear protective, so given these conflicting findings, future studies may consider just resigning fried potatoes to the unhealthy list. Now in terms of mortality, fried potatoes may not be as bad as fried meat, fried chicken, fried fish, but that's not really saying much. The French Fried Death data gave industry trade group PotatoesUSA a bit of a chip on their shoulder, reminding readers that observational studies can only prove correlation, not causation, to which the authors replied, our data added to the pressing public health calls to limit fried potato consumption. French fries may be so bad for you that it wouldn't be ethical to do an interventional study and randomize people to eat them. 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, you can 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. 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