Health Journal Online

Tag: Potatoes

  • How to Tame Blood Sugar Spikes after Eating Potatoes

    How to Tame Blood Sugar Spikes after Eating Potatoes

    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 rise and fall gently and naturally. But with high glycemic foods like potatoes, we get an exaggerated blood sugar spike. This leads our body to over-compensate with insulin, forcing our blood sugars lower than when we started, which results in negative metabolic consequences, such as a rise in triglyceride fats in the blood, as you can see below and at 0:34 in my video How to Reduce the Glycemic Impact of Potatoes.

    However, potatoes are a good source of vitamin C, potassium, and polyphenols, which may counterbalance their 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 blog, I explained how the act of chilling cooked 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 same way you make anything better in your nutritional life—add broccoli. Eating 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, as shown below and at 1:31 in my video.

    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, as well as in my video on the topic.

    Speaking of How Not to Diet, remember the section on vinegar? The graph below illustrates the blood sugar and insulin spikes that someone with prediabetes may experience after eating a bagel. When that same bagel is consumed alongside a tablespoon or so of apple cider vinegar diluted in about a quarter cup of water, though, the spikes are significantly reduced, as you can see below and at 2:10 in my video.

    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%. And that was just plain white distilled vinegar.

    Is it the vinegar itself, or would any acidic 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 about 30%, as you can see below and at 2:50 in my video.

    Now, the study participants were drinking a half cup of lemon juice, but that makes it even more remarkable that it was helpful 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 in people with diabetes, which is why clinicians may want to include vinegar consumption as part of their dietary recommendations for their patients with diabetes.

    Doctor’s Note

    This is the fourth video in a five-part series on potatoes. Missed the first three? See:

    What about the glycoalkaloid toxins in potatoes? I cover that and discuss the best kind of potato in my upcoming final video in the series: The Healthiest Type of Potato.



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  • Why Cooling Potatoes Lowers Their Glycemic Load

    Why Cooling Potatoes Lowers Their Glycemic Load

    If you eat potatoes when they’re cold, as in potato salad, or chilled and reheated, you can get a nearly 40% lower 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—but that’s 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, eating potatoes is not related to 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% 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, as you can see below and at 1:28 in my video Glycemic Index of Potatoes: Why You Should Chill and Reheat Them.

    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-edged sword.” The reason that potato consumption may have just a neutral impact on mortality risk is that all the fiber, vitamin C, and potassium in white potatoes might be counterbalanced by the adverse 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 potatoes does not affect blood sugar markers, when compared with the likes of Wonder Bread, that is, so that isn’t really saying very much. Foods with a glycemic index (GI) higher than 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, and white bread and white potatoes are also way up there as high glycemic index foods. But when you compare them to an intact grain, like barley groats (also known as pot barley), which is a super-low GI food, you can see how refined grains and potatoes are simply no match. Check out the numbers below or at 2:47 in my video.

    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, as you can see below and at 3:06 in my video.

    However, the amounts of this so-called resistant starch that are formed are relatively small, making it hard 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, shown below and at 3:23 in my video.

    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, people who want to minimize dietary glycemic index may consider precooking potatoes and having them chilled 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 first cooling them and 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, as you can see below and at 4:09 in my video.

    There is 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, as shown below and at 4:26 in my video.

    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 baked fries may be your BFF, they’re not very satiating.

    Doctor’s Note

    Just to be clear, you don’t have to reheat. Chilling is the crucial step to dramatically lower the glycemic index, so you can certainly enjoy a cold potato salad. If you’re trying to control your weight, though, you may want to avoid even baked fries.

    This is the third in a five-video series on potatoes. If you missed the first two, see Do Potatoes Increase the Risk of Diabetes? and Do Potatoes Increase the Risk of High Blood Pressure and Death?.

    Chilling isn’t the only trick to blunt the glycemic impact. You can also add vinegar, lemon, or broccoli.

    Stay tuned for the final two videos in this series: How to Reduce the Glycemic Impact of Potatoes and The Healthiest Type of Potato.

    Join the resistance! Check out related posts below.



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  • Do Potatoes Shorten Your Life?

    Do Potatoes Shorten Your Life?

    Do potato eaters live longer or shorter lives than non-potato eaters?

    Is there a link between 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—not only French fries and potato chips, but even mashed, boiled, or baked—appeared to be at higher risk of developing high blood pressure. But what do people put on potatoes? Salt, not to mention butter, so might the potatoes just be innocent bystanders? 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 meat-and-potatoes people. After all, these same Harvard researchers found that meat, including poultry, seemed to be associated on its own with an increased risk of hypertension, and the same goes for even a moderate amount of canned tuna. So, in 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 an increased risk and became concerned that associating potato intake with hypertension could be a “critical public health problem.” It was assumed potatoes might actually decrease high blood pressure, given their high potassium content, but they found evidence of the opposite effect.

    As I discuss in my video Do Potatoes Increase the Risk of High Blood Pressure and Death?, 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 researchers tried to control for the 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.

    One of the main reasons 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. No relationship between potato consumption and risk of premature death was found in Southern Italy either. In the United States, however, potato consumption was associated with increased mortality: a whopping 65% increased risk of dying from heart disease, a 26% increased risk of fatal stroke, a 50% increased risk of dying from cancer, and an increased risk of dying from all causes put together. However, this association disappeared after adjusting for confounding factors. In other words, it wasn’t the potatoes at all. Potato eaters must just smoke more, 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 NIH-AARP study, the largest such study of diet and health in human history. If you separate out just the potatoes, researchers find they are not associated with increased risk of death, with the possible exception of French fries, which are associated with an 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 one’s risk of dying prematurely, independently of other factors, but the consumption of unfried potatoes seemed to be neutral.

    I’ve talked a lot about how all plant foods are not created equal, as well as healthy versus unhealthy plant-based diets. To this end, researchers created not only an overall plant-based diet index (PDI)—just scoring plant versus animal foods—but also a healthy plant-based diet index (hPDI) and an unhealthy plant-based diet index (uPDI). 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, cake, and Wonder Bread. When you run the numbers, the more plant-based you eat, the longer you live, and 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. However, the researchers were surprised that those eating the less healthy plant-based diets with processed plant-based junk did not live significantly shorter lives. 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 is because potatoes were kind of coming to the rescue. And indeed, higher intake of potatoes did appear protective; so, given these conflicting results, 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 and fried fish—but that’s not really saying much. The French fry/death data gave the industry trade group Potatoes USA a bit of a chip on its shoulder, reminding readers that observational studies can only prove correlation, not causation, to which the authors replied, “Our data add 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.

    Doctor’s Note

    This is the second in a five-part series on potatoes. The first installment was Do Potatoes Increase the Risk of Diabetes?.

    Aside from French fries, potato consumption is not associated with mortality. Potato eaters tend to live just as long as non-potato eaters. That’s actually bad news. A whole plant food that’s not associated with living longer? One that has a neutral effect on lifespan? That’s a lost opportunity. But what if you really like white potatoes? Then you should chill and reheat them, as I explain in my next video.

    Coming up:

    For more on preventing and treating high blood pressure, see related posts below.



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  • Potatoes and Diabetes: It’s Complicated

    Potatoes and Diabetes: It’s Complicated

    Does the link between white potatoes and diabetes extend to non-fried potatoes without butter or sour cream?

    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 a greater likelihood of getting type 2 diabetes. However, of the hundred or so pounds of potatoes Americans eat every year, most are in the deep-fried forms of potato chips, french fries, or other processed products. What happened when they looked specifically at mashed or baked potatoes? They found the same link with diabetes. Okay, but what might potato eaters eat more of? Maybe I should rephrase that: What might meat-and-potatoes people eat more of? Indeed, people who ate more potatoes ate more meat, and we know that animal protein may be 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 and 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. Yet, still, there seemed to be this association between potatoes and diabetes.

    Okay, 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, but the current evidence “casts serious doubts on this classification.” Walter Willett, the chair of Harvard’s nutrition department at the time, went a step further, suggesting potatoes should be siloed up there with candy, as you can see below and at 2:18 in my video Do Potatoes Increase the Risk of Diabetes?.

    A meta-analysis of potato consumption and risk of type 2 diabetes published in 2018 combined all six of the prospective studies that had been done to date, and the researchers found about a 20% increase in diabetes risk associated with each serving of potatoes a day, concluding “[l]ong-term high consumption of potato…may be strongly associated with increased risk of diabetes.” But, again, the great majority of the potatoes consumed were fried, and we know deep-fried foods contain all sorts of nasty things, like advanced glycation end-products. The researchers weren’t able 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. Claiming to make one in three fries eaten on planet Earth to the tune of billions of dollars, the company has the money to fund reviews to cast doubt on the science. One review said that the scientific literature should be read with caution because the impact of potatoes on disease risk factors may depend on the foods they’re grouped with as part of a dietary pattern. Indeed, they do have an actual point. Observational studies 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 separate the effects of potatoes and fries from the effects of the overall crappy Standard American Diet.

    Is there a country where potato consumption is associated with a healthy diet? If potato consumption was still associated with diabetes there, then that would be concerning. Enter a seventh study, but this time out of Iran, where most potato consumption is of boiled potatoes. In fact, those who ate potatoes had the healthiest diets and ate the most whole plant foods—fruits, vegetables, legumes, and whole grains. And though the researchers tried to tease out those other dietary factors, those 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 potatoes. The bottom line, this systematic review concluded, is that we really don’t have “convincing evidence” that the intake of potatoes in general is linked to type 2 diabetes, but we should still probably hold the fries.

    Doctor’s Note

    This is the first in a five-part series on potatoes. Stay tuned for:

    Interested in a sampling of diabetes videos? Check out the related posts below.



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