Potatoes can be prepared in a variety of ways, including baked, mashed, hashed, fried, scalloped, roasted, and more, but should we eat them at all?
Diabetes and potatoes
The Harvard Nurses’ Health Study, which followed the diets and diseases of tens of thousands of women for 20 years, found in 2006 that eating more potatoes was linked to a higher risk of developing type 2 diabetes. However, most of the roughly 100 pounds of white potatoes that Americans consume each year are deep fried and used to make potato chips or french fries. Deep-fried foods are known to contain AGEs, which are known to be harmful to health. A mere three servings of french fries per week is linked to a nearly 20% increased risk of type 2 diabetes, whereas potatoes in general, including fries, were only slightly linked to a tiny risk.
Mashed or baked potatoes continued to be linked to diabetes, but individuals who consume more potatoes may also consume more meat, and we are aware that animal protein itself is linked to an increased risk of diabetes. However, even after statistically correcting for that, researchers discovered a higher risk associated with potatoes. If you dig deeper, you’ll see that mashed and baked potatoes frequently contain butter and sour cream. However, even after adjusting for these and other dietary factors, such as the ratio of plant to animal fats and whether potato eaters consumed more soda or fewer vegetables, the association between potato consumption and diabetes appeared to persist.
By 2015, Harvard researchers had also looked at other cohorts, including the all-male Health Professionals Follow-Up Study to complement the all-female Nurses studies. They found that baked, boiled, or mashed potatoes had a small increase in diabetes risk, but french fries seemed to be nearly five times worse. Despite the fact that recent research casts serious doubt on that classification, the authors came to the conclusion that the Dietary Guidelines classify potatoes as a healthy vegetable. (Walter Willett, who at the time was the chair of the nutrition department at Harvard, suggested that candy and potatoes should be separated.)
Then, in 2018, a meta-analysis published on potato consumption and risk of type 2 diabetes combined all six of the prospective studies that had been done to date and found about a 20 percent increase in diabetes risk associated with each serving of potatoes a day. The researchers came to the conclusion that eating a lot of potatoes over a long period of time may strongly raise the risk of developing diabetes. Is that the end of the story? Ideally, potato consumption would be associated with a healthy diet in every nation. If potato consumption was still associated with diabetes there, then that would be concerning. As I discuss in my video Do Potatoes Increase the Risk of Diabetes?, a study out of Iran found that those eating the most boiled potatoes had only half the odds of developing diabetes. In Iran, not only is most of the potato consumption in the form of boiled potatoes, but those who eat potatoes have the healthiest diets and eat the most whole plant foods, such as fruits, vegetables, whole grains, and beans.
The bottom line is we 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.
Potatoes and High Blood Pressure
What about potatoes and hypertension? And the end? In my video, “Do Potatoes Increase the Risk of High Blood Pressure and Death?,” I delves into those issues. According to the findings of a study conducted at Harvard, individuals who consumed potatoes in any form—baked, boiled, or mashed—on the majority of their days, as opposed to only french fries and potato chips, appeared to be more likely to develop high blood pressure.
As mentioned above, salt and butter are often added to potatoes, but when they attempted to tease out the effects of salt and saturated fat, there still seemed to be a link between potato consumption and high blood pressure.
However, what exactly is the “meat” in “meat and potatoes”? According to the same Harvard researchers, consuming moderate amounts of canned tuna and meat, including poultry, appeared to be linked to an increased risk of hypertension. So, in the potato study, they endeavored to factor out any effects from the consumption of all types of meat yet still found an increased risk of hypertension associated with potato intake.
However, there was no correlation found between potato consumption and high blood pressure in two similar studies conducted in Europe’s Mediterranean region. This may be due to the fact that potatoes are frequently eaten alongside other vegetables in that region of the world and are not typically topped with butter and sour cream.
So, Are Potatoes Bad for Us?
We are concerned about the repercussions, which is one of the primary reasons we care about blood pressure. 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 was found between potato consumption and risk of premature death in Southern Italy either. However, potato consumption has been linked to an increased risk of death in the United States: an increased risk of death from all causes combined, an increased risk of death from heart disease by 65%, an increased risk of death from stroke by 26%, and an increased risk of death from cancer by 50%. However, after accounting for confounding factors, everything vanished. In other words, it wasn’t the potatoes at all.
People who eat potatoes must just smoke more, drink more, or eat more saturated fat, for instance. The link between potatoes and death disappears once all of these other factors are taken into account. The largest study of diet and health in human history, the NIH-AARP study, confirmed this. With the possible exception of french fries, which are linked to an increased risk of dying from cancer, researchers discovered that potatoes alone are not associated with an increased risk of death. 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 if eaten 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.
(In terms of mortality, fried potatoes may not be as harmful as fried meat, such as fried fish and chicken, but that isn’t much of a statement.) Nuts, fruits, vegetables, and legumes (beans, split peas, chickpeas, and lentils) are other whole plant foods that are linked to longer lives, a lower risk of dying from cardiovascular diseases like heart attacks and cancer, and a 25% lower risk of premature death from all causes together. However, 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. However, keep in mind that white potatoes may have an opportunity cost because every bite is a missed opportunity to consume something even healthier—something that may actively increase our lifespan—in contrast to meat, which, like potatoes, may actually actively shorten lifespan. Therefore, potatoes are somewhat of a paradox. All of the fiber, vitamin C, and potassium in white potatoes may be counterbalanced by the negative effects of their high glycemic index, which I discuss in my video Glycemic Index of Potatoes: Why You Should Chill and Reheat Them. This explains why potato consumption may only have a neutral impact on mortality risk. Not only are high-glycemic-impact diets strongly linked to the development of type 2 diabetes, but current research also suggests that this connection is causal.
The Potato Glycemic Index
Foods with a glycemic index (GI) above 70 are classified as high-GI foods, and those with a GI lower than 55 are low-GI foods. White bread and white potatoes, on the other hand, have a high glycemic index, and pure sugar water, for instance, is frequently standardized at 100. Is there a way to lower the potatoes’ glycemic index? When potatoes are boiled, then cooled in the refrigerator, some of the starch crystallizes into a form that can no longer be broken down by the starch-munching enzymes in our gut.
When put to the test, cold potatoes actually had a significantly lower glycemic index than hot potatoes. So, by consuming potatoes as potato salad, for instance, we can get nearly a 40 percent lower glycemic impact. Therefore, the chilling effect may also slow the rate of starch breakdown and absorption. 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 we may get the best of both worlds by cooling them and then reheating them, which is exactly what was done in a famous study I profiled in my book How Not to Diet. Out of the dozens of foods tested, only boiled, cooled, and reheated potatoes were the most filling. There’s an appetite-suppressing protein in potatoes called potato protease inhibitor II, but the way potatoes are prepared makes a difference. Compared to french fries, mashed or boiled potatoes are significantly more filling. However, that was for fried french fries. Fries that have been baked? Individuals 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, as well as baked french fries.