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.
