Do Potatoes Increase the Risk of High Blood Pressure and Death?

Michael Greger M.D. FACLM · February 9, 2022 · Volume 56

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

Discuss

Transcript

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

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 higher risk of developing high blood pressure. Okay, but what 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, these same Harvard researchers found that meat, including poultry alone, appeared associated with an increased risk of hypertension, and the same with 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 potato risk, and got concerned that the association of potato intake with hypertension could be a critical public health problem. We had 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.

A 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 U.S., however, potato consumption was associated with increased mortality: a whopping 65 percent increased risk of dying from heart disease, a 26 percent increased fatal stroke risk, a 50 percent increased risk of dying from cancer, and increased risk of dying from all causes put together. However, this all disappeared after adjustment for confounding factors. In other words, it wasn’t the potatoes at all. Potato eaters must just smoke more, 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 NIH-AARP study, the largest such study of diet and health in human history. If you just separate out 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.

You know, it’s funny. I’ve done a bunch of videos on how all plant foods are not created equal, talking about healthy vs. unhealthy plant-based diets. To this end, researchers created not just an overall plant-based diet index—just scoring plant vs. 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. 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 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 their 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.

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Sources

Acknowledgements

Motion graphics by Avo Media

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

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 higher risk of developing high blood pressure. Okay, but what 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, these same Harvard researchers found that meat, including poultry alone, appeared associated with an increased risk of hypertension, and the same with 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 potato risk, and got concerned that the association of potato intake with hypertension could be a critical public health problem. We had 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.

A 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 U.S., however, potato consumption was associated with increased mortality: a whopping 65 percent increased risk of dying from heart disease, a 26 percent increased fatal stroke risk, a 50 percent increased risk of dying from cancer, and increased risk of dying from all causes put together. However, this all disappeared after adjustment for confounding factors. In other words, it wasn’t the potatoes at all. Potato eaters must just smoke more, 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 NIH-AARP study, the largest such study of diet and health in human history. If you just separate out 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.

You know, it’s funny. I’ve done a bunch of videos on how all plant foods are not created equal, talking about healthy vs. unhealthy plant-based diets. To this end, researchers created not just an overall plant-based diet index—just scoring plant vs. 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. 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 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 their 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.

Please consider volunteering to help out on the site.

Motion graphics by Avo Media

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:

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