Does the link between white potatoes and diabetes extend to non-fried potatoes without butter or cream?
The white potato problem began in 2006, when the Harvard Nurses’ Health Study, which had followed the diets and illnesses of tens of thousands of women for 20 years, I establish that greater potato intake was associated with a greater likelihood of developing type 2 diabetes. However, of the hundred or so pounds of potatoes Americans eat each year, most are in the form of fried chips, french fries, or other processed products. What happened when they look specifically on mashed or baked potato? They found the same relationship with diabetes. OK, but what can potato eaters eat the most? Maybe I should rephrase that: What can people eat more meat and potatoes? Indeed, people who ate more potatoes ate more meat, and we know it can also be animal protein which are related with an increased risk of diabetes. But the researchers tried to statistics adapt for this and still found an increased risk with potatoes.
So what do people do? put in baked goods and mashed potatoes? Butter and cream. Again, the researchers tried to adapt for other dietary factors like these, as well as effectively looking at the ratio between vegetable and animal fats and whether potato eaters drank more soda or perhaps skipped other vegetables. However, still, there seemed to be this relationship between potatoes and diabetes.
OK, but this was just one study. By 2015, Harvard researchers had too look in other cohorts, including the follow-up study of all-male health professionals to complement the all-female nurses’ studies, and they continued to find a small increased risk of diabetes associated with baked, boiled or mashed potatoes, although French fries did seem almost five times worse. The authors concluded that potatoes are considered a healthy vegetable in dietary guidelines, but current evidence “casts serious doubt on this classification”. Walter Willett, the chair of Harvard’s nutrition department at the time, went a step further, suggesting the fries should be slathered up there with caramel 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 prospective studies done to date, and researchers found about a 20% increase in diabetes risk associated with each potato serving per day, concluding “[l]long term high potato consumption…can be powerful which are related with an increased risk of diabetes”. But, then again, the vast majority of potatoes eaten were fried, and we know that fried foods contain all kinds of nasty stuff, like advanced glycation end products. The researchers were unable to evaluate french fries versus non-fries. Even just three servings of potatoes per week was associated with a nearly 20% greater risk of type 2 diabetes, while there was only a small risk associated with potatoes in general, and that included French fries mixed in.
The world’s largest manufacturer of frozen French fries took issue with this conclusion. Claim To make one in three billion-dollar French fries eaten on planet Earth, the company has the money to fund reviews to challenge the science. A review he said that the scientific literature should be read with caution because the effect of potatoes on disease risk factors may depend on the foods with which they are grouped as part of a dietary pattern. Indeed, they have a real meaning. Observational studies can never prove cause and effect, and perhaps eating potatoes—even eating baked potatoes—may just be an indicator of 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 point out, remind us, it is not possible to separate the effects of potatoes and potatoes from the effects of the generally miserable Standard American Diet.
Is there a country where potato consumption is associated with a healthy diet? If potato consumption was still linked to diabetes there, then that would be a concern. Enter a seventh study, but this time outside of Iran, where the greatest consumption of potatoes it is of boiled potatoes. In fact, those who ate potatoes had the healthiest diets and ate the most plant-based foods—fruits, vegetables, legumes, and whole grains. And even though the researchers tried to play out these other dietary factors, those who ate the most boiled potatoes were only half as likely to develop diabetes. This supports the idea that it may be difficult to completely distinguish potatoes alone. The bottom line, this systematic review he concludedis that we really don’t have “compelling evidence” that potato intake in general is linked to type 2 diabetes, but we should probably stick with the fries.
Doctor’s note
This is the first in a five-part series on potatoes. Stay tuned for:
Interested in sampling diabetes videos? See related posts below.
