In 10 years of writing health articles for Moonshine Ink, I’ve rarely found such conflicting information as I have on the topic of potatoes. I set out to answer questions like: Are potatoes nutritious? Do they cause weight gain? Do they contribute to diabetes? And I found that, depending on the study, the answer to all those questions was yes, and no.
Part of the problem is that potatoes can be mashed, baked, boiled, and fried into such a variety of forms that asking, “Are potatoes healthy?” can only be answered, “That depends.” If, like most Americans, you consume most of your annual 126 pounds of potatoes in the forms of French fries and potato chips, then no, potatoes are not healthy. But that doesn’t mean they’re inherently bad.
First, some nutritional facts. A medium potato contains 130 to 140 calories, which, ounce for ounce, is fewer calories than you’ll find in rice or bread. Potatoes contain vitamins C and B6 (folate), and are particularly high in potassium — higher even than bananas. Potassium helps lower blood pressure, and since most of us get only half of the recommended daily amount, potatoes can help fill this niche.
Potatoes provide fiber (if you eat the skin), as well as some iron, protein, magnesium, and beneficial plant compounds called phytonutrients. Colorful blue, purple, and red potatoes also contain antioxidants.
But what about all that starch? This is where things get complicated. Potatoes score high on the glycemic index (GI), a system that rates how quickly a food breaks down into sugar. In theory, high GI foods cause a rapid rise in blood sugar and a spike in insulin, which, over time, sets the stage for increased fat storage, obesity, and diabetes.
If this is true, then eating lots of potatoes should contribute to diabetes and weight gain, and some studies seem to bear this out. One of these, published in 2006 in the American Journal of Clinical Nutrition, used data from the Nurses’ Health Study, an ongoing study of 85,000 nurses. The study found a 20 percent increase in type 2 diabetes in women who ate potatoes every day or fries twice a week. Another study in the Journal of the American Dietetic Association in 2009 connected potato intake to an expanding waistline in women, but oddly, not men.
But there are problems with implicating potatoes and their high GI rating in these maladies. First, potatoes come in many varieties, and some, like red potatoes, score only moderately on the GI scale. Secondly, some people can eat a high GI diet and never gain weight or develop diabetes, while others, especially overweight and sedentary people who may be insulin resistant, fare much worse. And third, the GI score of any food changes depending on what else it’s eaten with. A baked potato eaten alongside chicken and broccoli won’t cause the blood sugar and insulin spike that eating a plain baked potato by itself might. Even adding sour cream and butter, though not necessarily healthy, will lower a potato’s GI rating.
And speaking of sour cream and butter, the weight gain often associated with potatoes may be due more to the fattening stuff that goes along with eating spuds; potato salad is coated in mayonnaise, French fries and potato chips are fried in oil, and mashed potatoes are usually smothered in gravy.
But is there something about eating potatoes, in particular, that makes us pack on the pounds? According to a 2011 Harvard study, published in the New England Journal of Medicine, the answer is yes.
Researchers analyzed data from three long-term studies of more than 120,000 participants during the course of 20 years. Every four years, researchers recorded changes in the subjects’ weights, based on their food consumption, exercise, sleep, and other lifestyle choices. The study’s conclusion: All foods are not equal, and some caused more weight gain than others. It was no surprise that fruits and veggies helped prevent gradual weight gain over the years. Even nuts, which are high in calories, and yogurt helped keep off the pounds.
But potatoes didn’t fare so well. Each additional daily serving of potatoes that participants ate caused them to gain an extra pound every four years. This doesn’t sound like much, but after 20 years, it could add up to five extra pounds. (Keep in mind this is the weight gain associated with potatoes alone. Other foods and activities, such as watching TV, also caused additional weight gain.) French fries were especially fattening, with each additional daily serving causing 3.3 extra pounds every four years, while potato chips caused 1.69 extra pounds, and boiled potatoes, about one-half pound in the same time period.
But before you swear off taters, consider a study done by the University of Sydney, in which participants ate 220-calorie portions of different foods and recorded how full they stayed over the next two hours. The resulting “Satiety Index of Common Foods” was published in 1995. The idea behind satiety is that if foods satisfy your hunger, you won’t head back to the refrigerator as often.
The most filling food by a long shot was boiled potatoes, probably because of their weight. (The study found that heavy foods satisfied hunger.) But potatoes also contain resistant starch, which makes you feel full and has been shown in studies to combat abdominal fat and keep blood sugar levels steady. In addition, potatoes contain enzyme inhibitors which may curb appetite.
Wait — potatoes keep blood sugar stable, control appetite, and shrink your waistline? Isn’t that the exact opposite of what the Harvard study and glycemic index say? (Another baffler: Nuts and yogurt, which in the Harvard study prevented weight gain, both rated low on the Satiety Index, meaning you’ll be hungry soon after eating them.)
So what’s a person to do? Use common sense and listen to your body. If you enjoy potatoes, choose healthy ways to eat them, like roasting and baking. And — need I say it? — make chips and fries occasional indulgences, not daily go-to snacks. If you’re overweight or sedentary, you may not tolerate potatoes well; choose other forms of resistant starch, like beans, slightly green bananas, corn, yams, and brown rice.
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