Many people fear that potatoes will make them fat or cause other health problems. Are potatoes really such villains? Are they any better or worse than bread, rice, or other starchy grains?
A Half-baked Myth About Potatoes
Potatoes have a bad reputation, in part, because they have a high glycemic index (GI), meaning that their carbohydrates are quickly broken down into sugar, causing blood sugar and insulin levels to rise rapidly. This, in turn, increases fat storage and the risk of obesity and diabetes—at least in theory.
A few studies have implicated potatoes in weight gain and diabetes. For instance, a 2009 study in the Journal of the American Dietetic Association found a link between potato consumption and waist circumference in women (but not men). Earlier data from the Nurses' Health Study, in the American Journal of Clinical Nutrition in 2006, linked potato intake and the risk of type 2 diabetes in obese women—especially when potatoes were eaten in place of whole grains.
But there are plenty of caveats to consider before you drop the potato. For one, not all studies support the idea that high GI diets—let alone potatoes, in particular—have such adverse effects. Several have found no relationship between high GI-diets and body fat or diabetes. In any case, the GI of potatoes (and other foods) depends on many factors, including how they're cooked and what they're eaten with. And not all varieties have such a high GI (russet potatoes do, for example, but red potatoes rank moderately).
Moreover, it's hard to separate the effects of potatoes from those of other foods in a typical Western diet. That is, the undesirable associations seen in some studies could be due to the meat, refined grains, sugars, and trans fats (as in French fries) in a "meat and potatoes" diet, rather than the potatoes. People also vary in their responses to carbohydrates, and some research suggests that potatoes may be more problematic in overweight and/or sedentary people, who are more likely to have insulin resistance.
Are Potatoes Good for Weight Loss?
On the flip side, some research suggests that potatoes may help with weight control. They rate high in satiety, meaning they help fill you up, so you may eat less. Potatoes also contain proteinase inhibitors, which may suppress appetite. And preliminary experimental work suggests that potato extracts may improve insulin sensitivity and decrease diabetes risk due to their polyphenols. There's even a weight-loss supplement that contains a potato extract, which is claimed to act as an appetite suppressant, though there's no evidence it works. More research is needed, certainly, to confirm any weight-loss potential of potato extracts.
Fully Baked Nutrition Facts on Potatoes
In actuality, potatoes are relatively low in calories—just 130 to 140 in a medium plain baked potato (5 ounces after cooking). That's more per ounce than non-starchy vegetables, but fewer than the calories in bread and rice. The problem is that potatoes are often prepared and served with lots of high-calorie ingredients. A 5-ounce potato with two tablespoons of butter and three tablespoons of sour cream has 415 calories (and 30 grams of fat). A 5-ounce portion of hash browns, cooked in oil or butter, has 375 calories, while 5 ounces of fast-food French fries has 435 calories. Ounce for ounce, potato chips have more than five times as many calories as a plain potato.
Potatoes are also a good source of fiber (leave the skin on), potassium (more than bananas), and vitamin C, and they provide some protein, iron, B vitamins (notably folate), and magnesium, along with other potentially beneficial plant compounds. The more colorful the potato, the higher the antioxidants.
Final thoughts: There's plenty of room for potatoes in a healthy diet that's rich in vegetables, fruits, legumes, and whole grains. Eat them in moderation and go easy on the oil, cheese, and cream when preparing them. By the way, sweet potatoes are technically unrelated to potatoes, but are a nutritious vegetable that provides lots of beta carotene and other carotenoids. You'd do well serving them up in place of white potatoes on occasion.
Originally published in The University of California, Berkeley Wellness Letter (May 2011)