Nutrition Update: Sweet or Regular...Which Potato is Best? It’s an age-old debate: the sweet vs. the regular potato. Which should you be eating for maximum health? Well, in today’s article, we’ll look to the research and crown an undisputed champion. Why’s there a debate in the first place? In recent years, the sweet potato (but not the regular potato) has enjoyed “superfood” status among healthy eaters and regular exercisers. Some researchers have suggested that potatoes might carry harmful anti-nutrients. Others that their glycemic index (GI) is too high. As a result, the humble spud has taken a mashing in the recent low-carb years. But, here’s the thing. Both regular potatoes and sweet potatoes are healthy, awesome, and delicious heritage foods. You can eat and enjoy both, regardless of your goals. With that in mind, let’s dig up the truth about our tuberous friends. You say potato, I say potahto. But they’re not the same They’re both called “potatoes”. They’re both nutritious, energy-rich tubers and ancient, honored foods whose cultivation stretches back thousands of years. They both originated in Central and South America and have since spread throughout the world. They both taste great and make a fine side dish. Yet, botanically, potatoes and sweet potatoes are completely unrelated. Potatoes (Solanum tuberosum) are in the Solanaceae family, related to tomatoes, peppers, and eggplant along with deadly nightshade. Plants in this family produce solanine, which is poisonous. So don’t eat the leaves or stems of any plant in this group, or potatoes that have gone green. Solanum phureja is a rarer, more wild-type species of potato cultivated in South America. Sweet potatoes (Ipomoea batatas) are in the Convolvulaceae family with flowering morning glory vines. Unlike potatoes, you can also eat the leaves of sweet potatoes, which are very nutritious. Also note: sweet potatoes aren’t yams. True yams are another type of tuber (genus Dioscorea). (In New Zealand and the South Pacific, the tubers called yams are Oxalis tuberosa, a genus related to sorrel and shamrocks.) BIODIVERSITY There are about 4,000 known varieties of potatoes (with about 3,000 in the Andes alone) and about 5,000 varieties of sweet potatoes grown worldwide. Both potatoes and sweet potatoes come in colors ranging from white to orange to purple. Of course, we usually don’t see that diversity in the average supermarket. Commercial breeding ensures that we buy only a few potato or sweet potato types. For instance, fast-food restaurants demand a potato type (such as Russets) that has a particular size and shape, cuts well into French fries and holds together when deep-fried, but has a mealy, floury texture on the inside. Indeed, most of the potatoes grown in North America are destined for the deep fryer. POTATO TYPES Potatoes can also differ in their starch content and type, which affects not only how fast they’re digested, but how they act when cooked. Floury or “mealy” potatoes, which have a fluffy texture and are thus ideal for baking or mashing, are higher in starch, particularly amylose. “Waxy” potatoes have less total starch but are higher in amylopectin, which helps the potato hold together and gives it a slightly “gluey” texture. This makes them better for boiling. They also digest more slowly, especially if they’re cooked and then cooled. Similarly, sweet potato types can vary in their texture, cooking properties, moisture, and sugar levels: White, yellow and purple-fleshed sweet potatoes are typically the dry type, while the orange-fleshed are moist. Carbohydrates Tubers are enlarged roots or stems that plants use to store nutrients. This is what makes them a good source of energy — in this case, starchy carbohydrates. Tubers have been a food source for humans for millennia. But in recent years, eaters have gotten concerned about carbs. People wonder about whether they should eat potatoes at all… aren’t they too “high carb”? For one thing, “high carb” often isn’t the real problem. Most people in North America, western Europe, and Australia consume potatoes in some processed form — as French fries, tater tots, or potato chips. And in North America — especially in the Southern US — the phrase “sweet potato” is often followed by “pie”. We typically slather spuds with other stuff, like butter or sour cream — and for our poutine-loving Canadian friends, gravy and cheese curds. So the tubers themselves are not necessarily to blame. It’s all the stuff we serve them with. CARBS AND SATIETY In fact, partially due to their carbohydrate content, potatoes and sweet potatoes are highly satiating foods. You eat them, they “stick to your ribs”, and you feel full for a long time. (There’s a reason that “meat and potatoes” is used to describe a satisfying meal.) In fact, in 2010, Chris Voigt, the executive director of the Washington State Potato Commission, tried a crazy experiment: 2 months of eating only potatoes. At first, he ate only when he felt hungry, and lost 12 lb in 3 weeks. To get enough calories, he then increased his intake to 20 potatoes a day… and he said he’d never felt so stuffed. Despite apparently meeting his calorie needs, Voigt lost 9 more pounds throughout the rest of the experiment. Not only that, his blood measures (such as cholesterol, triglycerides, and blood glucose) improved. Now of course, we don’t recommend the 20-potato-a-day diet. But Voigt’s results suggest — at least anecdotally — that in fact, starchy tubers are more satisfying and less fat-promoting than low-carb advocates might expect. In part, this is because of the type of carbohydrate that occurs in potatoes and sweet potatoes. In general, potatoes and sweet potatoes are roughly similar in their vitamin and mineral content. But when it comes to vitamins and minerals, orange sweet potatoes are vitamin A superstars. Vitamin A occurs in retinol form in animal foods such as eggs, and in rich industrialized countries, many people can afford to eat these foods. Many processed foods are also vitamin A fortified, so few of us in North America suffer vitamin A deficiency. However, in poorer countries, vitamin A deficiency is a common problem, causing blindness, other health problems, and over 600,000 deaths per year (mostly of young children or pregnant women). Along with other colorful fruits and vegetables (such as leafy greens and squash), orange sweet potatoes contain high levels of the carotenoid form of vitamin A. As little as a cupped handful of sweet potato a day can provide all the vitamin A that a small child needs. Improving access to sweet potatoes and breeding vitamin-A-rich sweet potatoes are thus important nutritional strategies for preventing vitamin A deficiency. You might have guessed that while we rely a lot on clinical research, we also try to keep a sense of perspective. We try not to get bogged down in the numbers, or look at single nutrients or foods in isolation. After all, people don’t eat “nutrients”. They eat food. They eat meals. Having a baked potato with a meal or enjoying Grandma’s potato salad at a family reunion along with 7 other dishes is a lot different than being a fasted test subject who is fed exactly 200 grams of baked potato and nothing else. precisionnutrition/regular-vs-sweet-potatoes
Posted on: Tue, 05 Nov 2013 14:48:42 +0000
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