MIREILLE BLACKE, MA, RD, CD-N (this article was first published in SEPTEMBER 2012)
“How often when they find a sage,
As sweet as Socrates or Plato;
They hand him hemlock for his wage,
Or bake him like a sweet potato!”
-Don Marquis (1878-1937)
Fall is finally here! With the impending seasonal activities, it made sense to discuss a nutritious food that will be popping up frequently over the next few months. Sweet potatoes are bold in flavor, striking in color, and warmly comforting – the perfect food for the cooler autumn months. With an outer skin in various hues of orange and brown, the inner flesh of the sweet potato ranges from pure white to deep orange to vibrant purple, adding visual beauty to the autumnal table. Despite its name, the sweet potato is not a potato; common white potatoes are categorized as tubers while sweet potatoes are considered roots. Though sweet potatoes are available year-round across the country, they peak during the autumn season. Whether you enjoy them roasted, baked, fried, or mashed or in the traditional Southern sweet potato pie like this one from Lea’s Lunchroom in Lecompte, Louisiana, sweet potatoes are a staple in many fall meals across the United States and around the world.
Sweet potatoes originated in South America; archaeologists have identified remnants of this vegetable in caves of Peru dating to approximately 8,000 years BC/BCE. When Columbus arrived to the Americas in 1492, sweet potatoes were already growing, and he brought them back to Europe. Later explorers carried them to other continents by the 16th century.
Today’s top producers of sweet potatoes include China, Uganda, Nigeria, Indonesia, Tanzania, Vietnam, India, and Japan. In the United States, North Carolina leads in sweet potato production, followed by Louisiana, California, Mississippi, and Texas.
The sweet potato remains a staple in traditional Southern cuisine, and is celebrated in towns across the Southern United States, with festivals such as Opelousas, Louisiana‘s Yambilee (for yams and sweet potatoes), the National Sweet Potato Festival in Vardaman, Mississippi, the Tater Day Festival in Benton, Kentucky, and the Tater Town Special in Gleason, Tennessee, and others. Get in the mood these festivals by trying this recipe for for Cazuela (Pumpkin) Pie using sweet potatoes.
- Sweet Potato Pie is a popular Fall treat. Photo by Ernesto Andrade (San Francisco, California), via Wikimedia Commons
The sweet potato is often mistakenly called a yam in North America, but sweet potatoes and yams are not only distinct from one another, they are completely different species. The yam (botanical species: D. alata) differs from the sweet potato (I. batatas) in taste, texture, appearance, and some nutrients (most notably, yams have very little vitamin A). True yams are starchy tubers that are generally imported into the United States from tropical climates, and are often drier than sweet potatoes, with rougher, scalier skin. Some confusion stems from the adoption of the term “yam” by sweet potato producers and shippers in Louisiana during the mid-20th century. In order to distinguish orange sweet potatoes from white-fleshed counterparts grown in other parts of the country, “yams” were considered Louisiana-grown sweet potatoes. Today, the USDA requires accurate labeling to distinguish between sweet potatoes and yams, but the mistaken identity continues despite this effort.
- Caption: I Yam What I Yam: True Yam (L) and Sweet Potato (R). Photo courtesy of the North Carolina Sweet Potato Commission
One cup or one medium sweet potato with its skin (5”) contains 114 calories, 4 grams fiber, 2.1 grams protein, 40 mg sodium, and is negligible in saturated fat and cholesterol. Sweet potatoes are most notable as excellent sources of vitamin A in the form of beta-carotene, a cancer-fighter and antioxidant that helps to prevent sun damage and premature aging. Sweet potatoes with dark orange flesh are richest in carotenoid pigments and bioavailable beta-carotene.
As a rich source of complex carbohydrates, sweet potatoes provide sustained energy. With regard to complex carbohydrates, dietary fiber, protein, vitamins A and C, iron, and calcium, the sweet potato ranks higher in nutritional value than the white potato, spinach, or broccoli.
Health benefits associated with sweet potatoes include blood sugar regulation, reduced inflammation, and successful blood clotting. As starchy root vegetables, many people would expect sweet potatoes to quickly elevate blood sugar levels, because concentrated starches are easily converted by the digestive tract into simple sugars. However, sweet potatoes contain dietary fiber (4 grams per medium sweet potato) and help to modify insulin metabolism, and actually improve blood sugar regulation, even in Type 2 diabetics. Boiling sweet potatoes seems to favorably impact glucose regulation more than roasting or baking.
Reduced inflammation following the consumption of sweet potatoes has been linked to vitamins A and C in particular, especially in purple sweet potatoes. These anti-inflammatory properties are due to the phytochemical and antioxidant anthocyanin and other color-related pigments; the purple sweet potato owes its rich color from phytochemical anthocyanin and other polyphenols. In addition to reducing inflammation, these substances help to reduce cardiovascular disease, improve vision, and increase memory.
Some of the same color-related phytochemicals in sweet potatoes impact fibrinogen, which is critical for successful blood clotting (stopping blood loss and closing wounds). It is important for individuals who take medications for clotting issues to keep this in mind if sweet potato consumption is high.
- James Hopkinson’s Plantation. Planting sweet potatoes. African American men and women hoe and plow the earth while others cut piles of sweet potatoes for planting. One man sits in a horse-drawn cart. Image from the Civil War Treasures from the New-York Historical Society, via Wikimedia Commons.
Recommendations from this Registered Dietitian (RD):
- Explore your roots. Sweet potatoes are related to the morning glory family (Convolvulaceae), and are not in the yam family (Dioscoreaceae) or that of the common potato (Solanaceae). These foods also differ in taste, texture, flavor, and nutrients. There seem to be regional preferences for the sweet potato; Yankees seem to prefer their sweet potatoes with a granular and gritty consistency, while southern sweet potato consumers enjoy moister textures. Southern states with Sweet Potato Festivals include Alabama, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina , Tennessee, and Texas. If you have a Sweet Potato Festival in your area that you’d like to add to this list, let OKRA know!
- Mix and mash. Sweet potatoes are any easy substitute for white potatoes in most recipes, including baking, mashing, roasting, and frying. Add layers of flavor with peppers (black, white, cayenne, or chile), onion, or cloves, as with this Sweet Potato Guacamole. After baking, serve them cold or use in packed lunches. (Remember: Include the skins for the most nutritional benefit)
- Beware the couch potato. Particularly with holiday season looming, it is important to practice portion control and exercise. Even healthy foods have calories and can lead to weight gain if eaten in excess, so moderation is key. Note that one cup of canned sweet potatoes equals one medium-sized, cooked fresh sweet potato. For more information, refer to the USDA’s Sweet Potato Nutritional Analysis.
- Have your cake and eat it too. Despite its name, the “sweet” potato may be beneficial for people with diabetes. Aside from the low calories and nutritional content found in sweet potatoes (particularly when eaten with the skin), persons with diabetes can benefit from the slow breakdown of these root vegetables in the body, leading to more stable blood glucose and insulin levels. More information can be found at http://www.ncsweetpotatoes.com/nutrition/usda-sweet-potato-nutritional-analysis/
- Chew the fat. Eating sweet potatoes with small amounts of fat will increase the absorption of their beta-carotene. Toss sweet potato spears with olive oil, roast at 400F for 30 minutes, and enjoy healthier fries. [Note: Sweet potatoes cook more quickly than regular potatoes, so you can skip preheating the oven.] Consider adding a chopped walnut topping (with its heart-healthy fats) to a puree of cooked sweet potatoes with bananas, maple syrup and cinnamon.
- Don’t get stoned. Sweet potatoes are high in oxalates, naturally occurring substances which can form insoluble salts with calcium in the body. If oxalates become too concentrated and crystallize, problems such as kidney stones (usually comprised of calcium oxalate) can occur in susceptible individuals. Hydration and proper diet (with regard to protein and calcium) may help to prevent stone formation in individuals prone to them, and some may avoid certain high-oxalate foods (such as rhubarb, beets, spinach, peanuts, okra, chocolate, and sweet potatoes). In these cases, because oxalates may interfere with absorption of calcium from the body, it is important to consult with a healthcare practitioner to ensure calcium requirements are being met.
- Sweet Potato Fries are trendier and healthier. Photo courtesy Tennessee Department of Agriculture.
Whether white, orange, or purple, sweet potatoes offer seasonal color and benefit your health when adding them to your table. Make the most of sweet potatoes this season!
For more information about this nutritious root vegetable, check out the Louisiana Sweet Potato Commission (link to http://www.sweetpotato.org/) and the North Carolina Sweet Potato Commission (link to http://www.ncsweetpotatoes.com).