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Sweet Potatoes: A Nutritious Powerhouse With a Rich History

By David Yeager

“As a food for human consumption, the sweet potato has been, and always will be, held in very high esteem, and its popularity will increase in this direction as we learn more about its many possibilities.”
— George Washington Carver

The sweet potato, a staple of many a holiday dish, is packed with nutrients. Unfortunately, most traditional ways of preparing sweet potatoes include copious amounts of sugar and fat. With a few simple adjustments, however, revelers (and those who feed them) can serve up the tasty root with fewer calories and plenty of flavor.

Sweet potatoes, Ipomoea batatas, a member of the Morning Glory family, have been cultivated since sometime between 2500 BC and 1850 BC, and archaeological evidence suggests that humans have eaten them for as long as 10,000 years.1,2 By the time Christopher Columbus landed in the New World, sweet potatoes were a well-established crop in Central and South America and the Caribbean Islands.1,3 Columbus took them to Spain, and they were considered a delicacy in Europe in the 16th and 17th centuries, as well as a powerful aphrodisiac.1,3 Legend has it that King Henry VIII of England was a voracious consumer of sweet potatoes, especially spiced sweet potato pies.1

Although they’re often confused with yams, sweet potatoes are in a different food family than yams and white potatoes.2 Many grocery stores in the United States market sweet potatoes as yams, but yam production in the United States is rare, and consumers should assume that they’re buying sweet potatoes, regardless of how they’re marketed.2 The flesh color of sweet potatoes can be white/cream, yellow, orange, pink, or deep purple, but white/cream and yellow-orange are the most common.2

While they’re often associated with American Thanksgiving celebrations, sweet potatoes were most likely unknown to the Native Americans of New England who celebrated with the pilgrims in 1621. Sweet potatoes weren’t cultivated in New England at that time, as they grow best in warm, humid places.3 By the 1880s, however, most Americans were familiar with some variation of glazed sweet potatoes; several cookbooks of the time included glazed sweet potato recipes.1 In the early 1900s, George Washington Carver, a noted black American botanist and inventor, also chronicled more than 100 sweet potato recipes in his bulletins.1,4

In modern times, the sweet potato has become regarded as a nutrient-rich powerhouse. A 200 g (1 cup) serving of baked sweet potato contains 180 kcal, 214% DV for vitamin A, 52% DV for vitamin C, 50% DV for manganese, 36% DV for copper, 35% DV for pantothenic acid, 34% DV for vitamin B6, 29% DV for biotin, 27% DV for potassium, and 26% DV for fiber.2 All of these nutrient concentrations are higher, in some cases significantly, than they are in 1 cup of baked white potato.5 Sweet potatoes also are high in beta-carotene and anthocyanins.2 Purple sweet potatoes, in particular, have high anthocyanin concentrations.2 Sweet potatoes also contain 30 mg to 40 mg of oxalates per 1/2 cup; therefore, people with existing or untreated kidney or gallbladder problems may want to avoid them.2

As with any vegetable, one drawback to boiling sweet potatoes is that some of their nutrients leach into the cooking water. Libby Mills, MS, RDN, LDN, a nutrition and cooking coach and a spokesperson for the Academy of Nutrition and Dietetics (the Academy), says one way to save the lost nutrients is to save the cooking water and use it as vegetable stock for soup. To retain more of the nutrients, Mills recommends steaming the sweet potatoes.

Cut Calories, Not Festivities
With many dishes competing for holiday table space, preventing the sweet potatoes from getting lost in the mealtime shuffle can present a challenge. Preparing them without lots of sugar and butter also can be challenging. To better enjoy the taste and health benefits of sweet potatoes, Mills suggests giving them some space—and a bit of a makeover.

“Let’s face it, the holidays are loaded with tables of food,” Mills says. “Moving the sweet potato from the main dinner to another place in the day can be a really cool way to celebrate with it.”

For example, blending cooked sweet potato with banana, low-fat milk, and pumpkin pie spices, with pecans on top, can make a delicious breakfast smoothie. Mills recommends using nuts or low-fat milk because a little bit of fat can aid beta-carotene absorption in the body. Or, for more traditional breakfast fare, sweet potato pancakes topped with low-fat vanilla Greek yogurt and a drizzle of maple syrup can be a great way to kick off the holiday celebration.

Clients also can turn the versatile vegetable into custard, substituting evaporated low-fat milk for cream. They also can make a healthful savory or sweet slaw, Mills says. She also suggests combining peeled and julienned lightly steamed sweet potatoes with apples, golden beets, jicama, and kale into a salad, which can be served with a citrus maple dressing or a whole grain mustard shallot vinaigrette. For those who prefer their sweet potatoes mashed, Mills recommends adding a little bit of low-sodium vegetable or chicken broth and sage, or skim milk and pumpkin pie spices to add flavor without adding many calories.

A common problem with holiday dinners is that many dishes need to be cooked at the same time. Isabel Maples, MEd, RD, a food safety expert and spokesperson for the Academy, says one advantage of sweet potatoes is that they can be cooked at a range of temperatures to accommodate other dishes, as long as cooking times are adjusted accordingly. To free up oven space, some dishes can be made ahead of time.

A trend that Maples has noticed is the use of a slow cooker to prepare some dishes. She says sweet potatoes can be sliced and cooked with or without their skins in this way. Whether they’re cooked sweet with nutmeg and allspice or savory with oregano and sage, spices and herbs can add an extra layer of flavor, Maples says. Maples recommends adding about 1/2 cup of liquid, such as broth or orange juice, to 4 lbs of sweet potatoes, along with the desired spices. Cook them for 5 to 6 hours on low heat. Start them in the morning, and they will be ready by dinnertime.

One of Maples’ favorite sweet potato dishes is twice-baked sweet potatoes, which can be made early, refrigerated, and reheated when needed. They can be served as halves or whole and can be made sweet or savory. After baking, the flesh of the potatoes is scooped out, mashed with fat-free or low-fat milk, and combined with any number of ingredients. Toasted nuts, such as pepitas or pistachios; cranberries or raisins; and orange zest work well, Maples says. For something a little different, she recommends adding chipotle peppers with yogurt, sour cream, or goat cheese.

“Twice-baked sweet potatoes can range from 150 to 450 calories per serving, so there’s a big range; but if you alter the recipe a little, it should be easy to keep it around 250 calories per serving,” Maples says. “If you’re baking for the holidays, you don’t want your guests to feel like they’re being deprived, so it’s OK to use traditional flavors, such as marshmallow, brown sugar, or butter; just don’t use too much.”

— David Yeager is a freelance writer and editor in southeastern Pennsylvania.

References
1. Harbster J. A sweet potato history. Library of Congress website.
http://blogs.loc.gov/inside_adams/2010/11/a-sweet-potato-history/. Updated October 6, 2012. Accessed November 23, 2015.

2. Sweet potatoes: what’s new and beneficial about sweet potatoes. The World’s Healthiest Foods website.
http://whfoods.org/genpage.php?dbid=64&tname=foodspice. Accessed December 8, 2015.

3. American Thanksgiving. Food Timeline website.
http://www.foodtimeline.org/foodthanksgiving.html. Updated March 18, 2015. Accessed November 23, 2015.

4. Carver GW. Vegetable resources: How the farmer can save his sweet potatoes and ways of preparing them for the table. Bulletin No. 38, November 1936. Texas A&M AgriLife Extension website.
http://aggie-horticulture.tamu.edu/vegetable/additional-resources/carver-sweetpotatoes/. Accessed November 23, 2015.

5. Potatoes: about potatoes. The World’s Healthiest Foods website.
http://whfoods.org/genpage.php?tname=foodspice&dbid=48. Accessed December 8, 2015.

Recipes

Sweet Potato Banana Nut Smoothie • Sweet Potato Apple Slaw • Morocco Vegetable Tagine With Couscous • Smoky Chili with Sweet Potatoes

Sweet Potato Banana Nut Smoothie

Serves 1

Ingredients
1 small sweet potato, prebaked (about 1/2 cup)
1 small banana
3/4 cup skim milk
A dash of dried ginger
A couple of shakes of powdered cinnamon
A pinch of allspice, mace, and/or cloves
2 tsp chopped pecans (optional)

Directions
Blend together all ingredients, topping with chopped pecans as desired.

— Recipe courtesy of Libby Mills, MS, RDN, LDN

Nutrient Analysis per serving
Calories: 339; Total fat: 4 g; Sat fat: <1 g; Trans fat: 0 g; Cholesterol: 5 mg; Sodium: 158 mg; Total carbohydrate: 67 g; Dietary fiber: 8 g; Sugar: 28 g; Protein: 13 g

Sweet Potato Apple Slaw

Serves 8 to 10

Ingredients
1 large or 2 small sweet potatoes
1 small jicama (aka Mexican turnip)
2 small to medium golden beets
2 medium to large apples (preferably tart, such as Granny Smith)
1 cup kale leaves, torn into bite-sized pieces

Directions
1. Peel and julienne the sweet potatoes. Steam for 1 minute, then spread them out evenly in a single layer on a flat surface covered with a clean paper towel to cool. When cool, place them in a large mixing bowl.
2. Julienne the jicama, beets, and apples (shredding them is an alternative), and add to the large mixing bowl.
3. Remove the large rib from the kale leaf. Tear or cut into bite-sized pieces. Dress with Citrus Maple Mustard Dressing.

Citrus Maple Mustard Dressing

Ingredients
2 T extra virgin olive oil
3 T orange juice
2 T minced shallot
1 T white balsamic vinegar
1 T maple syrup
2 tsp coarse Dijon mustard
1/4 tsp salt
1/2 tsp organic orange zest
fresh cracked pepper, to taste

Directions
In a medium-sized mixing bowl, whisk together all of the ingredients. Pour over salad in bowl and toss to coat. Season to taste with salt and pepper.

— Recipe and photo courtesy of Libby Mills, MS, RDN, LDN

Nutrient Analysis per serving of salad with dressing (based on 10 servings)
Calories: 86; Total fat: 2 g; Sat fat: <1 g; Trans fat: 0 g; Cholesterol: 0 mg; Sodium: 95 mg; Total carbohydrate: 18 g; Dietary fiber: 3 g; Sugar: 9 g; Protein: 1 g

Morocco Vegetable Tagine With Couscous

Serves 8

Ingredients
Tagine
1 T extra-virgin olive oil
1 medium onion, chopped
2 medium garlic cloves, minced
1 tsp minced fresh ginger
3 T harissa (see notes)
2 tsp cumin
1/2 tsp cardamom
1 tsp coriander
1/2 tsp turmeric
1/4 tsp black pepper
2 T tomato paste
1 1/2 cups reduced-sodium vegetable broth
1 14.5-oz can diced tomatoes, no salt added, with liquid
1 15-oz can chickpeas, no salt added, rinsed and drained (or 1 3/4 cups cooked)
2 medium sweet potatoes, chopped
2 medium carrots, sliced
1/2 small head cauliflower, chopped into small florets (about 1 1/3 cups)
1/2 medium eggplant, diced into small cubes

Couscous and Toppings
2 cups water
2 cups uncooked whole grain couscous
1/4 cup raisins, not packed
1/4 cup chopped dried apricots, not packed

Directions
1. Lower the baking rack in the oven to accommodate the tangine (see notes) and preheat the oven to 350° F.
2. In a large, ovenproof tangine with a lid (11 inches across), combine the olive oil, onion, garlic, ginger, harissa, cumin, cardamom, coriander, turmeric, black pepper, tomato paste, broth, tomatoes, chickpeas, sweet potatoes, carrots, cauliflower, and eggplant. Stir well. Cover and bake for 1 1/2 hours, stirring every 30 minutes, until vegetables are tender.
3. About 10 minutes before serving, bring the water to a boil in a medium pot. When boiling, remove from the heat and add the couscous. Cover the pot and set aside for 5 minutes, then lift the lid, toss the couscous with a fork, and transfer it to a serving dish. Remove the lid from the tagine and sprinkle with the raisins and apricots. Serve the tagine over the couscous.

Notes: Harissa is a traditional North African condiment made of chiles that provides an essential flavor to this dish. You usually can find it in Mediterranean markets, as well as some gourmet food stores, international markets, and online purveyors. You can find a tagine in many kitchen stores, but if you don’t have one, use a deep casserole dish or Dutch oven with a tight-fitting lid.

Variations: Substitute 1 1/3 cups cooked lentils or beans for the chickpeas, or add 8 oz diced firm tofu (pressed, for best results), if desired. To make this gluten-free, use brown rice couscous.

— Recipe and photo courtesy of Sharon Palmer, RDN
From Plant-Powered for Life: Eat Your Way to Lasting Health with 52 Simple Steps and 125 Delicious Recipes. Copyright © 2014 Sharon Palmer.

Nutrient Analysis per serving (about 1 1/3 cups)
Calories 340; Total fat: 5 g; Sat fat: <1 g; Trans fat: 0 g; Cholesterol: 0 mg; Sodium: 230 mg; Total carbohydrate: 67 g; Dietary fiber: 13 g; Sugar: 15 g; Protein: 13 g

Smoky Chili with Sweet Potatoes

Serves 10

Ingredients
2 cups dried small red beans (eg, anasazi or kidney)
4 1/2 cups water, plus more for soaking
1 tsp reduced-sodium vegetable broth base
1 14.5-oz can fire-roasted diced tomatoes, no salt added, with liquid
2 T tomato paste
1 medium yellow onion, diced
2 medium sweet potatoes, diced
3 celery stalks, diced
2 medium garlic cloves, minced
1 tsp smoked paprika
1 tsp chili powder
1 tsp cumin
1 tsp liquid smoke

Directions
1. Cover the beans with water and soak overnight.
2. Drain the beans and add to a large pot with the 4 1/2 cups of water and the broth base. Bring to a boil, covered, over medium-high heat, then reduce the heat to medium and simmer for 20 minutes.
3. Add the tomatoes, tomato paste, onion, sweet potatoes, celery, garlic, paprika, chili powder, cumin, and liquid smoke, and stir well.
4. Cover and cook for an additional 40 to 45 minutes, stirring occasionally, until the sweet potatoes are tender yet firm and the beans are tender. Add water as needed to replace moisture lost to evaporation, although the consistency should be thick.

Notes: Liquid smoke is available in many supermarkets in the spice or seasoning section; it’s made by smoking wood and collecting the condensed droplets, so it adds a wonderful smoky flavor to dishes. To prepare the dish in a slow cooker, place the soaked beans and the remaining ingredients into the container and cook for 4 to 5 hours on high or 8 to 10 hours on low.

Variation: Substitute dried white beans, garbanzo beans, or heirloom beans for the red beans.

Nutrient Analysis per serving (about 1 cup)
Calories: 167; Total fat: <1 g; Sat fat: 0 g; Trans fat: 0 g; Cholesterol: 0 mg; Sodium: 134 mg; Total carbohydrate: 32 g; Dietary fiber: 11 g; Sugar: 5 g; Protein: 10 g