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Sweet potatoes—and yams—are orange or yellow tubers of a plant that is related to the morning glory. They originated in the West Indies and came to North America by way of Europe.
There are two main types of sweet potatoes. The one most commonly called a sweet potato has flesh that is relatively dry and fluffy, with a yellow color and starchy texture. Sweet potatoes that are moister, sweeter, more slender, and have skins that range from orange to purple are often mistakenly referred to as yams. In fact, they are another variety of sweet potato. True yams, which are grown in the tropics, are almost ivory in color, and are more starchy than sweet.
Sweet potatoes are sold either fresh or canned. The canned ones are either vacuum-packed or packed in a syrup.
Sweet potatoes are cured for long-term storage so that they are available year-round. They are at their best from late August to October, when fresh, uncured potatoes are harvested and come to market.
To prepare sweet potatoes, scrub them well with a vegetable brush.
To boil
Peel the sweet potatoes and cut into chunks. Boil until tender—about 25 to 30 minutes. Boiled sweet potatoes can be mashed with butter or margarine and a small amount of orange juice for extra flavor. Or add brown sugar, cinnamon, and nutmeg.
To fry
Julienne-cut sweet potatoes can be deep fried to make French fries.
To roast
Cut unpeeled sweet potatoes into wedges, toss with olive oil and herbs, and roast at 375°F (190°C) for 25 to 30 minutes, until tender.
To bake
Pierce the skin of each sweet potato in several places with a fork, and then bake for 15 minutes at 400°F (220°C), followed by 45 to 60 minutes more at 375°F (190°C). They should be placed on a baking tray since they produce a sticky syrup while baking. Sweet potato slices can also be layered with slices of apple and then topped with brown sugar and butter or margarine and baked in a covered casserole dish at 375°F (190°C) for about 30 minutes.
To microwave
Pierce the skin in several places and bake whole potatoes on high for 5 to 9 minutes.
To grill
Peel the sweet potatoes and slice them lengthwise into 1/2 (1.25cm) inch thick slices. Grill until browned, about four minutes on each side. Serve grilled sweet potatoes brush with melted butter and brown sugar.
Puréed, boiled sweet potatoes—particularly the type known as yams—can be used in baked goods, and can replace pumpkin in pumpkin pie or pumpkin bread. Sweet potato pie is a traditional dish in the southern United States. Finely diced sweet potatoes make good hash browns.
Good flavors for seasoning sweet potatoes include orange, pineapple, apples, pecans, cinnamon, nutmeg, brown sugar, maple syrup, chile peppers, cilantro, lemon, lime, and curry.
Sweet potato, 1 sweet potato (raw)
Calories: 136
Protein: 2.1g
Carbohydrate: 31.5g
Total Fat: 0.39g
Fiber: 3.9g
*Excellent source of: Vitamin C (29.5mg), and Vitamin A (26,082 IU)
*Foods that are an “excellent source” of a particular nutrient provide 20% or more of the Recommended Daily Value. Foods that are a “good source” of a particular nutrient provide between 10 and 20% of the Recommended Daily Value.
Vitamin C, present in fruits and vegetables, is a powerful antioxidant and anti-inflammatory. This anti-inflammatory activity may influence the development of asthma symptoms. A large preliminary study has shown that young children with asthma experience significantly less wheezing if they eat a diet high in fruits rich in vitamin C.
Diets high in insoluble fiber (found in some vegetables) are associated with protection against heart disease in both men and women.
Carbohydrate food is the most efficient fuel for energy production and can also be stored as glycogen in muscle and liver, functioning as a readily available energy source for prolonged, strenuous exercise. For these reasons, carbohydrates may be the most important nutrient for sports performance. Depending on training intensity and duration, athletes require up to 4.5 grams of carbohydrates per day per pound of body weight or 60 to 70 percent of total dietary calories from carbohydrates, whichever is greater. Including starchy vegetables in the diet is one good way to obtain these carbohydrates.
Many Americans eat insufficient amounts of foods containing vitamin C; the disease caused by vitamin C deficiency, scurvy, causes easy bruising. While very few people actually have scurvy, even minor deficiencies of vitamin C can increase the incidence of bruising. People who experience easy bruising may want to try eating more fruits and vegetables—common dietary sources of vitamin C.
The strong association between increased intake of beta-carotene from food and a reduced risk of lung cancer does not necessarily mean that supplementation with natural beta-carotene supplements would reduce the risk of lung cancer. Dietary beta-carotene may be a marker for diets high in certain fruits and vegetables that contain other anticancer substances that may be responsible for the protective effects. Until more is known, some doctors advise smokers to avoid all forms of beta-carotene supplementation—even natural beta-carotene.
Eating plenty of flavonoid- and vitamin C-rich fruits and vegetables helps to support the structure of capillaries.
Some, but not all, studies have reported that eating more foods rich in beta-carotene or vitamin A was associated with a lower risk of cataracts. Synthetic beta-carotene supplementation has not been found to reduce the risk of cataract formation. It remains unclear whether natural beta-carotene from food or supplements would protect the eye or whether beta-carotene in food is merely a marker for other protective factors in fruits and vegetables high in beta-carotene.
A controlled trial showed that eating a diet high in fruits and vegetables containing folic acid, beta-carotene, and vitamin C effectively lowered homocysteine levels. Healthy people were assigned to either a diet containing a pound of fruits and vegetables per day, or to a diet containing 3 1/2 ounces (99g) of fruits and vegetables per day. After four weeks, those eating the higher amount of fruits and vegetables had an 11 percent lower homocysteine level compared to those eating the lower amount of fruits and vegetables.
Some foods, such as rapeseed (used to make canola oil) and Brassica family vegetables (cabbage, Brussels sprouts, broccoli, and cauliflower), contain natural substances that can interfere with thyroid hormone synthesis, resulting in goiter. Cooking has been reported to inactivate this effect in Brussels sprouts.
People who eat plenty of fruits and vegetables high in beta-carotene appear to be at lower risk for macular degeneration than people who do not eat these foods. However, another study found no association between age-related macular degeneration and intake of antioxidants, either from the diet, from supplements, or from both combined. More research is needed to reconcile these differences. In the meantime, beta-carotene-rich vegetables continue to be part of a healthful diet.
Multiple sclerosis (MS)
In one survey, researchers gathered information from nearly 400 people (half with MS) over three years. They found that consumption of vegetable protein, fruit juice, and foods rich in vitamin C, thiamine, riboflavin, calcium, and potassium correlated with a decreased MS risk.
Low intake of fruits and vegetables containing beta-carotene, which the body can convert into vitamin A, may contribute to a vitamin A deficiency.
Most dietary studies have found that women receiving high amounts of nutrients from fruits and vegetables have less risk of cervical dysplasia. Protective effects may be especially strong from diets high in dark yellow and orange vegetables (carrots, winter squash, etc.) and tomatoes.
Health benefits and
concerns for vegetables
Many health benefits and concerns associated with this food are applicable to other
vegetables. Read about health benefits and concerns
for vegetables for a full description.
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The information presented in Foodnotes is for informational purposes only and was created by a team of U.S. registered dietitians and food experts. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements, making dietary changes, or before making any changes in prescribed medications. Information expires March 2005.