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Sweet potato, with skin

Although sweet potatoes may be part of the Thanksgiving tradition, be sure to add these wonderful naturally sweet vegetables to your meals throughout the year; they are some of the most nutritious vegetables around. Sweet potatoes can be found in your local markets year-round, however they are in season in November and December.

The sweet potato has yellow or orange flesh, and its thin skin may either be white, yellow, orange, red or purple. Sometimes this root vegetable will be shaped like a potato, being short and blocky with rounded ends, while other times it will be longer with tapered ends. There is often much confusion between sweet potatoes and yams; the moist-fleshed, orange-colored root vegetable that is often called a "yam" is actually a sweet potato.


Health Benefits

How sweet it is for your health to eat sweet potatoes! Not only do they taste like dessert, here's the latest research on sweet potatoes surprising benefits.

Unique Proteins with Potent Antioxidant Effects

Recent research studies on sweet potato focus on two areas of unique health benefit. First are some unique root storage proteins in this food that have been observed to have significant antioxidant capacities. In one study, these proteins had about one-third the antioxidant activity of glutathione – one of the body’s most impressive internally produced antioxidants. Although future studies are needed in this area, count on these root proteins to help explain sweet potatoes' healing properties.

An "Antidiabetic" Food

Second is the recent classification of sweet potato as an “antidiabetic” food. Sweet potato has been given this label because of some recent animal studies in which sweet potato helped stabilize blood sugar levels and lowered insulin resistance. (Insulin resistance is a problem caused when cells don’t respond to the hormone insulin, which is supposed to act as a key and unlock the cell in order to allow sugar to pass from the blood into the cell). Some of its blood sugar regulatory properties may come from come from the fact that sweet potatoes are concentrated in carotenoids. Research has suggested that physiological levels, as well as dietary intake, of carotenoids may be inversely associated with insulin resistance and high blood sugar levels. Once again, more research is needed in this area, but the stage is set for sweet potato to show unique healing properties in the area of blood sugar control.

A Sweet Source of Good Nutrition

Our food ranking system also showed sweet potato to be a strong performer in terms of traditional nutrients. This root vegetable qualified as an excellent source of vitamin A (in the form of beta-carotene), a very good source of vitamin C and manganese, and a good source of copper, dietary fiber, vitamin B6, potassium and iron. How do these sweet potato components support our health?

An Antioxidant-Rich, Anti-Inflammatory Food

As an excellent source of vitamin A (in the form of beta-carotene) and a very good source of vitamin C, sweet potatoes have healing properties as an antioxidant food. Both beta-carotene and vitamin C are very powerful antioxidants that work in the body to eliminate free radicals. Free radicals are chemicals that damage cells and cell membranes and are associated with the development of conditions like atherosclerosis, diabetic heart disease, and colon cancer. This may explain why beta-carotene and vitamin C have both been shown to be helpful for preventing these conditions.

Since these nutrients are also anti-inflammatory, they can be helpful in reducing the severity of conditions where inflammation plays a role, such as asthma, osteoarthritis, and rheumatoid arthritis. In addition, sweet potatoes are a good source of vitamin B6, which is needed to convert homocysteine, an interim product created during an important chemical process in cells called methylation, into other benign molecules. Since high homocysteine levels are associated with an increased risk of heart attack and stroke, having a little extra vitamin B6 on hand is a good idea.

Protection against Emphysema

If you or someone you love is a smoker, or if you are frequently exposed to secondhand smoke, then making vitamin A-rich foods, such as sweet potatoes, part of your healthy way of eating, may save your life, suggests research conducted at Kansas State University.

While studying the relationship between vitamin A, lung inflammation, and emphysema, Richard Baybutt, associate professor of nutrition at Kansas State, made a surprising discovery: a common carcinogen in cigarette smoke, benzo(a)pyrene, induces vitamin A deficiency.

Baybutt's earlier research had shown that rats fed a vitamin A-deficient diet developed emphysema. His latest animal studies indicate that not only does the benzo(a)pyrene in cigarette smoke cause vitamin A deficiency, but that a diet rich in vitamin A can help counter this effect, thus greatly reducing emphysema.

In his initial research, Baybutt took just weaned male rats and divided them into two groups, one of which was exposed to cigarette smoke, and the other to air. In the rats exposed to cigarette smoke, levels of vitamin A dropped significantly in direct correlation with their development of emphysema. In the second study, both groups of rats were exposed to cigarette smoke, but one group was given a diet rich in vitamin A. Among those rats receiving the vitamin A-rich foods, emphysema was effectively reduced.

Baybutt believes vitamin A's protective effects may help explain why some smokers do not develop emphysema. "There are a lot of people who live to be 90 years old and are smokers," he said. "Why? Probably because of their diet…The implications are that those who start smoking at an early age are more likely to become vitamin A deficient and develop complications associated with cancer and emphysema. And if they have a poor diet, forget it." If you or someone you love smokes, or if your work necessitates exposure to second hand smoke, protect yourself by making sure at least one of the World's Healthiest Foods that are rich in vitamin A, such as sweet potatoes, is a daily part of your healthy way of eating. (October 21, 2004)

So, the next time you have the urge for something sweet, how about a thick slice of sweet potato pie? It's one dessert guaranteed to satisfy your whole body, not just your sweet tooth.

Description

Depending upon the sweet potato variety, of which there are about 400, its flesh may be either white, yellow or orange, and its thin skin may either be white, yellow, orange, red or purple. Sometimes this root vegetable will be shaped like a potato, being short and blocky with rounded ends, while other times it will be longer with tapered ends.

Sweet potatoes are grouped into two different categories depending upon the texture they have when cooked: some are firm, dry, and mealy, while others are soft and moist. In both types, the taste is starchy and sweet with different varieties having different unique tastes.

The moist-fleshed, orange-colored root vegetable that is often thought of as a "yam" is actually a sweet potato. It was given this name after this variety of sweet potato was introduced into the United States in the mid-20th century in order to distinguish it from the white-fleshed sweet potato to which most people were accustomed. The name "yam" was adopted from “nyami”, the African word for the root of the Dioscoreae genus of plants which are considered true yams. While there are attempts to distinguish between the two, such as the mandatory labeling by the U.S. Department of Agriculture that the moist-fleshed, orange-colored sweet potatoes that are labeled as "yams" also be accompanied by the label "sweet potato", when many people hear the term "yam" they usually think of the orange-colored sweet potato as opposed to the true yam, the traditional Dioscoreae family root vegetable.

Sweet potatoes belong to the Convolvulaceae plant family and are known by the scientific name of Ipomoea batatas.

History

Sweet potatoes are native to Central America and are one of the oldest vegetables known to man. They have been consumed since prehistoric times as evidenced by sweet potato relics dating back 10,000 years that have been discovered in Peruvian caves.

Christopher Columbus brought sweet potatoes to Europe after his first voyage to the New World in 1492. By the 16th century, they were brought to the Philippines by Spanish explorers and to Africa, India, Indonesia and southern Asia by the Portuguese. Around this same time, sweet potatoes began to be cultivated in the southern United States, where they still remain a staple food in the traditional cuisine. In the mid-20th century, the orange-fleshed sweet potato was introduced to the United States and given the name "yam" to distinguish it from other sweet potatoes. Sweet potatoes are a featured food in many Asian and Latin American cultures. Today, the main commercial producers of sweet potatoes include China, Indonesia, Vietnam, Japan, India and Uganda.

How to Select and Store

Choose sweet potatoes that are firm and do not have any cracks, bruises or soft spots. Avoid those that are displayed in the refrigerated section of the produce department since cold temperature negatively alters their taste.

Sweet potatoes should be stored in a cool, dark and well-ventilated place, where they will keep fresh for up to ten days. They should be stored loose and not kept in a plastic bag. Keep them away from exposure to sunlight or temperatures above 60F since this will cause them to sprout or ferment. Uncooked sweet potatoes should not be kept in the refrigerator.

How to Enjoy

For some of our favorite recipes, click Recipes.

Tips for Preparing Sweet Potatoes:

If you purchase organically grown sweet potatoes, you can eat the entire tuber, flesh and skin. Yet, if you buy conventionally grown ones, you should peel them before eating since sometimes the skin is treated with dye or wax; if preparing the sweet potato whole, just peel it after cooking.

As the flesh of sweet potatoes will darken upon contact with the air, you should cook them immediately after peeling and/or cutting them. If this is not possible, to prevent oxidation, keep them in a bowl covered completely with water until you are ready to cook them.

A Few Quick Serving Ideas:

Pure cooked sweet potatoes with bananas, maple syrup and cinnamon. Top with chopped walnuts.

Steam cubed sweet potatoes, tofu, and broccoli. Mix in raisins and serve hot or cold with a curried vinaigrette dressing.

Desserts made with sweet potatoes are an autumn favorite but can be enjoyed year round. Try making sweet potato pie, bread, muffins or pudding.

Baked sweet potatoes are delicious even when served cold and therefore make a great food to pack in to-go lunches.

Safety

Sweet Potatoes and Oxalates

Sweet potatoes are among a small number of foods that contain any measurable amount of oxalates, naturally-occurring substances found in plants, animals, and human beings. When oxalates become too concentrated in body fluids, they can crystallize and cause health problems. For this reason, individuals with already existing and untreated kidney or gallbladder problems may want to avoid eating sweet potatoes. Oxalates may also interfere with absorption of calcium from the body. For this reason, individuals trying to increase their calcium stores may want to avoid sweet potatoes, or if taking calcium supplements, may want to eat sweet potatoes 2-3 hours before or after taking their supplements.

Sweet Potato and Pesticides

Even though pesticides are present in food at very small trace levels, their negative impact on health is well documented. The liver’s ability to process other toxins, the cells’ ability to produce energy, and the nerves’ ability to send messages can all be compromised by pesticide exposure. Since sweet potatoes are among the 20 foods on which pesticide residues have been most frequently found, individuals wanting to avoid these health risks may want to avoid consumption of sweet potatoes unless grown organically.

Nutritional Profile

Introduction to Food Rating System Chart

The following chart shows the nutrients for which this food is either an excellent, very good or good source. Next to the nutrient name you will find the following information: the amount of the nutrient that is included in the noted serving of this food; the %Daily Value (DV) that amount represents; the nutrient density rating; and, the food's World's Healthiest Foods Rating. Not all of our Daily Value standards are obtained from the FDA. In most instances, we used FDA Daily Values when available because they are widely recognized and apply to both men and women. However, when unavailable, we've used other science-based research to establish nutritional standards. Underneath the chart is a table that summarizes how the ratings were devised. Read more about our Food and Recipe Rating System.

Sweet Potato (small, baked with skin)
1.00 each
95.39 calories
Nutrient Amount DV
(%)
Nutrient
Density
World's Healthiest
Foods Rating
vitamin A 13107.70 IU 262.2 49.5 excellent
vitamin C 17.06 mg 28.4 5.4 very good
manganese 0.52 mg 26.0 4.9 very good
copper 0.26 mg 13.0 2.5 good
dietary fiber 3.14 g 12.6 2.4 good
vitamin B6 (pyridoxine) 0.25 mg 12.5 2.4 good
potassium 306.05 mg 8.7 1.7 good
iron 1.46 mg 8.1 1.5 good
World's Healthiest
Foods Rating
Rule
excellent DV>=75% OR Density>=7.6 AND DV>=10%
very good DV>=50% OR Density>=3.4 AND DV>=5%
good DV>=25% OR Density>=1.5 AND DV>=2.5%

In Depth Nutritional Profile for Sweet potato, with skin

References

  • Baybutt RC, Hu L, Molteni A. Vitamin A deficiency injures lung and liver parenchyma and impairs function of rat type II pneumocytes. J Nutr. 2000 May;130(5):1159-65.
  • Ensminger AH, Ensminger, ME, Kondale JE, Robson JRK. Foods & Nutriton Encyclopedia. Pegus Press, Clovis, California.
  • Ensminger AH, Esminger M. K. J. e. al. Food for Health: A Nutrition Encyclopedia. Clovis, California: Pegus Press; 1986.
  • Fortin, Francois, Editorial Director. The Visual Foods Encyclopedia. Macmillan, New York.
  • Hou WC, Chen YC, Chen HJ, et al. Antioxidant activities of trypsin inhibitor, a 33 KDa root storage protein of sweet potato (Ipomoea batatas (L.) Lam cv. Tainong 57). J Agric Food Chem 2001 Jun;49(6):2978-81.
  • Kusano S, Abe H. Antidiabetic activity of white skinned sweet potato (Ipomoea batatas L.) in obese Zucker fatty rats. Biol Pharm Bull 2000 Jan;23(1):23-6.
  • Li T, Molteni A, Latkovich P, Castellani W, Baybutt RC. Vitamin A depletion induced by cigarette smoke is associated with the development of emphysema in rats. J Nutr.<./i> 2003 Aug;133(8):2629-34.
  • Suzuki K, Ito Y, Nakamura S et al. Relationship between serum carotenoids and hyperglycemia: a population- based cross-sectional study. J Epidemiol 2002 Sep;12(5):357-66.
  • Terahara N, Konczak-Islam I, Nakatani M, et al. Anthocyanins in callus induced from purple storage root of Ipomoea batatas L. Phytochemistry 2000 Aug;54(8):919-22.
  • Wallerstein C. New sweet potato could help combat blindness in Africa. BMJ 2000 Sep 30;321(7264):786.
  • Wood, Rebecca. The Whole Foods Encyclopedia. New York, NY: Prentice-Hall Press; 1988.
  • Ylonen K, Alfthan G, Groop, L et al. Dietary intakes and plasma concentrations of carotenoids and tocopherols in relation to glucose metabolism in subjects at high risk of type 2 diabetes: the Botnia Dietary Study. Am J Clin Nutr. 2003 Jun; 77(6):1434-41.

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