EXTENSION REPORT

Of Sweet Potatoes and Yams

          I receive a number of online newsletters on nutrition and food topics, all of which I carefully screen for the writers’ credentials, i.e. to verify that they are Registered Dietitians or Food Scientists, and that agency sources are those which I know to be reputable.  Recently I was intrigued by a discussion of the nutritional and appearance characteristics of sweet potatoes and yams.  I realize that only a food scientist could be intrigued by such a topic, but nevertheless, I was.  I thought you might be interested in what I learned about yams and sweet potatoes, especially since they are in season and popular holiday foods.

          A reader in cyberspace had asked Dr. Irene’s Nutrition Tidbits (www.healthandage.com) to clarify distinctions in nutrition and color of these two vegetables.  The reader had commented that food stores display white or yellow “sweet potatoes”.  The “yams” alongside them are orange.  Which was more nutritious?  Turns out, the facts are confusing, and surprising!

          The path to the answer began with a consultation of a government database of nutritional values of foods.   Sweet potato data, as expected, shows outstanding nutritional value.  They are an excellent source of fiber and Vitamin C but are best known for their richness in Vitamin A.  Vitamin A is critical in many body functions, including vision, growth, cell health and bone remodeling.   In the sweet potato Vitamin A is primarily in the form of beta-carotene, a precursor to Vitamin A, which our bodies modify into Vitamin A.  We are capable of storing up to two years’ supply in our livers, and, if the source of Vitamin A is food, not supplements, there is no risk of toxicity.  It is beta-carotene which gives the sweet potato its rich orange color.

          Sweet potatoes also are a fair source of Vitamin B-6 (pyridoxine), folic acid and several other essential nutrients.  Essential nutrients are those which our human bodies cannot make for ourselves and therefore must be obtained from food sources.  While sweet potatoes are a good source of these nutrients, sometimes deficient in fast-paced American diets, they have the benefit of being low in a couple of others that we get too much of, namely fat and sodium.  This holds true, if you don’t load them down with butter and salt, not to mention brown sugar.   Sweet potatoes are a nutritional bargain for the 160 calories in a small baked sweet potato (about ½ cup). 

            References on yams, on the other hand, show that they do not contain any Vitamin A!  They have roughly the same nutritional value as Irish potatoes - which aren’t at all bad.  But how can it be that they lack Vitamin A, since what we see being sold as yams is often even deeper orange than sweet potatoes?  The answer is that what you are buying in the United States is not a yam, but a different variety of sweet potato!

             As it turns out, some years back Louisiana farmers started calling their sweet potatoes "yams" to differentiate them from varieties of sweet potatoes grown further north.  True yams are never orange or sweet. They are an African and/or Asian crop which has a rough, dark outer skin and pale insides.  They are considered staples in many parts of the world and you will usually find them in the ethnic section of a supermarket.  Sweet potatoes, on the other hand, appear to have originated in Mexico and Central and South America. 

          Whether you plan to have Yams or Sweet Potatoes for the holidays, it probably will be a sweet potato, an excellent and delicious addition to your diet during the holidays. They are available most all year round as well, but those in the market at this time are the freshest and most nutrient-packed. 

            PotA'to? PoTAH'to? Either way, sweet potatoes are loaded with vitamin A and are a good source of fiber.  Although that sweet potato casserole looks attractive in the middle of the holiday table, my recommendation would be to eat them year round!

For more information concerning this topic, contact Amelia McGrew, Regional Extension Agent with the Alabama Cooperative Extension System at 251-574-8445 or email at mcgreaj@auburn.edu.

Email address: mcgreaj@aces.edu
Phone number: (251) 574-8445

Issued in furtherance of Cooperative Extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, and other related acts, in cooperation with the U.S. Department of Agriculture. The Alabama Cooperative Extension System (Alabama A&M University and Auburn University) offers educational programs, materials, and equal opportunity employment to all people without regard to race, color, national origin, religion, sex, age, veteran status, or disability.