The World's Healthiest Foods

Are sweet potatoes just orange-colored regular potatoes?

Introduction

Sweet potatoes are actually a completely different vegetable than regular potatoes. They are not even in the same botanical family. While each is an important vegetable, deserving of a place in a healthy diet, these two foods feature different tastes and unique nutritional benefits. Sweet potatoes are considered an 'anti-diabetic food', offering a host of nutrients and an impressive array of antioxidants. They taste delicious, are easy to prepare and can be used in a variety of dishes, even in some that call for white potatoes.

Sweet potatoes are not "potatoes"

While there are over 100 varieties of edible potatoes that range in size, shape, color, starch content and flavor, the sweet potato is not one of them. These two root vegetables are in fact from two completely different families. The potato's scientific name, Solanum tuberosum reflects that it belongs to the Solanaceae family whose other members include tomatoes, eggplants, peppers, and tomatillos.

The sweet potato, on the other hand, belongs to the Convolvulaceae plant family and is known by the scientific name of Ipomoea batatas. The well-known flower called "Morning Glory" belongs to the same botanical family as the sweet potato.

Sweet potato history

Although sweet potatoes were introduced into U.S. supermarkets relatively recently in comparison to other staple foods, they are by no means new to the global grocery. Cultivation of sweet potatoes dates back about 4,500 years to farming practices in Central and South America. Even Christopher Columbus recognized their uniqueness, and he brought them back to Spain following his first voyage to North American in 1492.

Sweet potato basics

Sweet potatoes have a starchy and sweet taste with different varieties having their own unique flavor profiles. They are oftentimes grouped into two categories depending upon texture since some are firm, dry and mealy when cooked while others are soft and moist.

The most well-known of the sweet potatoes is probably the vegetable that most people refer to as a "yam". This moist-fleshed, orange-colored sweet potato which was introduced in the mid-20th century was given the name 'yam' in order to distinguish it from the white-fleshed sweet potato to which most people were accustomed. Unfortunately, this has served to render some confusion as many people mix up the true yam - root vegetable from Dioscoreaea genus - with this orange colored sweet potato.

The sweetness of sweet potatoes

The "sweet" part of the sweet potato is fascinating from a health perspective. Without a doubt, cooked sweet potatoes taste sweeter than cooked "white" potatoes. Usually when one food tastes sweeter than another, it's because it contains more sugar, which also gives it the potential to make our blood sugar less stable. With sweet versus regular potatoes, it's exactly the opposite. Sweet potatoes, despite their sweetness, appear to act almost like an "anti-diabetic" food in some respects, and do not appear to place our blood sugar at risk as much as their more common counterpart.

This "blood sugar friendly" character of sweet potato seems related to two aspects of its composition. First, sweet potatoes are about twice as high in dietary fiber as ordinary Russet Burbank white baking potatoes, and this doubled fiber slows down digestion and the release of sugar. Second, sweet potato has actually been examined in the lab for its specific "antidiabetic" effects. In an animal study, sweet potato has been shown to be comparable to a prescription drug in enhancing the effectiveness of insulin under certain circumstances.

Vitamins and minerals in sweet potato vs regular potato

Sweet potatoes and regular potatoes share some nutritional similarities, yet also share a host of unique features. Like potatoes, sweet potatoes are a very good source of vitamin C, and a good source of copper, fiber, vitamin B6, and potassium. While potatoes are a good source of manganese, sweet potatoes are a very good source of this trace mineral and a good source of iron. See Table 1 for a review of the nutrients in which sweet potato is concentrated.

Sweet potatoes feature many antioxidants

When it comes to antioxidants, sweet potatoes may offer a bit of an advantage. Not only are they a more concentrated source of vitamin C, but they are an excellent source of vitamin A, in the form of beta-carotene (potatoes contain hardly any beta-carotene). The vitamin C and beta-carotene in the sweet potatoes work as powerful antioxidants to help to eliminate free radicals, molecules that damage cells and cell membranes and which are associated with the development of conditions such as colon cancer, atherosclerosis and diabetic heart disease.

Yet, the antioxidant profile of sweet potatoes extends even further. Some of the proteins found in sweet potato, usually referred to as root storage proteins, have been found to have antioxidant activity. In fact, one of the compounds studied (an as yet to be named compound simply referred to as 33 kDa TI) has been shown to be about 1/3 as active as glutathione, one of the most active antioxidant compounds in the body.

Unlike potatoes, sweet potatoes do not contain nightshade alkaloids

For some individuals, the botanical difference between sweet potato and the more common baking potato might be particularly important. The Solanaceae family to which common Russet baking potatoes belong is also known as the nightshade family. Nightshade plants contain a variety of substances called alkaloids, and these substances can sometimes provoke allergy-related symptoms. The nightshade alkaloids are completely avoided with a change from baking potatoes to sweet potatoes, because sweet potatoes are not part of the nightshade family. Although not clearly demonstrated in research, a switch from potatoes over to sweet potatoes might be especially helpful for individuals with inflammatory joint-related problems like rheumatoid arthritis.

Practical tips - preparing sweet potatoes

If you purchase organically grown sweet potatoes (which we highly recommend) you can eat the entire tuber - skin and flesh. This way you can benefit from all the nutrition benefits and delightful tastes that this wonderful vegetable has to offer. If you buy conventionally grown ones, we recommend that you do not eat the skin since it may be contaminated with pesticides or other synthetic processing chemicals. You can either peel them before eating if you are cooking them in pieces or peel them just before cooking if preparing whole.

To keep the sweet potatoes looking fresh, you should cook them immediately after peeling and/or cutting them since the flesh darkens upon contact with air. If that is not possible, place the cut pieces in a bowl covered with water until you are ready to cook them as this will retard oxidation from occurring.

Sweet potatoes can be used just like potatoes in many dishes where a little extra sweetness would be appreciated. They can be baked, mashed, "oven-fried" or stuffed just like any good old spud. For more ideas on quick serving suggestions for sweet potatoes, refer to the How to Enjoy section of the article on Sweet Potatoes.

Table 1: Profile of Concentrated Nutrients: Sweet Potato (serving size = 1 small)

Nutrient Amount %DV Density Quality
Vitamin A 43644.0 IU 262.2 49.5 Excellent
Vitamin C 49.2 mg 28.4 5.4 Very good
Manganese 0.52 mg 26.0 4.9 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

References

Hou, W. C.; Chen, Y. C.; Chen, H. J.; Lin, Y. H.; Yang, L. L., and Lee, M. H. 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. and 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