Q: I have always been told that sweet potatoes are healthier than white potatoes. Is this true?
A: Both sweet potatoes and white potatoes are healthy complex carbohydrates that contain vital nutrients. The question you are asking is one that comes up quite frequently. Generally the debate ends with the sweet potato being declared the winner, but I think close examination would actually call it a draw.
In the first place even though we call them both potatoes, we are talking about two completely different plants. The regular potato (Solanum tuberosum) is related to tomatoes, peppers and eggplants which are from the nightshade family. The leaves and stems of these plants are not edible and in fact we should avoid eating a potato that has gone ‘green’, meaning it was exposed to light. Nightshade family plants produce solanine, which is poisonous, in their leaves and stems. However the fruits of these plants and the root of the potato are edible and nutritious.
Sweet potatoes (Ipomoea batatas) are in the same family of plants as morning glory fines. The leaves of sweet potatoes are edible and like the roots, nutritious. Sweet potatoes are different than yams, which are another type of root vegetable.
Both regular potatoes and sweet potatoes originated in central and south America. There are about 4000 varieties of regular potatoes and about 5000 varieties of sweet potatoes, but in our stores we see very, very few of these and in fact most people may know the regular potato as just one or two types. Both regular and sweet potatoes range in color from white to reddish to purple.
Nutritional Analysis of Potatoes
When you first look at a potato versus a sweet potato, it appears they are very similar. For 100 grams of a baked white or sweet potato you will find:
White potato = 21 grams carbohydrate and 3 grams protein
Sweet potato = 21 grams carbohydrate and 2 grams protein
Looking at just this we see that the white potato has slightly more protein, however if we take a closer look at the carbohydrates we will see a few more differences.
White potato carbohydrates (21 grams total) = 17 grams starch, 2 grams fiber and 1 gram sugar
Sweet potato carbohydrates (21 grams total) = 7 grams starch, 3 grams fiber and 6 grams sugar
Here we are seeing some key differences. the white potato has more than double the starch, but the sweet potato has 6 times the sugar. Both the sweet and white potato will cause a similar effect on blood sugar but much of this depends on the type of potato and how the potato is prepared. Flowery types of white potatoes (those often chosen for baking) have a higher glycemic index than the waxy types favored for boiling. There are also differences in sweet potato varieties that effect their sugar content. For all potatoes, no matter the type, processing them (such as for potato chips) will make them convert to sugar faster than if they are served as a baked potato.
Vitamin Analysis of Potatoes
When we look at the vitamin content of the white versus the sweet potato we start to see greater differences. As I mentioned before, the white potato has slightly more protein than the sweet potato per serving. The white potato also has a slightly more complete protein and the sweet potato lacks lysine in its protein structure so it would need a complementary protein to balance it out. Of course most people don’t use potatoes as their primary proteins.
In looking at other nutrients such as vitamin A, vitamin C, Folate and Potassium for 100 grams of baked potato:
White potato = 10 IU vitamin A, 10 mg vitamin C, 28 mcg folate and 535 mg potassium
Sweet potato = 19200 IU vitamin A, 20 mg vitamin C, 6 mcg folate and 475 mg potassium
Here finally we can see that sweet potatoes are clearly more nutritious in the amount of vitamin A and vitamin C offered yet white potatoes have more folate and more potassium. In the category of vitamins it would depend on what you were seeking as to which would prove more beneficial.
Hopefully in this comparison what clearly shows is that both white and sweet potatoes are nutritious at least when they are baked. Whichever you choose will offer you good forms of carbohydrate and healthy amounts of fiber, vitamins and minerals.