There is a lot of information out there about what is a yam, and what is a sweet potato, and how nutritious they are. But it isn't so easy to take these facts (like: yams are not related to sweet potatoes as yams are a monocot and sweet potatoes are a dicot and part of the morning glory family), and make a decision on what you should get at the store. But as the season of sweet potatoes, or, er, maybe it's yams, is upon us, I thought I would dig up some answers.
I read a ton of information, but what the useful stuff boils down to is this. Everything at your U.S. store is a sweet potato. Yams are from Africa and aren't grown or marketed in the U.S. except at specialty or international markets, and they are much larger. Do not be fooled by the fact that commonly, orange sweet potatoes are referred to as yams in the U.S. If they are canned, they are required to have "sweet potato" somewhere on the label. I will just refer to them as sweet potatoes in this post.
Sweet potatoes are nutritionally very desirable. They are high in fiber and packed with beta-carotine, vitamin A, carotenoids, and potassium while low calories and no fat. They are recommended for their complex carbohydrates, anti-oxidants, protein and iron and even though they are truly quite sweet, they have a low glycemic index. The Center for Science in the Public Interest rated the sweet potato more nutritious than spinach, kale, or brussel sprouts!
In the stores around here, the sweet potatoes I can find are:
Red Garnet "yams", which have dark red skin and bright orange flesh.
Jewel "yams", which have an orangey brown skin and orange flesh.
Sweet Potatoes, which have light yellow or white skin and flesh.
Which to buy? Nutritionally, the darker, orange flesh has a lot of beta carotene, where the whiter tubers have none (which is why they aren't orange). Other than that, they are both very healthful and good choices. What about taste? I prefer the Red Garnet, as they seem smoother and oh, more cozy-by-the-fire fall like. (So my opinion is rather subjective, you don't have to follow it.) Some literature says the white is sweeter, but I seem to think the Garnets are. The Jewel is comparable, but some I feel like it's starchier (?) and not as smooth, dark and sweet to me as the Garnet. I've tried the sweet potato casserole with all three, and though all are acceptable, my first choice is the Garnet, second is the Jewel.
Last week I took one of each kind of sweet potato and a white potato
peeled them (keeping them in order for all of these shots so you can see what they look like--Red Garnet, white sweet potato, Jewel, and a regular white potato)
sliced them into fries (cutting off points as they get too sharp! also I couldn't fit all of all 4 potatoes on this pan), brushed with olive oil and sprinkled with salt
and made baked fries with them. (400 degrees for about 30-40 min., flipping them at some point--I probably should have cooked mine longer or cut the sweet potatoes thinner than the regular potato if I wanted them to be crispy, but I still liked them.)
I served them with chicken nuggets and chicken fingers and a veggie plate and we had a dipping night. My real purpose was to get the kids to try all the different kinds of fries and see how they went. The white sweet potato was more like the regular white potato, so it went over more easily with the jaded teenagers. The little ones (and us big ones) liked the orange fries just as well.
I had several dips available for all the things on the table, and my favorite for the sweet potato fries was this honey-lime dip I found on ourbestbites.com. It's with their recipe for sweet potato fries, which I didn't follow. I also didn't have lime juice on hand and used lemon, still loved it. And it's mostly plain yogurt, so skip the guilt you'd find in a fry sauce or even the typical corn-syrupy ketchup.
6 oz. plain yogurt
1 T mayo (low cal is fine)
1/2 T honey
1 Tbs fresh lime juice
1/4 t cumin
1/8 t oregano
1 t parsley
1/2 t onion powder
1/2 t salt
Just mix, chill, and dip!