Sweet potatoes have been part of the typical Thanksgiving menu for a century or more, although neither they nor regular everyday potatoes were present at the first Thanksgiving feasts on either side of the border. If you grew up in the United States, you probably remember eating candied yams or sweet potato casserole topped with marshmallows alongside your turkey and cranberries.
If you grew up in the American south, you may have also eaten sweet potato pie at Thanksgiving for dessert – instead of pumpkin pie. (And that rivalry between sweet potato pie and pumpkin pie is the stuff of a whole ‘nother conversation!)
Here in Canada, these dishes are not nearly as common as they are in the United States but sweet potatoes are still one of our Thanksgiving sides – usually just baked and served with a pat of butter. We also eat sweet potatoes with our Christmas dinner, and pretty much any other time we cook a turkey with all the trimmings. In fact for many Canadians, these are probably the only times in the year that we eat a sweet potato, more’s the shame!
But is it a Sweet Potato or a Yam?
The question of whether we’re actually eating a sweet potato or a yam is a confusing one. Let me share a personal experience with you to illustrate what I mean. Thanksgiving is celebrated in early October here in Canada, so we had our big turkey dinner a little over a month ago. And as every year, there was a bowl on the table filled with small, foil-wrapped nuggets still steaming from the oven.
“Do you want sweet potatoes?” my mother asked as she held the bowl out towards me. “Well, they’re really yams.” she added. “I made sure to get yams instead of sweet potatoes.” She then went on to explain that the yams were smaller, sweeter, and softer when cooked than sweet potatoes are. And they have a darker-coloured flesh.
Well, this was news to me!
Why was Mom Calling Sweet Potatoes, ‘Yams’?
In all my 50 years on the planet, we’ve never called those lovely, orange-fleshed tubers “yams” in our family. And I generally see this vegetable sold as “sweet potato” in the stores. Most of my friends call them sweet potatoes too, so I had always kind of assumed that “sweet potato” was more of a Canadian expression, while our American neighbours seem to prefer “yam.” (There is, of course, a completely unrelated African tuber properly called a yam, that has been available in North American grocery stores for several years now. If you’ve ever had those yams, you know they are very different from a sweet potato, whatever we choose to call it in Canada and the US.)
So why was Mom suddenly calling our sweet potatoes “yams”? And why was she talking about there being some sort of difference in the size, colour, and firmness of the flesh?
What is a Sweet Potato?
The scientific name for the sweet potato is Ipomoea batatas. If you’re familiar with botanical names for popular flowers, you might recognize that sweet potatoes are related to morning glories. In fact, the resemblance between the flowers of the two plants is remarkable. Could you tell one from the other if you saw these two plants growing side by side?
Sweet potatoes are a New World vegetable. They were first domesticated about 5,000 years ago, probably in Central America. But today they are grown throughout much of the Americas. They are also cultivated in some parts of Africa, in India, China, and other Asian nations, and also in Polynesia and Australasia.
Although the common name implies that these are potatoes, the sweet potato is only distantly related to potatoes. The potato belongs to the nightshade family (Solanaceae,) along with tomatoes, peppers, and eggplant. The sweet potato belongs to the morning glory family (Convolvulaceae.) Both families are members of the order Solanales. That makes the two root vegetables sort of distant cousins. Sweet potatoes are also not related to yams, which are tubers in the family Dioscoreaceae. The yam is an Old World vegetable native to Africa and Asia, and is more closely related to grasses and lilies than to either potatoes or sweet potatoes.
What Does a Sweet Potato Look Like?
Sweet potatoes have tapered ends and smooth, thin skin. The skin can range in colour from copper or brown to red or even purple. The flesh of a sweet potato is usually orange, varying in saturation from deep orange all the way to yellow or beige. Sweet potatoes can also have white or purple flesh.
By contrast, yams have coarse, scaly skin that is sometimes compared to a tree trunk. They are cylindrical tubers, usually with white flesh. Some North American grocery stores stock African yams, but you’ll probably need to go to an import store or specialty market unless you live in a big city.
Why Do We Sometimes Call Sweet Potatoes Yams?
There seem to be two main reasons for the use of the word “yam” when we are actually talking about sweet potatoes:
African slaves used this name:
Yams are one of the staple foods in Africa. West African people saw a resemblance between yams and sweet potatoes, so they used the same word for both vegetables. Some accounts say Europeans introduced sweet potatoes to the people of West Africa, who later came to the New World as slaves. Other stories say the slaves first encountered sweet potatoes once they’d arrived in America. As the slave trade was carried on for some three centuries, it’s likely both are true. In any case, the West African people used sweet potatoes the same way they did yams, and they used the same name for both.
Farmers in Louisiana used this name:
All sweet potatoes originally had white or pale yellow flesh. So darker-fleshed sweet potatoes were a pretty cool development! Farmers in Louisiana had a sweeter, orange-fleshed variety of the sweet potato in about the 1920s or 1930s. Because you can’t tell what the inside of a vegetable looks like from its skin and you don’t know how sweet it is until you eat it, they needed to find a clever way to set their sweet potato apart from the rest.
The farmers called their vegetable a “yam,” sweet potatoes. The Louisiana crops contrasted with the drier, firmer fleshed sweet potatoes that farmers elsewhere in the US were growing. This is why you’ll sometimes see people using “yam” to describe a sweet potato that has soft, moist, richly coloured flesh, and “sweet potato” for those vegetables whose flesh is firm, dry, and often more pale in colour.
Although we all have our preferences when it comes to the type of sweet potatoes we like to eat, you should know that the “yam” type of sweet potato is better suited to some recipes and the more firm, dry-fleshed sweet potato is better for others. Sweet potatoes that are softer are great for baking, mashing, and of course making a sweet potato casserole or baking a sweet potato pie. But those with a firmer flesh will make great sweet potato fries.
Sweet Potato Nutrition
Some folks say that the sweet potato is a superfood. If you look at its nutritional content, it’s not hard to see why. One average sweet potato, baked in its skin, contains 438% of our recommended daily intake for vitamin A – a nutrient that about half of North Americans are lacking in their diet.
Sweet potato also scores high for several other nutrients: 37% of vitamin C; 27% of potassium; 25% each of vitamin B6 and manganese; 15% each of vitamin B6, potassium, and dietary fibre; 10% of thiamine (vitamin B1.) Sweet potatoes also supply lesser amounts of magnesium, iron, calcium, phosphorus, zinc, sodium, several additional B vitamins, and protein. Wow!
Baking Increases Vitamin C in Your Sweet Potato
Baking is a preferred cooking method for sweet potatoes, as it increases the vitamin C content of the vegetable. If you prepare it by a different method, you won’t get as much of the vitamin C but it’s still a nutritious vegetable. One baked sweet potato provides 103 calories (compared with 163 calories for a medium baked potato or 174 calories for 1 cup of potatoes mashed with whole milk.)
If you are eating sweet potatoes for their vitamin A and carotenoid content, choose those with the richer orange colour to their flesh. If you decide to experiment with purple sweet potatoes you’ll benefit from anthocyanins, the same flavonoids found in blueberries. White-, cream-, or yellow-coloured sweet potato flesh contains mostly beta-zea-carotene.
When it’s time to eat that turkey dinner, choose a baked potato and other high-fibre vegetables. Eat these and a healthy portion of turkey before you move onto other foods and drinks. Research shows that eating lean protein and high-fibre vegetables at the beginning of your meal can reduce both blood sugar and insulin levels, compared to consuming foods like bread or fruit juices first.
Do you include sweet potatoes in your Thanksgiving dinner sides? Or “yams”? How does your family like to serve them? Please share your traditions in the comments below. And to all my American readers who will be celebrating with family this week, Happy Thanksgiving!
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Original content © 2017 Kyla Matton Osborne, aka #RubyWriter
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