Yams and sweet potatoes are often confused, but actually they do not have a great deal in common. There are obvious differences in appearances, and the yam can grow to a whopping 100 pounds or 45 kilos whereas the sweet potato is smaller. The yam has a rough scaly skin with some nodules on it but the sweet potato has a smooth much thinner skin. This being so you can tell by looking, usually which is which.
In Britain yams are more prevalent as they grow in the Caribbean and are imported from there into both the UK and the US. Britain has had a West Indian community since the 1950s, so they have been used there for more than half a century.
The yam originates in West Africa, while the sweet potato comes originally from Peru and Ecuador in the South American continent, and is now grown in Asia. In Pakistan we have lots of sweet potatoes but I haven’t seen a yam, here yet. The sweet potato is not related to the yam which is a member of the lily family or Dioscorea family, while the sweet potato is Ipomoea batatas, and a member of the Convolvulaceae family which means it is related to Morning Glory and field bindweed. Scientists believe this has been around since prehistoric times, but the yam has only been with us since 50,000 BC or thereabouts.
The US department of Agriculture requires that sweet potatoes be labeled as yams- sweet potatoes, so look carefully at the label on the packaging when you buy one of these edible roots.
There are clearly health benefits from both vegetables, but the sweet potato contains more sugars in the form of glucose, fructose and sucrose. It is useful for desserts as well as an accompaniment to the Thanksgiving turkey.
The sweet potato has the edge over the yam in terms of nutritional content, as it contains more beta-carotene, easily recognized because this is what gives fruit and vegetables the distinctive orange colour; carrots contain a lot of it for example. Both contain Omega-3 and -6 fatty acids, and as we don’t get enough of Omega-3 in our traditional Western diets, these ‘potatoes’ are useful sources, especially if you are not fond of salmon and other oily fish.
Sweet potatoes are rich in vitamins A and C and also contain vitamins E, K and the B-complex vitamins which are essential for our mental and physical health. Nutritionally it has the edge as long as you don’t mind the sugar content and its sweetness. It is good for the immune system and the vitamins C, A and E have potent antioxidant properties and this means that the free radicals which damage our healthy cells and can cause them to become cancerous are inhibited. They are a good source of dietary fibre too and surprisingly low in calories if baked. These are moist but yams are dry and not so watery.
Personally I prefer the sweet variety because I am not fond of the more starchy taste of the yam, but they both have dietary fibre and so prevent constipation and reduce the risks of colon cancer.
The Ipomoea batatas variety is the one to go for if you don’t have a problem with sugar, but having said that, the dioscorin present in yams is thought to help lower blood pressure effectively.
I suppose it’s a matter of taste as to which you eat, but remember that neither of these vegetables are actually related to the true potato, although you can use both in exactly the same ways as you do the potato which is related to tomatoes and aubergines (egg plants). The flavour and texture is different and these two vegetables arguably have more health benefits.
Why not sample both and find out which you prefer?