Are sweet potatoes healthier than potatoes for us and should we be eating either of these tubers? With low carb high fat (LCHF) diets the buzz word at the moment, the poor potato and sweet potato have been side lined. Let’s look at these two vegetables and see what they offer.
Although both of these vegetables have “potato” in their name, botanically they are totally unrelated. Potatoes, Solanum tuberosum, belong to the nightshade or Solanaceae family together with tomatoes, peppers, brinjals and deadly nightshade. Plants in this family produce solanine, which is poisonous, so don’t eat the leaves or stems of these plants, or potatoes that have gone green.
Sweet potatoes, Ipomoea batatas, are part of the morning glory or Convolvulaceae family and their leaves are edible, in comparison, and actually very nutritious.
The truth about starch
Both potatoes and sweet potatoes come in a variety of colours, ranging from white to orange to red and purple. Potatoes also differ in their starch content and type, which affects how fast they are digested as well as how they act when they are cooked.
“Floury” potatoes have a fluffy texture and are ideal for baking or mashing and have a higher starch content, especially amylose. “Waxy” potatoes have less total starch, but are higher in amylopectin, which gives the potato a slightly “gluey” texture and holds the potato together. This makes them better for boiling, as well as them digesting more slowly, especially if they are cooked and then cooled, as this changes the nature of the starch.
Not all starch is the same. Some of the starch in both potatoes and sweet potatoes is “resistant starch”, which takes a long time to break down in the body. It helps one to feel full for hours and provides energy as well as that satisfied, full feeling called satiety. This resistant starch is one of the reasons why you shouldn’t lump these vegetables in the same category as high carb processed foods, as they react very differently in the body.
The cooking method also changes the starch content and glycemic index of these two vegetables. Boiling them reduces their glycemic index and starch content, due to the fact that the starch can bind with the water. The dry heat of baking or roasting lowers the moisture in the vegetable, concentrating the sugars. Also, cutting potatoes and sweet potatoes up helps to preserve their starchiness, while cooking them whole results in more sugariness. A boiled potato therefore has a lower glycemic index than a baked sweet potato.
Both potatoes and sweet potatoes contain a variety of vitamins and minerals, with orange sweet potatoes being vitamin A superstars. They also contain many antioxidants and phytonutrients which help keep us healthy and keep chronic disease away.
What really interests me though is an extract found in the white sweet potatoes, called “caiapo”, which has been found to be promising in the treatment of type 2 diabetes. It has also been shown to improve many markers of metabolic disease. The diagram below shows a comparison of the blood glucose response to glucose, sweet potatoes, regular potatoes and then regular potatoes with caiapo.
In conclusion, with nearly 20 grams of net carbs per serving, neither potato or sweet potato works on a very low carb diet. If you are aiming for 50 to 150 grams of net carbs a day, which has still been found to be beneficial for weight loss, then you can add a little of these delicious vegetables into your diet. Their health benefits are definitely worth it.