Sweet potato vs Yam - Health impact and Nutrition Comparison

INTRODUCTION

I am absolutely sure that just once you have seen tuberous root vegetable named yam in US supermarkets, but I am fairly sure that it has been a type of sweet potato. And furthermore, you have never tasted or even seen real yam, unless you haven’t bought it in special ethnic or international markets. So, as you can already guess from what has been said, sweet potatoes and yams are completely different vegetables, although they have some similarities and their names are sometimes used interchangeably. Let’s deal with this confusion.

Differences between sweet potato and yam

Both sweet potato and yam are tuber vegetables. Sweet potatoes are tapered and prolonged vegetables, covered with smooth skin, which color varies from beige, yellow, orange to red, purple or brown. The flesh also varies depending on the type from purple to orange or to white. The flavor is sweet, flesh is moist and juicy. Sweet potatoes originated in South and Central America. On the other hand, yams are bigger, the skin is rough and bark-like, the flesh is white, yellow, purple or pink, starchy and dry, less sweet. Yams originated in Asia and Africa; nowadays they are common in the Caribbean and Central America.

There are few reasons for sweet potato and yam confusion. First stared in the 30s of 20th Century, when Louisiana farmers had marked their sweet potatoes as “yam” to differentiate them from the other types of sweet potatoes, growing in other states. According to another version, US slaves from Africa had called the local sweet potatoes “nyami”, which became yam, owing to the resemblance with the true yams, which they had known in Africa.

NUTRITIONAL COMPARISON

It seems essential to emphasize that in terms of nutrition sweet potatoes and yams are different too. Yam is higher in Fiber, lower in Sugars, Sodium, and Glycemic index; although sweet potato is lower in Saturated Fat. Thus, in macronutrients content yam is the winner.

Mineral comparison

As you can easy see from the charts of comparison below in this part it’s a tie. Yam is extremely higher in Potassium, fairly higher in Sodium, and slightly higher in Phosphorus, and less in Sodium. On the other side, sweet potato is fairly higher in Calcium, slightly higher in Zinc, Magnesium and Iron.

Vitamin comparison

From the viewpoint of vitamins yam hands wins on again. Yam is hugely higher in Vitamin C, reasonably higher in Vitamin E, Vitamin K, Vitamins B1 and B6. Sweet potato, on the contrary, is dreadfully higher in Vitamin A, strongly higher in Vitamins B2 and B5.

HEALTH IMPACT

Yam is higher in fiber and resistant starches, which contributes to our digestive health. They prevent constipation, feed our healthy gut bacteria, and reduce the risk of colorectal cancer and inflammation. Besides, they help with weight lose, since fiber turns into a gel, which feels stomach and keeps us full for a long time. Sweet potatoes, on the other side, help to gain weight, since they are good source of complex starches, vitamins, minerals and proteins, and are easy to digest.

Sweet potato is higher in vitamin A and carotenoids, which ensure the light-detecting function of eyes. And vitamin A deficiency may lead to a xerophtalmia – special type of blindness. Purple sweet potatoes are also beneficial to our eyesight with special antioxidants - anthocyanins, which protect eyes.

In vitro and in vivo studies on mice claim that anthocianins, extracted from purple sweet potatoes, have slowed the growth of stomach, bladder, colon, colorectal and breast cancer cells (1, 2, 3), have significant anti proliferative and anti metastatic effects, preventing and protecting by this way from different types of cancer. Besides, there are also studies on mice (7, 8), showing that anthocianins extracted from purple sweet potato improve learning and memory, that is, they contribute to brain function improvement.

Then, it is worth mentioning that yams have special compounds called saponins, which include dioscorin, diosgenin and dioscin. The study (4) discovers immunomodulatory, anti hypertensive and anti oxidant activities of dioscorins, extracted from different types of yams. Diocsorins can also protect airway epithelial cells from allergen destruction. Diosgenin has been used to create the first contraceptive pills, although there isn’t any suggestion that it was used for this purpose in the past. According to the studies (5, 6) diosgenin in yam contributes to improving the status of sex hormones, antioxidants and lipids, reducing by this way the risk of cardiovascular diseases and breast cancer in postmenopausal women.

It is worthy to note, that both, sweet potato and yam have anti diabetic effect. There are studies, demonstrating that white skinned sweet potatoes and yams improve glucose and lipid metabolism by decreasing insulin resistance (9, 10, 11, 12).

CONCLUSION

The aim of what has been said is that yams and sweet potatoes are completely different vegetables. Yam is richer in fiber and lower in Glycemic Index, Sodium and Sugars than sweet potatoes in nutritional comparison. In mineral content there isn’t obvious winner, because of extremely high Potassium and Sodium in yam, and fairly higher Calcium and Zinc in sweet potato. Yam is higher in vitamins too than sweet potato, except for Vitamin A, Vitamin B2 and vitamin B5. Both of them have anti diabetic, anti oxidative and anti proliferative effects. Besides sweet potatoes contribute to our eyesight, and yams are very useful for women hormonal health. Don’t forget about differences!