Sweet potato vs Yam - Health impact and Nutrition Comparison

Summary

Yams and sweet potatoes are entirely different vegetables. In nutritional comparison, yam is richer in fiber and has a lower glycemic index, sodium and sugar content than sweet potatoes.

There isn’t an obvious winner in mineral comparison because of the extremely high potassium and sodium levels in yam and fairly higher content of calcium and zinc in sweet potato.

Yam is also richer in most vitamins compared to sweet potato, with the exceptions of vitamin A, vitamin B2, and vitamin B5.

Both of them have anti-diabetic, antioxidant, and anti-proliferative effects. Besides, sweet potatoes contribute to good eyesight, while yams can be useful for women’s hormonal health.

Introduction

Most people have at least once seen a tuberous root vegetable named yam in US supermarkets, but oftentimes it is actually a type of sweet potato. Furthermore, there’s a chance you’ve never tasted or even seen real yam unless you bought it in specialized 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.

Main Differences

Both sweet potato and yam are tuber vegetables.

Sweet potatoes are tapered and prolonged vegetables, covered with smooth skin, the color of which varies from beige, yellow, orange, or red to purple or brown. The flesh also varies depending on the type, from purple and orange to white. The flavor of the flesh is sweet, and the texture 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, while the flesh is white, yellow, purple or pink, starchy, dry, and less sweet. Yams originated in Asia and Africa; nowadays, they are common in the Caribbean and Central America.

There are a few reasons for the sweet potato and yam confusion. It first started in the 30s of the 20th Century, when Louisiana farmers had marketed their sweet potatoes as “yam” to differentiate them from the other types of sweet potatoes growing in other states.

According to another version, enslaved Africans in the US had called the local sweet potatoes “nyami,” which became yam, owing to the resemblance with the true yams they had known in Africa.

Nutritional Comparison

It seems essential to emphasize that sweet potatoes and yams are also different in terms of nutrition.

Yam is higher in fiber and lower in sugars, sodium, and glycemic index, while sweet potato is lower in saturated fat. Thus, in macronutrients content, yam is the winner.

Minerals

As you can easily see from the charts of comparison below, in this section, it’s a tie between these two vegetables.

Yam is significantly higher in potassium, somewhat higher in sodium, slightly higher in phosphorus, and lower in sodium.

On the other hand, sweet potato is relatively higher in calcium and slightly higher in zinc, magnesium, and iron.

Mineral Comparison

Mineral comparison score is based on the number of minerals by which one or the other food is richer. The "coverage" chart below show how much of the daily needs can be covered by 300 grams of the food

Yam

4

:

4

Sweet potato

Contains more Phosphorus +17%

Contains more Potassium +142.1%

Contains less Sodium -83.6%

Contains more Copper +17.9%

Contains more Calcium +76.5%

Contains more Iron +13%

Contains more Magnesium +19%

Contains more Zinc +25%

Yam

Sweet potato

Contains more Phosphorus +17%

Contains more Potassium +142.1%

Contains less Sodium -83.6%

Contains more Copper +17.9%

Contains more Calcium +76.5%

Contains more Iron +13%

Contains more Magnesium +19%

Contains more Zinc +25%

Vitamins

From the viewpoint of vitamins, yam wins hands down again.

Yam is greatly richer in vitamin C and reasonably higher in vitamin E, vitamin K, vitamins B1 and B6.

Sweet potato, on the other hand, is significantly higher in vitamin A, as well as vitamins B2 and B5.

Vitamin Comparison

Vitamin comparison score is based on the number of vitamins by which one or the other food is richer. The "coverage" chart below show how much of the daily needs can be covered by 300 grams of the food

Yam

6

:

4

Sweet potato

Contains more Vitamin E +34.6%

Contains more Vitamin C +612.5%

Contains more Vitamin B1 +43.6%

Contains more Vitamin B6 +40.2%

Contains more Folate +109.1%

Contains more Vitamin K +27.8%

Contains more Vitamin A +10180.4%

Contains more Vitamin B2 +90.6%

Contains more Vitamin B5 +154.8%

Equal in Vitamin B3 - 0.557

Yam

Sweet potato

Contains more Vitamin E +34.6%

Contains more Vitamin C +612.5%

Contains more Vitamin B1 +43.6%

Contains more Vitamin B6 +40.2%

Contains more Folate +109.1%

Contains more Vitamin K +27.8%

Contains more Vitamin A +10180.4%

Contains more Vitamin B2 +90.6%

Contains more Vitamin B5 +154.8%

Equal in Vitamin B3 - 0.557

Health Impact

Yam is higher in fiber and resistant starches, contributing to our digestive health. Fiber prevents constipation, feeds our healthy gut bacteria, and reduces the risk of colorectal cancer and inflammation. Besides, fiber helps with weight loss since it turns into a gel, filling up the stomach and keeping us full for a long time.

On the other hand, sweet potatoes help gain weight since they are a 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 the eyes. A vitamin A deficiency may lead to xerophthalmia – pathologically dry eyes that can, in turn, lead to night blindness. Purple sweet potatoes are also beneficial to our eyesight due to special antioxidants, anthocyanins, which protect the eyes.

In vitro and in vivo studies on mice claim that anthocyanins extracted from purple sweet potatoes have slowed the growth of stomach, bladder, colon, colorectal, and breast cancer cells (1, 2, 3). These antioxidants have expressed significant anti-proliferative and anti-metastatic effects, preventing different types of cancer. Besides, studies on mice show that anthocyanins extracted from purple sweet potatoes can improve learning and memory by contributing to brain function improvement (7, 8).

It is worthy to note that both sweet potato and yam possess anti-diabetic effects. Studies demonstrate that white-skinned sweet potatoes and yams improve glucose and lipid metabolism by decreasing insulin resistance (9, 10, 11, 12).

It is worth mentioning that yams have specific compounds called saponins, such as dioscorin, diosgenin, and dioscin. One study has discovered immunomodulatory, blood pressure-lowering, and antioxidant activities of dioscorins extracted from different types of yams (4). Diocsorins can also protect airway epithelial cells from allergen destruction. According to research, diosgenin in yam contributes to improving the status of sex hormones, antioxidants, and lipids, reducing the risk of cardiovascular diseases and breast cancer in postmenopausal women (5, 6).

References

1. https://www.ncbi.nlm.nih.gov/pubmed/23784800
2. https://www.ncbi.nlm.nih.gov/pubmed/29749527
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4609785/
4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3943009/
5. https://www.ncbi.nlm.nih.gov/pubmed/11428178
6. https://www.ncbi.nlm.nih.gov/pubmed/16093400
7. https://www.ncbi.nlm.nih.gov/pubmed/14609130
8. https://www.ncbi.nlm.nih.gov/pubmed/19863544
9. https://www.ncbi.nlm.nih.gov/pubmed/10706405
10. https://www.ncbi.nlm.nih.gov/pubmed/17645559
11. https://www.ncbi.nlm.nih.gov/pubmed/19629697
12. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4632431/