I was just peeling a yam, but my hands were itching to hit someone! What's going on?

Yam is a type of potato food and is a common ingredient in daily life.

Candied yam, pork ribs and yam soup, fried yam with pork slices, blueberry yam... According to different taste preferences, many delicious dishes can be made, whether it is steamed, fried, candied or made into soup, it is super versatile.

However, although yam is delicious, there is one thing that makes many people distressed: every time they handle yam, their hands will itch and scratch! In severe cases, small red spots will appear, and even swelling will occur.

Why is this? Is there any good way to avoid it? In this article, we will talk about this matter, so that everyone can handle yam with confidence in the future, without fear!

01

What ingredients cause itchy hands?

Allantoin! Perhaps saponins are also to blame

Anyone who has handled yam will remember that after it is cut open, a sticky liquid will flow out. This is yam mucus, which has antioxidant, immune-enhancing, and lipid-lowering effects. [2]

The main components of yam mucus are water, polysaccharides and proteins, and the water content is very high. The water content of iron stick yam and ordinary yam is 70.3% and 89.6% respectively. [1] The main components of polysaccharides are mannose and glucose. In addition, yam mucus also includes a small amount of allantoin, amino acids, lipids, diosgenin, catecholamines, yam hydrochloride, etc.

Some people believe that saponins (also known as "saponins") contained in mucus are the cause of itchy hands, but there is currently no scientific research literature to clearly confirm that saponins in yam are the "real culprit" that causes sensitive skin itching.

However, there are studies that have observed the effects of allantoin in yam mucus on the skin.

The researchers divided mice into two groups, shaved the hair on their necks and backs, injected allantoin into the necks of the mice in the experimental group and injected saline into the necks of the mice in the control group, and observed and collected the number of times the two groups of mice scratched within 1 hour. The results showed that the number of times the mice in the experimental group scratched their necks was significantly higher than that in the control group. [3] This shows that allantoin can irritate the skin of mice. Therefore, the "real culprit" that causes itchy hands due to yam mucus may be allantoin, but it is not ruled out that saponins may have a similar effect.

02

Cooking before processing can keep your hands away from itchy hands

Once it is stained, use soapy water for emergency treatment

Find out why your hands itch, so that you can have a delicious taste without any pain or itching! The trick is that allantoin is afraid of heat, it will decompose when it is heated, and it is also afraid of alkaline liquids. Therefore, when you handle yam in the future, you only need to do the following 4 points to say goodbye to itchy hands:

① Wear gloves when handling yam: Put on disposable gloves before peeling the yam. Gloves have a protective effect and can prevent the skin from direct contact with yam mucus.

② Steam first, then peel: If you feel uncomfortable working with gloves, steam the yam first and then peel it. Wash the yam, cut it into sections with the skin on and steam it directly. Generally, it will take 15 to 20 minutes to steam it after the water boils. During the steaming process, the allergenic substances in the yam will decompose when exposed to heat. After that, no matter how you handle it, your hands will not itch!

③ If your hands accidentally touch the yam mucus and start to itch, wash your hands with soap immediately. Baking soda water and hot water will also work, both of which can relieve the itching symptoms.

④ If washing is not enough to relieve the itching symptoms, you can warm your hands closer to a heat source, such as using the hot air block of a hair dryer, but be sure to pay attention to the temperature to avoid burns.

03

Iron stick yam is most suitable as a staple food

A study compared Qichun yam, Tiegun yam, and Huai yam, and the results showed that Tiegun yam had the highest polysaccharide content among the three, which can be used as a substance to store energy in organisms. [4]

According to the recommendations of the Chinese Dietary Guidelines, the daily intake of potatoes is 50 to 100 g. If you are eating yam, it is about 4 to 6 finger-sized yams. [5]

To summarize:

The main reason why yam makes people's hands itchy may be related to the allantoin and saponins in its mucus.

When handling yams, you can avoid direct contact with the mucus of raw yams by wearing gloves or heating the yams before further contact and handling. Once the skin has begun to itch, soapy water, soda water and hot water that does not cause scalding can relieve the symptoms.

If you eat yam as a meal, you must reduce the intake of rice accordingly, otherwise you will get fat in the long run.

References:

[1] Zhang Jiaojiao. Study on the properties of yam mucilage and enzymatic hydrolysis and flour making process. Jiangnan University, 2014.

[2] Zhao Guohua, Wang Yun, Li Zhixiao, et al. Immunomodulatory effects of yam polysaccharides[J]. Journal of Nutrition, 2002.

[3] Yang Yan, Zhu Jing, Li Defeng, et al. Study on itch-causing substances and itch-causing mechanisms in yam[J]. Progress in Biochemistry and Biophysics, 2019, 046(010):1012-1019.

[4] Jiang Fangcheng, Li Aoran, He Jingren, et al. Analysis of nutritional components of different varieties of yam and study on the in vitro antioxidant capacity of their aqueous extracts [J]. Food Industry Science and Technology, 2018, 039(004):6-11.

[5] Chinese Nutrition Society. Dietary Guidelines for Chinese Residents[M]. People's Medical Publishing House, 2016

Author | Xue Qingxin, member of Chinese Nutrition Society, registered nutrition technician, health manager, public nutritionist

Review | Song Shuang, Associate Researcher, Institute of Nutrition and Health, Chinese Center for Disease Control and Prevention

This article was first published on the "Science Rumor Refutation Platform"