Overnight water and overnight dishes do not cause cancer! What really can’t be eaten overnight is it, a lot of people get it wrong!

In a “family group,” overnighting is a terrible thing.

They often say: overnight water, overnight tea, overnight vegetables, and overnight watermelon are all carcinogenic…

Is it really okay to eat overnight food?

Stop being scary!

This is the only one that may be poisonous (the impatient ones can go directly to Part 2).

1. Overnight water is OK


Overnight water does contain nitrite, but talking about toxicity out of dose is hooliganism.

In my country’s drinking water hygiene standards, the nitrite content is specified as ≤1 mg/L[1]. Studies have found that after bottled water, purified water, and tap water are placed for 3 days, the nitrite is still in the safe range [2], and it is safe to drink.

The real thing to remember when drinking overnight water is: keep the lid on.

2. Overnight tea is OK


I just said that talking about toxicity without doses is hooliganism.

According to the experimental test of Beijing Institute of Nutrition Sources[4], whether it is Pu’er tea, chrysanthemum tea, or Longjing tea, the nitrite content is within the safe range after being placed for 12 hours and 24 hours inside, will not cause cancer.

Image source: Zhanku Hailuo

The reason why the overnight tea changes color is because the tea polyphenols in it are oxidized, and the tannic acid increases after a long time, which makes the taste worse, but it will not harm health.

3. It’s not a big problem to store overnight dishes in the refrigerator


Zhejiang Ningbo Food Inspection Institute has tested 30 home-cooked dishes[5] and found:

All kinds of vegetables stored at 4℃ (simulated refrigerator environment), the nitrite content after 24 hours is the same as when it was just out of the pot, which is less than the nitrite limit stipulated by the state 1/3[6] of the value, you can eat it.

At 25°C (simulating room temperature), meat dishes are fine overnight, but the nitrites of leafy vegetables will increase a lot, and it is best to eat them within 6 hours.

(Image credit: soogif)

So it’s not that you can’t eat overnight dishes, but remember to put them in the refrigerator. It’s best to leave no meat or vegetables, and don’t keep cold dishes.

In addition, the second meal of the overnight dish must be fully heated (100 ℃ for more than 3 minutes), it is best to add some onion, ginger and garlic to season and sterilize.

4. Refrigeration of watermelon overnight is fine


In the past, most of the watermelon harm incidents that happened in the news were caused by the fact that the watermelon cutting knife and the storage environment were not clean enough, and the pathogenic bacteria multiplied in the watermelon.

Researchers from Fujian Academy of Agricultural Sciences have conducted a special test. After cutting three kinds of watermelons, cover them with plastic wrap, and put them in the refrigerator (4°C) for 16 hours [7]. The results showed that: overnight The total number of colonies of fresh watermelon and fresh watermelon is similar, and it is safe to eat.

If you want to eat more at ease, it is best to clean the knife, watermelon, hands and chopping board before cutting the watermelon. Cover the watermelon with air-permeable plastic wrap before refrigerating.

Foamed fungus, white fungus and fermented rice noodles and starch products are easily contaminated by Pseudomonas cocoa, producing high temperature resistant rice yeast at room temperature Bacterial acid toxins.

If people eat it, it will not only cause abdominal pain, bloating, diarrhea, nausea and vomiting, but excessive intake can lead to multiple organ failure and even death!

(Image source: Internet)

It was initially identified as the culprit of the previous Heilongjiang sour soup poisoning incident (resulting in 9 deaths).

Soak fungus and white fungus by yourself, usually soak in cold water for 1~2 hours before processing and eating.

It is too late, preferably no more than 4 hours, and the time is even shorter if you use hot water. If mucus is produced, the surface is sticky, and it smells bad, it is best to throw it away.

Of course, there is another one that cannot be asked for:

An overnight feud.

A long time anger hurts the body!

Finally, I send you four sentences “Don’t be angry”:

I am not angry when others are angry,

Out of breath, there is no one to replace.

If I’m angry, who’s going to be happy,

It’s frustrating and exhausting.

Contributing Author: Huang Yuanyuan

Registered Dietitian

Reviewer: Zuo Xiaoxia

Director, Department of Nutrition, Eighth Medical Center, PLA General Hospital


[1]GB5749-2006, Sanitation Standard for Drinking Water.

[2] Chen Ying, Xiao Yanjie, Liu Xiaolin. Changes of nitrite and nitrate content in drinking water after being boiled for different times [J]. Journal of Jinzhou Medical University, 2018, Vol.39 , Issue 6.

[3] Qin Pinzhang. Several opinions on revising the hygienic standards for the use of food additives nitrate and nitrite [J], Chinese Journal of Preventive Medicine, 2005, 6: 150-151.

[4] Overnight tea is as poisonous as a snake? CCTV experiment is still innocent [J], China Tea, 2014, 36(06): 23.

[5]http:https://py.zjol.com.cn/rdgz/201907/t20190724_10651911.shtmlZhejiang Online “Overnight Vegetables Are Poisonous? Ningbo Food Inspection Institute uses 450 data to tell you the answer”.

[6]GB 2762-2005, Limits of Contaminants in Food.

[7] Lv Xin, Chen Lihua, Li Xiaolin, Liu Lanying, Huang Wei, Li Hren. Eating safety evaluation of fresh-cut watermelon after overnight refrigeration [J]. Fujian Agricultural Journal, 2018, 33(08):865-869.

Editors: Zhao Yanan, Guo Qian, Zhang Liang

*The content of this article is for the popularization of health knowledge and cannot be used as a specific diagnosis and treatment suggestion, nor can it replace the face-to-face consultation of a licensed physician, and is for reference only.

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