Will watermelon and crayfish cause poisoning? Will watermelon and peach cause diarrhea? Are there so many rules for eating watermelon?

In the hot summer, people often feel the heat is unbearable. At this time, a piece of iced watermelon can not only quickly quench thirst, but also bring an unprecedented cool feeling. Ice-cold watermelon is simply a perfect match for summer!

Summer and chilled watermelon are a perfect match (Source: Photo by the author)

Watermelon in summer always becomes a hot search on Weibo, such as "Three taboos of eating watermelon in summer", "Foods that cannot be eaten with watermelon", etc. Are there really so many taboos when eating watermelon? Why should I consider so much when eating watermelon? Let's debunk these rumors one by one today!

Can’t watermelon be eaten with crayfish and peaches? (Source: Screenshot of Weibo hot search)

Can’t watermelon be eaten with crayfish?

Let's first talk about the rumor that "watermelon cannot be eaten with crayfish". People often worry that crayfish may contain pentavalent arsenic, which is mainly due to concerns about the environment in which crayfish live. Due to pollution, arsenic may exist in some water bodies, and aquatic organisms such as crayfish may indeed absorb trace amounts of arsenic from the environment.

Theoretically, vitamin C (ascorbic acid) has reducing properties and can reduce pentavalent arsenic to trivalent arsenic. However, this reaction requires specific conditions, including high concentrations of vitamin C and appropriate pH values. Under normal dietary conditions, the content and environment of vitamin C and pentavalent arsenic in food are not suitable for this reaction.

If under certain conditions, vitamin C reduces pentavalent arsenic to trivalent arsenic, trivalent arsenic is indeed more toxic than pentavalent arsenic. However, this chemical reaction is extremely unlikely to occur in the human digestive system because the pH and environment in the gastrointestinal tract are not suitable for this reaction. In addition, the human body has multiple mechanisms that can effectively eliminate and detoxify small amounts of arsenic compounds.

Watermelon can be eaten with crayfish (Source: Photo by the author)

According to the World Health Organization (WHO) standards, the safe limit of arsenic in drinking water is 10 micrograms per liter. Long-term exposure to arsenic above this limit increases a variety of health risks, including skin lesions, cancer, and cardiovascular disease. The lethal dose of acute arsenic poisoning is approximately 1 to 4 milligrams (mg) per kilogram of body weight. According to studies, in some seriously polluted water bodies, the arsenic content in crayfish may reach tens to hundreds of micrograms per kilogram.

However, based on the arsenic content of 100 micrograms (0.1 milligrams) per kilogram in crayfish, we can estimate how much crayfish needs to be consumed to reach the risk of acute arsenic poisoning. For an adult weighing 70 kilograms, the minimum dose of acute arsenic poisoning is about 70 milligrams (1 milligram/kilogram). Since each kilogram of crayfish contains 0.1 milligrams of arsenic, 70 milligrams of arsenic is equivalent to eating 700 kilograms of crayfish. Obviously, under normal circumstances, it is impossible for people to eat such a large amount of crayfish in a short period of time. Therefore, under normal diet conditions, the risk of acute arsenic poisoning caused by eating crayfish is extremely low. The reality is that crayfish and watermelon are both safe foods. As long as they are from a regular source and have been tested, they will not cause harm to your health.

Of course, considering that there are many ways to cook crayfish, some of which are very strong and put a greater burden on the digestive system, eating such crayfish with any fruit may cause gastrointestinal discomfort, but this has nothing to do with arsenic poisoning. It should be noted that there are many variations of this rumor, usually in the form of "eating a seafood or river fish + a fruit together will cause arsenic poisoning", so don't take it seriously.

Can’t watermelon be eaten with peaches?

Regarding the rumor that eating watermelon and peaches together may cause bloating and diarrhea, first of all, watermelon and peaches are both fruits rich in water and fiber, and both contain high levels of fructose. For some people who have malabsorption of fructose, these fruits may cause gastrointestinal discomfort. Similar to lactose intolerance, which causes bloating when drinking milk, fructose malabsorption refers to the body's inability to effectively absorb fructose in the small intestine, resulting in symptoms such as bloating and diarrhea. However, this situation mainly depends on the individual's gastrointestinal health and is not a universal phenomenon.

Watermelon can be eaten with peaches (Source: AI generated by the author)

Fructose intolerance does affect the intake of certain high-fructose foods, including watermelon and peaches. If you can't eat watermelon and peaches together because of fructose intolerance, these fruits alone may also trigger symptoms. In addition, there are many other foods that contain a lot of fructose that need to be avoided or limited.
In general, eating watermelon and peaches together does not necessarily lead to bloating and diarrhea, unless the consumer has poor fructose absorption or suffers from irritable bowel syndrome. It is generally safe for healthy people to eat these two fruits in moderation, and they help replenish water and nutrition. The only thing to note is that you should not eat too much at one time just because the fruits are delicious.

Can’t eat frozen watermelon? (Source: Screenshot of Weibo trending search, edited)

Can’t eat chilled watermelon?

The rumor claims that chilled watermelon can cause gastrointestinal discomfort or even induce heart disease, which is a misunderstanding.

Eating iced watermelon in moderation will not have adverse effects on health. In fact, watermelon is rich in water and vitamins, which helps to replenish the water and electrolytes lost in summer. And moderately chilled watermelon will not only make us feel cooler, but also make the watermelon taste sweeter.

Summer is more suitable for iced watermelon (Source: Photo by the author)

Authoritative medical organizations such as the American Heart Association do not list chilled food as a risk factor for heart disease. The main risk factors for heart disease include high blood pressure, high cholesterol, smoking, diabetes, etc., which have nothing to do with eating chilled watermelon.

At the same time, the rumor says that watermelon should be refrigerated at 15℃, but the refrigeration temperature of household refrigerators is generally between 1℃ and 4℃, and 15℃ refrigerators are not common! The temperature range of 1-4℃ helps to maintain the freshness of food and extend its shelf life, while preventing the growth of bacteria.

It should be noted that the refrigerator is not a disinfection cabinet or a sterile box. It can only reduce the reproduction rate of germs, but cannot eliminate them. Therefore, it is best to wrap the watermelon with a layer of plastic wrap before putting it in the refrigerator to reduce the chance of contact with germs. Do not let the watermelon stay in the refrigerator for too long. Try to cut and freeze the watermelon and eat it on the same day. Otherwise, the reproduction of germs may cause gastrointestinal discomfort after eating.

Can’t watermelon be eaten before or after meals?

There are also rumors claiming that eating watermelon before or after meals will dilute gastric juice, affect the digestion and absorption of food, and cause bloating and stomach pain.

There is no basis for this statement. The main component of gastric juice is dilute hydrochloric acid, which helps digestion and sterilizes. The secretion and concentration of gastric juice are automatically regulated by the body and will not be significantly diluted by the intake of a small amount of water . The intake of liquid in a normal diet will not affect the digestive function of gastric juice.

Watermelon is mainly composed of water, and is rich in vitamins A and C and antioxidants such as lycopene. These ingredients are good for health and can help replenish water and promote metabolism. Eating watermelon in moderation, whether before or after meals, will not have a negative impact on the digestive system.

It should be noted that what was said above was for adults, while young children need a lot of nutrition for their growth and development, but they have small appetites and lack self-control. When eating fruits such as watermelon, it is best to wait a long time between meals, such as more than half an hour, to prevent the baby from eating too much watermelon and affecting the nutritional intake of the main meal.

In summary, eating watermelon in moderation before or after meals will not affect the function of gastric juice, nor will it have adverse effects on the digestive system. Eating watermelon before or after meals does not bring any risks.

Summarize

We can clearly see that many rumors about watermelon diets lack scientific basis. Watermelon is not only a great choice for summer heat relief, but its rich nutrients also have many health benefits. Whether it is eaten with crayfish and peaches, or enjoyed before or after meals, eating watermelon in moderation will not have adverse effects on health. We should decide whether to eat watermelon, how much to eat, and how to eat it based on our own health conditions. There is no need to let rumors on the Internet affect our mood to eat watermelon happily.

Author: Denovo, PhD in Analytical Chemistry, University of Chinese Academy of Sciences

Review | Ruan Guangfeng, Deputy Director of Kexin Food and Health Information Exchange Center