September 2024 "Science" Rumors List: Mooncakes last a long time because they contain a lot of preservatives? The sooner children get their teeth straightened, the better?

The monthly "science" rumor list is guided by the Beijing Association for Science and Technology, the Beijing Municipal Cyberspace Administration, and the Capital Internet Association, and jointly released by the Beijing Science and Technology Journalists and Editors Association and the Beijing Regional Website Joint Rumor-Refuting Platform, and is supported by the Science and Technology Journalists and Editors Professional Committee of the China Science Writers Association, the China Evening News Science Editors and Journalists Association, the Shanghai Science Communication Association, and the Institute of Science and Technology Information of the Beijing Academy of Science and Technology.

1. People with high uric acid cannot drink tea?

gossip:

Drinking tea will affect the uric acid level in the body. People with high uric acid should not drink tea.

the truth:

This statement is too absolute. People with high uric acid can drink tea in moderation, but they need to control the amount and choose the right variety.

Generally speaking, the ingredients in tea itself will not directly lead to increased uric acid levels. Drinking tea in moderation can increase water intake and promote uric acid excretion. However, people with high uric acid should avoid drinking strong tea. Because strong tea contains ingredients such as oxalic acid and caffeine, it may irritate the gastrointestinal tract, affect sleep and metabolism, and indirectly have an adverse effect on uric acid levels. Experts recommend drinking light tea and limit the amount of tea consumed to 2-3 cups per day.

In addition, studies have found that ingredients such as gallic acid and tea polyphenols in tea can inhibit the production of uric acid in the body. Among them, tea with a low degree of fermentation has a stronger inhibitory effect than tea with a high degree of fermentation. Therefore, friends with high uric acid can drink green tea, white tea and oolong tea appropriately.

2.Are large gatherings of mayflies a precursor to earthquakes?

gossip:

A large number of mayflies gathering together like "snow", which is a precursor to an earthquake in the area.

the truth:

The gathering of large numbers of mayflies is not necessarily related to the occurrence of natural disasters such as earthquakes, and cannot be interpreted as a sign of natural disasters.

The larval stage of mayflies is spent in water, and this aquatic stage can last for several months or even more than a year. During this period, the larvae feed on aquatic grasses, algae, etc. When mayflies gather in large numbers, they are in the stage of entering the pupation stage, which only lasts one or two days, so there is a saying that "born in the morning and dead in the evening". The above behavior of mayflies is mainly for mating and reproduction. This phenomenon is called "nuptial flight". Not only mayflies, but also caddisflies, stoneflies, and dipteran insects have the habit of nuptial flight. When insects are on "nuptial flight", groups of male insects produce pheromones or make sounds to attract distant females, thereby increasing the chances of finding a mate for mating.

This kind of phenomenon occurs in many places, but due to the limitations of their own activity range, many people have not seen the "nuptial flight" of mayflies in other areas.

3. Is it better for children to have their teeth corrected as early as possible?

gossip:

The earlier a child has orthodontic treatment, the better. The earlier the orthodontic treatment, the faster the process and the better the effect.

the truth:

There is no strict age requirement for orthodontic treatment. It can be performed by children in the deciduous teeth and replacement teeth periods, as well as adolescents and adults in the permanent teeth period. It is not necessarily the earlier the better.

Specifically, the timing of orthodontic treatment varies from person to person and depends on many factors, including the type of malocclusion, the severity of the malocclusion, the patient's age, the development of the teeth and jaws, etc. Whether orthodontic intervention is needed needs to be evaluated by a professional doctor in a regular medical institution.

Take children's orthodontics, which parents are very concerned about, for example. When children have large gaps between teeth and uneven teeth during the tooth replacement period, parents may wish to wait, because the child's tooth replacement period is long. During this period, factors such as the eruption speed and size of different teeth will cause the tooth arrangement to change continuously. In the short term, the gaps between teeth may be large and the teeth may be uneven, but with the growth of the jaw and dental arch, and the gradual eruption of permanent teeth, the gaps between teeth may decrease and the arrangement may gradually improve.

The root development of children during the tooth replacement period is incomplete. Applying improper correction force too early may affect the normal development of the root and the stability of the teeth, which is not conducive to the oral health of children. If there are no special circumstances, and there are only gaps between teeth or mild tooth misalignment, it is not too late to do orthodontics after the child has completed the tooth replacement. If there is a need for orthodontics, experts recommend going to a regular medical institution, consulting a professional orthodontist, and choosing an appropriate treatment plan. In this way, the uneven teeth can be corrected in a healthy way.

4. The more probiotics in yogurt, the better?

gossip:

A popular yogurt claims that "each cup contains 500 billion active probiotics", which is almost 100 times the recommended daily amount of probiotics (1 billion to 5 billion). This is because the probiotics in yogurt can promote gastrointestinal health, and the more added, the better.

the truth:

Probiotics refer to normal bacteria isolated from animals, plants, and humans, and are produced as live bacterial preparations after multiple processes. From a nutritional point of view, probiotics are beneficial to intestinal health, and some probiotics can also promote the metabolism of fat and sugar.

However, the more probiotics, the better. The human flora should be kept in a balanced state. Excessive intake and supplementation of probiotics not only fail to have a positive effect on the human body, but may also disrupt the intestinal environment and produce serious negative effects, such as bloating, abdominal pain and even diarrhea.

5. Is it because mooncakes contain too many preservatives that they last for a long time?

gossip:

Mooncakes can be stored for a long time without going bad because they contain a lot of preservatives, so you should buy mooncakes with a short shelf life, which contain even less preservatives.

the truth:

The shelf life of mooncakes is affected by many factors, not just the amount of preservatives added.

There are three main reasons why mooncakes can be preserved for a long time: first, they undergo high-temperature baking and multiple sterilization treatments during the production process, which basically kills all microorganisms; second, modern packaging technology is constantly improving, ensuring the integrity of the product's sealing, and further extending the shelf life by filling with nitrogen and adding deoxidizers; third, mooncakes are high-sugar and high-oil foods with low water content, which is not conducive to the growth and reproduction of microorganisms. Therefore, even if no preservatives are added or only a small amount is added, mooncakes can be preserved for a long time.

A short shelf life does not mean that the mooncakes are fresher or have fewer preservatives. The shelf life of mooncakes is related to the freshness of the raw materials, the processing process and conditions, and the subsequent storage conditions. Some mooncakes are prone to microbial growth due to the characteristics of the raw materials or fillings (such as high water content and high protein content), resulting in a relatively short shelf life. Some mooncakes with a long shelf life may be because their raw materials and production processes make the mooncakes themselves more durable in storage. Therefore, the freshness or preservative content of mooncakes cannot be judged simply based on the length of the shelf life.

6. Is the white frost on grapes pesticide residue?

gossip:

The white frost on grapes is actually pesticide residue, so don't buy grapes with too much white frost on them.

the truth:

When grapes, blueberries, plums, etc. are ripe, they will have a layer of white frost on their surface. This is the fruit powder produced by the fruit itself, which belongs to the sugar alcohol substance. This layer of fruit powder is evenly distributed on the surface of the fruit and is insoluble in water. It is not only non-toxic, but also has certain nutritional value. To some extent, the white frost is a sign of fresh grapes.

Of course, if the grapes are sprayed with pesticides during their growth, there will also be a light layer of white frost. To distinguish whether this layer of white frost is natural fruit powder or pesticide residue, the method is very simple: natural fruit powder is naturally evenly distributed, it will not cover the color of the grape skin itself, it will only make the grapes look more beautiful; while the white frost formed by pesticides is unevenly distributed, and sometimes there may be water droplet-shaped drug spots.

7. Don’t buy “near-expiry food” because eating it is bad for your health?

gossip:

Food cannot be eaten after it has passed its expiration date, and you should also avoid buying “near-expiry food” as it is bad for your health.

the truth:

The shelf life is the manufacturer's commitment to product quality. It means that if the product does not meet the set conditions within the period, the manufacturer will bear all consequences. Food is not necessarily inedible after the expiration date. When setting the expiration date, the manufacturer will leave some "margin". For some room temperature or frozen foods, as long as the packaging is not broken and the properties are intact, they can still be eaten after the expiration date; but for refrigerated or short-shelf-life foods, it is recommended not to eat them after the expiration date.

Near-expiry foods are also safe. As long as they are within their shelf life, their quality is guaranteed. Many countries will sell near-expiry foods at a reduced price or donate them to charity organizations, with the goal of maximizing the social benefits of food. This saves low-income people the cost of purchasing, which is beneficial to both buyers and sellers.

However, consumers should be reminded that when purchasing near-expiry foods, they should choose regular shopping malls or supermarkets and pay attention to the shelf life. After purchase, they should be consumed as soon as possible to avoid impulse consumption and waste.

8. Can drinking "Bulletproof Coffee" help you lose weight?

gossip:

"Bulletproof coffee" is rich in fat. Using it to replace staple meals for a long time can achieve effective weight loss.

the truth:

Bulletproof coffee is a mixture of black coffee, grass-fed butter and coconut oil, and some may have a little protein powder added. According to experts from the Department of Clinical Nutrition at Peking University People's Hospital, compared with regular coffee, Bulletproof coffee has a higher fat content, especially saturated fatty acids.

The weight loss principle of "Bulletproof Coffee" is similar to the ketogenic diet that has become popular in recent years. Both of them reduce carbohydrate intake, increase fat intake, and appropriately control protein intake to induce the human body to enter a metabolic state called "ketosis". In this state, the human body will break down the fat stored in the body in order to maintain normal physiological functions. However, this approach only focuses on fat intake, but ignores the supplementation of essential nutrients such as protein, vitamins and minerals, which can easily lead to muscle loss during weight loss. In addition, "Bulletproof Coffee" has a high fat content, and excessive intake of fat will increase the burden on the gastrointestinal tract, or cause symptoms such as indigestion, bloating, and diarrhea. It may also increase blood lipid levels and increase the risk of cardiovascular disease, which is not worth the loss.

The ketogenic diet was originally designed as a treatment for epilepsy patients and was later found to have the effect of controlling weight. Studies have shown that long-term use of the ketogenic diet increases the risk of cardiovascular and cerebrovascular diseases such as angina pectoris and stroke.

It should be noted that neither Bulletproof Coffee nor the Ketogenic Diet is suitable for special groups such as pregnant women, breastfeeding women and the elderly. It is okay for ordinary people to taste Bulletproof Coffee occasionally, but the amount must be controlled. Once the daily caffeine intake exceeds 400 mg or a single intake exceeds 200 mg, it may induce negative emotions such as anxiety, tension and irritability.

8. Off-season fruits and vegetables use a lot of pesticides. Are they harmful to health?

gossip:

Off-season fruits and vegetables use a lot of pesticides, which are harmful to health.

the truth:

This statement is inappropriate. Off-season fruits and vegetables do not mean fruits and vegetables that use a lot of pesticides. Eating off-season vegetables in moderation can also supplement nutrition. The key lies in scientific selection and cleaning methods.

Pesticides cannot be used whenever you want. Whether it is seasonal or off-season fruits and vegetables, using too much or using the wrong pesticides will harm the fruits and vegetables themselves, increase production costs, and may also lead to problems such as unqualified inspections.

The cultivation technology of off-season fruits and vegetables does not rely mainly on the large-scale use of pesticides, but is achieved through a series of scientific agricultural technical means. For example, the use of greenhouses and other technical means to adjust the environment, as well as the use of biological control, physical control and other means to reduce the use of chemical pesticides.

my country has strict standards for pesticide residues. When purchasing fruits and vegetables, you should choose regular channels and pay attention to the origin, certification and other information of the fruits and vegetables. In addition, correct cleaning and handling methods can also effectively reduce the risk of pesticide residues. For example, using running water to rinse, soaking and then washing can effectively remove pesticide residues on the surface of fruits and vegetables.

10. The crabs I bought have "pinholes". Is it because they have been pierced by something artificially?

gossip:

The crabs I bought had "pin holes" and it was suspected that they were injected with water, glue or stimulants.

the truth:

The small holes on the crabs on the market are not caused by water or glue injection.

The crab's shell is very hard. If you want to penetrate it and inject liquid, you will inevitably damage the crab shell. Once the crab shell is damaged, the osmotic pressure environment of the crab's internal organs will change dramatically, quickly leading to the death of the crab. This is not worth the loss for the merchants. These small holes are usually the result of crabs colliding with each other during fishing and transportation.

The transparent gelatinous substance in the crab's body is actually crab paste, which is the secretion of the male crab's accessory glands. It is not only nutritious but also delicious. As for the claim of injecting hormones or stimulants, it is also untrue. These drugs are ineffective on crabs, but will damage the water quality and cause the crabs to die. Crab farming requires good water quality, and the introduction of any harmful substances will affect their survival.

Sources of this issue: Science Refutes Rumors, Xiaoxiang Morning News, "Shanghai Online Rumor Refutes" WeChat Official Account, China Consumer News, Tencent Jiuzhen, Science and Technology Daily