What would happen if you really ate 300 lychees a day?

This is the 3161th article of Da Yi Xiao Hu

In the mid-spring and early summer, all kinds of fresh fruits are on the market, which makes people enjoy a feast. Especially after May, fresh lychees produced in southern my country begin to appear.

The flesh of fresh lychees is crystal clear and tastes sweet, juicy, fresh and delicious. It is also rich in nutrients and is loved by the people.

Throughout the long history of thousands of years, due to the limitations of production, storage and transportation conditions, it is difficult for ordinary people in most parts of my country to taste fresh lychees. "A horse gallops through the red dust, and the concubine smiles, but no one knows that the lychees are coming." Only in the summer can they go to the south, which is a remote place for the ancients, to satisfy their cravings.

This is why Su Dongpo sighed: "If I can eat 300 lychees a day, I would be willing to live in Lingnan forever."

Nowadays, with the rapid development of fresh fruit storage and transportation conditions, people can enjoy seasonal lychee fruits with excellent color, fragrance and taste in time no matter where they are. Therefore, it does not seem to be a literary exaggeration that it is difficult to "indulge" as in the poems of great writers.

But can we really eat all the fresh lychees without hesitation?

In recent years, every early summer when lychees are on the market, reports of serious adverse reactions and critical situations caused by improper consumption of lychees have appeared in the news media from time to time. In particular, some children ate large amounts of fresh lychees on an empty stomach and then experienced nausea, vomiting, panic, cold sweats, and even coma and were sent to the hospital for emergency treatment.

You may wonder: "Are fresh lychees poisonous?" Of course not! The causes of the acute symptoms in children are: hypoglycemia and hyperlactatemia.

"Lychees are so sweet, eating too much can actually cause hypoglycemia?!"

To explain this problem, let's do some "preparatory activities" first - understand "blood sugar"

What we call "blood sugar" refers to the glucose in the blood. Glucose is a monosaccharide, and monosaccharides include fructose, galactose, sorbitol, arabinose, etc. Sucrose and lactose are disaccharides; starch and plant cellulose are both polysaccharides.

Among so many types of sugars, only glucose among monosaccharides can be directly used by human cells as a source of energy; after the starch and sucrose in food are absorbed by the human body, they must be broken down into glucose to function; after entering the human body, other monosaccharides such as fructose need to go through a series of biochemical processes to be converted into glucose before they can be used by cells.

The "processing factories" where polysaccharides, disaccharides and other monosaccharides are broken down or converted into glucose in the human body are mainly liver cells, with a small number located in the kidneys and small intestine.

Our brain cells are pure "consumers" of glucose. They do not have the ability to "process and produce" glucose, but they need to continuously consume glucose to provide energy, and they can only use glucose. Therefore, when the blood sugar level is lower than a certain level, brain cells are most likely to be "injured".

Hypoglycemia can cause impaired brain function, resulting in decreased cognition, judgment, and consciousness changes. In severe cases, a large number of brain cells will degenerate and die, causing irreversible damage to brain function, which directly endangers life.

During the process of hypoglycemia, multiple tissues and systems such as the heart and autonomic nervous system will experience functional disorders or pathological damage, resulting in a series of symptoms such as increased heart rate, palpitations, sweating, etc.

Under normal circumstances, when we do not eat for a long time, the blood sugar concentration gradually decreases. In order to maintain the normal physiological level of blood sugar, there are three main ways:

①Eating

The glucose in the food directly contributes; each molecule of sucrose can be decomposed into one molecule of glucose and one molecule of fructose; starch is gradually hydrolyzed into glucose; other monosaccharides such as fructose and galactose are converted into glucose;

② Glycogenolysis

When blood sugar rises to a certain level, part of the glucose is synthesized into glycogen and temporarily stored in liver cells. When blood sugar starts to drop and it is impossible to eat in time, the glycogen in these liver cells can be broken down into glucose; however, the capacity of the "warehouse" is limited after all. This method of maintaining blood sugar levels through liver glycogenolysis is a short-term, emergency supplement.

③ Gluconeogenesis

When a person has not eaten sugary foods for a long time and the stored glycogen has been consumed in large quantities, the protein and fat stored in the human body can be "requisitioned" and converted into glucose through a series of processes in the liver cells.

Now let's get back to the lychee issue.

The reason why lychees are so sweet is that in addition to sucrose and glucose, lychee flesh also contains a lot of fructose. Fructose is the sweetest monosaccharide in nature. If you eat a lot of fresh lychees on an empty stomach, a lot of fructose will be absorbed by the body in a short period of time.

Fructose is converted into triose through several "processes" in liver cells. At this time, it has two "choices": some triose will eventually be converted into lactic acid, and the other part can continue to be converted into glucose. "A flower blooms at two ends, but only one branch is visible." Let's talk about the second case first: the conversion of triose into glucose requires multiple "processing procedures" in the middle, and requires multiple "skilled workers of different types of work" - enzymes to participate in catalysis, and also consumes energy.

However, there is a large amount of fructose and triose waiting to be "processed" in a short period of time, and the number of various "skilled workers" (enzymes) is limited, which limits the speed of these transformation processes and the efficiency of "producing" glucose is not very high. At the same time, due to the large amount of fresh lychee pulp that gives a sense of fullness, the desire to eat further is suppressed; as time goes by, the glycogen in the liver has also been "exhausted", and gluconeogenesis has a common "process" with fructose to glucose in the final stage: from fructose 6-phosphate to glucose 6-phosphate, and requires the participation of the same "worker" - an isomerase, which causes the enzyme to be consumed faster, the speed of both "production lines" is affected, and gluconeogenesis is also hindered.

To sum up, eating a large amount of fresh lychees on an empty stomach may, firstly, significantly suppress the desire to consume staple food, hindering the rapid and effective way of producing glucose by decomposing starch; secondly, consuming a large amount of fructose in a short period of time will quickly consume the necessary enzymes, making the conversion of fructose into glucose slower and slower, while also limiting the gluconeogenesis pathway, making it impossible to generate enough glucose to maintain blood sugar levels, resulting in a tendency to hypoglycemia.

Because children's body functions are relatively weak and their metabolic and compensatory abilities are insufficient, they are more likely to suffer from hypoglycemia and their condition changes more rapidly after eating a large amount of lychees on an empty stomach, so the symptoms are often more severe.

At the same time, as mentioned earlier, a large amount of fructose will also produce a large amount of lactic acid during metabolism. Increased blood lactate levels can cause acute symptoms such as nausea, vomiting, headache, rapid breathing, and even low blood pressure.

The elderly have reduced body functions and are also more likely to suffer from serious symptoms in the above situations. Although young and middle-aged people have relatively strong metabolic and compensatory abilities, if they eat litchi improperly, it will still have adverse effects on the body.

When it is realized that hypoglycemia is caused by excessive consumption of lychees, the fastest and most effective treatment method is to give the patient some water (beverages) containing more glucose or sucrose, or eat sugary foods as soon as possible; for patients with impaired consciousness, once confirmed, medical staff will immediately intravenously inject high-concentration glucose solution. With timely symptomatic and supportive measures, hypoglycemia and other symptoms can be effectively relieved.

Lychees are a delicacy among fruits, but we must eat them at the right time and in the right amount according to the individual. Parents should correctly guide their children's eating habits. The same should be done when facing other delicacies, so that we can enjoy our food and improve our health!

Emergency Department, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine

Written by He Miao, deputy chief physician