Adolescent myopia is a common problem. You can also imagine the degree of parents’ attention to their children’s myopia. You may have heard a lot of the various myopia sciences that have been extended from this, such as the saying that "eating sugar will cause myopia". Even some ophthalmologists think so, but is it true?

  1. The statement about the relationship between sugar and vision

Searching for "sugar, myopia" on the Internet, the results basically "confirmed" the statement that "sugar will cause myopia". According to related descriptions, the reasons can be roughly summarized as two points:

  1. Consuming too much sugar will cause the loss of calcium from the body, affect the toughness of the eyeball wall, make the eye axis easy to elongate and promote the occurrence of myopia.
  1. Eating too much sugar leads to increased blood sugar and lower body fluid osmotic pressure. The aqueous humor in the eyeball penetrates into the lens, causing lens deformation and increased refractive power, which may cause or aggravate myopia.

Let’s take a look at the first statement: "Excess sugar is consumed and calcium is lost from the body." If it does cause calcium loss, the first thing that affects is probably the growth and development of bones rather than the so-called toughness of the eyeball wall.

In addition, although the lengthening of the eye axis is indeed the cause of myopia, there is no very definite conclusion about the cause of myopia. It is clear that genetic genes play a relatively large role.

Therefore, no matter how complete the online description of the relationship between sugar and myopia is, it is only a theoretical guess, and there is no evidence to support it.

What about the second statement?

  1. The only disease that can link sugar with vision

The only disease that affects vision with sugar is diabetes.

Diabetes can cause temporary nearsightedness or hyperopia, which is caused by the change in the refractive power of the lens of the eye due to the loss of blood sugar control, but after the blood sugar returns to a normal level and stabilizes, the vision will return to normal.

Diabetes has a greater impact on the eyes and may cause diabetic retinopathy, such as retinal hemorrhage, macular edema, new blood vessels, retinal detachment, and even blindness.

Therefore, diabetic patients need regular fundus examinations. But it can be seen that diabetic retinopathy has nothing to do with myopia.

For healthy people, after eating sugar, the body will automatically adjust. In normal people, the blood sugar concentration can be kept within a certain range, so it will not cause blood sugar to lose control and affect vision. This is especially true for healthy children.

  1. Limited research on sugar and vision

There is very little evidence to really study the relationship between "eating sugar can cause myopia".

In 1956, Gardiner suggested that carbohydrates and fats in the diet can cause myopia, but this statement was later abandoned. Many theories were abandoned because they were proved to be wrong by later research, or because of the lack of relevant research.

In 2010, a study found that eating sugar does not increase the risk of myopia in adolescents, but found that excessive saturated fatty acids in the diet are related to myopia.

Recently, there was a French study using a questionnaire to survey 180 children aged 4-18. The method of this study was to compare the intake of fine carbohydrates (including sugar) of children with their dilated refraction results.

Studies have found that in girls, the frequency of fine carbohydrate intake is positively correlated with myopia, but in boys, it is negatively correlated.

To put it simply, the study found that "Girls who eat more sugar have more myopia, but among boys, those who eat more sugar have less myopia."

There are very few studies on sugar and myopia, and this 2020 study seems to be the only one that found that eating fine carbohydrates may be associated with myopia.

However, this study itself has many problems, such as not controlling variables (such as outdoor activities, a close reading of books, and the use time of electronic screens, etc.), the questionnaire format itself has many deviations, and the number of samples is not large...

But apart from this, this study only proposes the correlation between myopia and sugar consumption, rather than causality. Therefore, it is impossible to draw the conclusion that "myopia cannot eat sugar" based on this result.

  1. Don't be influenced by the lack of evidence and form an illusion

In summary, there is still no real evidence to prove that eating sugar will increase or reduce the risk of myopia.

Regular consumption of sugar (including fine carbohydrates) is of course not friendly to the body and teeth, but if the lack of evidence such as "don't eat sugar if children are afraid of myopia" is promoted, it may cause parents and children unnecessary fear of sugar, and it may also form an illusion: If you do not eat sugar, you can prevent and control myopia.

This will make parents neglect to make effective behavioral interventions to prevent and control myopia, such as increasing outdoor activities and reducing close eye use. Some people may even have a false sense of security: although the child’s outdoor activity time cannot be guaranteed, and the eye-using time cannot be well controlled, it’s not bad to be able to control myopia by not eating sugar.

Of course, regardless of whether sugar is related to myopia, from the perspective of obesity and tooth protection, sugar is indeed not encouraged to eat.

  1. What can baby eat to prevent myopia?

Some people worry that eating sugar will cause myopia, and some people want to know what to eat to prevent myopia, such as lutein, blueberries, or carrots. They often claim that it is good for protecting eyesight.

But in fact, these claims currently lack evidence, and there is no evidence that what kind of food to eat can effectively prevent myopia or be good for eyesight.

If you just want to know: What kind of food is best for your eyesight? My answer is: a balanced diet is good.

Insist on ensuring 2 hours of outdoor activities a day and reducing the use of close eyes, which are the scientific methods that can really prevent myopia.