Including this nutrient in your children's diet can help prevent myopia in children.

A diet rich in omega-3 fatty acids, found primarily in fish oils, may help prevent the development of myopia in children, while a high intake of saturated fats, found in products such as palm oil and ultra-processed foods , may increase the risk of developing this eye problem, according to a study published in the British Journal of Ophthalmology.

The global prevalence of myopia is increasing, especially in East Asia, and about half of the world's population is expected to be nearsighted by 2050, researchers note.

Spending too much time in front of a screen and too little time outdoors, as well as a hereditary susceptibility, are some of the risk factors, they explain.

Omega-3 polyunsaturated fatty acids, which can only be obtained through diet, are believed to improve or prevent various chronic eye conditions, such as dry eye and age-related macular degeneration . However, it is unclear whether they can help prevent myopia, as studies to date have been experimental and have not included people.

To explore this further, the researchers turned to 1,005 Chinese children aged 6 to 8, randomly recruited from the Hong Kong Children's Eye Study, which tracks the development of eye diseases and potential risk factors.

The children's vision and habitual diet were assessed using a food frequency questionnaire, completed with the help of their parents. The questionnaire included 280 foods classified into 10 groups: bread/cereals/pasta/rice/noodles; vegetables and legumes; fruit; meat; fish; eggs; milk and dairy products; beverages; dim sum/snacks/fats/oils; and soups.

Energy, carbohydrate, protein, total fat, saturated fat, monounsaturated fat, omega-3, cholesterol, iron, calcium, vitamins A and C, fiber, starch, sugar, and nutrient intakes were then calculated based on the questionnaire responses.

The time children spent outdoors in leisure and sports activities, reading and writing, and in front of screens during weekdays and weekends was also taken into account.

Approximately one-quarter of the children (276; 27.5%) had myopia. A higher dietary intake of omega-3 fatty acids was associated with a lower risk of developing it.

Axial length (the measurement of the eye from the cornea at the front to the retina at the back, and an indicator of myopia progression) was longer in the 25% of children with the lowest dietary intake of omega-3 fatty acids, after accounting for influencing factors including age, sex, weight (BMI), amount of time spent in near and outdoor work, and parental myopia.

It was shorter in the 25% of children with the highest dietary intake of omega-3 fatty acids. Similarly, the cycloplegic spherical equivalent (SE), which measures refractive error such as the degree of myopia, was higher in those with the lowest intake of omega-3 fatty acids and lower in those with the highest intake.

However, these findings were reversed in the 25% of children with the highest saturated fat intake, compared to the 25% of those with the lowest. None of the other nutrients were associated with myopia.

This is an observational study and therefore cannot establish causal or temporal factors. The researchers acknowledge that food frequency questionnaires rely on recall and only provide a snapshot of the diet. No objective evidence of nutritional intake was found from blood samples.

The prevalence of myopia in Hong Kong is also among the highest in the world. It remains to be seen whether the findings could be applied to other ethnic groups with different lifestyles and lower myopia, they add.

But researchers suggest that omega-3 fatty acids may suppress myopia by increasing blood flow through the choroid, a vascular layer of the eye responsible for transporting nutrients and oxygen, thereby preventing scleral hypoxia (oxygen deficiency in the white part of the eye and a key factor in the development of myopia).

"This study provides human evidence that higher dietary intake of omega-3 fatty acids is associated with shorter axial length and lower myopic refraction, highlighting omega-3 as a potential protective dietary factor against the development of myopia," they conclude.