In a recent study published in the journal Nutrients, researchers examined the relationship between ultra-processed food (UPF) intake and glaucoma incidence among Spanish university graduates.

Glaucoma? A Prospective Cohort Study including 19,255 Participants from the SUN Project. Image Credit: Africa Studio / Shutterstock

Background

Glaucoma is a leading cause of lifelong blindness globally, defined by the gradual loss of retinal ganglion cells. Elevated intraocular pressure, advanced age, non-Caucasian race, and family history increase glaucoma risk. However, alterable environmental variables like nutrition, exercise, and lifestyle are increasingly associated with its development. Alternative and complementary medicine for glaucoma therapy has gained popularity, but more study is required to tap their therapeutic potential. Nutrition is gaining scientific interest due to UPF ingredients heavy in salt, sugar, and fat. Previous research implies a link between food and glaucoma risk; however, the relationship is ambiguous. Further study is required to apply these findings to clinical care practices.

About the study

In the present observational, prospective cohort study, researchers investigated whether consuming UPF increases the incidence of glaucoma among university graduates in Spain.

The study included 19,255 Seguimiento Universidad de Navarra (SUN) Project participants (60% women, mean age, 38 years). The researchers followed the participants for 13 years (mean) through biennial questionnaires to be completed online or through mail. The baseline questionnaire (Q0) contained data on sociodemographic factors, physical measurements, dietary practices, lifestyle habits, and comorbidities. The researchers sent follow-up study questionnaires in two-year intervals (Q2 to Q20) to evaluate changes in diet, lifestyle, and medical conditions and monitored disease incidences. They used the Q10 study questionnaire to obtain updated data.

The team used food-frequency questionnaires (FFQ) to evaluate dietary intake and the NOVA food classification to determine UPF intake. They determined the glaucoma diagnosis by querying the study participants about ever receiving a glaucoma diagnosis from an ophthalmologist. In addition, they validated the self-reported diagnoses among 150 individuals following the European Glaucoma Society guidelines at baseline and a two-year interval during follow-up.

The researchers excluded individuals with glaucoma or ocular hypertension at baseline and those with energy intake values beyond predetermined limits. They used Cox regression models to determine the hazard ratios (HR), adjusting for sociodemographic variables, lifestyle and dietary variables, and medical history. Sociodemographic variables included age, sex, educational attainment, and body mass index. Lifestyle and diet variables included total calorie intake, Mediterranean dietary adherence, physical exercise, smoking habits, caffeine intake, ethanol intake, omega-3: omega-6 ratio, and specific diets. Comorbidities included hypertension, cardiovascular disease, diabetes, and cancer.

Results and discussion

During follow-up, the team noted 230 incidents of glaucoma cases and studied 176,963 individual years. Individuals with the highest ultra-processed food intake were younger and consumed more ethanol and coffee with a higher calorie intake. After covariate adjustments, individuals having the highest ultra-processed food intake (more than four servings of UPF per day) showed a higher glaucoma risk (HR, 1.8) compared to those with the lowest UPF intake (up to one serving of UPF per day).

The subgroup analysis showed statistically significant multiplicative associations for participant age and dietary omega-3: omega-6 ratio. However, a relationship between ultra-processed food intake and new-onset glaucoma was limited to older, physically active, non-smoker males aged ≥55 years with low omega-3: omega-6 fatty acid ratio and total calorie intake. Concerning UPF type, sweets showed a significantly high risk of glaucoma incidence (HR, 1.5). The validation findings for self-documented and clinical case diagnoses showed high agreement between, with high sensitivity and specificity, all validating open-angle-type glaucoma.

A high intake of UPFs can cause elevated blood glucose levels, oxidative stress, and inflammation, with sweets having the most contributory role. These processed meals have decreased nutritional density and a higher glycemic effect, which can lead to oxidative stress and inflammation. Retinal exposure to reactive oxygen species (ROS) increases inflammation and glaucoma risk. High UPF intake can also cause weight gain, endothelial dysfunction, elevated blood glucose levels, oxidative stress, and inflammation. The relationship between UPF intake and low-grade inflammation is not entirely understood; however, it is likely due to their robust pro-inflammatory activities. UPFs have a detrimental influence on dietary consumption since they include high quantities of added sugars, trans fats, and salt, resulting in nutrient displacement when substituted with healthy alternatives such as fruits and vegetables.

Conclusions

Overall, the study found that individuals with the highest UPF consumption had a higher likelihood of glaucoma development than those with the lowest UPF consumption. Furthermore, when examined individually, UPF from sweets revealed a significant glaucoma risk. The findings underscore the importance of health monitoring and controlling the intake of UPFs (particularly high-sugar ones) to reduce incident glaucoma cases.

Given the growing cultural tendency toward UPF consumption, healthcare professionals must promote food patterns characterized by increased intake of unprocessed or less processed foods. Furthermore, several governments have implemented policies like front-side labeling, taxes on unhealthy food items, advertising limitations, and promotion of healthier choices to discourage UPF consumption.