Some nutrients may have benefits for myopia control, but evidence lacking
Click Here to Manage Email Alerts
Key takeaways:
- The relationship between diet and nearsightedness remains unclear.
- Contradictory results on some possible influences, such as vitamin D and breastfeeding, should be explored.
The current body of evidence shows no association between myopia and diet, but the potential influence of specific nutrients and dietary elements should be explored further, according to a systematic review in Optometry and Vision Science.
Analyzing 27 published studies, researchers found that most nutrients showed inconsistent associations with myopia from one noninterventional study to another. In interventional trials, three nutrients were implicated in myopia control, but improvements were clinically minimal in two of three trials.
Some studies under review supported theories suggesting possible roles in myopia control for nutrients including vitamin D; trace elements such as zinc, copper and selenium; as well as breastfeeding during infancy.
“Given the vast, diverse and complex nature of nutrition, more systematic investigation is warranted to comprehend the extent to which these specific nutrients and dietary elements are associated with myopia through longitudinal studies by subduing the limitations in the existing literature,” Sruthi Chamarty, MSOpt, and colleagues from the Myopia Research Lab at LV Prasad Eye Institute in India wrote.
Ultimately included in the review were 24 noninterventional studies (including 11 cross-sectional, eight birth cohort and five retrospective) and three interventional studies. The researchers noted they were not able to perform a meta-analysis of the studies because their methodologies and reported outcomes were too diverse, and instead they opted to qualitatively describe the outcomes of the studies.
Their review found that any relationship between diet and myopia demonstrated in the noninterventional studies was “rather a limited association,” noting that the studies’ odds ratios mostly “lay closer to the line of unity” and “the 95% confidence intervals were wide or overlapped with the unity line.” Most nutrients had inconsistent relationships with myopia between studies, being associated with increased risk in one study and decreased risk — or no association — in another.
However, the review highlighted a possible correlation between zinc and myopia. Higher zinc levels were found in the hair of individuals with myopia, and lower levels in their serum, across two studies by the same authors, who speculated that there was less zinc in available in myopic eyes due to over-accumulation in the hair.
The three interventional studies under review assessed the impacts of proteins, 7-methylxanthine and crocetin supplements, respectively. Animal protein was found to slow myopia progression by 0.22 D to 0.42 D at 1 year in children consuming it as 10% of their caloric intake. Children taking crocetin had 0.08 D (P = .049) less progression at 24 weeks.
Myopia progression saw no significant impact from 7-methylxanthine. However, axial elongation in treated children was lesser by 98 m (P = .048) over 24 months compared with control — but only in children with moderate axial growth at baseline.
After their analysis, researchers said the relationship between diet and myopia “remains unclear,” with contradictory findings on several theories still to be clarified.
For example, most studies found that serum concentration of vitamin D was lower in individuals with myopia, but other findings make it unclear whether it is a causal relationship. One study showed that breastfed children had reduced myopia risk, while another study found no association, but correlated breastfeeding with a more hyperopic refractive error.
The three noninterventional studies all provided evidence toward a theory that myopia could emerge from insulin resistance, prompted by consumption of high-glycemic-load carbohydrates. That diet could increase levels of free circulating insulin-like growth factor I, causing a cascade that leads to proliferation of scleral tissue and ocular elongation.
Most of the studies under review (n = 23) were limited by their lack of adjustment for all potential confounding factors in myopia progression, and in three studies, assessments of nutritional status and refractive error were done at different times. The review’s limitations included its qualitative nature and lack of data on nutrients’ associations with refractive error and axial length.
Collapse
Chamarty S, et al. Optom Vis Sci. 2023;doi:10.1097/OPX.0000000000002035.
Read more about
Click Here to Manage Email Alerts