A low-fat diet that increases vegetable, fruit, and grain intake does not reduce incident primary open-angle glaucoma (POAG) in women who are postmenopausal, according to research published in Ophthalmology. In fact, reducing fat intake for individuals who already have a low fat baseline may increase the risk of POAG, researchers say.
The final analysis included 23,217 women (mean age 64.4 ± 5.8 years). It included 9340 patients who followed a low-fat diet with increased vegetable, fruit and grain intake, and 13,877 placed into a control group who were asked to follow their usual diet.
Analyses were based on an intent-to-treat design, with a follow-up to the end of continuous Medicare coverage, death, or the last claims date, whichever occurred first. The researchers defined POAG as the first claim with the International Classification of Diseases 9 or 10 codes, and dietary data was assessed using a food frequency questionnaire.
The study found that POAG incidence in the study group was 11.1 per 1000 woman-years (mean follow-up 11.6±7.4 years; mean diet duration 5.2±3.2 years). No overall benefit of the diet in reducing incident POAG was recorded (HR=1.04, 95%CI, 0.96-1.12). This relationship was not modified by race (P =.24) and participant age (P =.44). In analyses of baseline nutrient and food intake stratified by quartile groups, the researchers found that a low-fat diet in participants in the lowest quartile group for percentage calories (kcal) from total fat (33.8 or lower) had increased risk of developing POAG (HR=1.22, 95% CI, 1.05-1.41; P =.007).
The researchers explained that, although the study did not show a significant association between primary OAG and the low-fat modified diet trialed in the female participants, existing literature suggests that a combination of behavioral factors, including DM, may affect OAG outcomes.
“A careful design of future lifestyle and diet modifications is needed given that a healthy balance of fat intake may play a critical role,” the researchers explain.
The study’s limitations include a lack of inclusion data on ocular risk factors and an upward bias for baseline food frequency questionnaire (FFQ) data for fat and energy intake.
Mehta R, Ray RM, Tussing-Humphreys LM, et al. Effect of low-fat dietary modification on incident open-angle glaucoma. Ophthalmology. Published online November 18, 2022. doi:10.1016/j.ophtha.2022.11.014.