A plant-based diet is associated with decreased risk of cataracts, according to findings published in the Journal of the Academy of Nutrition and Dietetics. 

Researchers in Taiwan performed a prospective cohort study to determine whether a vegetarian diet lowers the risk of experiencing cataracts. The study recruited 6002 participants from 2007 to 2009 who were 40 years old and older without a diagnosis of cataracts until the end of 2014. 

Because plant-based diets tend to include a wide variety of antioxidants, the research speculates that they pose a lower risk for cataracts, which can be caused by oxidative stress in the lenses. However, levels of vitamin B-12 that are too low, a condition some vegetarians experience, can actually increase the risk of cortical cataracts via elevating homocysteine levels. 

Of the study’s participants, 3095 were nonvegetarians and 1341 were vegetarians. After adjusting for confounders such as smoking, drinking habits, hypertension, diabetes, and body mass index (BMI), researchers found that a vegetarian diet was associated with a 20% reduced risk of cataracts (P =.04). The most pronounced association, the study explains, was among participants who were defined as overweight in Taiwan (BMI >24, P =.04). 


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Participants who entered the study were interviewed using a structured questionnaire which included questions about diet, such as a food-frequency checklist containing 64 items and questions about the use of supplements. The researchers defined vegetarians as participants who abstained from meat and fish for a least 1 month before the enrollment date.

Despite some vegetarians’ lower B-12 status, which is more common among those in countries with limited access to certain foods fortified with the vitamin, the research concludes that plant-based diets have a protective, rather than a harmful, association with cataracts overall.

The researchers explain that the study may not be generalizable to other populations, because the vegetarians and some nonvegetarians included were Tzu Chi Buddhists, and their religion completely prohibits alcohol and tobacco. Due to this fact, there was limited variability within that group in terms of lifestyle features, so it is possible that cataract risk would be higher for other populations. 

Another limitation included the researchers’ lack of assessment of cataract risk factors, such as sunlight or ultraviolet light exposure and the use of sunglasses.

Reference

Chiu T, Chang C, Lin C, Lin M. A vegetarian diet is associated with a lower risk of cataract, particularly among individuals with overweight: a prospective study. J Acad Nutr Diet. Published online December 11, 2020. doi:10.1016/j.jand.2020.11.003.