Abstract
BackgroundThe antioxidant properties of tea extracts are considered to be effective in protecting against cataracts. However, there is still insufficient epidemiological knowledge about the protective effects of different types of tea on age-related cataracts.MethodsThe data was derived from the Zhejiang Major Public Health Surveillance (ZJMPHS) Program on health and related factors in the elderly. The relationships between consumption of different types of tea and risk of age-related cataracts were assessed after adjusting for related covariates.ResultsThe prevalence of age-related cataracts in this study population was 4.4% (409/9343). After adjustment for potential confounders, tea drinking was associated with reduced risk of age-related cataracts (adjusted odds ratio [OR] 0.65; 95% confidence interval [CI], 0.47–0.91). Compared to nondrinkers, green tea drinkers had a significantly reduced risk of cataracts (adjusted OR 0.58; 95% CI, 0.40–0.85). Average tea consumption of 14–27 cups (adjusted OR 0.55; 95% CI, 0.33–0.93) and over 28 cups (adjusted OR 0.58; 95% CI, 0.34–0.99) per week had a protective effect against cataracts in comparison to no consumption. In addition, ingesting a moderate concentration of tea significantly decreased the risk of cataract compared to no consumption (adjusted OR 0.43; 95% CI, 0.27–0.71).ConclusionsTea ingestion was associated with reduced risk of age-related cataracts. In light of these findings, we suggest that reasonable tea consumption (ie, favoring green tea and consuming an average of over 500 mL per day at moderate concentration) should offer protection against age-related cataracts.
Highlights
Cataracts are the main cause of blindness and are responsible for approximately 50% of the number of people in China who are blind, or around 2.5 million people, and the incidence is increasing.[1]
About 14% of participants with cataracts and 28% of those without cataracts reported drinking tea, with a significant association between tea consumption and cataracts after adjustment for sex; ethnic group; age; body mass index (BMI); education; marriage status; exposure to pesticides, dust, irritant gas, and heavy metals; family income; health insurance status; presence of high blood pressure, hyperlipidemia, or diabetes; family history of cataract; smoking, alcohol drinking, and physical activity status; and intake of vitamin A, β-carotene, vitamin B, vitamin C, vitamin E, calcium tablets, and iron
Stratified analyses showed a family history of cataracts and tea consumption had an independent effect on cataracts, with odds ratios of 13.12 and 0.45, respectively
Summary
Cataracts are the main cause of blindness and are responsible for approximately 50% of the number of people in China who are blind, or around 2.5 million people, and the incidence is increasing.[1] Age-related cataracts are the predominant type, and over 80% of cataract-disabled people in China are aged 65 years or older.[2] Age-related cataracts are considered a multifactorial ophthalmic disease that might be related to the environment, nutrition, metabolism, genetics, and other unknown factors Many factors, such as smoking, alcohol use, ultraviolet radiation exposure, diabetes, diarrhea, and some nutritional factors significantly increase the risk of age-related cataracts.[3] Other factors, including consumption of many types of vegetables, fruits, and micronutrients, might reduce the risk of this disease.[4] Green and black teas are considered to be protective against cataracts, with a proposed mechanism related to the antioxidant properties of compounds found in tea extracts, such as catechin (C), catechin gallate (CG), epicatechin gallate (ECG), epigallocatechin gallate (EGCG), theaflavins (TFs), and thearubigins (TGs).[5] To our knowledge, only a few epidemiologic research studies have examined the relationship between tea consumption and risk of cataracts.[6,7] Further, epidemiological knowledge about the protective effects of different types of tea on age-related cataracts remains insufficient. In light of these findings, we suggest that reasonable tea consumption (ie, favoring green tea and consuming an average of over 500 mL per day at moderate concentration) should offer protection against age-related cataracts
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