EFFECT OF TEA ON GLAUCOMA

 

A study has been performed by Wu et al, to evaluate the association between the consumption of coffee, tea, or soft drinks, and glaucoma.

The study is based on the participants of the 2005–2006 National Health and Nutrition Examination Survey (NHANES), conducted in the USA.

The authors reported that individuals who consumed at least one cup of hot tea daily had 74% decreased odds of having glaucoma compared with those who did not consume hot tea (adjusted OR=0.26, 95%CI 0.09 to 0.72, P=0.004 for trend).

No significant associations were found between the consumption of coffee, iced tea, decaffeinated tea, and soft drinks, and glaucoma risk.

Caffeine has been postulated to increase glaucoma risk by promoting increases in intraocular pressure (IOP) and homocysteine levels in the body.

Caffeine transiently increases IOP ranging from 1-2 mmHg within one hour of ingestion. However, other studies have shown that drinking non-caffeinated fluids ranging from 250-1000 mL also increases IOP, indicating that the fluid overload could be the cause of the rise in the IOP and not due to the effect of caffeine alone.

Tea contains phytochemicals and flavonoids, which have been observed to have anti-inflammatory, anticarcinogenic, antioxidant, and neuroprotective properties, which help in the prevention of cardiovascular disease, cancer, and diabetes.

Flavonoids have been shown to inhibit the vascular endothelial growth factor receptor and potentially prevent neovascular glaucoma, fibrotic scar tissue formation after glaucoma surgery, and neurodegeneration. They may also play a protective role by promoting vasodilation.

Caffeinated teas have been found to have greater antioxidant capacity compared with decaffeinated teas, which may explain why decaffeinated tea consumption was not correlated with decreased glaucoma risk.

Compared with tea, coffee contains more caffeine and a different profile of polyphenols comprising fewer flavonoids but more hydroxycinnamic acids, which may explain why tea is better at modulating the risk of glaucoma.

REFERENCE:

Wu CM, Wu AM, Tseng VL, Yu F, Coleman AL. Frequency of a diagnosis of glaucoma in individuals who consume coffee, tea and/or soft drinks. Br J Ophthalmol. 2018 Aug;102(8):1127-1133. doi: 10.1136/bjophthalmol-2017-310924. Epub 2017 Dec 14. PMID: 29242183.