Leafy greens like spinach, lettuce and kale could lower the risk of glaucoma by up to 30%, research has found.
A diet of nitrate-rich vegetables is good for blood circulation which means it could prevent primary open-angle glaucoma (POAG), one of four types of the condition, Harvard Medical School discovered.
Dr Jae Kang explained: “Higher dietary nitrate and green leafy vegetable intake was associated with a lower POAG risk.”
The study, published in the journal JAMA Ophthalmol, looked at more than 104,000 patients.
It found those who ate a nitrate-rich diet had lower levels of the rare condition, which involves chronic or acute sudden painful build-up of pressure in the eye.
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Increased pressure and a disruption in the flow of optic nerve blood flow have been implicated in POAG.
Previous studies suggested nitrate or nitrite, precursors for nitric oxide, is beneficial for blood circulation so scientists from Harvard Medical School looked at the link of diet and POAG.
Assistant Professor of Medicine Jae Kang said: “Evidence suggests that nitrate or nitrite is beneficial for blood circulation.
“Dietary nitrate is predominately derived from green leafy vegetables, which contribute approximately 80 per cent of nitrate intake.
“To our knowledge, dietary nitrate intake as a specific nutrient has not been evaluated – therefore, we evalated it in a longer-than-25-year prospective study of 63,893 women and 41,094 men.
“These findings could have important implications if the association of higher dietary nitrate and green leafy vegetable intake with a lower POAG risk is confirmed.”
The study followed participants in the two studies who were over 40, free of POAG, and had results of eye examinations.
Information on diet was updated with questionnaires.
During follow-up, 1,483 incident cases of POAG were identified.
They were divided into five groups dependent upon nitrate levels in their diet.
It was found greater intake of dietary nitrate and green leafy vegetables was associated with a 20 per cent to 30 per cent lower POAG risk.