"We found people consume green leafy vegetables, has a risk of 20 to 30 percent less likely to develop glaucoma," said study leader Kang Jae. Kang is an assistant professor of medicine at Brigham and Women's Hospital and Harvard Medical School in Boston.
Glaucoma is an eye condition that occurs because of the increased amount of fluid in the front of the eye, causing pressure on the eye and damages the optic nerve. Glaucoma can lead to vision loss, according to the US National Eye Institute.
Although the study found an association between green leafy vegetables with a reduced risk of glaucoma, the relationship is not causal relationships.
Tim Kang examined data on nearly 64,000 participants of the Nurses' Health Study from 1984 to 2012, and more than 41,000 participants in the Health Professionals Follow-up Study from 1986 to 2014. The male and female participants aged 40 years and over.
At the beginning of the study, they all do not suffer from glaucoma and eyes examined regularly every two years.
During 25 years of research found nearly 1,500 people suffering from glaucoma. Then the researchers evaluated the pattern of consumption of green leafy vegetables among the participants.
The researchers divided the participants into five groups, ranging from who ate the most green leafy vegetables to lowest.
Most servings are consumed 1.5 servings a day, or about one and a half cups a day. While the portion is at least one serving of vegetables every three days.
"There is a disruption of blood flow to the optic nerve is the eye in patients with glaucoma," said Kang. "And the important factors that regulate blood flow to the eye is a substance called nitric oxide." Green leafy vegetables contain nitrates, which is a precursor to nitric oxide.