Eating leafy green vegetables could reduce your risk of glaucoma, according to a study published in the journal JAMA Ophthalmology earlier this month. An increase in dietary nitrates found in green vegetables significantly reduces the risk of primary open-angle glaucoma, which is the most common form of the disease, found a research team from Boston’s Brigham & Women's Hospital and Harvard Medical School.

Researchers used data from the Nurses' Health Study and the Health Professionals Follow-up Study for the analysis. Participants included 63,893 women and 41,094 men, all of whom were over the age of 40 and had no history of primary open-angle glaucoma. During the follow-up period of data collection, 1,483 participants developed primary open-angle glaucoma.

Primary open-angle glaucoma is caused by a clogging of the eye’s drainage canals, which slowly increases eye pressure. Impaired blood flow in the optic nerve also plays a role in the disease. Dietary nitrate, which mostly comes from leafy green vegetables, has been shown to improve blood circulation

In the study, researchers assessed the green vegetable content of participants’ diets and calculated nitrate intake. Participants were divided into one of five groups based on the amount of nitrate intake. The group with the highest intake consumed about 240 mg per day; the lowest averaged about 80 mg per day.

Those who ate the highest levels of nitrogen had a 20-30% lower risk of primary open-angle glaucoma. Participants in this group also had a 40-50% lower risk of developing a subtype of glaucoma called primary open-angle glaucoma with early paracentral visual field loss. The two vegetables that were strongly associated with a reduction in glaucoma were kale and collard greens.

Because of the study’s design, it’s impossible to determine cause and effect from these findings. However, the findings were strong enough that researchers recommended future observational and intervention studies to establish cause and effect.

Leafy green vegetables are a healthful part of the diet, glaucoma or otherwise. They are thought to maintain high levels of oxygen in the blood, lower blood pressure, and prevent clotting. Including lots of these vegetables in your diet, especially kale and collard greens, could lower your risk of glaucoma and bring many different health benefits.

Kang, J. H., Willett, W. C., Rosner, B. A., Buys, E., Wiggs, J. L., & Pasquale, L. R. Association of Dietary Nitrate Intake With Primary Open-Angle Glaucoma: A Prospective Analysis From the Nurses’ Health Study and Health Professionals Follow-up Study. JAMA Ophthalmology, 1-11.

Newman, T. (2016, Jan. 15). Eating your greens might stave off glaucoma. Medical News Today. Retrieved Jan. 20, 2016 from http://www.medicalnewstoday.com/articles/305099.php.