Harvard Men's Health Watch

Dietary nitrate may lower risk of glaucoma

In the Journals

Eating more dietary nitrate, especially from green leafy vegetables, may help lower your risk of glaucoma, according to a study published online Jan. 14, 2016, by JAMA Ophthalmology.

More than 104,000 people were divided into five groups based on their dietary nitrate intake, which ranged from a daily average of 80 milligrams (mg) to 240 mg. The researchers found that being in the highest nitrate category was associated with a 20% to 30% lower risk for primary open-angle glaucoma (POAG), the most common type.

Specifically, 10 servings of green leafy vegetables per week, or about 1.5 cups per day, had the greatest influence to reduce POAG risk. The top food sources included iceberg and romaine lettuce, kale, mustard, chard, and raw and cooked spinach.

Frequency appears to be just as important as the food, says lead researcher Dr. Jae Hee Kang of Harvard-affiliated Brigham and Women's Hospital. "For instance, beets have a high amount of nitrate, but few people eat them regularly. Green leafy vegetables had the strongest association probably because people eat more of them on a regular basis."

Glaucoma can occur when pressure builds up from eye fluid that does not drain properly. This pressure can damage the optic nerve and nerve fibers from the retina and lead to vision loss. Glaucoma can also develop when there is low blood circulation to the optic nerve.

Nitrate can help with both problems. "Higher nitrate intake leads to increased nitric oxide in the body, and nitric oxide can maintain normal eye pressure by regulating tissues of the drainage pathway," says Dr. Kang. "In addition, nitric oxide helps to relax blood vessels and can improve blood flow to the optic nerve."