Perspectives on Glaucoma

Intake of green, leafy vegetables associated with lower POAG risk

Greater intake of dietary nitrate and green, leafy vegetables was associated with a 20% to 30% lower primary open-angle glaucoma risk, particularly with early paracentral visual field loss, according to researchers in JAMA Ophthalmology.

Kang and colleagues followed up with participants in the Nurses’ Health Study (53,893 women, 1984 to 2012) and the Health Professionals Follow-up Study (41,094 men, 1986 to 2012) at each 2-year risk period who were 40 years or older, were free of primary open-angle glaucoma (POAG) and underwent eye exams.

The study encompassed 1,678,713 person-years of follow-up, with 1,483 cases of POAG identified, according to the study.

The highest consumers of dietary nitrate received more antioxidants (carotenoids, vitamin C, vitamin E), flavonoids, folate and vitamin A; exercised more; and were more often African American, according to researchers. They were also leaner and smoked less.

Compared with the lowest quintile (quintile 1) of approximately 80 mg/d nitrate, the pooled multivariate relative risk (MVRR) of POAG in the main model (model 1) was 0.81 for quintile 2, 0.88 for quintile 3, 0.90 for quintile 4 and 0.79 for quintile 5, according to researchers.

The researchers found that when compared with those consuming a median of 0.31 servings per day of green, leafy vegetables (quintile 1), the pooled MVRR for 1.45 servings per day (quintile 2) was 0.82 for overall POAG and 0.52 for POAG with early paracentral visual field loss.

The pooled MVRR for quintile 5 vs. quintile 1 ranged from 0.72 to 0.89 for overall POAG.

In POAG with paracentral visual field loss, the pooled MVRRs were 0.69 for iceberg lettuce; 0.71 for romaine lettuce; and 0.33 for kale, mustard or chard greens, according to researchers.

Dietary nitrate supplementation represent a practical method to increase nitrate levels, according to the study. – by Abigail Sutton

Disclosure: The researchers reported no relevant financial disclosures.

Greater intake of dietary nitrate and green, leafy vegetables was associated with a 20% to 30% lower primary open-angle glaucoma risk, particularly with early paracentral visual field loss, according to researchers in JAMA Ophthalmology.

Kang and colleagues followed up with participants in the Nurses’ Health Study (53,893 women, 1984 to 2012) and the Health Professionals Follow-up Study (41,094 men, 1986 to 2012) at each 2-year risk period who were 40 years or older, were free of primary open-angle glaucoma (POAG) and underwent eye exams.

The study encompassed 1,678,713 person-years of follow-up, with 1,483 cases of POAG identified, according to the study.

The highest consumers of dietary nitrate received more antioxidants (carotenoids, vitamin C, vitamin E), flavonoids, folate and vitamin A; exercised more; and were more often African American, according to researchers. They were also leaner and smoked less.

Compared with the lowest quintile (quintile 1) of approximately 80 mg/d nitrate, the pooled multivariate relative risk (MVRR) of POAG in the main model (model 1) was 0.81 for quintile 2, 0.88 for quintile 3, 0.90 for quintile 4 and 0.79 for quintile 5, according to researchers.

The researchers found that when compared with those consuming a median of 0.31 servings per day of green, leafy vegetables (quintile 1), the pooled MVRR for 1.45 servings per day (quintile 2) was 0.82 for overall POAG and 0.52 for POAG with early paracentral visual field loss.

The pooled MVRR for quintile 5 vs. quintile 1 ranged from 0.72 to 0.89 for overall POAG.

In POAG with paracentral visual field loss, the pooled MVRRs were 0.69 for iceberg lettuce; 0.71 for romaine lettuce; and 0.33 for kale, mustard or chard greens, according to researchers.

Dietary nitrate supplementation represent a practical method to increase nitrate levels, according to the study. – by Abigail Sutton

Disclosure: The researchers reported no relevant financial disclosures.

    Perspective
    Blair Lonsberry

    Blair Lonsberry

    Primary open angle glaucoma has been linked to elevated intraocular pressure and impaired autoregulation of optic nerve head blood flow. Nitric oxide is known to improve vascular function. Dietary nitrate (found in green leafy vegetables and 80% of nitrate intake) can be converted into nitrite by commensal bacteria.

    With the above facts in mind, this study evaluated dietary nitrate and incident primary open angle glaucoma (POAG) in a longer-than-25-year prospective study of more than 100,000 patients. The analysis demonstrated that a greater intake of dietary nitrate and green leafy vegetables was associated with a 20% to 30% lower POAG risk. From their survey results, the authors determined the highest consumers of dietary nitrate consumed more antioxidants, flavonoids, folate and vitamin A. These individuals exercised more, were frequently African American, were also leaner and smoked less. Clearly, factors other than nitric oxide may be at play.

    Nitric oxide is currently being evaluated as a potential treatment for glaucoma. This observational study needs to be confirmed by an interventional study but points favorably to the role of recommending dietary nitrate and increased consumption of green leafy vegetables to our patients. Apparently, we need to recommend green leafy vegetables for more than our patients at risk for macular degeneration.

    • Blair Lonsberry, OD, FAAO
    • Pacific University College of Optometry

    Disclosures: Lonsberry is on the speakers bureau for Carl Zeiss Meditec.