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Editors Selection IGR 16-4
Miscellaneous: Dietary Nitrate Intake and Glaucoma
Comment by Marissé Masís & Shan Lin on:
66567 Association of Dietary Nitrate Intake With Primary Open-Angle Glaucoma: A Prospective Analysis From the Nurses' Health Study and Health Professionals Follow-up Study, Kang JH; Willett WC; Rosner BA et al., JAMA ophthalmology, 2016; 0: 1-11
Glaucomatous injury to the retinal ganglion cells has been associated with anatomical damage even to the level of the central nervous system such as the lateral geniculate nucleus and visual cortex. Accelerated apoptosis, oxidative stress, cytokine-related inflammatory processes, and abnormal protein accumulation are some of the proposed cell injury mechanisms which help define glaucoma as a neurodegenerative disease.1
Population-based studies are a valuable tool to assess several mechanistic pathways including risk factors that may lead to neurodegeneration. Several papers have been published regarding the effect of diet and nutrients in glaucoma. In 2003, data from the Nurses' Health Study showed no relationship between carotenoids, vitamins C and E, and vegetables and glaucoma risk. Although the relative risk wasn't statistically significant, the trend was in the direction of protection against with antioxidants, and there was no specific analysis of nitrate intake.2 In 2008 a population based study supported that a higher intake of fruits and vegetables may be associated with a decreased risk of glaucoma in women,3 and in 2012 similar findings were uncovered in a cohort study of African-American women.4
This study by Kang et al. adds several promising findings related to dietary intake and glaucoma. It is the first study that assessed eating habits in relation to specific visual field loss patterns (peripheral loss only vs. early paracentral loss). Dietary nitrate intake, mostly in the form of green leafy vegetables, appeared to have more protective effect against POAG related to early paracentral visual field defects. In clinical practice, usually these findings are related to normal tension glaucoma, which is the type of glaucoma more susceptible to oxidative stress and vascular dysregulation. The protective effect of nitrates appears to be dose-dependent and it resulted in a 20-30% lower POAG risk.
Of course associations found in population studies do not necessarily prove causation or mechanism. Prospective, randomized studies are needed to show causal effects between nutrients and glaucoma development. The evidence for environmental factors in optic nerve damage is growing and a better understanding of these factors may lead us to a more systemic and integrated approach to glaucoma care.
References
- Neeru, G Yeni, Y. Glaucoma as a neurodegenerative disease. Current Opinion in Ophthalmology Vol 18 (2), 2007
- Kang JH, Pasquale LR, Willett W, Rosner B, Egan KM, Faberowski N, Hankinson SE. Antioxidant intake and primary open-angle glaucoma: a prospective study. Am J Epidemiol. 2003;158:337-46
- Coleman AL, Stone KL, Kodjebacheva G, Yu F, Pedula KL, Ensrud KE, Cauley JA, Hochberg MC, Topouzis F, Badala F, Mangione CM, Study of Osteoporotic Fractures Research Group. Glaucoma risk and the consumption of fruits and vegetables among older women in the study of osteoporotic fractures. Am J Ophthalmol. 2008;145:1081-9. 3.
- Giaconi JA, Yu F, Stone KL, Pedula KL, Ensrud KE, Cauley JA, Hochberg MC, Coleman AL, Study of Osteoporotic Fractures Research Group. The association of consumption of fruits/vegetables with decreased risk of glaucoma among older African-American women in the study of osteoporotic fractures. Am J Ophthalmol. 2012;154:635-44.
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