In the News: Produce & Glaucoma Risk; Vitamin D & Inflammation; Oxidative Stress in CRVO

Fruits & Veggies Linked to Glaucoma Risk

Greater intake of certain fruits and vegetables rich in vitamins A and C and carotenoids is associated with a lower risk of glaucoma in older African-American women according to research from the Jules Stein Eye Institute, UCLA (1).

Five hundred and eighty four African-American participants in the Study of Osteoporotic Fractures were included in this evaluation of diet and the presence of glaucoma. Glaucoma was diagnosed in at least 1 eye in 77 subjects using disc photographs and supra-threshold visual field tests.

Women who ate at least 3 daily servings of fruits/fruit juices were 79% less likely to have glaucoma than those consuming one or no servings per day. Fresh oranges and peaches in particular, were protective.

For vegetables, more than 1 weekly serving of green leafy vegetables (collard greens/kale) decreased the odds of glaucoma by 57% compared to those eating about 1 serving monthly.

Protective trends were found for individual nutrient intakes of vitamins A, C and alpha carotene. Close to significant trends were seen for beta-carotene, folate, and lutein/zeaxanthin.

It’s biologically plausible for antioxidant nutrients found in fruits and vegetables to modify the risk of glaucoma, as some evidence suggests that oxidative stress contributes to the etiology of this disease. These dietary nutrients may help protect the trabecular meshwork, retinal ganglion cells, and/or the vascular system that nourishes the optic nerve.

Vitamin D May Reduce Retinal Inflammation

Vitamin D3 plays a key role in immune regulation, and has recently been linked epidemiologically to protection against age-related macular degeneration.

To explore the effects of this vitamin in the retina, researchers at University College London’s Institute of Ophthalmology supplemented the diets of aged mice with vitamin D3 for 6 weeks (2). Compared to controls, the supplemented mice showed significant reductions in retinal inflammation and levels of amyloid beta accumulation, which is a hallmark of aging.

According to the investigators, the outer retina has the highest metabolic demand in the body. With age, the depositing of amyloid beta makes the interface between the outer retina and its blood supply less permeable.

The researchers also found significant reductions in retinal macrophage numbers, a marker of chronic inflammation, and marked shifts in macrophage morphology in treated mice. These changes were reflected in a significant improvement in visual function.

Homocysteine & Oxidative Stress in CRVO

Elevated homocysteine can damage the vascular endothelium, and is considered to be a risk factor for central retinal vein occlusion (CRVO) in young adults.

Investigators from the Department of Biochemistry and Cell Biology, Vision and Medical Research Foundation in India wanted to determine whether oxidative stress is an independent risk factor for CRVO, or whether it’s dependent on high homocysteine levels (3). Twenty-three young adult CRVO patients and 54 age and sex-matched controls were included in their study.

Plasma TBARS (a marker of oxidative damage) were significantly higher, while superoxide dismutase and total antioxidant capacity (markers of oxidative stress) were significantly lower in CRVO cases compared with controls. They found that total antioxidant capacity and homocysteine both influence TBARS significantly.

In cultured retinal endothelial cells, they observed that homocysteine increased TBARS in a dose and time dependent manner. Since oxidative stress (TBARS) can be influenced by both elevated homocysteine and poor antioxidant status, it is possible that homocysteine-lowering folic acid, as well as increased intake of antioxidants, could be helpful in some cases of CRVO.

References

1. Giacona JA et al. 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,154:635-44, 2012. 
2. Lee V et al. Vitamin D rejuvenates aging eyes by reducing inflammation, clearing amyloid beta and improving visual function. Neurobiology Aging, 33:2382-89, 2012.
3. Devi SR et al. Homocysteine induces oxidative stress in young adult central retinal vein occlusion. Br J Ophthalmol, 96:1122-26, 2012.