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Naphthalene is known to cause cataracts (clouding over of the lens of the eye) in rats and rabbits. Therefore experimental animals are treated with naphthalene in order to model and study cataracts of elderly humans. It is thought that naphthalene causes cataracts through oxidative stress. Curcumin is the most active chemical part of turmeric, a spice used in Indian curry dishes. It is an effective antioxidant. These scientists studied whether low amounts of dietary curcumin slowed the formation of the cataracts usually caused by naphthalene in rats. They looked for apoptotic cells in the cells covering the lens by measuring DNA formation. Both treated rats and control rats were given naphalene to produce experimental cataracts. Only 0.005% (w/w) curcumin was added to the diet of the treated rats. The treated rats had significantly less clouding of their lenses as compared to the control rats. They found, for the first time, that cataracts caused by naphthalene involved apoptosis of the cells covering the lens. Apoptosis is a type of programmed, deliberate cell death in which the cell corpses and fragments are safely disposed. They also found that that curcumin reduced the apoptotic effect of naphthalene.

Cataracts in the elderly are an important health problem worldwide. Cataracts (clouding over of the lens of the eye) are thought to be caused by oxidative stress. Increasing the antioxidant defenses of the lens prevents or delays the formation of cataracts. Anti-oxidants are chemicals that reduce free radicals. Because free radicals cause chain reactions that damage cells, anti-oxidants are thought to help in a number of illnesses. These scientists tested whether curcumin, an antioxidant, present in the spice turmeric, prevented cataract formation in rats. Rats were maintained on a standard diet for 2 weeks. Then they were divided into two groups. One was given a dose of corn oil alone for 14 days. The other group was fed 75 milligrams of curcumin in corn oil per kilogram of weight for 14 days. Their lenses were removed and grown for 72 hours in test tubes. The test tubes contained either no or 100 micromoles of 4-hydroxy-2-nonenal (4-HNE). 4-HNE was used to artificially produce cataracts through a process called lipid peroxidation. As expected, 4-HNE caused clouding of the lenses. The lenses from curcumin fed rats were much more resistant to 4-HNE-induced clouding than were lenses from rats fed oil alone. The lenses from the curcumin fed rats contained significantly more glutathione S-transferase isozyme rGST8-8. By increasing this enzyme curcumin may have reduced the amount of 4-HNE, thereby reducing the cataracts. These studies suggest that curcumin protects against cataracts caused by lipid peroxidation.

Curcumin protects against 4-hydroxy-2-trans-nonena…[Am J Clin Nutr. 1996]