Vitamin C and eye health:
Age-related macular degeneration (AMD) is an aging change in the back of the eye that may lead to loss of the central vision. Antioxidants including vitamin C, 500 mg; vitamin E, 400 IU; beta carotene, 15 mg; and zinc, 80 mg as zinc oxide with 2 mg of cupric oxide) may be beneficial in reducing risk of AMD progression as seen among Age-Related Eye Disease Study (AREDS) participants. (14)
Vitamin C and colds:
When vitamin C was tested for treatment of colds in 7 separate studies that included 3294 cold episodes, vitamin C was no more effective than placebo at shortening the duration of cold symptoms except in one study that found patients taking 8g of vitamin C when cold symptoms started had shorter colds than those taking 4g. A review of 30 prevention trials (N=11,350) revealed that, while severity remained unchanged, when taken daily at 1g, vitamin C very slightly shortened cold duration—by 8% in adults and 18% in children. This means a shorter cold episode by 1.5 to 2 days assuming the typical cold runs 7 to 10 days. Finally, researchers found the most effect in subjects who were in extreme conditions, such as marathon runners. In this group of 642 individuals (6 trials), taking vitamin C at 200 to 2000 mg/d cut their risk of catching a cold in half. (15)