Vitamin C (also known as ascorbic acid) is a water-soluble vitamin and a powerful antioxidant. Abundant in fruits and vegetables, especially citrus fruits.
Vitamin C is used to prevent and treat scurvy, a disease caused by vitamin C deficiency. Vitamin C helps the body not only build strong immune system but also repair and maintain connective tissue. Vitamin C is involved in collagen formation and enzymatic production of certain neurotransmitters.
Vitamin C plays a critical role in maintaining eye and vision health, of which not all of us are aware. Vitamin C is important to maintain the integrity of connective tissues and healthy blood vessels among the eye especially the cornea of the eye. In fact, researchers have revealed that high concentration of Vitamin C in retina is crucial for photocells perform efficiently.
Thanks to its powerful antioxidant capabilities, Vitamin C protects eye tissues from oxidative damages caused by free radicals, which is more important during advanced aging, reducing possible risks of degenerative eye conditions and impaired vision.
Vitamin C and Cataracts
Cataracts is a common age-related eye condition when protein builds up in the lens of eye and make the lens cloudy. Cataracts keeps light passing through lenses clearly, causing blurred vision, faded color or double vision. This may result in trouble driving, reading or recognizing faces, in serious cases, it may lead to blindness. Cataracts affect more than 24.4 million Americans age 40 and older. By age 75, approximately half of all Americans have cataracts according to American Academy of Ophthalmology.
It was discovered in one study that, during the baseline measurement, diets rich in vitamin C were associated with a 20% risk reduction for cataract. Scientists examined data for more than 1,000 pair of twins from UK and followed up with 324 pairs of twins about 10 years later. After 10 years, researchers found that women who reported consuming more vitamin C-rich foods had a 33% risk reduction of cataract progression. The study also found that 35% of the difference in cataract progression is attributed to genetic factors. However, environmental factors, such as diet, contributed to the remaining 65%.
According to American Optometric Association, “Numerous studies have linked vitamin C intake and decreased risk of cataracts. In one study, women taking vitamin C for 10 years or more experienced a 64 percent reduction in the risk of developing nuclear cataracts. Researchers estimate that by delaying the onset of cataracts for 10 years, half of cataract-related surgeries could be averted. Other research showed that women taking a daily supplement with a dosage of 364 mg experienced a 57 percent reduction in their risk of certain types of cataracts.” The association recommends taking a supplement with at least 300 mg/day vitamin C to help reduce the risk of cataract development.
In a meta-analysis study published on “Acta Ophthalmol” in 2016, the authors concluded “higher vitamin C intake and serum ascorbate might be inversely associated with risk of cataract. Vitamin C intake should be advocated for the primary prevention of cataract.”
Vitamin C and Age-related Macular Degeneration (AMD)
Macular Degeneration or Age-related macular degeneration (AMD) is an eye disease that can blur the central vision. AMD is a common condition and a leading cause of vision loss for people age 50 and older. AMD doesn’t cause complete blindness, but impaired central vision can make it harder to see faces, read and drive. AMD affects around 11 million Americans and it is expected to affect nearly 22 million by 2050. The risk of getting advanced AMD increases from 2% for those ages 50-59 to close to 30% for those over the age of 75.
The Age-Related Eye Disease Study (AREDS) was clinical trial sponsored by the National Eye Institute between 1992 and 2001. The AREDS was designed to learn more about the natural history and risk factors of age-related macular degeneration (AMD) and cataract and to evaluate the effect of high doses of vitamin C, vitamin E, beta-carotene and zinc on the progression of AMD and cataract. The study followed 3,640 individuals for an average of 6.3 years. The researchers concluded that high levels of antioxidants and zinc significantly (by about 25%) reduce the risk of advanced AMD and its associated vision loss. However, these same nutrients had no significant effect on the development or progression of cataract.
The AREDS study was followed by a second study AREDS 2 by the same research group in NEI to if AREDS formulation would be improved by adding Omega 3 fatty acids, substituting beta-carotene with Lutein and Zeaxanthin or reducing zinc. Beta-carotene had been associated with an increased risk of lung cancer in smokers in previous study.
The AREDS2 trial found that adding lutein and zeaxanthin or omega-3 fatty acids to the original AREDS formulation (with beta-carotene) had no overall effect on the risk of late AMD. However, the trial also found that replacing beta-carotene with lutein and zeaxanthin may help further reduce the risk of late AMD for people that has very little dietary intake of lutein and zeaxanthin. Low dose of zinc at 25mg provided similar benefits to lower the risk of progression of advanced AMD.
Dietary Sources of Vitamin C
Vitamin C is abundant in fruit and vegetables, including citrus fruits such as orange, grapefruit, lemons and limes. Vegetables such as red pepper, spinach, broccoli, tomato are also high in Vitamin C.