Vitamin C protects against cataract

As we get older, the ability to see well often starts to fade due to eye problems such as cataract. In this report by Sade Oguntola, Vitamin C supplement and consumption of diets rich in other Vitamins like A and E can be protective against cataract.

IT seems like magic. Our eyes transform light into nerve signals that somehow tell our brains what we see. But as we get older, the magic often starts to fade due to eye problems such as cataract. There is growing evidence that the intake of certain foods and nutrients may help maintain healthy eyes. In addition to vitamin A which plays a role in eyesight, evidence suggests that vitamins C and E and the carotenoids lutein and zeaxanthin may be linked to a reduced risk for age-related eye diseases, in particular, cataracts.

Cataracts, found in nearly half of adults aged 65 years and above are created in the eye when proteins clump together and cloud the lens of the eye. They can cause blurred vision and poor night vision. The lens in the eye is composed of a transparent, jelly-like material that is rich in protein. Over time, the protein in the lens may become damaged, causing it to become cloudy. This process is similar to the change that is plain to see when the white part of an egg is cooked; while the white part of a raw egg white is transparent, it becomes opaque when the protein within it is damaged during the cooking process.

Researchers from Boston’s Tufts University studied data on 492 women aged 53 to 73, to see how nutrition will affect their risk of having cataracts. They found a significant link between age and vitamin C intake for risk of cortical cataracts, a very common form. For women younger than 60, a vitamin C intake greater than 362 mg/day reduced risk of cataracts by 57percent compared with those who had an intake less than 140 mg/day. Those who took vitamin C supplements for more than 10 years had 60 per cent lower odds of cataracts than those who took no supplements.

The lead author, Allen Taylor, a researcher with the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, in a comment on the finding, said: “This is interesting because recommended dietary allowances are considered to be significantly greater than the vitamin C intakes required to prevent vitamin C deficiency-related disease.” The study appeared in an issue of the American Journal of Clinical Nutrition. Another follow-up study from the same university similarly found that vitamin C, antioxidant vitamin, may reduce the risk of cataracts in women by as much as 77 percent.

In this study that tried finding out the long term effect of vitamin C on age-related lens opacities evaluated 247 women, aged 56 to 71. It found that women who had taken vitamin C for long periods of time showed fewer signs of cataracts. “Use of vitamin C supplements for 10 years or more was associated with a 77 percent lower prevalence of early lens opacities at any lens site and an 83 percent lower prevalence of moderate lens opacities at any lens site compared with women who did not use Vitamin C supplements,” the study said.

The study further suggested that vitamin C reduces the risk of cataracts because it acts as an antioxidant. Antioxidants are compounds that protect the body from the formation of oxygen free radicals — unstable oxygen molecules that can line the interior of blood vessels, thus restricting blood flow. The formation of free radicals can lead to an array of diseases. Vitamin C in particular may also protect the eye against damage from sunlight.

Vitamin C can be found in most fruits and vegetables, especially corn, blueberries, kale, spinach, oranges and beets, all of which have high concentration of antioxidants. Eating a variety of foods that contain vitamin C is the best way to get an adequate amount. It is found in fruits such as guava, kiwi, mangoes, oranges, strawberries, papaya, tangerines and grapefruit, and vegetables including tomatoes, peppers and broccoli, cauliflower and sweet potato, among others. Animal products contain almost no vitamin C. Some juices such as grape and apple have vitamin C added. Most ready-to-eat cereals are also fortified with vitamin C. Check the labels on the packages for the percentage of the RDA.

Vitamin C is highest in fresh, raw, foods as it is easily destroyed during food preparation, such as chopping, exposure to air, cooking, and when it is submerged in water. Because vitamin C is water-soluble and excess is flushed out, it is hard to get too much. However, many adults, including the elderly, do not get enough vitamin C in their diet. Many doctors recommend daily supplements of 250-500 milligrams of vitamin C for the best health benefits.

While the Tufts study on vitamin C showed the best results for women who had taken supplements of 400-800 milligrams daily, Dr. Susan E. Hankinson, Sc.D., Associate epidemiologist in the Channing Laboratory at Brigham and Women’s Hospital in Boston and other researchers at the Harvard School of Public Health an average intake of 250 to 500 milligrams daily gave a 45 percent less chance of developing cataracts In another study, people taking 300 to 600 milligrams of supplemental vitamin C a day experienced a 70 percent decrease in risk compared with people who were not taking as much.

“Our finding makes sense, because cataracts generally form over a long period of time,” Dr. Hankinson explains. “It’s reasonable to think that long-term use of preventive agents such as vitamin C would result in lowered risk.” Doctors who recommend vitamin C to people at risk for cataracts suggest from 500 to 3,000 milligrams a day. However, the National Institutes of Health (NIH), in a finding published in the Proceedings of the National Academy of Sciences, said that 200 milligrams of vitamin C might be an appropriate daily amount for healthy men. This is equivalent to eating five fruits and vegetables a day

It’s true that many doctors believe vitamin C is harmless even in high amounts. Ben C. Lane, O.D., Director of the Nutritional Optometry Institute in Lake Hiawatha, New Jersey, suggested that it may be wise to get at least some of your daily vitamin C from citrus fruits. That’s because chemical compounds called bioflavonoids, which are closely related to vitamin C and are found in the white membranes of oranges and grapefruit, also seem to offer antioxidant protection and, may even be more important.

Dr Ayotunde Ajayeoba, a consultant ophthalmologist at the University College Hospital, (UCH), Ibadan, confirmed that diets rich in certain vitamins, particularly vitamins A, C and E are beneficial to the eye in that they ate protective against some eye diseases like cataract. “These vitamins (A, C and E) are known as anti-oxidants. They have the ability to combine with substances known as “free radicals” in the cells during its metabolic process. Elimination of these “free radicals” relieve “oxidative stress” in the cells and refreshes “tired cells”,” he said.

He affirmed that since formation of cataract is due to a chemical reaction which leads to coagulation of proteins within the lens, consumption of diets rich in anti-oxidants that are known to delay or inhibit such reactions that lead to formation of cataract would be beneficial.