By Dr. Mercola
By the age of 80, more than half of Americans have cataracts or have had cataract surgery.1 A cataract is a clouding of the lens in your eye that affects your vision, and although they can often be treated with surgery, cataracts remain the No. 1 cause of blindness worldwide.2
It's quite telling that, according to the National Eye Institute (NEI), cataract removal is one of the most common operations performed in the U.S.
Your risk increases with age, and cataracts are often said to be a result of age, but just because they're common does not mean they're an inevitable part of getting older.
Recent research published in the journal Ophthalmology used data from 1,000 pairs of twins and found that while genetic factors explained 35 percent of the variation in cataract progression over a 10-year period, environmental factors accounted for the rest (which means they're more influential than genetics).3
In particular, vitamin C was found to play a protective role, and if you value your vision this is one vitamin you'll want to consume regularly.
Vitamin C Reduces Risk of Cataracts
Researchers from King's College London in the U.K measured the opacity of participants' cataracts over a 10-year period, starting when the participants were about 60 years old. They also surveyed the participants about their nutrient intake.
The first measurement revealed those with a high intake of vitamin C had a 20 percent lower risk of cataracts.
Ten years later, a vitamin-C-rich diet was linked to a 33 percent lower risk of cataract progression. Study author Dr. Christopher Hammond, professor of ophthalmology at King's College London, told Medical News Today:4
"The most important finding was that vitamin C intake from food seemed to protect against cataract progression. While we cannot totally avoid developing cataracts, we may be able to delay their onset and keep them from worsening significantly by eating a diet rich in vitamin C."
The study only evaluated dietary intake of vitamin C, although past research has also shown long-term vitamin C supplementation may also be useful.
According to research published in the American Journal of Clinical Nutrition, long-term use of vitamin C reduced the risk of early lens opacities — loss of transparency in a small area of the lens — by 77 percent.5
It also lowered the risk of moderate opacities by 83 percent in a group of women whose average age was about 62 years old.
In fact, none of the women who took vitamin C supplements for 10 years or more developed moderate opacities in the core of the lens. It's estimated that delaying the onset of cataracts for 10 years could cut the number of U.S. cataract surgeries in half.6
Vitamin C May Benefit Cataracts by Fighting Oxidative Stress
Vitamin C has numerous functions in the human body, including acting as an essential cofactor in enzymatic reactions.
In this way, it plays a role in your body's production of collagen (including collagen found in the cornea of your eye), carnitine (which helps your body turn fat into energy), and catecholamines (hormones made by your adrenal glands).7
Vitamin C is also used by your body for wound healing, repairing, and maintaining the health of your bones and teeth, and plays a role in helping your body absorb iron.
A powerful antioxidant, vitamin C also helps prevent damage caused by free radicals. Over time, free radical damage may accelerate aging and contribute to the development of heart disease and other health conditions.
It's through this antioxidant effect that it's thought vitamin C may play a role in reducing cataracts. It's thought cataracts may be related to oxidative stress, and vitamin C may work against oxidative stress by preventing free radicals from causing molecular damage to lens tissue, particularly its proteins.
How much vitamin C per day might be needed to gain its anti-cataract benefit? According to the American Journal of Clinical Nutrition study authors, 250 milligrams (mg) per day should saturate your eye tissue with vitamin C.
The American Optometric Association states at least 300 mg/day of vitamin C appears to help prevent cataract development.8 For comparison, one kiwi fruit contains about 64 mg of vitamin C.
Why You Should Get Your Vitamin C From Food
Vitamin C is a water-soluble vitamin, which means it doesn't get stored in your body and you must consume what you need from the foods you eat each day. Fortunately, vitamin C is relatively easy to find in a variety of foods.
Kiwi fruits are exceptionally high in vitamin C. Other foods high in vitamin C include: citrus fruits, red bell peppers, broccoli, Brussels sprouts, butternut squash, papaya, sweet potatoes, spinach and tomatoes.
You'll not only support your vision health by eating vitamin-C-rich foods; you'll also support your overall health.
Vitamin C is considered an anti-aging vitamin and actually reversed age-related abnormalities in mice with a premature aging disorder, restoring healthy aging.11 It has also been found to play a role in preventing the common cold, cancer, osteoarthritis, age-related macular degeneration, asthma and more.
Vitamin C May Prolong Proper Functioning of Your Retinal Cells
In 2011, researchers revealed that vitamin C may play a more important role in vision health than was previously recognized. Scientists at Oregon Health & Science University (OHSU) found that nerve cells in the eye require vitamin C to function properly.12
Study author Henrique von Gersdorff, Ph.D., a senior scientist at OHSU's Vollum Institute, said in a university news release:13
"We found that cells in the retina need to be 'bathed' in relatively high doses of vitamin C, inside and out, to function properly …
Because the retina is part of the central nervous system, this suggests there's likely an important role for vitamin C throughout our brains, to a degree we had not realized before."
When vitamin C was removed from retinal cells, GABA-type receptors in the brain, which help modulate communication between brain cells, stopped functioning properly.
The researchers believe GABA receptors elsewhere in the brain likely also require vitamin C for proper functioning, and that the antioxidant properties of the vitamin may "preserve the receptors and cells from premature breakdown."14
The finding could also have implications for people with glaucoma, which is caused by dysfunction of nerve cells in the retina and brain.
Von Gersdorff continued, "For example, maybe a vitamin C-rich diet could be neuroprotective for the retina — for people who are especially prone to glaucoma."15
How Else Does Vitamin C Benefit Your Vision?
Vitamin C is concentrated in eye tissues, where it supports the health of blood vessels among other uses. In addition to helping to prevent cataracts, research suggests vitamin C may lower your risk of age-related macular degeneration (AMD), a common cause of blindness among the elderly.
Like cataracts, AMD is thought to be largely driven by free radical damage. The Age-Related Eye Disease Study (AREDS), sponsored by the National Eye Institute, linked AMD with nutrition. It found that those at high risk who took 500 mg per day of vitamin C, along with beta-carotene, vitamin E and zinc, slowed the progression of advanced AMD by about 25 percent and visual acuity loss by 19 percent.16
The U.S. Food and Drug Administration (FDA) recommends only a modest amount of daily vitamin C—90 mg/day for men and 75 mg/day for women. You'll likely need more than this for vision health.
For instance, one study found women who consumed 362 mg or more of vitamin C daily had a 57 percent lower risk of developing cataracts by age 60 than women consumed less than 140 mg per day.17 People under stress also require more vitamin C than normal. This includes:18
✓ Smokers and alcoholics
✓ People under environmental stress (extreme heat or cold or radiation)
✓ People with diabetes and other chronic disease
✓ Pregnant or breastfeeding women
✓ Older adults
Bioflavonoids and Other Antioxidants for Vision Health
Vitamin C is just one type of antioxidant that benefits your vision. Others include bioflavonoids, which may have a complementary effect when taken along with vitamin C.
Fortunately, virtually every food that contains vitamin C also contains bioflavonoids, yet another reason why it's best to get your nutrients from whole foods. Excellent dietary sources of bioflavonoids include dark-colored berries, dark leafy greens, garlic, and onions.
Further, according to the journal Nutrition Reviews, "Epidemiologic literature suggests that the risk of cataracts can be diminished by diets that are optimized for vitamin C, lutein/zeaxanthin, B vitamins, omega-3 fatty acids, multivitamins, and carbohydrates."19 In short, other notable nutrients for vision health include:
Besides eating plenty of the nutrients above, carotenoids-rich vegetables, organic pastured egg yolks, omega-3 and astaxanthin-rich salmon are beneficial for vision health. Another really important dietary aspect is to normalize your blood sugar, as excessive sugar in your blood can pull fluid from the lens of your eye, affecting your ability to focus.
It can also damage the blood vessels in your retina, thereby obstructing blood flow. To keep your blood sugar in a healthy range, follow my comprehensive nutrition guidelines, avoid processed foods, as they tend to be loaded with processed fructose, and be sure to exercise regularly.