Which nutrients best support healthy vision?

Vitamin C
Vitamin C is an antioxidant found in fruits and vegetables. It supports healthy capillaries, gums, teeth, and cartilage. Vitamin C can be found in virtually every cell in the body, and its concentration is significantly higher in the retina than in the blood. Since the human body does not make vitamin C, it must be consumed as part of the diet.

Zinc
Zinc is a trace mineral that is found in high concentrations in the eye. It plays a critical role in transporting vitamin A to the retina. Zinc deficiency has been linked to poor night vision and cloudy cataracts.

Lutein & Zeaxanthin
Lutein and zeaxanthin are carotenoids and both serve as antioxidants, which help to neutralize free radicals and reduce oxidative stress. While neither of these nutrients were included as part of the original age related eye disease study (AREDS), the National Eye Institute is currently conducting a second study (AREDS2) to confirm if a supplement containing 10mg of lutein and 2mg of zeaxanthin reduces the risk of developing AMD.

Omega-3 Fatty Acids
Fats are an essential part of the human diet. The two families of essential fatty acids are omega-3 fatty acids and omega-6 fatty acids. Most individuals get enough of the essential omega-6 fatty acids; however low intakes of omega-3 fatty acids is common, particularly Docosahexaenoic acid (DHA) and Eicosapentaenoic acid (EPA). These fatty acids are important in many aspects of health, including: membrane structure, neural development, regulating heart rate, blood pressure and inflammation.
DHA is found in high concentrations in the retina. It has been shown that dietary deprivation of DHA in animals can result in visual impairment and retinal degradation. In addition to lutein and zeaxanthin, DHA and EPA are also being studied in the AREDS2.

Studies
Over the past two decades, there have been a significant advances in research related to nutrition and eye health. Researchers have a better understanding of how nutrition helps promote healthy vision and decreases the risk of developing age-related eye disorders.

AREDS is a study that was sponsored by the National Eye Institute. Research had previously linked eye health and nutrition, but they wanted to look more in depth at the potential connection. According to the research group, their purpose was 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 antioxidants and zinc on the progression of AMD and cataract.” The study involved 3640 subjects, age 55-80. The subjects in the test group were administered daily amounts of 500 mg vitamin C, 400 IU vitamin E, 15 mg beta-carotene (25,000 IU vitamin A), and 80 mg zinc*. The results showed that supplementation slowed AMD by 25% and visual acuity loss by 19% in high risk individuals. These results have since been confirmed in several smaller studies. In the years since the original AREDS study, new research has also shown beneficial results from lutein, zeaxanthin, DHA, and EPA.

AREDS 2, which was published in 2013, tested several variations of the original formula. One was using lutein/zeaxanthin instead of beta-carotene, one included fish oil, and one included a significantly reduced zinc level (25 mg). Removing the beta-carotene did not affect the outcomes, so it concluded that lutein and zeaxanthin were safe and effective alternatives to beta-carotene. The reduced zinc level (25 mg) was just as effective as the high zinc formula. Adding EPA and DHA (omega 3 fatty acids) did not provide any additional benefit in reducing ARMD progression. So, based on the actual results of the study, it would make sense to use lutein and zeaxanthin in place of beta-carotene, limit zinc dosage to a safer level, maintain the same or similar levels of vitamin C, E and copper, and eliminate the EPA and DHA.

Another landmark study was the Lutein Antioxidant Supplement Study (LAST) published in the journal Optometry. The results of this study showed that AMD symptoms may be improved through purified lutein supplementation or a supplement mix of lutein and other antioxidants such as vitamin A, vitamin C, vitamin E, and beta carotene. The dosage of lutein and zeaxanthin used in the study were 10 mg and 2 mg respectively.

Stringham JM, and Hammond BR performed a study on 40 healthy subjects with an average age of 23.9. They were assigned to receive daily supplements of lutein (10 mg) and zeaxanthin (2 mg) for six months. The subjects’ eyes were then tested for the effects of glare as experienced in everyday situations, including being outdoors on bright days, lengthy sessions of looking at a computer monitor, and nighttime exposure to oncoming headlights. Following six months of supplementation, the participant’s average macular pigment optical density (MPOD) increased significantly from the average value at the beginning of the study. Higher MPOD has been linked to increased visual acuity. After testing the subjects for their performance in visual tasks researchers concluded that four to six months of supplementation with lutein and zeaxanthin significantly improved visual performance in high glare situations.

In another study involving more than 100,000 participants from the Nurses’ Health Study and the Health Professionals Follow-up Study. All participants were aged 50 years or older and were free of diagnosed AMD, diabetes mellitus, cardiovascular disease, and cancer (except non-melanoma skin cancer) at baseline. The researcher’s analyzed carotenoid intake based on dietary food frequency questionnaires at baseline and follow-up, and then calculated predicted plasma carotenoid scores. The results of this study found that participants with the highest average plasma lutein and zeaxanthin levels had a 40% reduced risk of developing advanced AMD compared to those with the lowest average levels. “Lutein and zeaxanthin form macular pigments that may protect against AMD by reducing oxidative stress, absorbing blue light, and stabilizing cell membranes,” the authors explain.

References

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