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Summarized here are some of the studies relevant to carotenoids and omega-3 fatty acids.
There are many reasons to be concerned about a potential rise in eye diseases. The higher incidence of diseases related to visual health is one. Diabetes in the United States is currently estimated to reach nearly 26 million people. Of these, potentially 40% have some level of retinal disease. And, the risk of developing eye diseases may reach an even higher number, as according to recent National Institutes of Health statistics, 35% of U.S. adults have prediabetes. Millions more either have or are at risk for developing heart disease, which in itself presents risks for developing eye diseases. Add to this the reality that eye strain and fatigue is at an all-time high, thanks to the time we spend sitting in front of our computers, cell phones, televisions, and other such devices, and it’s no wonder, then, that eye health is front of mind from a research perspective. The interest in researching natural compounds that have the ability to prevent vision loss and preserve visual function is at its peak and will continue to be as long as these problems persist in our population.
For several years now, natural compounds and dietary factors have been known to play a significant role in eye health. Bilberries have been renowned for their reported beneficial effects, dating back decades, on night vision. This has led to research on anthocyanins and other polyphenols, with the objective of investigating their role in eye health. Likewise, the results of the National Eye Institute’s original Age-Related Eye Disease Study (AREDS), showing beneficial effects of a supplement containing a combination of vitamins and minerals in reducing the risk of age-related macular degeneration (AMD), also precipitated interest in the use of natural compounds for promoting healthy visual function.
Recently, researchers’ interest has been piqued by investigations into the carotenoids lutein and zeaxanthin, as well as omega-3 fatty acids, including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), which show potential beneficial associations with eye health.
The newest AREDS trial, AREDS 2, is a clinical trial currently underway to assess the benefits of carotenoids and fatty acids for eye health. Enrollment in this multicenter clinical trial was completed in 2008; however, results are not expected for another three or four years. In the meantime, other studies have shed light on the positive role of these nutrients, both in epidemiological research and in prospective studies, on multiple parameters of eye health. Summarized here are some of the studies relevant to carotenoids and omega-3 fatty acids.
Lutein and zeaxanthin are the only two carotenoids present in the retina and lens of the eye. Results of epidemiological studies have found that dietary intake of lutein and zeaxanthin is associated with slowing the development of cataracts and AMD. This is significant because AMD is the leading cause of blindness in older adults.
Lutein and zeaxanthin form the macular pigment-with the highest concentrations found in the macula (the center of the retina)-and are efficient absorbers of blue light. By absorbing blue light, lutein and zeaxanthin prevent it from reaching structures in the eye responsible for visual function, thus preserving their integrity and conferring a protective role. It’s likely that these carotenoids provide direct antioxidant benefits by quenching free radicals that form in the retina.
Recent clinical trials also support the findings from epidemiological studies for the important role of lutein and zeaxanthin in eye health. Richard Bone and John Landrum from Florida International University investigated the effects of different supplemental doses of lutein esters on macular pigment optical density, said to be a biomarker of AMD, in a paper published in December of last year. In contrast to placebo, lutein ester supplementation in amounts of 5, 10, or 20 mg of lutein daily for 140 days were all found to increase macular pigment density, with higher rates of increase achieved with higher doses of lutein.
A study published in the British Journal of Nutrition in 2009 investigated the impact of lutein supplementation in 37 healthy Chinese subjects with long-term computer-display light exposure. These young adults received 6 mg of lutein/day, 12 mg/day, or a placebo, for 12 weeks. Serum lutein concentrations, visual acuity, glare sensitivity, and contrast sensitivity were measured at baseline and after 12 weeks. There was a trend towards improvement in visual acuity in the 12 mg/day group, whereas statistically significant increases in contrast sensitivity were also seen in the group supplemented with 12 mg of lutein/day, indicating that higher intakes of lutein have greater benefits on visual function.
Furthermore, a study conducted in Japan by Akihiro Yagi and colleagues found that a lutein, zeaxanthin, and blackcurrant extract supplement reduced symptoms associated with visual fatigue. In this double-blind, placebo-controlled crossover trial, individuals took the supplement or placebo daily for two weeks, following which treatments were crossed over. Visual fatigue was induced by a two-hour proofreading task, and each participant underwent four such testing sessions. The results of various tests indicated that the lutein supplement significantly reduced visual fatigue compared to placebo.
Omega-3 fatty acids, especially EPA and DHA, are essential for normal brain development and are highly concentrated in neural and retinal membranes. Inadequate DHA intake in animals during early development results in decreased concentrations in the brain and retina and affects nerve growth and development as well as visual function. Furthermore, omega-3 fatty acids have anti-inflammatory effects, reducing the development of atherosclerosis and improving blood viscosity and circulation through the cardiovascular system. Given the link between cardiovascular disease and AMD, the fatty acids EPA and DHA are likely to play significant roles in eye health and visual function.
Epidemiological investigations, such as one published in the December 2010 issue of Ophthalmology, assessed the association between fish and shellfish intake and the development of AMD. The assessment included a random sample of 2520 individuals ages 65 to 84 and found that those with advanced cases of AMD were much less likely to consume fish and shellfish-indicating a protective effect of omega-3 fats against advanced AMD.
John SanGiovanni and colleagues from the National Eye Institute investigated the protective effects of omega-3 fatty acid consumption in a cohort from the first AREDS study. The group consisted of 1837 individuals deemed to be at moderate to high risk for developing AMD. Participants from this cohort reporting the highest omega-3 intake were found to be 30% less likely to develop neovascular (or wet) AMD than their peers.
Similar results were found in an Australian investigation known as the Blue Mountains Eye Study, in which 3654 participants were examined at baseline, and 2454 of these individuals were examined five and/or 10 years later. The results indicated that regular dietary consumption of fish rich in anti-inflammatory omega-3 fatty acids along with lower intakes of foods rich in linoleic acid (a pro-inflammatory omega-6 fatty acid) were protective against early development of AMD.
Moreover, a paper published in March this year in Archives of Opthalmology by William Christen and colleagues examined the intake of omega-3 fatty acids and fish on the incidence of AMD in 39,876 female health professionals. These individuals were followed for an average of 10 years. Over the course of follow-up, 235 cases of AMD were diagnosed. It was found that those women with the highest DHA and EPA intake and highest intake of fish had the greatest level of protection against the development of AMD.
Other areas of eye health may also benefit from omega-3 fatty acid consumption and supplementation. Meibum is a compound secreted by the meibomium glands that functions to prevent the evaporation of the eye’s tear film, supporting optimal eye moisture. Meibum is composed of lipids and omega-3 fatty acids (as a component of meibum) that may thus confer benefits for preventing and treating dry-eye syndrome.
A review article authored by Elana Rosenberg and Penny Asbell and published in January 2010 identified eight studies investigating the effects of omega-3 essential fatty acids on dry-eye syndrome, six of which were randomized controlled trials. All of the studies examined confirmed a beneficial relationship between essential fatty acids and improving symptoms of dry-eye syndrome; however, the authors concluded that larger studies are needed to confirm the benefits.
More recently, a pilot, randomized, double-blind clinical trial conducted by Jadwiga Wojtowicz and colleagues assessed the benefits of a particular supplement containing 450 mg of EPA, 300 mg of DHA, and 1000 mg of flaxseed oil for dry eyes. The supplement or a placebo was taken daily for 90 days by 36 participants who completed the study. In the supplement group, 70% of participants became asymptomatic, whereas only 7% of the participants in the placebo group experienced such improvement. The omega-3 essential fatty acid supplement was found to increase tear production and tear volume, conferring moisture-enhancing benefits in participants with dry-eye syndrome.
While both classes of nutrients may benefit eye health on their own, their combined benefits may be even greater.
Elizabeth Johnson and colleagues from the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University investigated the influence of lutein and DHA supplementation for four months on macular pigment optical density in 49 women. What the research team found was quite interesting in that both nutrients individually increased macular pigment density; however, they found that lutein increased the pigment density peripherally in the retina, while DHA increased it centrally.
While additional research-such as the AREDS 2 trial-will serve to delineate these benefits, it’s likely that carotenoids and omega-3 fatty acids have complementary and synergistic effects.
More advanced research is also showing that several carotenoids other than lutein have beneficial impacts on macular health. Among these are different forms of zeaxanthin.
One commercially available combination of carotenoids, Lutemax 2020 from OmniActive Health Technologies (Short Hills, NJ), provides two nutritionally relevant isomers of zeaxanthin-3R, 3’R zeaxanthin and meso-zeaxanthin-in addition to lutein. According to Hiren Doshi, vice president of OmniActive, “These isomers are critical players in fighting the natural effects of aging and in supplying the macula with vital, protective nutrients. Together, lutein; 3R, 3’R zeaxanthin; and meso-zeaxanthin protect and support the macula of the eye for overall eye health.”
Lutemax 2020 is available for use in dietary supplement applications and has achieved self-affirmed GRAS (Generally Recognized as Safe) status, which means it can also be used in food and beverage applications.
Another exciting development regarding lutein in the nutraceutical industry concerns Kemin Health (Des Moines, IA) and its FloraGLO lutein product. A study conducted by James Stringham and Billy Hammond from the University of Georgia using 10 mg of FloraGLO lutein, along with 2 mg of DSM Nutritional Products’ (Parsippany, NJ) OptiSharp zeaxanthin, found improvements in a number of visual parameters, including increased tolerance for glare, faster recovery from glare, and better contrast. This study confirmed the benefits of lutein and zeaxanthin supplementation for healthy adults who struggle with glare while playing sports or spending time outdoors. These benefits may also translate to those who have issues with glare while driving at night.
The exciting news for Kemin doesn’t end there, however. According to Linda Fullmer, senior vice president, “The National Eye Institute has chosen FloraGLO for the currently ongoing AREDS 2 study,” a choice that Kemin is obviously very proud of.
Eye health is of serious concern to millions of individuals.The good news is that natural compounds, including carotenoids and omega-3 fatty acids, are significantly beneficial for promoting and preserving visual function. As research continues to define the exact roles of lutein, zeaxanthin, and EPA/DHA, current studies support a strong scientific basis for supplementation with these nutrients.
The high level of safety associated with carotenoids and omega-3s, as well as the commercial availability of several high-quality preparations, makes supplementing with these beneficial compounds a prudent and convenient choice for the nutraceutical consumer looking to maintain healthy vision with age.
By Jennifer Kwok, Editor
A lot of the ongoing work surrounding lutein and zeaxanthin are long-term efforts. These include developing more research as well as facing head-on regulatory challenges such as getting agencies like FDA and EFSA to officially recognize macular pigment optical density as a valid biomarker for age-related macular degeneration. However, there’s one project that is relatively simple, yet effective, and showing immediate results: increasing consumer knowledge of these ingredients and their benefits on eye health. To this end, suppliers are playing a role.
“For now, we’re providing opportunities for consumers to get the information they need about these ingredients,” says Abhijit Bhattacharya, COO for OmniActive Health Technologies.
Earlier this year, OmniActive announced a new consumer-awareness campaign it is offering along with its ingredients. For instance, the company has developed pamphlets that marketers using ingredients like Lutemax 2020 in their products can distribute to their customers. The pamphlets clearly explain the benefits and mechanisms of lutein and zeaxanthin for eye health, and the documents can easily be customized with a marketer’s logo and company information. OmniActive has also developed educational videos, which include a presentation by a nutrition and eye disease researcher at Tufts University, Elizabeth Johnson, PhD. The videos can be viewed online at the Lutemax 2020 website, www.lutemax2020.com.
Likewise, Kemin Health has embarked on a national marketing campaign for FloraGLO lutein and its merits for eye health. In addition to brochures, the campaign combines the efforts of strategic media; point-of-purchase information; and publicity from celebrity spokespeople such as blind national and world paratriathlete champion Aaron Scheidies, supermodel and wellness advocate Emme, world-class athlete Lolo Jones, and celebrity nutritionist Jennifer Galardi. Very importantly, the campaign also targets educating doctors and other health professionals.
Part of Kemin’s effort is also educating consumers about how much lutein they should be getting. “Research indicates that people need 10 mg of lutein every day through diet and eye vitamins,” says Kemin senior vice president Linda Fullmer. “Most Americans are only getting 2 mg or less through their diet alone….Too many people are still unaware that there are easy steps, like taking a daily eye vitamin, that can protect, prolong, and improve their visual performance.”
Such public outreach efforts may pay off. Bhattacharya says that as more consumers learn more about lutein and zeaxanthin, they are learning enough to look for relevant, efficacious levels of these ingredients in the products they buy. “If you have the right kind of science available and the information about making the right kind of choices available, you’ll provide consumers with the information they need,” he says.