The old adage “you are what you eat” highlights the importance of a healthy, balanced diet for maintaining systemic health. Growing scientific evidence suggests that the role of nutrition extends beyond general well-being, and that diet can be an important determinant of the health of individual organs including the eye; and that, in fact: “your eyes are what you eat.” It’s hardly surprising then that as many as three-quarters of adults take dietary supplements for general or eye-health.1
The link between ocular health and nutrition is an exciting and evolving area of research; there is increasing interest in preventive nutrition and in providing an evidence-base for optimising dietary approaches for disease modification and long-term ocular health.
Blackmores Education Director and Naturopath, Pam Stone, said the research points to the role that certain nutrients play in the defence and protection and even in the treatment of some age related eye conditions.
“There have been a number of clinical trials, but one of the earlier ones that still stands out as groundbreaking research was the AREDS study – conducted over a six year period from 2001.”
The link between ocular health and nutrition is an exciting and evolving area of research
“That study took different groups with a high risk of developing advanced stage Age-related Macular Degeneration (AMD) and it showed one particular high dose anti-oxidant formula had the ability to slow down the rate of progression of the disease – so the quality of life that could bring to sufferers was immeasurable.”
That formula forms the basis of Blackmores Macuvision. The company also produced Lutein Vision Advanced, which contains lutein and zeaxanthin as well as selenium and omega 3 fatty acids.
Lutein and Zeaxanthin
Lutein and zeaxanthin are two dietary components that have been shown to be beneficial for retinal function. These yellow xanthophyll carotenoids are the only carotenoids present in both the macula and the crystalline lens. Their pigments have a specific spatial distribution within the retina; zeaxanthin predominates at the fovea, and is present in approximately twice the concentration of lutein.2 Dietary intake of zeaxanthin is derived from orange peppers, oranges, goji berries and tangerines,3 whereas lutein is the major carotenoid found in dark green, leafy vegetables (eg. spinach and kale), corn and egg yolks.4
The primary roles of lutein and zeaxanthin within the retina are anti-oxidant protection and the filtering of high-energy blue-light.2 Both of the macular carotenoids inhibit lipid peroxidation5 and reduce the accumulation of lipofuscin in cultured retinal pigment epithelial (RPE) cells.6 Their blue-light filtering properties optimise visual performance by reducing glare sensitivity, enhancing contrast acuity and improving colour vision.7 Research indicates that a higher dietary consumption of lutein and zaexanthin can produce an increase in macular pigment ocular density (MPOD).8-10 MPOD is an important measure of visual function; a higher MPOD has been correlated to a shortened photostress recovery time and reduced glare disability.7
There is also evidence that lutein and zeaxanthin supplementation can reduce the risk of AMD. The multi-centre Eye Disease Case-Control Study (1994) evaluated the relationship between dietary carotenoid intake and the risk of neovascular AMD and found that, following adjustment for risk factors, there was a 57 per cent reduction in risk of AMD in patients with the highest intake of lutein/zeaxanthin (6mg/day) compared with those with the lowest consumption (0.5mg/day).11 Other more recent studies have confirmed that supplementation with zeaxanthin and/or lutein can be beneficial for reducing the risk of progressive AMD.12-13 One such trial reported improved visual function measures in patients with AMD that were supplemented with 10mg/day of lutein alone or with co-antioxidants for 12 months; these changes were shown to be associated with improvements in MPOD.12
The results of the second Age-Related Eye Disease Study (AREDS-2) by the US National Eye Institute, a five-year multi-centre randomised trial evaluating the safety and efficacy of daily supplementation of carotenoids and polyunsaturated omega 3 fatty acids in retarding progression of AMD in at-risk patients, are highly anticipated; these data are expected to be released in 2013.
The bioavailability and retinal accumulation of carotenoids can be affected by multiple factors, including their source, method of preparation and other physiological factors such as gender, body fat, smoking, genetics and age.14,15 In Western diets, the average consumption of lutein and zeaxanthin combined is approximately 1–3mg per day.16 Although there are no specific guidelines with regard to the recommended dietary intake, current research suggests that an intake of at least 6mg per day is necessary to reduce the risk of AMD. To date no toxicities or adverse reactions have been reported in the scientific literature for lutein/zeaxanthin at doses of up to 40mg daily for two months.17 Carotenoid supplementation is currently considered appropriate for patients that are considered ‘at risk’ for developing AMD (ie. those with early drusen and/or experiencing symptoms that may be attributable to reduced MPOD, such as glare sensitivity, photophobia and reduced contrast sensitivity).
Stiltec released a supplement for AMD back in 2010 based on the AREDS formula with the addition of omega 3, lutein and zeaxanthin.
“Macutec is the first and only supplement to combine the AREDS-1 formula with omega 3, lutein and zeaxanthin,” said Steven Mann, Director at Stiltec. “Although we’re still waiting on results from AREDS-2, which have studied the benefits of these three ingredients on macular health, results from a number of other clinical trials have indicated their importance.”
The AREDS formula has been modified to reduce zinc levels to comply with Australian standards, remove beta carotene and replace synthetic Vitamin E with natural Vitamin E.
Beta-carotene
According to InterClinical Laboratories, the supplement Algotene is another rich natural source of mixed dietary carotenoid antioxidants.
Esther Lurie, Sales and Marketing Manager of InterClinical Laboratories, said Algotene was derived from an edible marine phytoplankton – or algae – called Dunaliella Salina.
“It’s an ocean algae that has been used as a ‘superfood’ for thousands of years by certain cultures living near warm climate waters,” Ms. Lurie said. “The algae is red as it is extremely high in antioxidant beta-carotene.”
Similar to Spirulina, the Dunaliella algae is farmed in saltwater ponds near Karratha in Western Australia.
InterClinical Laboratories claims the Algotene supplement has a myriad of benefits, including boosting immunity, energy and vitality and assisting in detoxification of the body, but the eye benefits are linked to its high beta-carotene levels.
Omega 3
Other major beneficial dietary components for ocular health are the long-chain polyunsaturated omega 3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).
Professor Algis Vingrys, Head of the Department at the School of Optometry and Vision Sciences at the University of Melbourne, says omega 3 and omega 6 fatty acids are called ‘essential’ because although they can’t be produced by the body, they are ‘essential’ for body functions. That means that they have to be ingested through your diet. “Omega 6 is essential to keep you alive but it doesn’t necessarily keep you in good health, whereas omega 3 does,” he said.
As the multiple systemic benefits of omega 3s are frequently reported in the media, many patients will be aware of their advantages. Several large-scale clinical trials have demonstrated the positive effects of these essential fatty acids for the treatment of heart disease18-19 and to enhance brain development during infancy.20 Within the eye, DHA and EPA are recognised to have a number of roles, including protection against oxidative damage, improving retinal photoreceptor membrane function, reducing inflammation and enhancing endothelial function.21
In relation to eye disease, the dietary consumption of omega 3 fatty acids has been shown to be inversely proportional to the incidence of AMD. A 2008 meta-analysis of epidemiological studies reported that a high intake of omega 3 fatty acids could reduce the risk of AMD by up to 38 per cent.22 More recently, the Women’s Health Study found that in a cohort of women who at baseline were not diagnosed with AMD, the regular consumption of DHA/EPA and fish was associated with a significantly reduced risk of incident AMD.23 Additionally, higher dietary intake of omega 3 fatty acids has been associated with a decreased incidence of dry eye.24
Thera Tears Nutrition blends flaxseed oil, which provides short-chain omega 3s that thicken the oil layer of the tear film, and fish oil, which provides long chain omega 3s that improve tear and salivary gland function. According to the company, a study has shown that as well as improving dry eyes, TheraTears Nutrition improves dry mouth.
This month (August), Stiltec will launch Lacritec, a supplement that has been developed off the back of several studies to help relieve this very condition.
Lacritec contains three different ingredients, each of which have independently been shown to have a positive effect on dry eye: gamma linolenic acid (GLA) – which is sourced from borage oil – and omega 3 and 6 fatty acids from fish and flaxseed oils. “People traditionally use eye drops to relieve dry eye which are more of a short term approach. Lacritec is a systemic approach that should be seen as complementary to eye drops, said Mr. Mann.
Experimental evidence suggests that omega 3s may be a useful adjunctive therapy for conventional glaucoma treatment.25
Research conducted by Dr. Christine Nguyen in conjunction with Professor Vingrys, has addressed an interesting concept she refers to as ‘the Japanese paradox’. That is, that the intraocular pressure (IOP) in Japanese people, as they get older, drops. In Western countries, the reverse is true – IOP goes up as people age, making Westerners more likely to develop glaucoma. Working on the presumption that a diet high in fish – or omega 3 – helped the Japanese and would be beneficial to IOP pressure, Dr. Nguyen raised rats on omega 3 deficient and replete diets and found that in the replete population, the IOP was 25 per cent less than in the omega 3 deficient group.
“This is about the same effect as you’d get with eye drops or surgery – so by modifying diet you can have almost the same effect,” said Prof. Vingrys.
“Dr. Nguyen also found that neurons became more robust and more able to withstand the insult of spikes by IOP that every person undergoes during day to day living. So ganglion cells function better on a diet high in omega 3.”
Dr. Vingrys said observations of rats in his labs have shown that omega 3 rich diets can also help prevent diabetes. “This is supported by epidemiologists who have found that Eskimos living on a traditional diet high in fish rarely get diabetes – yet as soon as they go on to a Western diet, they
get rampant diabetes.”
As essential omega 3 fatty acids cannot be synthesised by the body, their intake from the diet and/or supplementation is vital. Sources that are rich in omega 3s are certain fish (e.g. salmon, herring, sardines and tuna), canola oil and green leafy vegetables. Over-consumption of foods with high levels of the other type of essential fatty acids, omega 6s (e.g. sunflower oil and safflower seeds), which are common in Western diets, can result in the over-production of pro-inflammatory metabolites from this alternative pathway.
With regard to dietary consumption, it is recommended that for the maintenance of normal health, daily consumption of long-chain omega 3s (EPA and DHA) should be 500 mg/day, or one to two oily fish meals per week. Therapeutic doses, such as for the treatment of cardiovascular disease, are reported to be in the order of 1000mg/day.26 One important precautionary consideration with fish oil supplements is the potential for interaction with systemic medications such as warfarin and aspirin. Patients that use anti-coagulant therapy are therefore advised to seek medical advice from their general practitioner prior to commencing omega 3 fatty acid supplementation.
Eyecare professionals should also be aware that omega 3 takes a long time to express itself, due to what Prof. Vingrys terms ‘the omega 3 effect’. “When you’re treating dry eye or diabetes, omega 3 can take three to four months to kick in. This is because fat has a very slow turnover in the body,” he said.
“Additionally, the chemical structure of omega 3s makes them very susceptible to oxidation – so they need to be protected by an anti-oxidant – otherwise you can be doing more harm than good. The primary anti-oxidant that should be used is Vitamin E, which is usually included in commercially sold fish oil.”
Bilberry
One nutritional supplement currently attracting interest is Bilberry. According to Blackmores, Bilberry supports night vision and relieves eye fatigue and eyestrain that can be caused by daily computer use and fine detail work.
“Bilberry is a herb that, through analysis of science, we now understand to be active in delivering antioxidants and building tissue,” said Ms. Stone from Blackmores. “So it increases micro circulation and strengthens the capillaries, which helps relieve eye strain – it provides some level of support to people who spend their days working at computer screens, for example.”
Sydney ophthalmologist Goff Quinn said it looks promising. “Bilberry is an emerging product. There is limited epidemiological evidence that it strengthens pigments and there have been no side effects at the correct dose.
“I have colleagues I respect and they think it’s reasonable to take it – it’s a possibility for the future but we need bigger trials first… I’d like to see large randomised studies.”
Caution Required
Knowledge of the influence of nutrition on eye health is now an important element of optometric care. Educating patients about the importance and value of nutrition and dietary supplementation is complicit in providing holistic eye care that potentially has long-term benefits for both their general and ocular health.
Supplements always have recommended dosages on the packaging but according to Prof. Vingrys, the actual dosage should be determined on an individual basis, according to the patient’s age, sex and eye condition or risk factors.
As well as carefully considering dosage, eye care professionals recommending any supplement or prescription medication should do so in consultation with the patient’s GP to mitigate the risk of side effects or interference with other prescription medications or medical conditions. Bilberry, for example, can have a very mild blood thinning effect, and beta carotene should not be taken by smokers or by people who have been exposed to asbestos due to a potential risk of lung carcinogenesis. Omega 3 supplements can interact with a number of medications, including blood-thinning drugs such as warfarin.
Patient instruction is also vital. “When it comes to recommending supplements to patients who are on medications, a good rule of thumb is if you are prescribing anything with minerals, separate the dose by two hours from any prescribed medications – most minerals can have a binding effect in the gut to they may potentially lock onto the prescribed medication and slow its absorption,” said Ms. Stone.
For specific product information, eye care professionals should consult the supplement marketer. Optometrists can also refer to the Macular Degeneration Foundation for excellent research and good independent advice on AMD. The online resource PubMed (www. www.ncbi.nlm.nih.gov/pubmed) is also an appropriate source of information.
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Eye care practitioners can have an important role in the holistic management of patients’ eye health in the context of external, modifiable factors such as diet. The message to patients should be simple: exercise, eat fruit and vegetables, get enough rest and when it makes sense, supplement the diet with quality nutrients. And, of course, don’t smoke! “That’s a message optometrists can give – they’re in an empowering position with the contact they have with their patients to point out the lifestyle factors that influence our eyesight – we need to take a holistic approach,” says Pam Stone, Blackmores Education Director and Naturopath. “Our health is in our hands… we can influence what happens to our health as we age.” Ophthalmologist Godfrey Quinn agrees. “It’s important for optometrists to be able to talk to their patients about supplements because, combined with exercise and good diet, they do have a role to play in He said that unfortunately, the quality of advice on supplements varies enormously, “so when it comes to using supplements for eye health, it’s up to eye care professionals to learn the facts and offer judicial advice”. |
Vitamins and Supplements for Eye Health
(Click here for information on eye health supplements)
Dr. Laura Downie BOptom, PhD(Melb), PGCertOcTher, FACO, DipMus(Prac), AMusA is a clinical optometrist and contact lens specialist. She is a Fellow and Head of Cornea and Contact Lenses Services at the University of Melbourne, Department of Vision Sciences. Dr Downie has published several peer-reviewed scientific papers and is a regular contributor to mivision.
Melanie Kell is a senior writer for mivision.
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