Growing evidence shows a healthy diet improves and protects eye health

Nutrition for optimal eye health is an exciting area that has gained a huge amount of interest recently, and for good reason. Our ageing population, coupled with a decreasing death rate means eye care practitioners will be faced with an increasing number of patients suffering from age-related eye diseases in the future. The projected number of patients with age-related macular degeneration (AMD) is predicted to be 196 million in 2020, increasing to a whopping 288 million in 2040¹.

While new treatment options for conditions for AMD, dry eye and glaucoma are entering the market each year, prolonging eye health and prevention should be a primary focus. We need to be eye health practitioners in the fullest sense, and key to this is encouraging our patients to adopt a healthy diet to prolong the health of their eyes and their sight.

The evidence for diet

Epidemiological studies from the last two decades have shone some light on some of the risk factors associated with AMD, including smoking, ethnicity, age, diet, nutritional status, hypertension and also genetic markers². The ground-breaking, landmark Age-Related Eye Disease Study (AREDS), which began in 1992, closely followed 3640 patients over 6.3 years and found that taking high levels of antioxidants (vitamin A, C and E) and zinc can reduce the risk of developing advanced AMD by approximately 25% and can also reduce associated vision loss³. When considering the huge public health burden of AMD (including everything from treatment costs to falls in the elderly), this 25% reduction is significant. The success of AREDS began a cascade of new investigations into other potential supplements such as zeaxanthin, lutein, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), resveratrol and vitamin D in the prevention of AMD. One study showed progression of both dry and wet AMD is 25% less likely among those eating a diet rich in omega-3s, EPA and DHA. Plus, a high omega-3 diet combined with a low glycaemic index (GI) intake reduced the risk of progression to advanced disease even further, cutting it by 50%, while a high meat intake is associated with early onset AMD^4,5.

The Blue Mountains Study, a large 15-year population-based study in Australia, showed smoking is linked to both AMD and cataract. In fact, there is a four-fold increased risk of late-stage AMD among smokers compared with past or non-smokers and 10-year earlier onset⁶. The well-known Beaver Dam Eye Study also found an association of cigarette smoking with cataract and AMD⁷.

More recently, studies investigating vitamin D indicate it may play an important role in age-related disease. Vitamin D could have a function in immune regulation and barrier function in ocular barrier epithelial cells⁸. Macular thickness may also change in accordance with serum vitamin D concentration in older patients⁹. Furthermore, vitamin D is a powerful inhibitor of vascular neovascularisation¹⁰. With more than 50% of the world’s population at risk of vitamin D deficiency and decreased skin production of vitamin D as we age, it makes sense that vitamin D, with its role in combating inflammation, neovascularisation and fibrosis, might be the next contender to add to our list of supplements.

As well as AMD, theirs is also an abundance of nutrition and lifestyle research relating to other common age-related diseases, such as glaucoma and dry eye disease (DED). While there are no environmental factors clearly associated with primary open angle glaucoma¹¹, several studies have found risk factors relating to DED, such as age, sex, systemic disease (arthritis, diabetes and thyroid disease) smoking and medications (aspirin and antidepressants)¹². Higher intake of omega-3 fatty acids is associated with decreased DED incidence in women¹³. While both systemic and topical omega-3 and omega-6 fatty acids have showed promise as treatments in dry eye, omega-3 supplements remain the mainstay for nutritional management of DED today.

Taking an educator role

As eye health practitioners, we need to keep abreast of nutritional research developments and be proactive in educating patients on how to maintain their own eye health. Asking patients whether they smoke for instance and giving appropriate nutritional advice could have a major impact years down the line. So, it’s important patients understand the association between diet and lifestyle and the health of these incredible ocular organs so they can keep an eye on their diet and go for regular eye check-ups.

To this end, NZ Optics’ brings you our first feature dedicated to nutrition. With the help of Grant Watters, we look at some potential new nutraceuticals in the wings, which may help slow eye ageing and better protect our eyes against dry eye, presbyopia, cataract and macular degeneration; celebrity nutritionist Dr Libby Weaver discusses what to eat for eye health; and we take a peep inside the world of one of our own ocular nutrition scientists, Andrea Braakhuis, whose fascinating research on oxidative stress disease demonstrates the correlation between high meat consumption and eye disease. For the cooks among you, we even have a delicious recipe for you to try from the Feast your eyes cook book. Hopefully it will inspire us all to do a little more for ourselves and for our patients.

References

1. Wong, Wan Ling et al, Global prevalence of age-related macular degeneration and disease burden projection for 2020 and 2040L a systematic review and meta-analysis. The Lancet Global Health, Vol. 2, Issue 2, e106-e116.
2. Fletcher AE (2009). Healthy Ageing: The Eye. In: Stanner et al (eds). Healthy ageing: the role of nutrition and lifestyle. Wiley-Blackwell, Oxford, 2009.143- 158.
3. The Age-Related Eye Disease Study Research Group. A randomized, placebo-controlled, clinical trial of highdose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss. AREDS report no. 8. Arch Ophthalmol 2001;119:1417–36.
4. Chiu C-J, Klein R, Milton RC et al. Does eating particular diets alter risk of age- related macular degeneration in users of the age-related eye disease study supplements? Br J Ophthalmol 2009;93:1241-1246.
5. Chong EW, Simpson JA, Robman LD et al. Red meat and chicken consumption and its association with age-related macular degeneration. Am J Epidemiol 2009;169:7 867-76.
6. Multiple papers from the Blue Mountains Eye Study, including Cumming RG, Mitchell P, Smith W. Diet and cataract: the Blue Mountains Eye Study. Ophthalmology 2000 Mar; 107(3): 450-6; and Moshtaghiam H et al. Trends in added sugar intake and food sources etc. J. Hum Nutr Diet 2017 Jun: 30(3):339-348
7. Klein, R et al. Am J Epidemiol. 1993 Jan 15;137(2):190-200.The Beaver Dam Eye Study: the relation of age-related maculopathy to smoking.
8. Alsalem, JA. Characterization of vitamin D production by human ocular barrier cells. Invest Ophthalmol Vis Sci. 2014 Apr 7;55(4):2140-7.
9. Alsalem, JA. Characterization of vitamin D production by human ocular barrier cells. Invest Ophthalmol Vis Sci. 2014 Apr 7;55(4):2140-7.
10. Albert, D. et al. Calcitriol is a potent inhibitor of retinal neovascularization. Invest Ophthalmol Vis Sci. 2007 May;48(5):2327-34.
11. Pasquale LR and Kang JH. Lifestyle, nutrition and glaucoma. J Glaucoma 2009;18:6 423-8.
12. Scot E Moss et al. Arch Ophthalmol. 2000;118(9):1264-1268. doi:10.1001/archopht.118.9.1264 Prevalence of and Risk Factors for Dry Eye Syndrome
13. Miljanović B, Trivedi KA, Dana MR et al. Relation between dietary n-3 and n-6 fatty acids and clinically diagnosed dry eye syndrome in women. Am J Clin Nutr 2005; 82:4 887-93.

Ella Ewens is an optometrist at the Greenlane Clinical Centre who has a particular interest in nutrition for eye health, having lectured in the UK about this as part of her previous role as medical affairs manager with J&J.