It is widely understood that specific nutritional supplements can positively impact disease prevalence and progression, as well as visual outcome in patients with age-related macular degeneration (AMD). Yet, many nutritionists generally insist that actual food intake––rather than supplement use––may be the best source of nutrients to combat disease and promote wellness. In essence, nutritional supplements are just that: a supplement to––not a substitute for––a well-balanced, nutritious diet and healthy lifestyle.

So, what impact does a patient’s diet have on the likelihood that he or she will develop a progressive, sight-threatening condition, such as AMD?

The Research
Due to a wealth of evidence from several major studies including AREDS, TOZAL, the Lutein Antioxidant Supplementation Trial (LAST) and LAST II, we know the potential benefits of nutrient-based interventions for AMD.^1-4 AREDS was somewhat unique among these studies because, in addition to looking at the protective effect of specific nutritional supplements against AMD, its researchers collected extensive information regarding the dietary intake habits of the study population.

• AREDS report #22. Many individuals associate the “AREDS formula” with the research that was published in the original 2001 report, which suggested that “high levels of antioxidants and zinc” lowered the risk of vision loss from AMD and disease progression by 25%.⁵ However, more than 20 subsequent AREDS reports have further investigated the impact of nutritional supplementation and dietary alteration on ocular health.

In 2007, the AREDS research group released its 22nd report, which concluded that patients who have a higher dietary intake of the carotenoids lutein and zeaxanthin were at lower risk for the development of neovascular AMD, geographic atrophy, and large or extensive intermediate drusen.⁵ Additionally, the report indicated that increased intake levels of lutein and zeaxanthin decreased the progression of AMD, regardless of disease stage.

• AREDS report #23. In 2008, the AREDS researchers published data that suggested patients with bilateral drusen were 50% less likely to progress to central geographic atrophy following high dietary intake levels of omega-3 fatty acids (specifically DHA and EPA).⁶ It is important to note that the study was not specifically designed to determine how much EPA and DHA was “sufficient” to prevent disease progression.

• NHANES. The Centers for Disease Control and Prevention’s National Health and Nutrition Examination Survey (NHANES) evaluates overall wellness, nutrition and associated lifestyle habits (e.g., alcohol use, sleep disorders, smoking status) in American adults and children. The NHANES database is a valuable source of information that can be used to compare existing study results and/or stimulate further investigational trends.

One recent study analyzed NHANES data to look for trends between the food intake of different cultural groups and the associated risk for AMD development.⁷ The researchers concluded that Mexican Americans––who are at a relatively lower risk for AMD development than whites––had diets with a higher zeaxanthin to lutein intake ratio compared to individuals from other ethnic populations.

Nutrition in Clinical Practice
It is evident that overall ocular health and the prevention of degenerative macular disease are strongly linked to nutritional input, both in the form of food and dietary supplementation. And while we have a wealth of literature in these areas, it is sometimes challenging to incorporate all of this evidence into clinical practice––particularly when it comes to nutritional consultation. The sheer volume of information is intimidating. Further, it’s difficult to stay abreast of the most current study data, especially when some of the findings seem contradictory.

Our own unpublished survey data seemed to suggest that, while most optometrists do offer some form of nutritional counseling to their patients, many do not––due in large part due to a lack of sufficient knowledge about the subject.⁸ Interestingly, however, more survey
participants reported making the recommendation to “eat a variety of colorful fruits and vegetables every day” than “take an AREDS- or even an AREDS 2-formulated daily supplement.” More good news: Most practitioners who responded to our survey reported that they recommend smoking cessation to their patients with AMD.⁸ While these are positive trends, our results also clearly indicate a continued need to better integrate nutrition-based research findings into clinical practice.

We also have to consider the limitations associated with poor patient compliance. Although many individuals are aware of the benefits of eating adequate amounts of fruits and vegetables, a recent study showed that achieving––and sustaining––increased dietary intake levels of fruits and vegetables cannot be accomplished with behavioral interventions (goal setting, reminders, etc.) alone.⁹ Information from the NHANES database has shown that the average fruit and vegetable intake for American adults remains below recommended levels. More specifically, average daily intake levels of lutein via food sources is less than 2mg––far below the required levels to combat degenerative diseases, such as AMD.⁹ Even with the support of nutritional counseling, the average low-income American adult consumes an average of just 1.1 servings of lutein per day.⁹

What Can We Do?
Too often, patients who are at risk for AMD simply are instructed to take a multivitamin that contains lutein or an AREDS-formulated supplement.8 However, this advice might not be suitable for each patient, and may even be contraindicated (i.e., excess beta carotene intake in smokers). Further, patients are then faced with a bewildering array of supplement choices at their local retailers, with little to no information about the potential health benefits and risks, indications for use or dosing instructions.

So, it is critical that we actively partner with our patients to help them make informed choices about dietary consumption and nutritional supplement selection. Most importantly, we need to take a proactive stance and begin asking the right questions regarding our patients’ dietary and lifestyle habits before recommending any associated modifications. Keep in mind that such advice should be provided on an individual basis, rather than as a generalization for all patients.

Ultimately, however, being familiar with the research––and then analyzing and applying it in the context of the individual patient’s needs––will help you better incorporate nutritional education into optometric practice.

Thanks to Kimberly K. Reed, O.D., associate professor at Nova Southeastern University, for contributing this article.

1. Age-Related Eye Disease Study Research Group. The Age-Related Eye Disease Study (AREDS): design implications. AREDS report no. 1. Control Clin Trials. 1999 Dec;20(6):573-600.
2. Cangemi FE. TOZAL Study: an open case control study of an oral antioxidant and omega-3 supplement for dry AMD. BMC Ophthalmol. 2007 Feb 26;7:3.
3. Richer S, Stiles W, Statkute L, et al. Double-masked, placebo-controlled, randomized trial of lutein and antioxidant supplementation in the intervention of atrophic age-related macular degeneration: the Veterans LAST study (Lutein Antioxidant Supplementation Trial). Optometry. 2004 Apr;75(4):216-30.
4. Richer S, Devenport J, Lang JC. LAST II: Differential temporal responses of macular pigment optical density in patients with atrophic age-related macular degeneration to dietary supplementation with xanthophylls. Optometry. 2007 May;78(5):213-9.
5. SanGiovanni JP, Chew EY, Clemons TE, et al. The relationship of dietary carotenoid and vitamin A, E, and C intake with age-related macular degeneration in a case-control study: AREDS Report No. 22. Arch Ophthalmol. 2007 Sep;125(9):1225-32.
6. SanGiovanni JP, Chew EY, Agrón E, et al. The relationship of dietary omega-3 long-chain polyunsaturated fatty acid intake with incident age-related macular degeneration: AREDS report no. 23. Arch Ophthalmol. 2008 Sep;126(9):1274-9.
7. Johnson EJ, Maras JE, Rasmussen HM, Tucker KL. Intake of lutein and zeaxanthin differ with age, sex, and ethnicity. J Am Diet Assoc. 2010 Sep;110(9):1357-62.
8. Shechtman DL, Reed KK. Unpublished data on file.
9. Thomson CA, Ravia J. A systematic review of behavioral interventions to promote intake of fruit and vegetables. J Am Diet Assoc. 2011 Oct;111(10):1523-35.