Nutritional balancing act: More isn’t always better

Americans indeed know the importance of getting enough vitamins and nutrients, but a counterintuitive 'more-must-be-better' mindset can lead some into trouble.

Published Oct. 27 in JAMA Ophthalmology, a recent case report from the Moran Eye Center at the University of Utah illustrates what can happen when a patient takes his or her nutritional supplements above and beyond the recommended threshold.

The report describes a patient in her 60s with no age-related macular degeneration (AMD) presenting with bilateral intraretinal glistening deposits in the inner layers of her foveal region. It was determined that for the past eight years, the patient took a daily 20 mg lutein supplement—twice the generally agreed upon dosage—on top of consuming a lutein-rich smoothie daily, which included broccoli, kale, spinach and avocado.  

Lutein and zeaxanthin, carotenoids found in green, leafy vegetables, are antioxidants located in the eye that can reduce the risk of chronic eye disease, including AMD and cataracts. In fact, the Age-Related Eye Disease Studies (AREDS and AREDS2) found that taking certain nutritional supplements every day could reduce the risk of developing late AMD, but it only identifies the benefits of daily 10 mg lutein intake.  

"When we looked at the patient's carotenoid levels in serum, skin and the retina, all measurements were at least two times greater than carotenoid levels in patients not taking nutritional supplements," says study lead author Paul Bernstein, M.D., in a news release.  

After stopping her daily lutein supplement for seven months, the foveal crystals began resolving in the patient's right eye along with decreases in skin carotenoid levels, serum lutein and macular pigment, the study notes. Authors caution that a larger clinical trial is necessary to categorically determine whether lutein consumption above recommended levels can lead to negative effects, and encouraged an eye-healthy diet rich in fruits and vegetables. 

Supplement familiarity

Although 9 out of 10 Americans get healthy amounts of vitamins and nutrients through their diet or supplements, research shows that less than a quarter of supplements used by adults were recommended by a health care provider. This lack of physician input not only creates confusion about supplements' benefits, but also their appropriate use.  

Steven Newman, O.D., a certified nutrition specialist and advisory board member to the Ocular Nutrition Society, calls this case study an isolated event, but one that reinforces the need for better nutritional education.  

"They're called supplements for a reason," Dr. Newman says. "Many times, doctors recommend supplements without knowing the diet they're supplementing. This really isn't dangerous, but it's not recommended. However, in this case, the patient was overdosing on something normally healthy for her because the proper questions weren't asked."  

Of the 600 carotenoids found in nature, only lutein and zeaxanthin are deposited in high quantities in the macula. However, the body doesn't naturally produce these carotenoids, instead relying on dietary intake.  

Dr. Newman explains lutein and zeaxanthin prove effective against eye diseases, such as AMD, because the antioxidant nutrients neutralize free radicals associated with oxidative stress and retinal damage. But healthy eye nutrition isn't solely limited to lutein and zeaxanthin. Nutrients such as vitamin C, vitamin E, zinc, Omega-3 and lycopene all play roles in reducing risk of certain eye diseases.  

"We're not only talking about green, leafy veggies, but those tomatoes on your salad, too," Dr. Newman says.  

AMD and the Mediterranean diet  

Ongoing research suggests the popular Mediterranean diet, with its heart-healthy menu of plant-based foods, oils, fish, lean meats and whole grains, could reduce the risks of developing AMD by more than one-third.

New data from the Coimbra Eye Study shows the risk for macular degeneration was 35% higher for trial subjects who loosely or didn't adhere to a Mediterranean-style diet, and those not committed to the diet were 10% less likely to consume fruit. This last point is particularly noteworthy considering the study showed those subjects who ate the equivalent of two apples each day benefited from a 20% decrease in AMD risk.  

"We know the Mediterranean diet is going to help with hemoglobin A1C levels and your other cardiovascular diseases," Dr. Newman says. "AMD is a cardiovascular disease—even if it's not coded as such—and by taking care of your blood vessels with the Mediterranean diet, it doesn't surprise me that we find this correlation."  

Read more about ocular nutrition in the July/August 2015 edition of AOA Focus.