More is Not Always Better
Jason S. Slakter, MD
Not a day goes by in our offices that we are not confronted with patients carrying bags of vitamins and asking about the role of diet and nutritional supplementation in the management of their eye disease, particularly for age-related macular degeneration.
The issue of vitamin therapy for AMD is nicely addressed in this issue by Drs. Reddy and Fine. They carefully outline the information that is currently available from controlled clinical studies, both epidemiological and interventional in nature. They also appropriately point out that much remains to be learned in this area. In spite of the positive findings from the AREDS, the other trials have suggested a less dramatic impact of nutritional supplementation on the outcome of patients with AMD. The initiation of AREDS II, with its complex design intended to test multiple combinations of various micronutrients, should go a long way toward answering some of these questions.
So, given what we now know, what should we tell the patient with AMD or the family members of these patients with regard to nutritional supplementation? Certainly a thorough discussion of AREDS data and the role of nutritional supplementation should be carried out. Appropriate caution should be provided to those who are current and recent past smokers as well as individuals taking Coumadin and other drugs that may be affected by the vitamin supplements. We can suggest �all-in-one� combinations that are available from some of the pharmaceutical companies in the �AREDS formula,� or provide them with dosing instructions for beta-carotene, vitamins C & E, and zinc, thus allowing them to avoid components that may conflict with their own medical situation.
That�s the easy part, however, because usually patients� questions do not stop there. Patients with AMD, and family members as well, all want to know about other vitamins and nutritional supplements, such as, lutein, zeaxanthene, billberry, and omega III fatty acids. Often it is all too tempting to tell them �we just don�t know, so go ahead and take whatever you want.� After all, what harm is there in taking a little additional nutritional supplementation until we get more information. The problem is, however, that there indeed may be harm.
New Information on Dietary Supplements
A recent article in the British Journal of Ophthalmology from the Melbourne Visual Impairment Project suggests that higher dose dietary lutein and zeaxanthene intake may increase the risk of AMD.1 Specifically, researchers found that in patients with low levels of linoleic acid intake (omega III fatty acid found in flaxseed oil and other vegetable oils) there was a possible protective effect from high-dose lutein and zeaxanthene intake. However, when this same risk assessment was performed in individuals with a high linoleic acid intake, they found a harmful effect from increased lutein and zeaxanthene consumption. The researchers concluded their study by indicating that �based on these data, lutein and zeaxanthene could not be recommended.�
Proceed with Caution
Clearly, this is new and important information that will need to be carefully analyzed to determine its validity. In the face of the possibility that nutritional supplementation may be more complex than originally thought, there is a need for more vigilance on our part. I no longer believe that it is fair to say to patients �go ahead and take whatever you want� other than what is recommended in the AREDS trials. I think we owe it to our patients to pay more attention to the potential downsides of nutritional supplementation, both from point of view of interactions with medical conditions as indicated in AREDS, as well as with this new data that suggest varying doses of different supplements may have a positive as well as negative impact on each other.
Therefore, what should we tell our patients? I think the jury is still out. The best response may be a cautionary statement regarding our limited knowledge in this area, and perhaps the simplest and oldest recommendation of all, that is, �moderation in all things.� Truly, in nutritional supplementation as in other things in life, more is not always better.