Upfront
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.
Retinal Physician, Issue: May 2006