As a family physician, I have noticed a familiar refrain from patients seeing me after seeing their eye professional.
“Dr. X told me to take 5000 units of vitamin D”
“Dr. X told me to take omega-3 every day for my eyes”
“Dr. X told me to start Macuhealth”
My patients will typically ask me for my opinion about these supplements because they know I try to keep up to date from a variety of resources and will be able to give them an evidence-based opinion that respects their pocket book.
WIth the exception of the AREDS2 formula for macular degeneration (and 1 small RCT showing benefit of omega-3 supplementation in dry eye syndrome), the evidence for supplementation in the treatment and prevention of eye disorders is of poor quality. It is generally a hodgepodge of animal studies, small human studies, and proposed “mechanisms” to rationalize an effect.
So in the context of poor evidence, why are seeing such zeal from these health professionals about supplements? I am confident that the majority are not advocating for supplements out of any malice or any financial interests.
I had an interesting discussion this week with a local optometrist. We share many patients, many of whom have told her my opinions on the supplements that she recommends. She seemed genuinely convinced by the evidence she has read, and provided me with her two favourite resources: Vitamin D Wiki and GrassRootsHealth. She encouraged me to check out both, sure that I would be convinced by the overwhelming content on both sites.
After only a couple of minutes of perusing the sites, I noticed a glaring problem. Where were the negative studies? Both sites fanatically promote vitamin D deficiency as a plague in our society, and believe in supplementation as a panacea to our ills. They link to hundreds of studies of generally poor methodological quality, and most favour a benefit to vitamin D. But any negative studies they include are followed by multiple points that question the validity of the study (like this one). They are not critical of positive studies with the same skepticism. It’s all studies showing benefit, without a whisper of dissent.
And if you’re supposedly the #1 resource for all things vitamin D, shouldn’t this article be on your front page this month?
These resources are written by vitamin D believers. They see any evidence through the lens of someone who already believes in vitamin D. If it is counter to their belief, it is ignored. If it supports vitamin D, it is promoted. Quite simple. That’s quackery, not science.
The GrassRootsHealth website is particularly egregious, as they feature a link to Mercola’s supplement store, and also sell vitamin D tests to consumers, the profits of which go to further vitamin D advocacy. It’s a vicious cycle of supplementation. (Aside: if you link to Joe Mercola, you have lost scientific credibility until proven otherwise).
The Macuhealth product endorsed by many optometrists is another interesting study in questionable promotion methods. Check out their website. All promotion, little evidence. And the evidence they do provide is largely mechanism-based theory, not showing the hard clinical endpoints that we would expect from a product. The link on their site for health professionals to “become a provider” is an automatic red flag. What would my patients think if I were to sign up with Pfizer to “become a provider” for Viagra? The potential conflict of interest would be enormous.
So I ask all eye professionals to be skeptical. Don’t recommend supplements out of a sense of “needing to do something”. Patients deserve to receive evidence-based advice, and to have their pocket books respected. It is an uncomfortable feeling to have patients with vision-threatening disease and not take a flyer on a potential “cure”, but we need to take a critical, science- and evidence-based approach to our recommendations.