By JOE SCHWARCZ, Freelance July 11, 2010 Montreal Gazette
The toxin of the day is … retinyl palmitate! Avoid any sun protection product that contains it!
So says the Environmental Working Group (EWG), a non-profit, advocacy group dedicated “to bringing to light unsettling facts that you have a right to know.”
EWG does have some expert consultants, but its greatest expertise lies in garnering publicity for its pronouncements about toxins in our environment. The group also has expertise in the construction business, at least when it comes to making mountains out of molehills.
The usual ploy is to take some legitimate laboratory or animal finding and present it as evidence for human toxicity. The “uncovered” information is then widely publicized, and is usually accompanied by a plea for donations. EWG explains that it needs the funds to counter the muddled efforts of the Food and Drug Administration, which, either because of incompetence or veiled industrial influence, is failing to protect the public.
So what is retinyl palmitate? It is the naturally occurring storage form of retinol in the human body. Better known as vitamin A, retinol plays an important role in maintaining normal skin function. When added to creams or lotions, it can reduce the appearance of fine lines, giving the skin a more youthful appearance. But retinol is not particularly stable, so it is often added in the form of retinyl palmitate, which is converted first to retinol, then to retinaldehyde and finally to retinoic acid by enzymes in the skin. The latter is the actual active agent, enhancing collagen formation and increasing the rate of cell division.
Since collagen is an important structural protein in skin, and since more rapid turnover of cells leads to a larger number of more youthful cells, retinoic acid can be instrumental in improving the appearance of the skin.
Indeed, retinoic acid, as “tretinoin,” is often prescribed to treat acne, as well as to reduce wrinkles. However, topical retinoic acid can also cause skin irritation and increase the sensitivity of the skin to ultraviolet light, so its use is limited to prescription creams. Retinyl palmitate, on the other hand, is far less irritating, and can still deliver retinoic acid to skin cells, albeit in less effective doses than tretinoin. Since ultraviolet light from the sun is known to cause “photo aging,” it does make sense to try to mitigate this effect by incorporating retinyl palmitate into sunscreens.
What then is the fuss all about? It all starts with some animal and laboratory studies that have indicated an enhanced cancer-causing effect of ultraviolet light on skin treated with retinoic acid. Indeed, that’s why patients prescribed tretinoin are urged to use sunscreen liberally.
But interestingly, there are also studies showing a protective effect for retinoic acid against skin cancer! This is no great surprise, because vitamin A and its derivatives are known to promote free radical generation under some circumstances, and prevent their formation in others. Free radicals are those nasty electron deficient molecules generated in biological systems that are implicated in cancer as well as in the aging process.
Because retinyl palmitate is a precursor for retinoic acid, and because it is used in so many skin care products, it does merit scrutiny for possible carcinogenicity. Accordingly, the National Toxicology Program in the U.S. mounted several studies to this end, and it was the preliminary results from one of these that caused members of the Environmental Working Group to go into mental gyrations.
The study compared two groups of mice exposed to ultraviolet light -one group treated with retinyl palmitate, and the other not. While there was no difference in the number of tumours formed, the tumours did develop more rapidly in the retinyl palmitate group.
This was enough for EWG to crank up the fear-spewing machinery and trigger newspaper headlines that queried whether sunscreens protected against or caused cancer. “Sunscreen or smokescreen?” others asked in response to EWG’s allegation that the FDA was not forthcoming about the results of the carcinogenicity studies.
First of all, the study in question has not yet been published and has not been subjected to peer review, so drawing any conclusions from it is premature. Furthermore, the comparison was not between sunscreens that contained retinyl palmitate and ones that didn’t. A cream that contains only retinyl palmitate is not an appropriate model for a sunscreen preparation.
And why not mention a 2009 study that examined the combined effect of ultraviolet light and retinyl palmitate on hamster ovary cells, a protocol that is consistent with the current recommendations for effective testing of photogenotoxicity? This published, peer-reviewed study concluded that retinyl palmitate had no photo-genotoxic potential!
The fact is that you can take practically any chemical and construct a scary scenario by referring to the literature selectively. Want to show that oakmoss, present in numerous scented products, is phototoxic? No problem. How about lavender? Well, that’s estrogenic. And zinc oxide or titanium dioxide? These are two of the most effective sunblocks. They come highly recommended, justifiably, by EWG. But just dredge the literature and you’ll find that when exposed to ultraviolet light, they can trigger the formation of skin-damaging free radicals! Indeed, it wouldn’t be difficult to concoct a press release about the dangers of zinc oxide or titanium dioxide and scare people half to death. But it would be ridiculous. The benefits these compounds offer in protection from UV exposure far outweigh any risk.
Incidentally, retinyl palmitate is commonly added to milk to increase vitamin A content. This is an important health measure since vitamin A is important for vision, immune function, red blood cell formation and fetal development. Some ends up in the skin, yet nobody is, or should, raise the alarm about retinyl palmitate in milk.
With all that being said, I’m no advocate for retinyl palmitate in sunscreens. Frankly, I can’t find much evidence that in the amounts used it does much good.
But I am an advocate for proper scientific methodology and for making sure that the animal at the door is properly identified before crying wolf. Perhaps the people at the Environmental Working Group should take up zoology.
Joe Schwarcz is director of McGill University’s Office
for Science and Society ( www.OSS.McGill.ca).
He can be heard every Sunday from 3-4 p.m. on CJAD radio.
joe.schwarcz@mcgill.ca
