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Paul Saladino
Quote from David on March 28, 2025, 1:27 pmThanks Grant. What do you think about this paper: https://pubmed.ncbi.nlm.nih.gov/14708621/
It seems to state the exact opposite. Hard to know what to think!
Hey @david-3,
I only skimmed the abstract, and I think it is just nuts that they claim there’s a photoprotective effect by absorbing ultraviolet radiation. What the heck do they think actually happens to that absorbed energy? I guess the laws of physics don't apply somehow.
Plants use these terpene based molecules (carotenoids) to absorb the maximum amount of energy from the sun. Whereas, us humans should not because it will basically cook the skin.
Microwave ovens work on a similar principle. Microwave radiation is absorbed by acryl molecules ( usually water) causing the 02 to spin about its polar bond, in doing so causes it to heat up.
Accumulating retinoids in the skin causes people to become very sun-sensitive and to burn easily. Been there, done that. Back in 2014 I could not tolerate 10 seconds of even moderate sun exposure.
Anyways, this study looks similar to the 2012 National Toxicology study that I went through in my eBooks, where 100% of the test mice exposed to retinyl palmitate and UV light quickly developed skin cancer.
Well, I read through both articles in detail, and I have to say that my article is way more convincing, imho.
For your article, the authors' reasoning is basically that retinoids can cause reactive oxygen species (ROS) when irradiated in a test tube, and we know that ROS can cause DNA damage, therefore retinoids in the skin are a potential danger. However, as far as actually in vivo studies, they only make the following statement: "The effects of topically applied RA on photocarcinogenicity in mice have been investigated by several research groups (42–47). The results are quite varied, with retinoid application increasing, decreasing, or having no effect on photocarcinogenesis." So, if you look up references 42-47 that they cite, these references all involve the use of topical retinoic acid. Well, who cares about the effect of retinoic acid in our skin? There is practically zero retinoic acid in our skin. 90% of the retinoids in our skin are retinyl esters, not retinoic acid, and the other 10% are retinol. Which brings us to the paper that I mentioned. In that paper, they didn't apply retinoic acid to the skin. Rather, they applied a retinyl ester, mimicking what the body does naturally. And using a retinyl ester, they then measured the effects on DNA damage in actual living mice and they measured the degree of sunburn in actual living humans, and they found that there was about a 50% reduction of the former, and a near complete resolution of the latter! To me, that is the proof in the pudding.
Yet, I do not doubt your experience and that of your followers. Could it be that there is a bell-shaped curve, whereby moderate amounts of retinyl esters in our skin are protective against UV exposure, but excessive amounts are somehow harmful? Maybe excessive amounts lead to the formation of retinoic acid?
On the other hand, to critique myself, the study that I cited used UVB only. However, 95% of the UV light we get from the sun is UVA, only up to 5% UVB depending on time of year. It could be that most of the teratogenicity comes from UVA.
The 2012 study Grant mentioned used xenon arc lamps, which better simulate the blend of UV in natural sunlight. But that study was hugely confounded by the carrier cream itself being highly carcinogenic.
So, as usual, the research shows a mish-mash of confusing and contradictory results, and we are left having to use common sense, and our own personal experiences.
Common sense tells me that our bodies are not stupid. They are putting retinoids in our skin for a good reason. That reason is either to protect us from UV, or it is to help us detoxify excess retinoids, or perhaps both. Who knows. Regardless, my plan is the same: stay on a very low vA diet until my serum levels go to the bottom of the normal range (but not below), stay at the bottom of the normal range for a year or so, and then perhaps add back reasonable amounts of vA foods, all the while getting lots of sunlight.
Yeah, I would never use a retinoid cream!