I am starting to believe that the guests of the Peter Attia podcast should have been perhaps more prudent in their suggestions. A product that tends to sensitize the skin to UV rays, even if it is applied only at night, and that requires rigorous protection from the sun… Maybe is a seasonal product only.
Here people go to the beach in the summer and on the shoreline the UV radiation just about doubles from sea surface reflection.
Oh, that reminds me, and I don’t recall them saying this… I’ve always heard that using vit c during the day can enhance the effectiveness of your spf.
I don’t remember exactly what they said (I have a memory like a sieve), but if they didn’t, to your point, they should have strongly emphasized that if you are not going to be really careful about your sun protection, then you should definitely not be using retinoids. If one is living your lifestyle, than I, too, would consider making it seasonal. I make it a point not to get sun 
Some of the newer UVA/B screens available in Europe and elsewhere are pretty unlikely to go systemic given their relatively large molecular size.
Actually, I’ve abandoned the beach lifestyle; my skin does not tolerate solar radiation any longer, for unknown reasons, I only tolerate radiation if the weather is cloudy or at sunrise/sunset. Or if I can start getting a tan from early March, very gradually. This does not worry me, since after a life of sun exposure, my skin should probably take a rest, I won’t force my luck in that the damage might have been far worse.
However, in the Summer and especially around the solstice the radiation can be very strong and to me it’s impossible to wear a hat or stay in the shadow or apply sun protection several times a day. So, no retinol sounds like the best option, then I’ll use retinol only at night from september/October. Here the specialists usually advise its use only by night, but then they might be conservative, better safe than sorry…
I might have misspoken, so if I did…
Yes, you are correct, retinoids should definitely be used at night, just as your local specialists advise.
Hello, I am new here, but after reading this thread (awesome by the way) I would like to contribute some information that may be useful.
I am on 0.5% Tretinoin protocol for the last 4-5 years. I am 57 and I live in the Mediterranean, so you can guess that I am constantly exposed to the sun.
I do tan (in the shade, but that does not shield UV-UA, just makes it more pleasant). I don’t normally wear sunscreen, except few dubs on my nose, cheeks and chin when I am on a beach.
Sun exposure is essential for vit D production, which is important for older females. No explanation needed.
With all of the above in mind, I am theoretically should be very prone to skin hyperpigmentation. I pair Retin-A with Azelaic Acid in the mornings and oral Astaxanthin. Azelaic Acid is known for suppressing melanin production. Astaxanthin does exactly the same - inhibits tyrosinase.
With a prolonged use it works perfectly. It is unclear how long it will work. I may develop age spots by age 70, but there are other methods to deal with that if needed.
I hope this information will be helpful.
No mispeakings, in my opinion, it has been an interesting exchange across different spheres of influence and geographical territories, and that to a significant extent does impinge on skincare practices.
I think that a plausible conclusion is that retinoids do need care in their use, and that with extreme care they might be used everywhere, although extreme care is hard to achieve in very sunny areas.
Hi Rose2025, welcome into this forum!
I do take oral astaxanthin plus polypodium, but as a sun protection strategy, unfortunately, the effect does not appear to be significant. Evidently, its protective effect as an antioxidant has little to do with shielding from sun radiation. As you imply, it may even have an inhibitory effect on the melanine pathway.
In my case, the topical Azelaic Acid may make a difference. First year of Retin-A use I was diligently avoiding the sun exposure. I did experienced significant peeling of the skin. On my second year, I guess, the body adjusted and now I do not have any of that. The skin on the face still has higher level of desquamation, but it just rubs off, not peels.
Also, if you are interested, the red light irradiation has a sun protective effect. The only thing about it, as with any device, one has to develop a habit to use it on daily basis. 
Welcome! Thanks for chiming in!
You only wear spf on your nose and cheeks… my vain self’s jaw is on the ground HA. (I just take vit d and my levels are in the 70’s).
We all have such different genes. I’m someone who needs spf just to have lunch outdoors, otherwise I would resemble a tomato I also know too many lifelong south Florida women who resemble leather. I imagine you don’t see that in the Mediterranean due to different genes, but now I’m curious, do you?
Curious, is there is a reason you use your tret in the morning vs pm? Or perhaps it’s only the AA you use in the mornings?
Also, for anyone who is interested, I use the Dermatica tret combined with niacinamide, but they also offer it combined with azelaic acid. I don’t have redness/rosacea, so I didn’t choose AA, but it’s a great combo product for those who need it. Fwiw, they also have one combined with hydroquinone for those who need the big guns.
@mccoy I’m just learning about polypodium for the first time… I’d never use it in place of spf, but google says it’s interesting. What do you feel the benefits are?
Also, I see it could potentially help vitiligo which a family member has… do you know anything about this? Thx
Two new news items that may be relevant. Fist is a new study out of Japan showing the effects of Vitamin C on skin:
As we age, our skin naturally becomes thinner and more fragile due to a decline in cell production. Now, researchers have found that vitamin C (VC) can help counteract this aging process. Using a 3D human skin model, they showed that VC boosts epidermal thickness by activating genes linked to cell growth through DNA demethylation. These findings suggests that VC may help prevent age-related skin thinning and support healthier, stronger skin in aging individuals.
(Vitamin C has poor skin permeability; but putting some in a solution that includes DMSO might help. Though, I don’t know how safe DMSO use is.)
Second is a paper on methods of inducing mammals to regenerate tissue (an ability mammals have lost but that, for example, some amphibians and reptiles have):
Systemically treating mice with retinoic acid boosted ear regeneration. Retinol, on the other hand, did not have that effect, because in retinoic acid synthesis, it lies upstream of ALDH1A2. Conversely, blocking RA synthesis in rabbits impaired their natural ability to regenerate.
My personal experience is that it does not provide the protection I hoped, that is, my tolerance to sun radiation is not increased by an amount I can perceive. This fern is however well known for its beneficial effects on the skin. What follows is a description from the Deepseek AI.
Based on current scientific evidence from credible sources (peer-reviewed journals, clinical trials, and reviews), here’s a breakdown of the benefits of Polypodium leucotomos (PL) extract as a supplement, specifically regarding skin protection and vitiligo:
Source Credibility: The information below is primarily drawn from:
Mechanism of Action:
PL is rich in potent phenolic compounds (e.g., chlorogenic acid, ferulic acid, vanillic acid, caffeic acid). Its primary mechanisms relevant to skin include:
Benefits for General Skin Protection:
Photoprotection (Internal Sunscreen Adjuvant):
Anti-Photoaging:
Protection Against Hyperpigmentation:
Benefits for Vitiligo:
PL has shown significant promise as an adjunctive therapy for vitiligo, particularly in stabilizing active disease and enhancing the effects of phototherapy:
Stabilizes Active Vitiligo:
Enhances Efficacy of Phototherapy (NB-UVB):
Reduces Phototherapy Side Effects:
Mechanism in Vitiligo:
Safety & Dosing:
Important Considerations & Limitations:
Conclusion:
Scientific evidence supports Polypodium leucotomos extract as a beneficial oral supplement for skin health:
Consistent use and combination with standard protective measures (sunscreen) or treatments (phototherapy) are key to seeing benefits. Always consult a healthcare professional before use.
Sorry to mislead you. I mentioned AA in the morning, that is true, and you guessed it right - I apply Retin-A at night as many do.
Skin sensitivity may also depend on the skin type. My is Fitzpatrick III. It must be different for I and II. They are more photosensitive. Besides after years of using Retin-A the structure of the skin changes. It is possible that with a prolonged use the RA affects melanocytes too by inhibiting their mobility.
I definitely do not look that those Florida women “rode hard put away wet”…I am originally from FL, so I know what you are talking about. There are some of those types here too. Mediterranean climate is more comfortable and no fire ants…lol
I’ve been testing a home made Indolepropionamide (IPAM) cream. I’ve had some good results:
This substance has never been tested topically before but it shows impressive lifespan results in rotifers. Currently being tested in worms.
Looks amazing! Maybe it’s time to try on face.
My thoughts as well. I know one other person who purchased IPAM to test it out topically, I think they’re doing their face.
I’m going to continue with the hand as it is a small surface area so I can get a concentrated amount here. It looks promising doesn’t it? If the beneficial effects keep occurring I’ll look into buying a larger amount and start putting it on my face or maybe just do an eye cream or something, of course with before and after photos.
I also am wondering if this could be put into a topical scalp serum for hair loss, or maybe gray hair reversal.
It would be silly to not look further into this.
tirbanibulin:
I would love to know if this is safe and effective, 2-3x better than Tretinoin?
The reduction in crepeiness is impressive. Do you notice that or is just the difference in lighting?
Hi @AustraliaLongevity -
Thanks for this info! Do you have a source for the IPAM and a recipe for your topical?
Thanks!
Sally
I 100% notice it. My skin looks shiny.
This is the cheapest IPAM I could find: Indolepropionamide Powder (IPAM) – pglchem
I put a tiny bit of this in a glass jar: Daily Moisturizing Lotion | CeraVe
Then I added a bunch of IPAM powder to it and mixed it thoroughly.
Only problem with this method is the IPAM didn’t fully dissolve. This is good, it means the effect I’m getting isn’t even from the best method of preparation of this cream.
What I would do differently in the future is dissolve it in glycerine first, then mix it with a moisturizer.
By the way if anyone does this themselves I request that they take before and after pictures in the same location in the same lighting. As far as I am aware I am the first person on the planet to create this topical. The more data we can gather the better.
