I used to wear long sleeve lightweight wicking fabric t-shirts in summer -- inexpensive stuff from Champion, or Under Armor and others if I could snag a bargain at Marshall's or Ross. Didn't feel any hotter than going bare-armed.
And I have a Pearl Izumi snug fitting long sleeve jersey of ultra-thin material that's supposedly SPF 30. It's comfortable in all weather.
But my docs have been fretting at me over premature bone density loss, low vitamin D, calcium, etc. Full body scans (MRI or CT, I don't remember which) revealed I had a bunch of healed fractures that I wasn't aware of because I rarely visit a doctor or the ER for falls and impacts that I thought were just bumps and bruises, or rib injuries that can't be treated anyway if there's no compound fracture or perforation of organs. And supplements weren't helping. So after a year and reading a bunch of PubMed studies (not all were credible or peer reviewed, but some were useful), I decided to try a different approach.
Conventional wisdom said I needed sun to kick start my body into making vitamin D and hopefully improving my bone density.
Other studies indicated sunscreen might not even prevent skin cancer, and that there may not be any evidence of a connection between sun exposure and skin cancer. This was all new to me and I'm still skeptical.
But I was willing to give it a try.
I ride in midday summer heat with regular short sleeve jerseys (and I plan to get at least one sleeveless) and don't wear sunscreen. Nada. I just let the sun do its thing. My rides range from an hour to 4-5 hours.
The weirdest part of this experiment is I don't sunburn anymore. I used to burn like kindling at the slightest hint of sunlight. If I wore sandals the first day in summer, within 15-30 minutes I had beet-red stripes wherever there were gaps in the sandals.
But some of the studies I read (again, not all were peer reviewed and might be considered, at best, educated guesswork by qualified scientists) indicated that it's possible to affect our sun sensitivity through diet and body fat. Specifically, by lowering our sugar and alcohol intake and reducing body fat, we may be less vulnerable to sunburn.
I figured it was worth a try so I did that in springtime last year, 2019, fully expecting to go home cherry red and needing that lidocaine sunburn spray I already had in the bathroom.
Nope, I just tanned. No burn. I repeated that several more times. Same results. I just tanned. No sunscreen.
Looking back, it seemed like my worst sunburns occurred after I'd put on weight, ate a lot of sugary stuff, drank beer, etc. By the late 1990s I got up to 205 lbs for a few years when I seemed to burn worst. My optimal weight is around 150 so that's significantly overweight for me.
Resuming bike riding in 2015 got my weight down to 175, then 160 and stayed there through 2017. I ate and drank whatever I wanted, as much as I wanted.
Then thyroid cancer in 2018 made it really difficult to swallow so for much of that year I was on a liquid diet and soft foods. And the thyroid failure seemed to kill my ability to metabolize alcohol. I loved good beer and rarely got more than a mild buzz no matter how much I drank. But after the thyroid thing a single beer made me feel sick and hungover within an hour or two. So I switched to a mostly vegetarian, high protein diet that year. My weight dropped to 150. I've since switched to a more meat-heavy diet now that I can swallow again. But I'm still avoiding alcohol, sugar and most carbs, although I'll eat more carbs for heavy workout days and bike rides. I'm not a keto purist.
This year I'm still skipping the sun screen and UV resistant sleeves. I ride mostly during peak sun hours, although occasionally if it's too hot and humid I'll start later, after 6 pm. But I still don't sunburn. I'm not even as dark as I'd expected. My legs barely have any tan, other than my knees. Same with my face. There's no discernible helmet and sunglasses-tan pattern. There's a slight irregularity in the tan on the back of my neck, because I have a ponytail.
It's mostly my arms that get dark. I can't say it's a good look but that's just the way it goes with aging skin. At age 62 my skin looks my age, with that weird mottled old man tan. Oh, well, I'm not doing it for cosmetics, just trying to improve my bone health.
I'm looking forward to my next bone density scan and lab tests. Just curious to see whether this experiment makes any difference.
Anyway, don't take this as a recommendation. Just one odd anecdote. I guess I'll know in 10-20 years whether it was a good idea if I develop skin cancer.