The risks and benefits of sun exposure

Green et al. 2011,42 found in a prospective study that there may be an association between sunscreen use and reduced risk of melanoma. However, since the participants were told they were participants in a skin cancer prevention trial and were questioned periodically during the trial on their use of sunscreen, the likelihood that they were significantly more diligent in applying sunscreen in accordance with manufacturers' instructions than ordinary users of sunscreen cannot be discounted. (Bolding mine)

I'm sorry, it's just really hard for me to take this 2016 study seriously when it seeks to ding other studies by saying, "Maybe the problem is that people used the sunscreen PROPERLY and that's why the researchers got the data they did."

Regardless, this is one study surrounded by seas of other – and more recent – studies that do show a benefit in using broad-spectrum sunscreen to help prevent melanoma. Vitamin D deficiency is a real problem, of course, and one deserving of proper study. There could very well be a correlation between Vitamin D deficiency and increased melanoma/other skin cancer risks in a person who otherwise has a history of sunburns (like, for example, me: I was a very outdoorsy kid, I got burned on a pretty regular basis, including one really bad burn one year, but as I grew older, my interests became more indoor-based, and I didn't get out as much… and when I did, I typically burned (yay, super fair skin v_v)). But I think the link between UV radiation and skin cancers is pretty well-established by now. I also know that some sunscreens inflate their SPF factors and/or are just fancy lotion. But a reputable, broad-spectrum sunscreen still seems like a good idea to me.

Ultimately, I'm just not ever convinced by a single study on anything. One study says "eating eggs is good!" and another says "eating eggs is bad!" You have to look at the entire body of evidence, and a lot of times, what's good for one person is bad for another. But I am glad to see that there are more and newer studies out there than this one, because that means it is still being looked at! If we keep at it, our understanding will only grow!

I’ve followed this concept for years, even before being diagnosed with skin cancer. 

Ideally you should get your vitamin D from your diet.   If you do not 10 – 30 mins of exposure without sunscreen 3 times a week would be sufficient for most adults.  Add up the time you walk to/from your house, place of work/school, stores etc and I think you’ve got it  

However, if you are fair, if you have a previous skin cancer diagnosis or in anyway concerned about sun exposure you can eat right and take a supplement.  

"Life expectancy was reduced in nonsmokers of approximately 50 and 60 years of age who avoided sun exposure by 0.6 and 1.3 years, respectively, compared to those with the highest sun exposure during the 20‐year follow‐up.”

https://onlinelibrary.wiley.com/doi/full/10.1111/joim.12496

This study of women in Sweden was referenced in:
https://www.newscientist.com/article/mg24132210-100-too-much-sunscreen-why-avoiding-the-sun-could-damage-your-health/

A few minutes of sun exposer at noon is good for our health.  People living in Australia and the United States should spend much less time in the sun than people living in Sweden.  In summer in Texas and in New South Wales 1 to 5 minutes in the sun at noon is enough for a light skinned person.  Every sunburn makes melanoma more likely.