Here's the deal. I'm Asian in origin, and was born and grew up in South East Asia. Most advice about sunscreen is based on research on white people. So very little of it applies if you're not white! For instance, when UK researchers exposed a group of South Asians to varying amounts of UV equivalent to peak summer sun exposure in Manchester UK, they concluded:
The authors noted that in this follow-up study, even with a three-fold increase in UV exposure, those of South Asian ethnicity are not able to make sufficient vitamin D at northern latitudes wearing casual clothing. Those receiving the larger doses of UV radiation were left with an average vitamin D blood level of only 15 ng/mL.In case you're wondering, you're supposed to get 30ng/ml blood level to have "sufficient" vitamin D, and there's evidence that more is better, by quite a bit!
OK you think, that's Manchester England, not exactly famous for sunny times. But what about California? Surely you get sufficient sun exposure in California, right? Well, no. Not if you take the usual advice and wear sunscreen. In 2006, my doctor checked for vitamin D in my blood and concluded that I was suffering from vitamin D deficiency. This was despite being a cyclist and spending tons of time outside. The culprit: sunscreen. I took vitamin D supplements and stopped using sunscreen in the morning and evening hours.
OK, what if you're from more northern parts of the continent? My wife, who's northern Chinese and very pale, was also diagnosed last year with vitamin D deficiency. The same study concludes:
Based on the studies by these authors it will be difficult, if not impossible, for those with darker skin to achieve a natural vitamin D level from sun exposure alone, particularly if they do not commit to getting full-body sun exposure.So no, if you're Asian, or basically any color except white, ask your doctor for a vitamin D check the next time you have an annual. I bet you'll be shocked at the results. And no, if you're Asian you cannot possibly get sun burn on a cloudy day. No way, no how. That's white person talk.
Finally, if you're a whitey, you might want to take Mike Samuel's advice from the 2007 tour:
If you're the only fair-skinned whitey in the group, carry the sunscreen