YOUR BURNING QUESTIONS ABOUT SPF ANSWERED
Beth Thompson caught up with dermatologist Dr. Paul Cohen, owner of the Rosedale Dermatology Centre in Toronto, for the 411 on all things sunscreen
BT: Does using SPF stop vitamin D absorption?
PC: Too many people believe that using sunscreen leads to vitamin D deficiency, and that the best way to obtain enough of it is through unprotected sun exposure. Yes, using sunscreen decreases vitamin D absorption, but in all honesty, sunscreen doesn’t block all UVB rays from reaching your skin; SPF 30 blocks 93 percent of UVB and SPF 50 filters out 98 percent. This leaves anywhere from 2 to 7 percent of solar UVB reaching your skin. The truth is, it doesn’t take much sun exposure for the body to produce vitamin D. In my opinion, the risks of sun exposure outweigh this benefit, and I will stand by using a sunscreen every day.
More importantly, the sun isn’t the only way to get vitamin D. There are healthier alternatives including diet and supplements. You can easily take an oral supplement (1,000 – 2,000 units a day depending on age and health). In food, fatty fish such as tuna, mackerel and salmon are good sources, and many common foods such as milk and orange juice are fortified with vitamin D. Food, supplements and incidental, protected sun exposure will give you all the vitamin D you need, without subjecting yourself to the risks of unprotected sun exposure.
BT: If you put on SPF at 9 a.m., but don’t go out in the sun until noon are you still protected?
PC: I recommend applying sunscreen 10 to 15 minutes before sun exposure. That said, if you apply your sunscreen at 9 a.m., stay indoors and avoid any sweating, exercising or swimming, you should still be quite protected. As a general rule, reapply every two hours when in constant sun exposure.
BT: Can we talk technique? I see people rubbing lotion into their hands ahead of applying it to the body. Does that waste product?
PC: The best technique is whatever works to have you apply it consistently and correctly. The more important part of application is ensuring that you are applying the proper amount to skin (regardless of how much stays on your palms). You need to use a shot glass for a full application; always apply a thick, liberal layer to all exposed skin and reapply often (at least every two hours). Too many people underutilize sunscreen, applying too thin a layer to get the full protection factor.