One good reason to climb outdoors is you get some sun which helps us make Vitamin D. (As you’re getting sun, you risk getting bitten by mosquitoes, wasps, bees and being hit by falling rocks. But at least you’re getting some Vitamin D.) OK, but when it’s winter, we don’t get the type of sun’s rays we need to make Vitamin D. (Above 35 degrees latitude, we can’t make Vitamin D from mid October to March) So what to do? Well, read the links and you tell me.
“The application of sunscreen with an SPF factor of 8 reduces production of vitamin D by 95%. In latitudes around 40 degrees north or 40 degrees south (Boston is 42 degrees north), there is insufficient UVB radiation available for vitamin D synthesis from November to early March. Ten degrees farther north or south (Edmonton, Canada) the “vitamin D winter” extends from mid-October to mid-March. According to Dr. Michael Holick, as little as 5-10 minutes of sun exposure on arms and legs or face and arms three times weekly between 11:00 am and 2:00 pm during the spring, summer, and fall at 42 degrees latitude should provide a light-skinned individual with adequate vitamin D..”
The video below is a medical, biochemical and evolutionary view of Vitamin D and why we need it. It is from a lecture at the University of California at San Diego. (It’s 58 minutes but it moves fast and is quite entertaining. The first 28 minutes are the most important.)
Update. Lisa found this article:
“Vitamin D is an often overlooked element in athletic achievement, a “sleeper nutrient,” says John Anderson, a professor emeritus of nutrition at the University of North Carolina and one of the authors of a review article published online in May about Vitamin D and athletic performance.”