Actually 20 minutes of sun exposure, even in the winter time, on your face and your hands/arms can give you most, if not all, of your Vit. D needs.
Not necessarily. It totally depends on where you live, time of year, your age, etc...
The average woman uses 4000 IU of vitamin D per day. The average man uses 6000 IU. While mid day sun exposure can generate 10,000 IU in that time, most of us as not getting mid day sun exposure. In Winter, you are not going to generate near that level.
"Sun Exposure: Catching some rays each day is definitely desirable, and healthy young people can usually get the vitamin D they need from around 10 to 30 minutes of sun exposure per day - depending on their location and the time of year. Most adults in today`s modern world, however, do not even attempt to get this much sun exposure - much less achieve it. But even if they did, would it matter, or are there other variables standing in the way?
Location: Vitamin D is produced in the skin from a cholesterol derivative when we are exposed to UVB radiation from the sun. However, because of the axial tilt of the earth, the further north one lives, the less the sun`s UVB rays will be able to activate vitamin D in the skin. So sun exposure does not necessarily equal optimal vitamin D status if you`re living in the wrong location. Living down south is better, of course (south of the 35 N latitude line seems to be the best), but there is still more to consider.
Age: Say you do live close to the equator, or are significantly below the 35 N latitude line. That`s a good thing, and it probably helps. If you`re around 35-40 years old or above, however, you`re likely losing the ability to activate sufficient levels of vitamin D in your skin, even in the unlikely event that you`re getting adequate UVB sun exposure (4).
Dark Skin: What if you have dark skin? If you have a lot of pigment in your skin, this is going to shield you from the UVB radiation you need, and you`re probably deficient in vitamin D.
Weight: Vitamin D requirements are also relative to body weight. If you`re overweight, your body requires more vitamin D than if you are not overweight. If you get a lot of sun, but are on the heavy side, you`re probably still not getting enough vitamin D.
Chronic Illness: Chronically ill? Have cancer? The body demands more vitamin D when you`re sick, and is probably using it up faster than you can get it from the sun.
When one considers that many Americans are victims of not just one but many of the above drawbacks, it becomes readily obvious as to why there is such a widespread vitamin D deficiency epidemic. Not getting enough sun is bad enough, but lack of sun exposure combined with being middle-aged, overweight, and chronically ill is an absolute disaster - and it is the devastating situation that many (most?) Americans find themselves in today.
Is Sun Exposure Really Not Enough?
Yes, sun exposure is a good thing, but too often, it`s simply not sufficient to achieve the kind of levels necessary for disease prevention and treatment. This applies even in places like Hawaii, where individuals get plenty of sun exposure, and the latitude is around 21 (5, 6). The role of sunlight should not be downplayed too much, however. If you`re healthy, young, and live in a subtropical region, then you might have sufficient vitamin D levels. In fact, some young people in the subtropics who get sun exposure all day long have levels between 80-100 ng/ml. This is incredible, and it means that sun exposure really does work provided the conditions are right.*
The point being made in this article is simply that not everyone is young, not everyone is healthy, not everyone lives in Houston, and not everyone gets enough sun exposure every day. It is those people who need to supplement with vitamin D. This also happens to be most people.
Blood Testing is Crucial
How do you know if you`re getting enough vitamin D, and how much is enough? The only way to know is by testing your blood. Fortunately, testing vitamin D, as far as blood testing goes, is pretty cheap. You can set this up with your doctor, order tests online and get blood drawn at a local lab, or order a vitamin D home test kit, whereby you simply order the test, prick your finger, send in the blood, and wait for the results to come back to you."