Scientifically, that seems to be a tough question to answer. But it's probably better if your body makes it because it will be more easily usable. You only need 15 mins of direct sun exposure to produce more than enough for your daily requirements. The problem is my body has stopped producing Vitamin D. We've tried kick starting the system with the 50,000 IU dose and it barely moved my levels.

Of course, the sun is also free (unless you worry that 15 mins/day can cause cancer) while if you buy supplements you'd want the high quality ones and preferably in a fatty medium for easier absorption. The D3 form is more easily converted by the body into an active form.

I would assume that it gets turned into the same thing by the process they describe in the article. It ends up as 25-hydroxyvitamin D, which is what they measure in the end I believe. But I'm anything but an expert.

UV-B reacts with the 7-Dehydrocholesterol in your skin to produce cholecalciferol (D3) If you take vitamin D, make sure it is D3! So either way it will hit your liver as D3.

The body was designed to get D from sun, and it is difficult to overdose that way unless you are a lifeguard. It is easy enough to overdose on D if it is taken orally.

There are other effects than vitamin D from sun exposure- it would be presumptuous to assume you could achieve optimal health from a vitamin D supplement.

FTA: "Although more foods today are supplemented with vitamin D, experts say it is rarely possible to consume adequate amounts through foods."

I believe that vitamin D is best taken with and is absorbed in and later stored in fat (and the liver).

Excessive amounts of animal fat are bad since it is a saturated fat, but some is beneficial. I suspect that range fed beef has more vitamin D since animals in the open get more sun and would store vitamin D in a smaller amount of fat built up over more time.

Obese corn fed feed lot cattle are less healthy for other reasons also. The corn diet is very unnatural for them. It leads to rapid fat buildup with some meats containing over four times the fat of range fed animals. The diet causes the digestive system to become more acidic making the animals prone to various infections including E-coli a very dangerous bacteria. The E-coli mutates in the overly acidic animals becoming a form which humans often can't fight off without antibiotics if it wasn't already killed in cooking. The E-coli in range fed animals is not so troublesome. Bacterial that does survive in the animals loaded with antibiotics is also apt to be more resistant to treatment.

Because of the the danger of E-coli, ground beef must be cooked well done all the way through. Slaughter exposes meat from other parts of the animal to the bacteria and if gets mixed all the way through when ground. Other beef should be eaten fresh and washed well before cooking, and utensils and cutting boards used with the raw meat should be kept separate from those used for vegetables and other foods. Besides tasting better, non-ground beef is more nutritious if the color isn't cooked out. Meat that's still juicy contains a fair amount of iron in the blood.

PBS in the US has been running a documentary about corn production in Iowa. The subsidized inedible corn (tastes like cardboard, engineered for high yield per acre) is used mainly as cattle feed and to produce high fructose corn syrup, a non-nutritious addictive destructive AND CHEAP sweetener that's found its way into many of our foods. It's hurting us not only when consumed directly, but by degrading the beef produced as explained above. People consume more saturated fat in the beef. The excess fat and sugar has caused a major increase in diabetes in the last 20 years.

Although supplements help with vitamin D problems, we really should be looking closely at what we eat and how it is produced. END CORN SUBSIDIES!!! contact your representatives. The corn isn't profitable without subsidies, farmers (big business now) would switch to nutritious crops if not paid to do the wrong thing.

U.S. broadcasting has become dangerously consolidated in the hands of a small number of corporations and even more insidious venture capital groups. Pressure the F.C.C. and your representative for change, and watch and support your P.B.S. (non profit community tv) stations.

For all of us to be healthier we should step back and see what's going on, be educated, produce healthy foods, eat properly, and live a healthier lifestyle. Some would say that's all too costly, but disease treatment costs even more and there is no price tag on suffering.

As a corollary to this, I am also curious about vitamin D levels in people using UV tanning beds.

Assuming equal carcinogenic potential from sun exposure and from such beds (which is most likely an incorrect assumption), the results should be insightful.