Does taking vitamin D3 supplements really work for the OP?
There have been a number of HN posts about how the vitamin fad started by Linus Pauling has not been backed up scientifically, such as this one:
It's hard to actually know which action I take has the most effect. Vitamin D, bright lights, exercise all play a role. I've found it's important to try everything and hope for the best.
If I were to pick just one thing to do though, it would be the bright lights in the morning. I know for sure that those work. Not only for myself, but for many other people who have given it a try.
Yes, fixing your Vitamin D level gives a very effective boost, however it is absolutely not harmless to consume too much vit D as the article implies. More: http://en.wikipedia.org/wiki/Hypervitaminosis_D
Hypervitaminosis D is incredibly rare. Taking 1000 IU per day ought to be harmless for literally everyone. Even 10,000 IU per day is WAY below toxicity.
You are missing the point. Above a certain level, the negative side effects start out weighing the positive affects. So just because something is not close to toxicity, does not mean it is actually having a net benefit on your health. With vitamins, take the recommended dosage, or preferably slightly less, as it is likely you are getting at least something from your diet, not matter how poor. Anything above that is likely to start having negative effects that start to outweigh any benefits. Most adults get sufficient vitamins and minerals from their diet, even a poor western diet. Vitamin D however, is the exception if you don't get enough sun.
I'm not talking about vitamins in general; I'm talking about vitamin D and how embarrassingly low the U.S. RDA is.
There are a great many Americans who would see immense benefit by taking (say) 1,000 to 2,000 IU of vitamin D per day. And I feel pretty confident there are no people for whom an extra 2,000 IU would be negative.
Supplementing vitamin D is recommended by a few calm agencies and is reasonably sensible. Especially if you don't get much sun. UK children under 5 are recommended to take a multivitamin of A, C and D.
We're at the frustrating stage of having credible methods of action, but weak evidence for efficacy, for some vitamin interventions.
> The number of trials and outcomes reported are too limited, and in general are of low quality, to draw conclusions on the usefulness and safety of this intervention as a part of routine antenatal care. Further rigorous randomised trials are required to evaluate the role of vitamin D supplementation in pregnancy.
For further information about vitamin D, I always recommend one particular episode [1] of the TWiT Security Now podcast where the host Steve Gibson talks for about an hour on his research into the effects of vitamin D and how he thinks that taking it is important.
I can't vouch for the medical accuracy of what he is saying, but he does tend to research things pretty thoroughly before broadcasting them, and I generally trust his conclusions.
The OP is right that Vitamin D deficiency is common, and D3 supplementation is a good idea for almost everyone. It's super-easy, too; if you don't like taking it every day, you can actually take a big dose once a week because it's fat-soluble. (Vitamin D's fat-solubility means that there's a theoretical possibility of overdose, but in practice this almost never happens. You'd really have to go nuts with the dosage to be at risk.)
Last year, prior to beginning supplementation, I had my blood levels checked for Vitamin D (per the recommendation in Tim Ferriss's 4-Hour Body). I was amazed to discover that my levels were at the low end of normal, despite a diet rich in Vitamin D and regular direct sunlight (including frequently wearing a "suntan shirt" to let in the necessary UV). (I live in Pasadena, which is sunny year-round.) After supplementing for a couple of months, a second blood test confirmed that my blood Vitamin D levels were in the ideal range.
http://www.theatlantic.com/health/archive/2013/07/the-vitami...
but maybe there is more to it when it comes to SAD...