There is a big problem with Vit D deficiency, particularly with pregnant woman. It is as, Spacial said, linked to avoidance of sun. In Australia we are the Melanoma haven so we have advertising campaigns to avoid harsh sun and those campaigns have been linked with a drop in Vit D levels.
That said, anything beyond a normal level goes into the toilet, so I wouldn't super boost it, you don't absorb it and you don't store it.
Also be cautious about some of the claims. Many people got onto the super boost Vit C to prevent colds etc. After several big trials it was found to be of no benefit except to the people selling the vitamins.
Never boost Vit A, it will kill you, eventually.
Vit B maybe, particularly if you drink alcohol, it may also have some beneficial affects to brain function.
If you are on a proper balanced diet, extra Vitamins are probably a waste of money.
If BTW you are into fish oil to boost omega 3 levels you need at least 10,000 mgs per day to do anything. My Rheumatology colleague who was one of the pioneers in this study gets his patients to DRINK 25 mls of fish oil per day to see the positive effects. Typically that is 25 tablets a day at 1000mgs/capsule. Or a about the size of your morning coffee.
Do remember in many of these trials there is an incredible placebo effect. You would be amazed how high that effect can be, but it doesn't (usually) sustain.
Cindy
