IMHO the key to understanding vitamin supplementation is first, to know which are fat-soluble (and will be stored by your body) and which are water-soluble (and will be flushed by your body when you urinate).
So, it is almost impossible to over-dose on Vitamin C, since, your body will easily eliminate anything it doesn't need - C is water-soluble.
This article covers the differences well enough: http://www.medicinenet.com/script/main/art.asp?articlekey=10...
I think what drives vitamin taking is a combination of
i) people not fully trusting doctors
ii) knowing that today's food is factory-produced and may be deficient in micro-nutrients like vitamins and minerals
iii) being willing to spend a few dollars per day as an insurance policy; after all, how many drop $5 a day at Starbucks?
[1] it's a play on words and a homonym, "deke" comes from hockey where you dodge or fake out an opponent to get around them. It must be the Canadian school system further injecting hockey into our lives. :)
For those of us who want an insurance policy, have you got any recommendations on what multi-vitamins to aim for (a particular brand, maybe that you take?) Are all brands equal?
Which statement in that article do you believe supports the position that taking too much vitamin C is "quite harmful"?
Wait, are you really arguing that it's impossible to have too much of something that is water-soluble? What about sugar? What about salt?
Macro nutrients are what processed food loses.
We'd be sitting and coding for a few hours, and we're all just internally waiting for somebody to utter the magic words "...coffee run?".
At a moments notice we're all out the door, headphones are smashed, phones are flung, chairs are tipped over, papers are in the air!
http://www.informationisbeautiful.net/play/snake-oil-supplem...
But yes, mostly don't bother with anything apart from D.
For example a 2009 thorough review of all research on vitamin D and calcium supplements by US DHHS concluded:
The majority of the findings concerning vitamin D, calcium, or a combination of both nutrients on the different health outcomes were inconsistent.[4]
Most if not all of the studies initially finding these spurious correlations are large studies looking at lots of factors and outcomes. Unfortunately due to the nature of statistics there is always a small chance of a false positive or negative relationship and if many possible relationships are examined, such as in these large exploratory studies, it is almost a certainty that some false correlations will be found. This is why almost all of these studies say that confirmation in additional studies is required but this warning does not always make it into press reports. Occasionally a new relationship will be found that is confirmed in follow up studies. Unfortunately this confirmation has yet to be found for any supplement for any outcome in healthy people AFAIK.
FYI - Peter Norvig has a nice writeup of what to look out for when considering the results of a study.[5]
[1] Some supplements can help people with specific health issues but ask an expert such as your doctor as there are many false claims about supplements helping with specific conditions.
[2] http://www.medpagetoday.com/HematologyOncology/BreastCancer/...
[3] http://www.medicalnewstoday.com/articles/183880.php
[4] http://www.ahrq.gov/research/findings/evidence-based-reports...
I sort of agree with that, but I also know it is kind of a tautology. 'Healthy people' can't become 'healthier people', by definition. Yet, every healthy person can imagine himself, but slightly better: better vision, more willpower, stronger, faster runner, more intelligent, etc.
Because of that, there are no 'Healthiest people'. Even the hypothetical person who wins the decathlon at the Olympics at the age of 40 in the year they won their fifth Nobel will have something to desire (a bald spot? Feeling more tired after exercise than he used to be?). In that sense, nobody is truly healthy.
That is what all the supplement sellers play at.
And as Patrickg_zill said, fat soluble vitamins are the dangerous ones, as they accumulate instead of being flushed. Pretty much all of the other vitamins and minerals are well controlled by the body...
Back when I lived in Jakarta (very large urban area, very warm) I used to get mouth ulcers constantly, despite eating more than my fair share of fruits and vegetables. The solution, according to the family GP, was to supplement vitamin C. Yeah yeah, n=1 (well, n=a family of 5, but still), but it worked and seemed to lend some validity to this theory.
