Wikipedia: Vitamin/Talk

Vitamin D is not a true vitamin as in normal circumstances it is produced in sufficient quantities in the body on exposure to sunlight.

"Normal circumstances"? Why is our milk fortified with Vitamin D if most people produce enough? -- Janet Davis

Vitamin D is synthetized by human body, but in quantities that might be not sufficent. Level of synthesis depends on sun activity, so in winter and in polar areas it's more like a vitamin, and in summer and in equatorial areas it's less like a vitamin.

That's what I thought. I believe it also depends on how dark your skin is. So why does the fact that some people sometimes produce enough make it "not a true vitamin"? (I'm trying to understand this, rather than just striking it from Vitamin, since I don't consider myself an expert.) -- Janet Davis

Except that it is more probable that most people always make enough vitamin D. It requires only 45 minutes a week sun exposure with otherwise proper nutrition. Those few who live in polar climes in winter and those unfortunates that don't get out enough may need supplementing. It seems it is added to milk at least partly because vitamin D's job is promoting calcium adsorbtion in the intestines. I beleive vitamin D is the only vitamin naturally produced in the body.? --rmhermen

I find the bit about "Vitamin X" confusing. Can someone clarify? -- Janet Davis

BNF: Vitamin X ::= 'Vitamin' <Letter> | 'Vitamin' <Letter><Number>

                               -- Taw

:-) I still think it's confusing. Not everyone knows about formal grammars. I'll try to think of a better way to say it. -- Janet Davis

Your changes look good, Taw. -- Janet Davis

Given that

: Usage of names 'Vitamin <letter>' and 'Vitamin <letter><number>' is diminishing. Especially vitamins H, M, B1, B2, B3 and B5 are usually called with their proper chemical names.

Would it better to have the Wikilinks on the proper chemical names? (The "old" names could still be redirects, just not link to them here.)

You're completely right. Will fix that. --Taw

what are the symptoms of not getting enough of the proper vitamins? what about too much?

I imagine everyone knows about scurvy, one possible result of not having enough vitamin C over an extended period of time. A section on those last two questions would be fascinating, I think. --KQ

What is Niacin ? Is it Nicotinic Acid or Amide of Nicotinic Acid ? I'm confused. --Taw

the Oxford American Dictionary has it as "nicotinic acid." --KQ