"Natural" vs. "Synthetic" Vitamins...

[KathyF37]

What is “the straight dope” on what difference there is between the two, if any? I’m clueless as I can’t imagine, say tiny particles of broccoli, fitting into those little pills. So what’s “natural” about “natural vitamins”?

[mnemosyne]

Natural vitamins are those derived from a natural source, like a plant, but synthetic ones are made in a laboratory test tube. The pure molecule is basically the same, but there could be differences.

If I understand this link correctly, synthetic vitamins are more likely to be racemic mixtures rather than a pure isomer of the molecule. That means that at one location in the molecule, the natural vitamin will always be oriented the same way, while half of the the synthetic molecules might be oriented the other way (think of your two hands - basically the same, but with a different orientation). Your body might need just the right hand one and not use the left hand one at all, but in the lab its hard to make one without the other, so you get some left with the right and your body just gets rid of the extra.
http://www.nutritionfocus.com/nutrition_supplementation/vitamins/vitamin_e_retained.htm

Natural and synthetic vitamin E are not the same. Previous research has shown natural vitamin E is better retained and more biologically active than synthetic. To identify the kind of vitamin E in a supplement, it is necessary to read the ingredients listed on the label. Natural vitamin E begins with “d,” as in “d-alpha-tocopherol.” The synthetic version begins with “dl.”

…

“Both forms of vitamin E are absorbed equally well through the gut, but the liver clearly prefers the natural form, transferring it to lipoproteins to be transported through the blood for deposition into the tissues,” Burton said. “The natural vitamin E is retained by a two-to-one ratio over the synthetic.”

AFAIK, the “wrong” vitamin of most types isn’t dangerous to ingest, your body simply doesn’t use it. I suppose in the end it comes down to how much you’re ready to pay for the stuff, since the natural varieties are always more expensive.