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Capsules: Why is vitamin E oil so much thicker than vitamin A oil?
February 25, 2014 6:18 PM   Subscribe

I break open both vitamin E and A capsules for use on my skin sometimes. I notice E is very thick while A is light and runny. Is this a property of the molecules, or are they just in a different carrier? I don't know organic chemistry, so I can only speculate.
posted by Listener to Science & Nature (7 answers total) 2 users marked this as a favorite
 
It is a property of the molecules, having to do with the saturation of their hydrocarbon chains. More saturated = more solid.
posted by ocherdraco at 6:27 PM on February 25 [1 favorite]


If you do an image search for vitamin a and one for vitamin e, you'll find chemical diagrams that show each one as having a kind of tail. Those tails are made up of carbons and hydrogens. Whenever you see a double line in the tail, that is a location of unsaturation: a place where there aren't as many hydrogens as the carbons could potentially carry. When people talk about saturated and unsaturated fats, this is the characteristic they're referencing.
posted by ocherdraco at 6:32 PM on February 25


I think there's more going on than just the properties of the vitamin molecules themselves. Vitamin A isn't particularly good for you when taken in excess, and vitamin A capsules just don't contain all that much vitamin A--most of what's in there is a carrier, like soybean oil. They're only the same size because if the size of the pill were consistent with the size of the vitamin dose, you'd have to handle them with vitamin tweezers.

If you look at the labels of these supplements, you probably see the amount of vitamin indicated in IU, or international units. One IU of vitamin E and vitamin A are not the same because IUs are not a fixed unit--they're only used for vitamins A, E and D and are based on the amount humans need in their diet. One IU of vitamin A is 0.3 μg, while 1 IU of vitamin E is 2/3 mg, which is ~2000×--that's right, two thousand times, at least if I did the math right--more vitamin E by weight. (I'm glossing over the fact that most Vitamin A supplements are actually beta-carotene)

So, the consistency of the stuff in the vitamin E capsule may be the actual consistency of vitamin E, while the stuff in the vitamin A capsule is just the consistency of soybean oil with a weensy bit of vitamin A in it.
posted by pullayup at 6:51 PM on February 25 [4 favorites]


You will find that different brands of vitamin E capsules vary in viscosity. Some use soybean oil, others use gelatin & glycerin as a carrier.
posted by weapons-grade pandemonium at 8:11 PM on February 25


Following up on what pullayup said, doing the back of the envelope calculation on what Wikipedia cites as the IU to weight ratios for A and E (this is in the article on International Units) and using the numbers from the first couple of commercial supplements Google coughed up I got an A supplement having .6 mg of Beta Carotene (25,000 IU at .6 micrograms per IU) and an E capsule with 267 mg Alpha Tocopherol (400 IU at .667 mg/IU). So right off the bat, assuming the numbers are right it looks like the inert ingredients are going to be a far bigger factor for the A capsules. The A capsule I turned up had beeswax and glycerine in addition to soy while the E capsule was just soy (and again, a nomtrivial component of its volume was likely the E itself).

In general how "thick" a liquid seems is affected by both its density (specific gravity) and its viscosity (resistance to flow), both of which are affected by mechanical factors (the size and shape of the molecule) and its Chemical properties (how much its chemistry makes it stick to itself, basically - probably most affected by hydrogen bonding and Van der Waals forces in non-ionic substances (if you want a bunch of jargon to Google in search of a better understanding of viscosity). At the molecular level the line between mechanical and chemical properties is fuzzy anyway.

Which is a very long way around to saying it's hard to say exactly which factors are most significant in you particular case. The other possible take home is that to a much greater degree in the A capsules what you're spreading on your skin is a dietary carrier formulation - in the case of A in particular using something formulated for topical use might be worth consideration.
posted by nanojath at 5:28 AM on February 26 [2 favorites]


Regarding my calculation above, I wrote it down wrong the total for the beta carotene was 15 mg, still a big difference but comparatively off by an order of magnitude.
posted by nanojath at 6:12 AM on February 26


Don't forget that A and E are two of the fat/non-water soluble vitamins.

I still remember them as the Legend of KADE.
posted by Sphinx at 6:54 AM on February 26 [1 favorite]


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