Amount of D3 in wool
November 16, 2009 12:43 AM   Subscribe

Vitamin D3 is often extracted from lanolin. I would like to know how much wool is necessary to produce say 1000 IU of vitamin D.
posted by davar to Science & Nature (8 answers total) 1 user marked this as a favorite
Like sheep's wool?
posted by ageispolis at 1:07 AM on November 16, 2009

Here's one back-of-the-envelope approach. I could have some or all of these numbers and calculations wrong, though, so be warned.

1000 IU of vitamin D3 is equal to 25 µg.

That has to be a very small fraction of one sheep's coat of wool, so small that perhaps a more interesting number is how many pills of vitamin D3 might one sheep's coat of wool make?

Vitamin D3 has a molecular weight of 384.64 g/mol, or 384.64 µg/µmol, so one pill has 25/384.64 = 0.065 µmol of D3.

"Crude lanolin constitutes approximately 5-25% of the weight of freshly shorn wool. The wool from one Merino sheep will produce about 250-300 mL of recoverable wool grease."

Very roughly 50% of crude lanolin is made up of lanolin alcohols, which is a precursor to 7-hydroxycholesterol, which is what ends up getting converted into vitamin D3 (through UV irradiation).

Let's say that about 150 mL of lanolin precursor comes from one sheep, and that the specific density of lanolin is 0.99. If 1g = 1 mL of water then we have about 148 g of lanolin.

Let's say we have a chemical reaction that synthesizes 7-hydroxycholesterol from lanolin precursor with an efficiency of 50% (I am totally guessing this efficiency — I have no idea what the real efficiencies of the intermediate chemical reactions are).

Then 148 g of lanolin precursor would give us 74 g of 7-hydroxycholesterol. The molecular weight of 7-hydroxycholesterol is 402.653 g/mol. Therefore, we have 76/402.653 = 0.18 mol of 7-hydroxycholesterol from one sheep's coat of wool.

Let's say that we expose 7-hydroxycholesterol to UV light and extract vitamin D3 with 99% efficiency. (Again, I'm guessing this conversion rate.) So we end up with 0.18 mol of 7-hydroxycholesterol making 0.18 mol of vitamin D3.

We have 0.18 mol/sheep of vitamin D3, derived from one shorn sheep.

We also have 0.065 µmol/pill of vitamin D3, derived from a single 1000 IU D3 pill. We invert this to get 15.3 million 1000 IU pills per mol of vitamin D3.

Therefore, we have 0.18 mol/sheep * 15.3M pills/mol ~ 2.8 million pills per sheep's coat.

I think the calculations are okay, but the specific numbers involved could be complete and utter nonsense. Some breeds of sheep may have coats of wool that give different quantities of crude lanolin, and in that crude lanolin, different fractions of lanolin alcohols that are used to make the cholesterol precursor. The conversion efficiencies I used are completely made up. Hopefully this gives you an idea of how you might reach an answer, though.
posted by Blazecock Pileon at 2:24 AM on November 16, 2009 [5 favorites]

Yes. Lanolin is made from sheep's wool, and D3 can be made from lanolin.
posted by davar at 2:25 AM on November 16, 2009

(My first comment was to ageispolis, obviously)
Thanks Blazecock Pileon! That's exactly what I wanted to know. Thanks also for explaining it in a way that I could understand. It would be great if someone could say something about the efficiency guessings.
posted by davar at 2:44 AM on November 16, 2009

No doubt the efficiency has been improved in the past 45 years, but this 1964 patent on a process for extracting vitamin D from irradiated 7-hydroxycholesterol gives an example with 74% efficiency. Well, it calls it 7-dehydrocholesterol but I chalk that up to differences in nomenclature.

I could not find a patent describing the production of 7-hydroxycholesterol from lanolin alcohols. If anyone else wants to search the literature, it may be helpful to know that lanolin was more likely to be called wool fat or wool grease at the time.
posted by jedicus at 8:58 AM on November 16, 2009

Ah, I see that 7-dehydrocholesterol is the correct term after all. That may also be helpful for other searchers.
posted by jedicus at 9:37 AM on November 16, 2009

Blaze, what the heck do you for a living that you can do biochemistry on the fly?
posted by Cool Papa Bell at 10:17 AM on November 16, 2009

I have wanted to know this for years, really. I often googled, but never found useful information. I finally decided to ask Mefi, because I thought you never know, there may be someone here who works in the vitamin-supplement industry who happens to know this. It honestly never occured to me that you can calculate this, using publicly available information. It may sound simple to some, but my mind is blown. So thanks Blazecock Pileon and also Jedicus for the patent search.
posted by davar at 7:46 AM on November 17, 2009

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