Milk and Fat Soluble Vitamins Question

I’m starting here, because, frankly, the Dope is more reliable, IMNSHO than many other online resources.

I was just thinking about milk, specifically fat-free or skim milk, and noticed that it still is claimed to be enriched with vitamins A and D. Which didn’t seem exceptional, until I remembered: A and D are two of the fat soluble vitamins - so without the fat in normal milk what keeps them in solution and not dropping out as a precipitate?

I can think of several possibilities:

[li]Skim milk, I’d always thought, still had some small fraction of milk fat in it, even though the separation is being done mechanically (in lube oil purifiers, no less!*) and since vitamins are added in such small amounts, that may be enough to deliver the vitamin to the digestive system. But I am not sure that food labelling laws would allow “fat free” milk to use the same dodge, I don’t think.[/li][li]Milk is actually a colloidal suspension, not a solution in the traditional sense. That means that there are things supposedly in milk that aren’t actually dissolved - just being carried around through a variety of mechanisms. This was, more or less, what I’d always assumed happened - the vitamins would be dissolved into the particles of fat suspended in the milk. But without the fat in the milk, the people adding the vitamins would have to put them into their own colloidal suspension. [/li][li]Finally, I know that fats can be made partially soluble in water through a number of processes. Tacking on alcohol groups, or esters, have both been made to work with some compounds, I believe. [/ul][/li]
Obviously not an important, nor a vital question. Just something that bothered me while taking out the recycling.

Milk contains about 100 units (IU) per 8 ounce serving.
One IU is equal to 0.025 micrograms of cholecalciferol.
In order to precipitate out of solution each molecule of that 2.5 micrograms of vitamin D in a glass of milk, would have to a) find other molecules of vitamin D with which to aggregate, b) develop sufficient density as a floculate to fall out of suspension.
At those concentratiions neither a) or b) are likely in distilled water, much less a protein soup like milk.