There are other studies where rabbits were given 50,000 IU per day........ what's that in a human? 1 million IU per day? As in toxic?
Also as was evidenced by the study where only cholesterol was added to the rabbit chow, the rabbits that did not get cholesterol in their food did not have problems.
Unfortunately rabbits are not human. We create cholesterol from our livers even if we eat zero cholesterol in our diets. Rabbits are naturally low cholesterol animals. Feeding them cholesterol causes inflammation in their bodies.
Studies like this are invalid.
No body advocates that people take even 50,000 IU of either vitamin D2 or D3 per day. And since we are not rabbits, that would mean advocating for 1 million IU per day.
Reality check time.
Here is an exerpt on rabbit nutrition: nutrecocanada.com/docs/shur...
The primary role of Vitamin D is the regulation of calcium and phosphorus absorption,
influencing bone mineralization and mobilization. In most species, calcium absorption is
controlled by a calcium binding protein, which is regulated by vitamin D. Rabbits are unique in
that they do not require this calcium binding protein to absorb calcium. As discussed previously,
the amount of calcium absorbed is in relation to the dietary amount. Excess vitamin D, rather
than a deficiency, is more likely to be a problem in practical conditions. Levels as low as 2300-
3000 IU/kg, have been shown to be toxic to rabbits. Toxicity symptoms include impaired
movement, loss of appetite and calcification of the soft tissues, such as the arteries and kidneys.
Toxicity cases have been reported due to excessive levels added to rabbit feeds, and thus levels
of 1000 to 1500 IU/kg have been recommended (Mateos & de Blas, 1998).
As an aside, cats manufacture their own vitamin D and require no supplementation. And yes, cats are not human either.