The uper limit limit of tolerability is much higher than 4,000 IU/day. Only if someone suffers from certain rare illnesses that cause hypersensitivity to vitamind D are doses below 10,000 IU/day unsafe. But in those cases, patients are also instructed to limit exposure to the Sun. As pointed out here:
http://www.ajcn.org/content/85/1/6.full
doses up to 10,000 IU/day are safe, and even in cases of illnesses causing vitamin D hypersensitivity, doses below 10,000 IU/day are not likely to cause problems (although taking supplements without supervision is then not advised).
The precise way vitamin D overdose causes hypercalcemia in healthy people is not well understood, see here for details:
http://www.ajcn.org/content/88/2/582S.full
What is clear, however, is that the calcidiol level must be near 750 nmol/l before problems start to occur. This is way above 250 nmol/l which is considered to be the maximum value that can occur naturally, and which is typical for an intake of 10,000 IU/day.
Comment Reply
The uper limit limit of tolerability is much higher than 4,000 IU/day. Only if someone suffers from certain rare illnesses that cause hypersensitivity to vitamind D are doses below 10,000 IU/day unsafe. But in those cases, patients are also instructed to limit exposure to the Sun. As pointed out here:
http://www.ajcn.org/content/85/1/6.full
doses up to 10,000 IU/day are safe, and even in cases of illnesses causing vitamin D hypersensitivity, doses below 10,000 IU/day are not likely to cause problems (although taking supplements without supervision is then not advised).
The precise way vitamin D overdose causes hypercalcemia in healthy people is not well understood, see here for details:
http://www.ajcn.org/content/88/2/582S.full
What is clear, however, is that the calcidiol level must be near 750 nmol/l before problems start to occur. This is way above 250 nmol/l which is considered to be the maximum value that can occur naturally, and which is typical for an intake of 10,000 IU/day.
January 24, 2012 - 5:14pmThis Comment
Reply