Conventional advice tells us to supplement calcium, 1200 mg per day, to preserve bone health and reduce blood pressure.
Here's a curious observation I've now witnessed a number of times: Some people who supplement this dose of calcium while also supplementing vitamin D sufficient to increase 25-hydroxy vitamin D blood levels to 60-70 ng/ml develop abnormally high levels of blood calcium, hypercalcemia.
This makes sense when you realize that intestinal absorption of calcium doubles or quadruples when vitamin D approaches desirable levels. Full restoration of vitamin D therefore causes a large quantity of calcium to be absorbed, more than you may need. In addition, two studies from New Zealand suggest that 1200-1300 mg calcium with vitamin D per day doubles heart attack risk.
We have 20 years of clinical studies demonstrating the very small benefits of supplementing calcium to stop or slow the deterioration of bone density (osteopenia, osteoporosis). These studies were performed with no vitamin D or with trivial doses, too small to make a difference. I believe those data have been made irrelevant in the modern age in which we "normalize" vitamin D.
Should hypercalcemia develop, it is not good for you. Over long periods of time, abnormal calcium deposition can occur, leading to kidney stones, atherosclerosis, and arthritis.
Until we have clarification on this issue, I have been advising patients to take no more than 600 mg calcium supplements per day. I suspect, however, that the vast majority of us require no calcium at all, provided an overall healthy diet is followed, especially one that does not leach out bone calcium. This means no foods like those made with wheat or containing powerful acids, such as those in carbonated drinks.
I think I developed hypercalcemia when I doubled my vitamin D supplement. I woke up a month later with vertigo and later developed tinnitus. After a month of not taking any Vitamin D or calcium supplements, I am still suffering from the tinnitus. How long will it take to reverse the effects of the self-induced hypercalcemia caused by the increased vitamin D?