Is there a "best" time of day to take calcium supplements?

Vegetarian Journal, Jan-Feb, 2002 by Reed Mangels

Is it better to take a calcium supplement in the morning or the evening? In one large dose or several smaller doses? Researchers from Finland set out to answer these questions. They found that it does not matter whether you take a calcium supplement in the morning or in the evening. A smaller percentage of calcium was absorbed when a large dose was given, compared to when a smaller dose was given several times a day. However, a large dose of calcium decreased blood levels of parathyroid hormone, a hormone that stimulates calcium loss from bone. A decreased level of this hormone could decrease bone breakdown, but could also limit calcium absorption. So, we're still left with the question, is taking one large dose of calcium better or worse than taking several smaller doses of calcium throughout the day?

Karkkainen MUM, Lamberg-Allardt CJE, Ahonen S, et al. 2001. Does it make a difference how and when you take your calcium? The acute effects of calcium on calcium and bone metabolism. Am J Clin Nutr 74:335-342.