The answer, of course, is that every person has different needs, so it is important to find a calcium supplement that is right for you. For anyone taking Calcium, I recommend balancing it with Magnesium, Boron, and Vitamin D, as all of these are critical for healthy bones. Many people also find Calcium to be constipating; Magnesium tends to help things move along so a supplement containing both can be beneficial to the digestion.
Although there are many Calcium supplements out there, I carry three basic types of Calcium ath the Golden Naturopathic Clinic. Liquid Calcium Magnesium is what I use most often because it is easy to take and easy for the body to absorb. In addition to bone health benefits, this formula can help with constipation, muscle cramping and can improve the quality of sleep. For this reason I usually recommend taking this at night before bed. For people with greater severity of these symptoms, I will often use a formula with equal parts Magnesium and Calcium; otherwise there is a formula with equal parts of these minerals.
Cal-Mag Chela Max is a chelated formula that is very easy to break down and absorb. It is formulated specifically for people who have difficulty taking other calcium supplements because they irritate their digestive tract.
For people with osteopenia or osteoporosis, I use a formula called Osteoprime. This formula contains Strontium, the only mineral found to help replace bone rather than just prevent further bone loss. Osteoprime also has a full complement of Vitamins and Minerals so it can substitute for your regular multi.
If you are wondering how much Calcium you need, this will vary somewhat based on your individual needs. Pregnant, lactating, and postmenopausal women, for example will have greater Calcium needs than other adults. That said, shooting for somewhere between 1000 and 1200mg/day is a good rule of thumb.
It is important to remember that Calcium ideally should come from food sources. The amount you take as a supplement is just that: supplementary. To get a feel for calcium amounts in food, assume that an 8 oz glass of milk (including non-dairy milks as long as they are fortified) contains 300mg of calcium. Beyond milk, 1 oz of hard cheese, 1 cup of broccoli, collard greens or spinach, ½ cup of almonds, ½ cup of tofu (made with calcium), 4 canned sardines, or 8 dried figs all contain about 200mg of calcium. For a longer list, a good source is this document from Harvard: click here to view