Calcium is a major league mineral. Mainly because there is so much of the stuff in our body. Up to 2% of our body weight is made up of calcium, which is about 1.2kg for a 60kg person. That’s a lot of mineral.
99% of calcium is found in our bones, where it is responsible for adding strength to the protein matrix. One of the causes of the bone thinning disease, osteoporosis, is due to a loss of calcium from the bones. The other 1% of calcium in the body is not idle, it is important for regulating the heartbeat, contraction of muscles, clotting of blood and release of nerve messengers. Calcium can also help with blood pressure, including pregnancy induced hypertension.
Where to find it
The vegetable kale, a member of the cabbage and broccoli family, is extremely high in calcium (it’s also a good source of iron and vitamin C). The only problem is that kale sightings are fairly rare. Someone should start a ‘save the kale’ campaign. Other foods that are a good source of calcium include milk products (especially cheese), nuts, seeds, whole grains, figs, tofu, asian green vegetables, carob, and fish with edible bones such as sardines and canned salmon.
Foods that negatively impact on calcium include; salt, sugar, tea, coffee, animal protein (ie meat), and phosphates which are mainly found in fizzy soft drinks. Aluminium containing antacids are also bad news for calcium levels.
How much do we need?
Most of us have to work pretty hard to obtain enough calcium from our diet, but it can be done. We need between 800-1200mg per day. Post-menopausal, pregnant and lactating women and growing children need more calcium than others. Calcium supplements are often recommended when food alone is unlikely to provide sufficient calcium. There’s a host of different forms of calcium from which to choose, from ground up oyster shells to chalk (calcium carbonate) from the white cliffs of Dover. It’s very confusing, particularly when a large dose calcium tablet may not be the one that is best absorbed. As a rule the supplements that contain calcium citrate, calcium lactate, calcium gluconate or calcium hydroxyapatite are the best absorbed. Look for one that also has a few of the co-nutrients that assist in calcium absorption and utilisation, these include vitamin D, vitamin K and magnesium. Calcium is best taken at night.
There is some concern that calcium supplements may contribute to kidney stones. The calcium citrate variety has proven to be safe in this regard. However, play it safe and don’t overdo it. When it comes to calcium more is not necessarily merrier. Over 2g a day increase risk of kidney stones and soft-tissue calcification which can lead to arthritis-like symptoms.