Calcium is the most abundant mineral in the body. So it’s no surprise that it has many important functions. Calcium’s primary role is to build strong bones and teeth. Calcium helps muscles contract, nerves transmit signals, blood clot and blood vessels contract and expand. These functions are so important that your body will extract calcium from your skeleton if you aren’t getting enough from your diet.
Milk, cheese, yogurt, calcium-set tofu (tofu prepared with calcium salts; check the label), kale and broccoli are all good sources. If you are worried about the fat content in dairy foods, choose low-fat and fat-free versions, which are usually no different in their calcium content.
You may have heard that calcium from vegetables is not as available to your body as calcium from dairy sources. This is true to some extent. Calcium is poorly absorbed from some vegetables and beans, such as spinach, sweet potatoes, rhubarb, red beans and pinto beans. For example, just one-tenth of the calcium from spinach is absorbed compared to that from milk sources. However, just as much calcium is absorbed from vegetables in the kale family (broccoli, bok choy, cabbage, mustard greens) as from milk sources. While this is good news, keep in mind that some vegetables contain more calcium per gram than others. For example, you would have to consume much greater amounts of broccoli to get the same amount you might get from kale.
Chronically low intakes of calcium can contribute to the development of osteoporosis, a condition of increased bone fragility that can up your risk for bone fracture. In the United States each year, 1.5 million fractures are associated with osteoporosis.
Growing individuals (infants, children and adolescents) who do not get enough calcium will be unable to achieve optimal levels of bone mass, thus putting them at increased risk for osteoporosis as they age.
You may be wondering, are there any signs of calcium deficiency before someone develops osteoporosis? Unfortunately, one of the reasons that osteoporosis sneaks up on you is because simple dietary deficiency produces no obvious symptoms.
Excessively high intakes of calcium from supplements have been shown to cause kidney stones and poor kidney function. High levels of calcium can also prevent your body from absorbing other minerals properly, such as iron, phosphorus and zinc.