Almost all of the calcium in the body (~99%) is found in the bones (and teeth), where it is essential for building and maintaining bone to give the bone its strength. The remaining ~1% is dissolved in the bloodstream and other fluids where it is used for maintaining the function of the heart, muscles, blood and nerves. We continuously lose calcium each day through our skin, nails, sweat and urine.
What happens if your diet is low in calcium?
Our bodies cannot make calcium, therefore all our calcium requirements are provided by our diet. If our diets do not provide sufficient calcium, there will not be enough calcium available in the bloodstream for our bodies to function properly. This means some of the calcium crystals stored in the bone will dissolve to 'stock up' the calcium needed in the bloodstream. If your calcium intake remains too low, the calcium in your bone will continuously need to dissolve and be released into your bloodstream, and you risk losing bone strength.
As well as increasing your intake of calcium, it is also essential that the calcium is able to be absorbed by the body. Calcium absorption can be reduced by excessive alcohol or caffeine consumption, as well as consuming a diet high in animal proteins or drinking soft drinks that contain phosphates. As we age, calcium is absorbed less effectively from the intestine thus we need to increase our intake of calcium to avoid losing bone density which may result in osteoporosis.
The greatest rate of bone growth is reached by puberty, and by age 30 we reach our peak bone mass (maximum bone density). The higher our peak bone mass, the better our bone health will be in the future. This is particularly important for women as rapid bone loss occurs during the menopause. As puberty is an essential time for determining your overall bone health, it is critical that children and teenagers get enough calcium.
Your daily calcium requirements depend on your age and sex. Less than half of Australian adults get their daily recommended intake of calcium.
Sources of calcium
Dairy foods such as milk, yoghurt and most cheeses are calcium-rich and serve as the primary source of calcium in our diet. Calcium is also more easily absorbed from dairy products compared to other food groups.
Aim to eat 2-3 serves a day such as a glass of milk, a slice of hard cheese or a yoghurt.
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It's not only humans that have high levels of calcium in their bones. Consuming canned fish including the bones will also help you increase your calcium intake.
Try canned salmon or sardines!
Eat more fruit and veg!
Small amounts of calcium are also found in fruit and vegetables, particularly greens such as broccoli and kale. Nuts are also a great way to introduce more sources of calcium into your diet, particularly almonds.
Australian dietary guidelines 2013
Nutrient reference values for New Zealand and Australia
Calcium content of various foods
NHMRC Food for Health