So what happens if you don’t get enough from your diet? Your body ‘steals’ it from your bones.
The mineral is calcium. Your body contains more calcium than any other mineral. It’s vital for strong bones and teeth, as well as for the proper functioning of the muscles and heart, blood clotting, and transmitting messages through nerves. Communicating between your brain cells requires calcium – each time one brain cell sends a message to another, calcium is used.
But dietary surveys consistently show that at least half of Australian children from the age of 4 don’t consume enough calcium. Between the ages of 9 and 11, 45% of boys and 54% of girls get insufficient calcium.
By the time children hit adolescence, the figures get much worse. Between the ages of 14 and 18, 71% of boys, and 90% of girls aren’t consuming enough calcium.
When your children hit their mid 20s they reach what’s known as ‘peak bone mass’—their bones will not get any denser or stronger.
This makes it critical that children and adolescents get sufficient calcium from their diet. If children have sub-optimal bone mass in their 20s then they risk osteoporosis later in life, the bone thinning disease where bones are highly susceptible to fracture. While women are most affected by osteoporosis because they lose the protective effect of oestrogen after menopause, men get osteoporosis too.
The best sources of calcium? Milk (all types), soy milk and other dairy alternatives (as long as they are fortified with calcium), all cheeses particularly hard ones such as cheddar and parmesan, and yoghurt. Smaller amounts are found in sardines and salmon with bones, dried figs and apricots, sesame seeds and tahini, and almonds.
If you (or your child) is vegan or avoids dairy for other reasons, the good news is that a surprising amount of highly absorbable calcium is contained in certain greens such as kale and bok choy. These particular greens have low levels of oxalates, which are molecules in plants that bind tightly to calcium and prevent its absorption. Rhubarb, spinach, and silverbeet are high in oxalates not good sources of calcium.
To increase the absorption of calcium, you need vitamin D, potassium and magnesium. Too much protein can affect calcium absorption, as can excessive caffeine and coffee.
Children over 10 need 1000-1300mg of calcium per day, the upper level required during adolescence. One 250ml glass of milk, a 200g pot of yoghurt, or 30g cheese supplies about 300mg.