The complex nature of nutrition: calcium

Posted by kathryn in All In A Day's Work, The Micronutrients and A Balanced Diet

I’m writing an article at the moment for Wellbeing magazine about the new Nutrient Reference Values released by the health department. A whole series of changes have been made – RDIs have gone up for some nutrients, down for others, for all different reasons.

One that has increased is the RDI for calcium, because . . . we lose about 60mg of calcium every day in our sweat.  This simply wasn’t known when the old values were set. To add to the complexity, in order to get this 60mg, we actually have to consume an extra 320mg of calcium. Sounds bizarre doesn’t it?

For many vitamins and minerals there’s a difference between how much we eat and how much we actually digest, absorb and are then able to utilise in our bodies. This is sometimes called the bioavailability of the nutrient. One example is folate, we only absorb half of the folate from the foods we eat, the rest just passes straight through.

In the case of calcium, the more calcium we have in our bodies, the less we absorb. This is a safety mechanisms, to prevent you from over-dosing on calcium, which is a good thing. It does mean, however, in order to get that extra 60mg into our bodies where it can be used, we have to eat more than five times that amount.

320mg of calcium can be found in:

• 260ml of milk
• 160g yoghurt
• 130g ricotta (eg in wattleseed baked ricotta !)
• 40g cheddar / tasty cheese
• 140g almonds
• 285g pumpernickel bread
• 100g tinned salmon or sardines, including bones
• 160g dried figs
• 95g tahini (sesame seed paste)
• 700g chick peas
• 275ml soy milk

18 August, 2006