Calcium myths put to the test
By Kimberly Gillan|
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Calcium is to bones what pizza is to Ninja Turtles (essential).
Best known for its role in building a healthy skeleton, calcium also plays a role in transmitting nerve impulses, clotting blood and regulating the heart's rhythm.
But there’s a lot of conflicting info about the best ways to meet your daily calcium target. Here’s what the science says.
The claim: You can't absorb calcium from dairy
You can also get calcium from many foods such as dark leafy green vegetables, sesame seeds and fish like sardines and salmon with bones still in it — though the most well-known source is milk and dairy products.
However, when a large Harvard University study found high dairy intake wasn't clearly linked with a reduced fracture risk, plenty of people were left wondering if we really need the recommended two to three serves of dairy a day for strong bones.
"Milk and dairy products are a convenient source of calcium for many people," Harvard researchers write.
"Currently, there’s no good evidence that consuming more than one serving of milk per day in addition to a reasonable diet (which typically provides about 300 milligrams of calcium per day from non-dairy sources) will reduce fracture risk."
But that’s not strong enough evidence to do away with dairy just yet. The Australian Dietary Guidelines call for 2-3 daily servings a day, a recommendation accredited practicing dietitian Natasha Murray says has been developed after painstaking analysis.
"It's based on the research of over 50,000 studies and is high-level evidence for the general population," says Murray, who is a spokesperson for the Dietitians Association of Australia.
"We recommend dairy as a source of calcium because the evidence tells us it's one of the best sources of calcium we can access."
Murray says it's difficult to get comprehensive evidence due to the huge variety in lifestyle factors that influence how well individuals absorb nutrients.
"It's great that there are always new studies coming out looking at alternatives, but we cannot change recommendations based on one study because there are so many other things we need to look at,' she points out.
"What's the ethnicity of the people? What was the rest of their diet looking like? Were they being supplemented with calcium? Were they getting enough vitamin D?"
The claim: Humans aren't adapted to drink dairy
You've probably seen a Facebook thread or two about the fact humans are the only animals who drink milk from another mammal, which makes us sound… creepy.
But Sophie Medlin, nutrition and dietetics lecturer at King's College in London, says that if your ancestors are from northern Europe or North America then you've probably got the genetics to tolerate milk well – and will get nutritional benefits from it, beyond calcium.
For your biological information, all babies produce an enzyme called lactase than breaks down lactose, the sugar (lactose) in breast milk or formula, and allows it to pass through the gut walls and into the bloodstream.
But in countries that haven't historically drank milk beyond their baby years, most people have evolved to stop producing lactase after they wean — thus "producing almost entire populations that may be unable to absorb the lactose in milk".
"In populations where milk consumption has always been high, such as in Europe, most adults continue to produce lactase for their whole lives and can digest milk quite happily with only around five percent of the population being lactose intolerant," Medlin writes on The Conversation.
In fact, Medlin says people who had the genetic "mutation" to tolerate dairy ended up having an evolutionary advantage which they passed onto their offspring.
"Milk is a useful source of protein, energy, calcium, phosphate, B vitamins and iodine, meaning that those with the mutation were generally healthier and produced more children than those who couldn’t tolerate milk," she writes.
The claim: Adults don't need dairy
Studies seem to point to the fact that milk consumption in adulthood has no statistical link with reduced fracture risk, however people who got plenty of milk in childhood seem to have stronger bones.
"When we look at studies of children who have an allergy to cow’s milk, for example, we see that the strength of their bones is significantly compromised by the lack of milk in their diet," Medlin writes.
"Interestingly, children with this allergy who are given alternative sources of calcium other than milk still find the strength of their bones compromised. This suggests that calcium-containing alternatives to dairy are still not good enough at promoting bone density in children."
Medlin says dairy consumption in adulthood does not show the same association with increased bone strength — however that's not to say that dairy isn't a healthy food choice for adults who can tolerate it.
"While milk intake is really important for the healthy development of children’s bones, consuming milk as an adult doesn’t appear to decrease your risk of fractures," she writes.
The claim: There's no consequence from cutting dairy from your diet
There may not be a definitive word on whether dairy consumption in adulthood reduces fracture risk, but Medlin says that dairy offers more than just calcium.
"Milk and dairy foods are also a great source of all essential amino acids which are the small protein molecules that build muscles and repair tissue damage," she writes.
"Studies have found that if dairy is replaced in the diet by foods containing the same amount of calcium such as green leafy vegetables or soya milk fortified with calcium, the diet contains less protein, potassium, magnesium, phosphorus, riboflavin, vitamins A and B12."
So while dairy may not be essential to your diet, it's a convenient way to get nutrients.
"At moderate levels … consumption of calcium and dairy products has benefits beyond bone health, including possibly lowering the risk of high blood pressure and colon cancer," Harvard researchers write.
The claim: You're better off getting your calcium from green leafy vegetables
Vegetables like spinach and chard contain calcium — however they also contain oxalic acid, which Murray says prevents it being absorbed.
"It's sort of like the oxalic acid is the school crossing lollipop lady saying, 'No, you can't come through just yet'," Murray explains.
"If you're not having dairy, make sure you are choosing milks that are calcium fortified. Tofu, almonds and Brazil nuts are great, as is salmon or sardines with bones in them."
Obviously still go hammer and tong on your leafy green, just don't automatically think they tick your calcium box.
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