This is the last piece in our series on packs. We have covered what the claims on the front mean, the per 100g column, the health star rating and the ingredient list. This one is about the assumption sitting underneath all of it.
Every percentage daily intake figure on an Australian pack is calculated against the same reference person. An average adult eating 8700 kilojoules a day.
We need a standard. Without one, no two products could be compared and the percentages would mean nothing at all.
But that average is higher than most women need, and it misses the places where our requirements are different.
Iron, where the gap is clearest
The labelling reference for iron is 12mg. Women aged 19 to 50 need 18mg a day. Women over 51 need 8mg, and so do men.
So a product showing 100% of the labelling reference for iron is giving a woman aged 19 to 50 about two thirds of what she needs. For a woman over 51, or a man, the same amount is 150% of theirs.
One figure, three quite different answers, and the panel can only show you one.
Calcium is worse
The labelling reference for calcium is 800mg.
Women aged 19 to 50 need 1000mg a day. From 51 that rises to 1300mg, because falling oestrogen changes how bone is maintained.
So the reference figure sits below what a woman needs at any adult age. A product at 100% of the labelling reference is short for everyone reading this.
Where the system does distinguish
Foods made for infants and young children have their own reference figures. Iron is 6mg for children aged 1 to 3 against the general 12mg. Calcium is 700mg for children and 550mg for infants against the general 800mg.
So the framework can hold more than one reference person. Sex simply is not one of the axes it uses, and there is no mechanism to publish women specific percentages in the panel itself.
It runs the other way too
Falling short is only half of it, and the other half surprises people more.
Australia sets limits on how much of a nutrient can go into a food like this. Plenty of countries do not. So you will find products sold here from overseas carrying several times the reference intake of things like zinc and vitamin B6, in amounts that would not be permitted in an Australian made product.
More is not better with micronutrients. It is a range, and both ends have consequences. We go into what the percentages actually mean, and the number that matters more than 100%, here.
What to do about it
Use the percentage for what it is good at, which is comparing two products against each other. Both are measured against the same reference, so the comparison holds even when the reference does not describe you.
Then find out your own numbers for the handful of nutrients where women differ most. Iron, calcium, folate and iodine are the ones where the gap between the reference and the requirement is widest.
Our own formula page shows every percentage against Australian requirements for women, with age bands where the requirement changes. Same product, different answer depending on who is drinking it.
The takeaway: Percentage daily intake figures are calculated against an average adult on 8700kJ. The iron reference is 12mg against a requirement of 18mg for women 19 to 50. The calcium reference is 800mg against a requirement of 1000mg, rising to 1300mg after 50. None of it is wrong. It just was not calculated for you.
The science behind this post:
- Australia New Zealand Food Standards Code, Schedule 1: RDIs and ESADDIs. The Recommended Dietary Intake for labelling purposes is 12mg for iron and 800mg for calcium, with separate columns for children aged 1 to 3 and infants. foodstandards.gov.au
- Food Standards Australia New Zealand. Percentage daily intake labelling is based on an average adult reference diet of 8700kJ. foodstandards.gov.au
- National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand: Iron. RDI 18mg per day for women aged 19 to 50, 8mg from age 51, and 8mg for men aged 19 and over. nrv.gov.au
- National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand: Calcium. RDI 1000mg per day for women aged 19 to 50 and 1300mg from age 51. nrv.gov.au