'Weird' detail on Aussie milk carton explained

An Australian shopper has pointed out a major discrepancy between the health star ratings on two popular milk varieties.

The shopper compared a bottle of Farmdale Fresh full cream milk to a carton of Inner Goodness Organic soy, both believed to be from Aldi, and was surprised by what they learned.

The full-cream milk has a rating of 4 out of 5 stars, whereas the organic soy milk has just one.

The Health Star Rating (HSR) system is a voluntary and free front-of-pack labelling system that rates the overall nutritional profile of packaged food and assigns it a rating from ½ a star to 5 stars.

It provides a quick, easy, standard way to compare similar packaged foods. The more stars, the healthier the choice.

Noticing the difference between the two milk varieties, the shopper shared a photo on Reddit seeking some answers.

"Why is soy milk only 1 star when full cream is 4?" the Aldi shopper wrote online, presuming the soy variety would be "healthier."

"Soo weird, i have a bottle of So Good Soy Milk and it has a 4.5 star rating?' one person questions, prompting a possible explanation from others.

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"From my understanding, it is compared to equivalent products. So that full cream milk is 4 stars compared to other full cream milk. That soy milk is 1 star compared to other soy milk," one person suggested.

Therese O’Sullivan, Professor in Nutrition and Dietetics, confirmed that soy milk should only be compared to other soy milks with this system, not with dairy products, including full cream milk.

"The Heath Star Rating (HSR) is designed for comparison of similar products in the same food category — typically found in the same section of the shop. It only applies to packaged products," she told Yahoo News Australia.

Why do ratings vary?

Many pointed out that brands of soy milk vary significantly in terms of ingredients with products containing varying amounts of water, vegetable oil, sugars and additives. The same is said for other non-dairy milk alternatives.

"I got this one by accident the other day, the ALDI organic soy milk is full of sugar, oil and soy flavouring," one person said, noting "most soy milks are 4 or 5 star".

"My kids have dairy allergies, so we buy oat milk, but we can’t buy Aldi oat milk because it has no calcium in it. I imagine the soy milk is the same," another added.

Prof O’Sullivan agreed the health rating on this particular soy product was lower than normal, but it's probably because of the ingredient list.

"It's hard to say as the nutrition information panels are not visible, however I’d guess that the soy milk may have a higher sugar content compared to other soy milks (they can range from 1 to 10 per cent)," she said

"For dairy alternatives like soy milk, it also needs to have a minimum of 100mg of calcium per 100ml [to be compared to regular milks]. So that particular soy milk may not have been fortified with calcium, whereas other soy milks are."

How is the health rating calculated?

A spokesperson for the Department of Health and Aged Care explained to Yahoo exactly how the HSR is calculated.

"The system considers four components of a food associated with increasing the risk factors of chronic diseases — energy, saturated fat, sodium and total sugars content (negative components)," they said.

"[They're] balanced against foods beneficial components such as fruit, vegetable, dietary fibre, protein content, nut and legume (positive components)."

If two products in the same category have different ratings, the lower-rated product contains more of those components associated with increasing risk factors of chronic disease and/or fewer of those beneficial components.

"For a soy milk to be calculated in the same category as dairy milks, it needs to contain a certain amount of calcium," they said.

"In this case it may have a lower rating because it is in a different category and receives a lower rating as a result."

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