Researchers involved have described the findings as a “disconcerting discovery” since consumers tend to perceive plant-based milk as mineral-rich.
They have thus urged the country’s regulator to implement advisory labelling, especially for older women and adolescents who require a higher intake of micronutrients.
The analysis, said to be the first of its kind in Australia, looked at plant-based milk sold in major Australian supermarkets such as Woolworths, Coles and health foods stores from last November to January this year.
Out of the products analysed, 48 were tree nuts and seeds-derived milk, 27 from legumes, 10 from coconut, 19 from grains and 11 from mixed sources.
Low in micronutrient contents
Published in Nutrients, the findings showed that plant-based milk is especially low in vitamin A, vitamin B12, protein, zinc and iodine content.
This is despite the fact that 57% of the products studied were already fortified with micronutrients.
For example, except for the plant-based milk derived from mixed sources, all contained little to zero vitamin B12. About 0.5 to 0.8 µg/100ml of the vitamin can be found in cow’s milk.
The protein content of plant-based milk is also lower at 0 to 4.2g/100 ml, while that of cow’s milk was 3.2 to 4.7g/100ml.
None of the products examined was fortified with zinc or iodine, although one legume-based product contained kelp, a rich source of iodine.
In addition, only one-third contained similar calcium content to cow’s milk.
Perhaps the one key benefit of plant-based milk is its lower sugar content, ranging from 1.1 to 3.7g/100ml while that of cow’s milk is 5.3g/100ml.
“Despite the fortification of some products, plant-based milk alternatives were found to be poor sources of some micronutrients,” the researchers said.
Effects on adolescents and older women
A further examination was undertaken to examine how replace cow’s milk with plant-based milk would affect adolescents aged 12 to 18 and women over 50 years old.
This is because these age groups have “special physiological demands”, such as bone health, that are fulfilled by dairy food ingestion.
For the adolescents, drinking cow’s milk could fulfil 64% to 90% of their Estimated Average Requirements (EAR) of protein intake.
However, consuming plant-based milk could only fulfil 4% to 23% of the EAR, with the exception of legumes at 55% to 78%.
For women over 51 years old, the same trend was observed, where legumes were the only comparable source to cow’s milk when it comes to calcium content at 98% EAR for both.
Protein wise, drinking cow’s milk could fulfil 97% of the EAR, while drinking plant-based milk could only fulfil 5% to 24% of the EAR, with the exception of legumes at 84%.
“Our modelling suggested that cow’s milk was a significant source of protein, calcium and zinc in adolescents and older women, providing 50% or over of the daily recommended intake in both population groups.
“Indiscriminate substitutions might reduce intakes of protein and micronutrients, particularly vitamin A, B2, B12, iodine and zinc, and lead to reductions of more than 50% of the estimated average requirements for protein, zinc and calcium,” the researchers concluded.
This research received no external funding, but was supported by the Grains and Legumes Nutrition Council, a non-profit charity.
Got Mylk? The Emerging Role of Australian Plant-Based Milk Alternatives as A Cow’s Milk Substitute
Authors: Sara Grafenauer, et al