The study, carried out by Swiss scholars and nutrition experts, analyzed the nutrient profile of 27 samples of plant-based beverages and two of cow’s milk were compared. The plant drinks, 13 of which were fortified, were collected from two major supermarkets in Bern and included soy, almond, cashew, coconut, hemp, oat, rice and spelt.
To compare nutrient and energy intakes, the researchers used the dietary reference values for Germany, Austria and Switzerland and also estimated the quality of proteins through calculating the digestible indispensable amino acid score (DIAAS). Nutrients such as vitamins C, A, E, D2, K1 and K2 were analyzed as well as phosphorus, sodium, manganese, magnesium, potassium, iron, copper, calcium, zinc, iodine, biotin, niacin, pantothenic acid, and others.
Unlike similar research conducted in the past which relied on labelling information to determine nutrient content levels and only evaluated a handful of nutrients, the Swiss study investigated each product sample in a laboratory to determine its nutrient composition and quality.
Under the microscope
According to the laboratory analysis, vitamin C, A and K2 could not be detected in the measured plant-based drinks, with B2, B12 and D2 almost absent in non-fortified varieties. The researchers noted that the absence of some vitamins, such as the heat-sensitive C, B1 and A, could be down to food processing conditions. Meanwhile, plant-based alternatives offered high vitamin E content, particularly almond and soy, whilst K1 concentrations were ‘significant’ in cashew and soy drinks.
On minerals, soy drinks were richest in copper, magnesium, manganese, potassium, zinc and iron, and also came closest to dairy milk in terms of protein content. The second-highest mean protein contents were found in cashew and almond drinks, while protein levels were ‘very low’ in oat, coconut and rice-based beverages.
In terms of protein quality, milk came ahead of all plant-based samples with a higher DIAAS.
Mind the red algae and surcose levels
The researchers also noted that phytic acid, which is naturally contained in plant-based milk and is a key source of phosphorous, is a ‘known antinutrient able to chelate [i.e. to bond, note ed.] micronutrients such as calcium, zinc, magnesium and iron.’ The study also highlighted the use of red algae in some plant-based alternatives, which, while useful for boosting iodine levels, ‘should also be monitored because of possible arsenic accumulations,’ the study reads.
On sugar, the research noted that surcose - a simple sugar which had been linked with increased risk of obesity, cardiovascular disease and type-2 diabetes - was 'the main sugar in the plant-based drinks with a glycaemic index of 61'. In a previous study, plant-based alternatives had been found to have a higher GI of 47.52 to 99.96 compared to dairy milk's 46.93. “Despite the generally lower total carbohydrate content in plant-based drinks (except some rice and oat drinks), milk consumption appears therefore more favorable in terms of GI,” the Swiss study claims.
The way forward: A balanced diet and improved fortification
The researchers concluded that plant-based drinks were ‘limited’ in providing a ‘significant’ amount of micronutrients, unlike cow’s milk. “In future, nutritional quality of plant-based drinks with science-proven nutrient and micronutrient bioavailability should be equally considered and communicated than sustainability goals,” the authors wrote. “Practical solutions to mitigate nutritional gaps of specific plant-based drinks could be to opt, whenever possible, for a combination of plant-based alternatives as part of a balanced diet to ensure adequate fulfilment of nutrient and micronutrient needs.
"Finally, real innovation opportunities exist on evolving conventional and ultra-processing food manufacturing techniques, generally required in the manufacturing of plant-based products, toward simplified and/or natural processes such as microbial fermentation that can reduce antinutritional characteristics of foods/ingredients, improve protein digestibility and produce additional micro-or phytonutrients.”
Lower protein content 'not an issue'
DairyReporter contacted Sarah Coe, a nutrition scientist at the British Nutrition Foundation, for a comment on this research. “Plant-based drinks can provide many of the nutrients found in cow’s milk and contribute positively to overall nutrient intakes,” she told us. “We know that the nutrient content of plant-based drinks can vary between brands and varieties, depending on what nut, legume or cereal they are made from. Apart from soya, plant-based drinks are typically lower in protein than cow’s milk, however, this is not an issue for most people as average protein intakes in adults tend to be more than requirements.”
On fortification, she said: “As plant-based drinks do not naturally contain the same mix of vitamins and minerals as cow’s milk, it’s important to consider plant-based drinks that have been fortified. In the UK, most non-organic, plant-based drinks are fortified with calcium and vitamins B12 and B2 to levels similar to cow’s milk. Fortification with other micronutrients such as iodine and vitamin D is becoming more common but still varies between products."
“Organic plant-based drinks cannot be fortified due to EU regulations, so are not likely to be a suitable alternative to cow’s milk.”
On sustainability, Coe added that more independent research is needed to establish how dairy compares to plant-based alternatives. “We need more information on how plant-based drinks compare to dairy products in terms of their environmental impact. Plant-based drinks appear to have a lower environmental impact per unit weight than dairy foods for greenhouse gas emissions, water and land use, however, there are currently few studies directly comparing the impacts of dairy and alternative products, except for soya-based drinks. Limited data suggest that some plant-based drinks, such as rice and almond drinks, may be particularly water-intensive to produce.”
When consumers seek to replace dairy milk with plant-based drinks, they should aim for unsweetened varieties that are fortified with calcium and other micronutrients, she added, “as well as consider the rest of the diet to make sure it is balanced and contains a variety of sources of protein and the micronutrients that dairy milk can provide.”
Comparison of nutritional composition between plant-based drinks and cow’s milk
Published in: Frontiers in Nutrition, 28 October 2022