Plant-based drinks: The importance of nutrient quantity and quality

“I think sometimes nutrition and health are words that are not often taken into account in the development of these plant-based alternatives,” Marjolijn Bragt, programme manager for nutrition for optimal health at Wageningen Food and Biobased Research, told an audience at Food Ingredients Europe 2023.

Ultimately, she argued, plant-based drinks “are very different products” to traditional dairy products – with important ramifications for consumer health.

“They have a lower nutritional content and quality, a higher degree of processing, and I think we should do more research to understand: what does it mean for health if we incorporate those products in our daily diets?” she said.

She added: “I don't think we need to exclude food groups from our diet, but I think eating less meat and eating more plant-based foods is beneficial for health and planet. And I think there are massive opportunities to improve the plant-based offerings from what we have today.”

Dairy versus plant-based drinks: Considerations for product developers

Compared to cow's milk, plant-based drinks “have many differences”, Bragt said.

“There are differences in the number of micronutrients and the types, the protein quantity and quality, also the matrix – so the products and how the nutrients are embedded in the product – but also the degree of processing is very different,” she explained.

In the Netherlands, milk is still included in the country’s healthy eating guidelines, she said, as it “contains a lot of nutrients, so it's actually a quite efficient way to reach a lot of the dietary needs that we need per day”.

Milk contains micronutrients such as calcium, phosphorus, potassium, iodine, and very importantly, vitamins B2 and B12 – nutrients often lacking from plant-based alternatives, said Bragt. Many plant-based drinks fail to fulfil healthy eating criteria in terms of nutrient content, while only about half are fortified with calcium or other micronutrients.

So, is there a place for plant-based beverages in such consumer guidelines?

“There is a development challenge,” Bragt said. “I think there's a lot of opportunity still to look at the fortification and bioavailability of micronutrients in plant-based drinks, but also how to incorporate it… I think there are important challenges that we can still work on.”

Protein quantity and quality varies between plant-based and animal sources

Variations in protein quantity and quality present a crucial consideration for product development.

“Protein quality is actually determined by the presence of amino acids, but also the levels and the bioavailability of those amino acids… If you look at the amino acids, you see that most plant-based sources lack one or more of the essential amino acids but also are less well digested by our body,” Bragt explained.

One glass of cow’s milk “provides roughly 24% of the WHO [World Health Organization] requirements for essential amino acids”, she added.

“If you're looking at amino acid content and protein content of the alternatives, you see that, for example, to reach the similar amounts … you would need to consume 1.7 glasses of soy, 7.9 glasses of oat, [and] up to 246 glasses of rice drink to equal the amounts available in in cow's milk,” she said.

“I think if you position it from a perspective of nutritional quality and health, I think it's important to take this into account.”

Plant-based drinks, processing, and the question of digestibility  

Processing and post-processing conditions also have implications for protein quality, which can be measured using the protein digestibility-corrected amino acid score (PDCAAS) or the digestible indispensable amino acid score (DIAAS).

Both techniques compare the digestibility of a dietary protein against a reference protein to determine a score rating its protein quality, with a higher score indicating a higher-quality protein; the DIASS is the preferred method, however, as PDCAAS values are capped at a score of 1.0, making it impossible to categorise scores that exceed the reference protein, whereas the DIASS allows for scoring above 1.0.

“There are a lot of publications on the digestibility of protein, but they differ quite a lot – and that's where you can potentially see the impact of processing,” Bragt explained.

For example, the DIASS value for cow's milk or milk protein powders varies between 1.0 and 1.2, while for pea protein, it is 0.6; however, when pea protein is processed into a concentrate or isolates, values range between 0.7 and 1.0.

“You would expect if I buy a pea isolate, it's all the same, but that's not the case,” Bragt said.

She added: “It's important to critically assess each source that you buy or use for a product because it can have a different digestibility score based on how a company processes the protein.”

Muscle protein synthesis: Can plant-based drinks be as effective as animal sources?

One question Bragt said she was often asked is whether plant-based foods can be equally effective as animal sources in building muscles.

© iStock/AleksandarGeorgiev

“Plant-based protein sources can indeed also stimulate muscle protein synthesis,” she said. “But what you often see is that you would need 30 to 40 g of that protein to achieve the same effect as what you would reach with a milk protein where you only need 20 g to need the same effect.

“So I think yes, it can be equally effective but at higher dosages, and also there, it's important to look at the amino acids composition, because some plant proteins lack one amino acid but you can then combine it with a source that is richer in that amino acid so you have complementary combinations.”

She highlighted research comparing whey protein with duckweed that showed the duckweed protein was hardly absorbed by the body – apart from when it was ingested as an isolate.

“One thing you can see was plant-based protein is less well digested; two, you see that if you process it in a different way, the digestibility can be increased,” she said. “And what we also show is actually, if you look at individual responses of people, that people digest proteins very differently.”

The question of inter-individual variation is one that her team is seeking to better understand through its future research.

“We want to understand how food processing but also product design can support an optimal amino acid uptake,” she explained.