New Study Challenges Assumptions
By University of Copenhagen - Faculty of Science
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One key factor driving the demand for plant-based beverages
is their typically lower climate footprint compared to cow’s milk. However, a
new study by the University of Copenhagen, in collaboration
with the University of Brescia in Italy, reveals that these alternatives may
not necessarily be healthier than cow’s milk—a common misconception among
consumers.
In the study, researchers examined how chemical reactions
during processing affect the nutritional quality of ten different plant-based
drinks, comparing them with cow’s milk. The overall picture is clear:
“We definitely need to consume more plant-based foods. But
if you’re looking for proper nutrition and believe that plant-based drinks can
replace cow’s milk, you’d be mistaken,” says Department of Food Science
professor Marianne Nissen Lund, the study’s lead author.
Long shelf life at the expense of nutrition
While milk is essentially a finished product when it comes
out of a cow, oats, rice, and almonds require extensive processing during their
conversion to a drinkable beverage. Moreover, each of the plant-based drinks
tested underwent Ultra High Temperature (UHT) treatment, a
process that is widely used for long-life milks around the world. In Denmark,
milk is typically found only in the refrigerated sections of supermarkets and
is low-pasteurized, meaning that it receives a much gentler heat treatment.
“Despite increased plant-based drink sales, cow milk sales
remain higher. Consequently, plant-based drinks undergo more intense heat
treatments than the milk typically sold in Denmark, in order to extend their
shelf life. But such treatment comes at a cost,” says Marianne Nissen Lund.
UHT treatment triggers a so-called “Maillard reaction”, a
chemical reaction between protein and sugar that occurs when food is fried or
roasted at high temperatures. Among other things, this reaction impacts the
nutritional quality of the proteins in a given product.
“Most plant-based drinks already have significantly less
protein than cow’s milk. And the protein, which is present in low content, is
then additionally modified when heat treated. This leads to the loss of some
essential amino acids, which are incredibly important for us. While the
nutritional contents of plant-based drinks vary greatly, most of them have
relatively low nutritional quality,” explains the professor.
For comparison, the UHT-treated cow’s milk used in the study
contains 3.4 grams of protein per liter, whereas 8 of the 10 plant-based drinks
analyzed contained between 0.4 and 1.1 grams of protein. The levels of
essential amino acids were lower in all plant-based drinks. Furthermore, 7 out
of 10 plant-based drinks contained more sugar than cow’s milk.
Heat treatment may produce carcinogens
Besides reducing nutritional value, heat treatment also
generates new compounds in plant-based drinks. One such compound measured by
the researchers in four of the plant-based drinks made from almonds and oats is
acrylamide, a carcinogen that is also found in bread, cookies, coffee beans,
and fried potatoes, including French fries.
“We were surprised to find acrylamide because it isn’t
typically found in liquid food. One likely source is the roasted almonds used
in one of the products. The compound was measured at levels so low that it
poses no danger. But, if you consume small amounts of this substance from
various sources, it could add up to a level that does pose a health risk,” says
Marianne Nissen Lund.
Additionally, the researchers detected α-dicarbonyl
compounds and hydroxymethylfurfural (HMF) in several of the plant-based drinks.
Both are reactive substances that could potentially be harmful to human health
when present in high concentrations, although this is not the case here.
While professor of nutrition Lars Ove Dragsted is not
particularly concerned about the findings either, he believes that the study
highlights how little we know about the compounds formed during food
processing:
“The chemical compounds that result from Maillard reactions
are generally undesirable because they can increase inflammation in the body.
Some of these compounds are also linked to a higher risk of diabetes and
cardiovascular diseases. Although our gut bacteria break down some of them,
there are many that we either do not know of or have yet to study,” says Lars
Ove Dragsted of the Department of Nutrition, Exercise and Sports.
Professor Dragsted adds: “This study emphasizes why more
attention should be paid to the consequences of Maillard reactions when
developing plant-based foods and processed foods in general. The compounds
identified in this study represent only a small fraction of those we know can
arise from Maillard reactions.”
Make Your Own Food
According to Professor Marianne Nissen Lund, the study
highlights broader issues with ultra-processed foods:
“Ideally, a green transition in the food sector shouldn’t be
characterized by taking plant ingredients, ultra-process them, and then
assuming a healthy outcome. Even though these products are neither dangerous
nor explicitly unhealthy, they are often not particularly nutritious for us
either.”
Her advice to consumers is to: “generally opt for the least
processed foods and beverages, and to try to prepare as much of your own food
as possible. If you eat healthy to begin with, you can definitely include
plant-based drinks in your diet – just make sure that you’re getting your
nutrients from other foods.”
At the same time, Professor Lund hopes that the industry
will do more to address these issues:
“This is a call to manufacturers to further develop their products and
reconsider the extent of processing. Perhaps they could rethink whether UHT
treatment is necessary or whether shorter shelf lives for their products would
be acceptable.”
Reference: “Investigation of Maillard reaction products in
plant-based milk alternatives” by Mariachiara Pucci, Halise Gül Akıllıoğlu,
Marta Bevilacqua, Giulia Abate and Marianne Nissen Lund, 20 November
2024, Food Research International.
DOI: 10.1016/j.foodres.2024.115418
