Petra Schaller
Consumption of plant-based milk is constantly increasing. How does it compare to cow’s milk? There is no one-on-one alternative to cow milk in terms of nutrients. In order to lower our greenhouse gases, we need to decrease the consumption of dairy products. Therefore, the consumption of other products is essential to reach a nutritionally adequate diet.
What is plant-based milk?
The average consumption of dairy products in 2019 in Switzerland is of 235 kg per capita per year, this includes milk, yoghurt, cheese, butter and other products (BFS, 2022). Drinking milk alone makes up about 50 kg per year per capita (BFS, 2022). Unfortunately, no data is available for plant-based milk in Switzerland. In the USA the average per capita consumption per year of alternative milk is 2.2 kg (2019), in comparison to 64 kg of cow’s milk (Statista Research Department, 2021a, 2021b).
Figure 1 Plant-based milk with different main ingredients (source: own picture).
The most common plant-based milk is soy. Others are almond, oat, rice, coconut, flax, hazelnut, hemp, quinoa, peas and spalt. Research focuses usually on soy, almond and sometimes oat. There is an ongoing discussion if plant-based drinks are allowed to be called milk. The third definition of the oxford dictionary states milk as “a white liquid produced by or made from plants” (Oxford Advanced Learner’s Dictionary, 2022). Therefore, the term milk is used for both categories in this article.
To produce plant-based milk, raw material is homogenised, reduced and extracted in water. There are different processing methods. The method influences the concentration of micronutrients like vitamins in the final product. For example, water-soluble vitamins might be lost if the raw material is soaked before grinding. Moreover heat sensitive vitamins may be destroyed druing thermal treatment (Silva et al., 2020).
Plant based milk does not contain any lactose, which is a buying reason for lactose-intolerant people (Aydar et al., 2020; Sousa & Bolanz, 2017; Vanga & Raghavan, 2018). Another reason for choosing plant based milk could be an allergy against cow’s milk protein (called CMPA). A third reason is related to lifestyle choices (Silva et al., 2020). Many consumers perceive plant-based milk as more sustainable than cow’s milk (Schiano et al., 2020). Is plant-based milk part of a sustainable diet? A symposium by FAO came up with this definition: “Sustainable diets are those diets with low environmental impacts which contribute to food and nutrition security and to healthy life for present and future generations.“(FAO, 2010, S. 7).
Environmental impact
As the first condition of a sustainable diet is low environmental impact, let’s look at the environmental impact of plant-based milk and cow’s milk. A higher consumption of animal-based food is connected with a higher environmental impact. A global vegan diet could lead to a reduction of 7.8 Gt CO2-eq yr-1 (Mbow et al., 2019).
According to a literature review done by Carlsson Kanyama et al. (2021) 11 out of 12 studies showed plant-based milk have less greenhouse gas emissions than cow’s milk. The 12 studies looked at oat, soy and almond milk. The range of the calculated emissions is high . The researchers showed that oat drink has 0.21 – 0.37 times the emission cow’s milk has. The calculated percentages of soy drink are between 0.08 and 1.19 with a median of 0.31. Almond milk emits between 0.22 and 1.4 times the amount of greenhouse gases cow’s milk does. Only one study compared land use and concludes that soy drink needs 8% less land than cow’s milk. But again, the variation is large. In terms of water usage, producing almond beverages uses more water than the production of cow’s milk. Soy milk needs less water (Carlsson Kanyama et al., 2021).
As we can see it is difficult to quantify how much less of an environmental impact plant-based milk has. An important part of comparing different products is the functional unit (FU) (Grant & Hicks, 2018). The volumetric functional unit compares the nutrients or greenhouse gases in percentage of the volume (most likely litre). Another method is the nutritional functional unit. This method compares factors (e.g. greenhouse gases) based on the nutrition the product provides (e.g. 1 kg of protein). Most studies use the first method as plant-based milk is consumed in the same dimensions as cow’s milk. The two outliners in the greenhouse gas emissions of soy and almond were calculated with the latter method (Grant & Hicks, 2018).
We can conclude reducing cow’s milk and switching to plant-based alternatives has a lower environmental impact. A consumer does not have to switch fully to a vegan diet. A flexitarian diet may save between 3.4 – 5.3 Gt CO2-eq yr-1. In the study they defined flexitarian as the replacement of 75 % of meat and dairy (Mbow et al., 2019).
Nutritional comparison
Cows produce milk for their calves, it contains all nutrients essential for them. Milk provides humans protein, lipids, vitamins and minerals (Sousa & Bolanz, 2017). But what about the nutrition plant-based beverages provide?
Plant-based drinks have different nutritional profiles depending on their main ingredient. We also need to differentiate between the raw material (nuts, cereal etc.) and the processed drinks. Almonds for example are a good source of protein (Silva et al., 2020). However, Almond milk is mainly water, so the amount of protein in the end product is less than in cow’s milk. Almond milk contains fibre, vitamin E and manganese (Vanga & Raghavan, 2018). It also has good levels of antioxidant vitamins. Soy milk is the most similar to cow’s milk because of its high level of protein. It contains high concentration of essential amino acids, but of less quality than cow’s milk. Additionally, soy milk has a high level of dietary fibre (Aydar et al., 2020). Rice milk is good for people with allergies against soy and almond (Vanga & Raghavan, 2018). A disadvantage of rice milk is higher sugar levels and higher carbohydrate amounts while having less proteins. Coconut milk has low calories but no proteins. Coconuts are produced in tropical climates, which results in an increased storage time for European customers. With increasing storage time the nutritional value is being reduced. Oat milk is quite popular amongst consumers. However, it has the same deficiency of proteins and essential amino acids (Sousa & Bolanz, 2017). Calcium is sometimes added to plant-based milk to mimic the amount in cow’s milk (Sousa & Bolanz, 2017; Vanga & Raghavan, 2018). In Switzerland less than in the USA . Without this the amount of calcium in plant-based beverages is less than in cow’s milk. Almond, soy and quinoa milk have between 7 and 9 times less calcium.
Overall, plant-based milk lacks protein and a sufficient amount of (good quality) essential amino acids (Aydar et al., 2020; Sousa & Bolanz, 2017; Vanga & Raghavan, 2018). Naturally, most plant-based milk variants have low calcium values, which are sometimes altered with fortification. Sometimes sugar and salt are added, which is connected with health issues. On the other side, it has a higher concentration of fibre and unsaturated fatty acids. Plant-based milk contains isoflavone, which reduces cancer risk. Additionally, plant-based milk is free of cholesterol in contrast to cow’s milk. We can conclude that plant-based milk is part of a sustainable diet if the missing protein and other nutrients are provided by other products.
Sources:
Aydar, E. F., Tutuncu, S., & Ozcelik, B. (2020). Plant-based milk substitutes: Bioactive compounds, conventional and novel processes, bioavailability studies, and health effects. Journal of Functional Foods, 70(December 2019), 103975. https://doi.org/10.1016/j.jff.2020.103975
BFS (Bundesamt für Statistik). (2022). Entwicklung des Nahrungsmittelverbrauches in der Schweiz. Je Kopf und Jahr – 1980-2020. https://www.bfs.admin.ch/bfs/de/home/statistiken/land-forstwirtschaft/ernaehrung/konsum-gesundheit.assetdetail.20904913.html
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