In recent years, we have witnessed a replacement of milk with plant-based alternatives. The variety of options available on the market continues to increase – soy, rice, almond, oat, coconut, quinoa, and walnut drinks, with light, organic, sugar-free, calcium-enriched, chocolate-flavored, vanilla-flavored versions, among others. Many of these alternatives are known and popularly called "milk," when in reality they only resemble it in appearance and consistency. Plant-based drinks are also frequently perceived as healthy by consumers.
Therefore, given the rapid market growth and popularity of these beverages, it is important to clarify whether they constitute valid alternatives to milk from a nutritional standpoint.
Nutritional value of milk
We begin by presenting, in a simple and clear way, the nutritional value of milk.
Milk and some of its derivatives, such as yogurt or cheese, are foods that the human species has consumed for thousands of years. Its consumption has demonstrably been an evolutionary advantage for some primitive populations who could digest it, due to its high nutritional value. In fact, dairy products have a significant content of high biological value proteins, highly bioavailable calcium, and other vitamins and minerals, such as vitamins A, D, B2, and B12, or the minerals phosphorus, potassium, selenium, and iodine, making them foods with an important role in human nutrition. Dairy products are therefore one of the groups in the Portuguese Food Wheel, with recommendations ranging from two to three daily servings, depending on age.
Reasons for the decrease in milk consumption and the increase in plant-based beverages
Several reasons have contributed to the decrease in milk consumption and the subsequent increase in demand for plant-based alternatives. There are reasons directly related to health, such as food allergies and intolerances, but also those related to the adoption of vegetarian and vegan diets, diets with ethical considerations against milk consumption, or those reflecting environmental concerns. The controversial opinion on milk consumption and the dissemination of information, not always scientifically based, that associates milk consumption with negative effects on human health have also contributed to this reality, not forgetting those who replace milk with plant-based drinks because "it's fashionable".
Nutritional profile of plant-based beverages
Next, an analysis is made of the nutritional profile of plant-based drinks, both in terms of nutritional composition and nutrient bioavailability.
Protein
The main disadvantage of commercially available plant-based beverages is their low protein content. Some almond, rice, oat, hazelnut, cashew, and coconut beverages can have very low protein levels (
It is important to note that the protein content of various plant-based beverages varies significantly, even when using the same plant base (Figure 1)).
Similarly, the quality of plant-based proteins is also inferior to that of cow's milk proteins, due to lower levels of essential amino acids and lower digestibility. Among plant-based proteins, soy protein has the best protein quality.
Figure 1: Protein content of some plant-based drinks available on the Portuguese market.
Fat
The fat content of plant-based beverages varies considerably. Regarding their fatty acid profile, saturated fats are present in low quantities, while monounsaturated and polyunsaturated fatty acids are predominant. The exception to this trend is coconut beverages, which are distinctly rich in saturated fat. Naturally, plant-based milk alternatives contain no cholesterol.
Carbohydrates
The carbohydrate content of plant-based drinks can vary between 0.1 and 15.0 g per 100 g. Rice milk stands out for its high carbohydrate and sugar content, while almond milk is the opposite. In general, cereal-based drinks (rice, oat, spelt) have a higher carbohydrate content than cow's milk. In most plant-based milk alternatives, more than 70% of the carbohydrates present are sugars. None of these drinks contain lactose.
It is worth noting that the glycemic index of plant-based drinks is higher than that of cow's milk. Specifically, coconut and rice drinks exhibit a high glycemic index.
Calcium
Plant-based sources used in plant-based beverages, such as cereals, have reduced amounts of calcium. Therefore, many beverages are fortified with this micronutrient to make them comparable to cow's milk. When fortified, many show a higher calcium content than cow's milk, with values reaching 200 mg. However, most unfortified beverages contain between 0 and 10 mg of calcium. Thus, it is possible to see that the calcium content of plant-based beverages is highly variable.
Furthermore, the addition of calcium does not guarantee that plant-based beverages and cow's milk are nutritionally equivalent, even when the labeled calcium content is similar, since its bioavailability depends on the food matrix and the fortification agent.
The sedimentation of added calcium remains a problem. Analyses of commercial soy beverages revealed that, when not shaken, they contained only 31% of the labeled calcium content, and when shaken, close to 59%.
Other micronutrients
In order to combat potential nutritional deficiencies, some beverages are fortified with vitamins, mainly B12, B2, D, and A. Regarding minerals, they have lower levels of phosphorus, potassium, selenium, and iodine compared to milk.
Soy milk is the closest to cow's milk in terms of vitamin and mineral content.
Main nutritional differences for milk
From the above, it is observed that there are important differences between the vast majority of plant-based drinks and milk. The most relevant are the lower protein content (with the exception of soy milk) and quality, the lower bioavailability of calcium, a higher carbohydrate content, namely sugars, and a lower quantity of vitamins and minerals. Analyzing in more detail, we realize that the issue of protein is quite relevant, since dairy products can constitute a significant fraction of total protein intake. According to data from the 2016 National Food Survey, 15.9% of the protein intake of Portuguese people comes from dairy products, and this value may be even higher in age groups such as children. Even more significant are the data relating to calcium intake, where we can see that 44.8% of calcium intake comes from dairy products, confirming this group as the main supplier of this mineral. While it's true that about half of these plant-based drinks are fortified with calcium to make their levels similar to those of milk, their bioavailability is demonstrably lower. This is due to a different food matrix where factors such as the presence of phytates or oxalates prevent such efficient absorption of this micronutrient, or the precipitation/sedimentation of calcium salt in the packaging.
Regarding other micronutrients, studies show that equivalence with milk is only achieved when plant-based drinks are supplemented with these vitamins and minerals, especially vitamins B2, B12, D, and A. However, more recent studies show that this supplementation is far from universal.
Furthermore, some of these plant-based drinks, particularly those based on rice, generally have a significantly higher carbohydrate content, and consequently, energy content, than milk. Moreover, these carbohydrates are mostly sugars, which means that the glycemic load of rice milk is equivalent to that of soft drinks or cakes.
Risks associated with this replacement
There are no studies on the direct impact on human health of replacing milk with plant-based beverages. Some studies have compared the effects of consuming plant-based beverages with milk consumption on risk markers for certain diseases. A recent systematic review, including eight clinical trials, concluded that the available evidence on the impact of soy beverages on plasma lipids is limited and remains controversial. Thorning et al., in a 2016 study, conclude that the available evidence is insufficient to attribute any advantage to plant-based beverages over milk in terms of health benefits.
On the other hand, cases are increasingly reported in the literature associating nutritional deficiencies in children with the consumption of these beverages, notably rickets, kwashiorkor, or scurvy. Lower average height has also been described in children who preferentially consumed plant-based beveragescompared to those who consumed milk.
In conclusion, plant-based drinks cannot be considered alternatives to milk consumption from a nutritional standpoint. Although fortified soy milk may present a reasonable resemblance to milk, all others are sufficiently different that we cannot attribute that quality to them, and there are even some potential health risks, especially for children, that may be associated with this substitution.
Written by
FCNAUP Alumni.