Plant-based beverages (PBB) are a product category experiencing increasing consumer demand and diversity of offering. PBB defy a single definition due to the variety of their forms but are often marketed as alternatives to bovine milk (hereafter referred to just as milk) and attempt to replicate the functionality and sensory properties of milk.

Milk remains a key part of the diet for much of the global population. In total, 62% of United States households consumed dairy and little or no PBB in 2019 (1). Of the remainder, 16% of households regularly purchased both milk and PBB, and 23% purchased almost exclusively PBB. Globally, dairy is an important contributor to population nutrition, providing 49% of global food calcium, 15% of dietary fat, and 12% of dietary protein (2). Evidence is also clear in the literature for the beneficial health impacts of milk consumption across a variety of outcomes (3), whereas the health impacts of PBB are less clear, likely given their diversity and more recent emergence as widely consumed items (4, 5).

PBB are gaining popularity, with sales in the United Kingdom increasing 32% from 2019 to 2020, taking the market value of PBB to around 12% the size of milk (6). PBB are often chosen by consumers for: dietary and health reasons, including as a dairy substitute for those with lactose intolerance and dairy allergies; as a lower fat option; for inclusion in a vegan diet; due to beliefs on animal welfare; or due to perceived reductions in environmental footprints (7).

Here, the price and nutritional value of PBB on the New Zealand market were analyzed. Both product label data and nutritional content derived from laboratory analysis were employed, due to previous results highlighting lower nutrient contents in PBB than stated on product labels (8).

Plant-based beverages are widely consumed as substitutes in foods and meals that traditionally contained milk. However, the recently emerged and growing body of literature comparing the nutritional properties of PBB to milk has demonstrated that they are not nutritionally equivalent (19–25). This study, for the first time, quantifies the nutritional differences between milk and the PBB available on the New Zealand market.

The nutritional information reported on product labels varied, with some reporting content for an extensive list of nutrients, while others reported minimal information. There was considerable variation in the reported composition of the PBB. Compared to the PBB, from both product labels and the analyzed samples, the milk products assessed were cheaper and had a higher protein, energy, fat, sugar, potassium, phosphorus, and zinc content than the PBB. Contrastingly, the PBB had higher fiber, sodium, iron, and copper contents than milk. The PBB type most comparable to milk in terms of cost and nutrient content was the soy type. This was true for several nutrients, but notably protein and the amino acids. Protein and calcium were focused on in this report due to the importance of milk to the global supply of these essential nutrients in food (2) and their important role in the current New Zealand diet (26, 27).

In this study, PBB products were more expensive both per unit volume and per gram of protein than milk (Table 3). Indeed, except for the soy products, the majority of PBB products had protein contents below 1 g per 100 g. This may be attributed to the lack of a robust regulatory framework for PBB in New Zealand. While milk must contain at least 3 g protein per 100 g, among other requirements (28), there are currently no regulations in New Zealand controlling the nutritional content of PBB. This indicates the need for a review of regulatory standards for PBB to better control their nutritional content if they are to be marketed as alternatives to milk.

Previously, Drewnowski et al. (29) proposed standards for PBB nutritional content, particularly those marketed as “milks.” These standards encompassed energy, protein, sugar, saturated fat, sodium, calcium, and vitamin content, as well as protein quality and optional guidelines for fiber, carbohydrates, and potassium. The standards reflected the nutritional quality of milk, with additional plant-specific nutrient standards based on soy PBB. These authors surveyed 641 existing PBB products on the US market and found that <5% (all of which were soy products) met their criteria, largely due to low protein content.

Applying their standards to the product labels surveyed in this study, it was found that a maximum of 22 out of 103 PBB products (21%) would qualify. This set of 22 contained 20 soy products, one almond product, and one rice product. However, not all products reported values for every assessed nutrient on their labels and assessment of protein quality was beyond the scope of this study. Thus, it is likely that fewer of these 22 products would meet the strictest standards proposed. Drewnowski et al. (29) also proposed that 1–2 g of fiber per 100 g was a suitable target for PBB; only nine of the 103 products surveyed here stated fiber contents above 1 g per 100 g. New Zealand regulations require that only products with a fiber content above 2 g per serving may make nutrition content claims relating to dietary fiber, which is a stronger condition than proposed by Drewnowski et al. (29) and would exclude all but one of the surveyed products (30). The United States results complement those presented here and the authors questioned whether the majority of PBB available to consumers should be marketed as “milks.”

It has been reported elsewhere that 90% of PBB in the USDA Branded Food Products Database met the criteria for ultra-processed foods due to the presence of added caloric or non-caloric sweeteners, hydrogenated oils, hydrolyzed proteins, flavors, flavor enhancers, emulsifiers, emulsifying salts, thickeners, and bulking and gelling agents, added salt, and/or added fat (31). These additives were also found in the product survey carried out here (Supplementary material). The author concluded that “dietary guidelines that promote plant-based diets but penalize industrial processing may need to acknowledge the fact that most PBB milk alternatives… are ultra-processed foods.”

Many other authors have performed analyses of the nutritional content of PBB and made similar conclusions to those presented here. The majority of these studies analyzed product labels or label databases alone, finding similarly high variability in the nutritional content of different products as reported here, both between and within PBB types (19–25). Others have undertaken laboratory analysis of the nutritional content of PBB, again with conclusions matching those reported here (8, 25, 32–34).

Previous work has also considered the glycemic index (GI) of PBB in comparison to milk, finding that rice and coconut PBB had the highest GI, and milk the lowest (32). Others considered price, finding that PBB products (as well as plant-based alternatives to yogurt and cheese) on the United Kingdom market were all more expensive than milk, in some cases up to twice the price (22). By matching their nutritional analysis to United Kingdom dairy intakes, these authors identified cost and nutritional risks of substituting milk with PBB, particularly to consumer groups for whom milk makes a major contribution to nutrient intakes and/or those who have higher nutrient requirements, such as children and pregnant women.

Interestingly, single-serve PBB products have been found to have higher nutritional content than multi-serve products (such as those analyzed here). An analysis of 51 such products on the US market found that these products generally had higher protein content, and higher levels of calcium and vitamin B12 fortification (35). This was likely due to the raised nutrient requirements of the target consumers of the products: children and the elderly. However, only 18% of these products met the nutritional requirements for inclusion in United States school lunch programs.

Several studies on the nutritional content of PBB have emphasized that, while their content of nutrients commonly associated with milk are low, these products contain other essential nutrients not found in milk. Iron, copper, and fiber are often mentioned, as well as plant-specific compounds, such as plant sterols (33, 36). The contribution of a serving of PBB to the RDI for these essential nutrients was found to be small here, with soy products making the greatest contributions to iron (5%), copper (12%), and iodine (14%) RDI. The remaining PBB made lesser contributions, and as mentioned earlier, the fiber content of most PBB was below 1 g per 100 g.

The low nutrient content of PBB is partly due to their low content of the named plant ingredient. Using the values in Table 1, a 250 g serving of the almond products surveyed here contained on average 9 g of almonds, which is around 6 almonds. For the other PBB, a 250 g serving contains on average 22 g soy, 33 g oats, 50 g rice, and 63 g of coconut. The low nutrient content is thus unsurprising given the low content of nutritious plant material. Further, the ability of the human digestive system to absorb these nutrients from PBB must be considered.

It has been found that the bioaccessibility of phosphorus and zinc is significantly lower in soy PBB products compared to milk (34). The bioavailability of other nutrients, particularly calcium, is also a concern. The calcium contents of the majority of surveyed and analyzed products were within 30% of the content of milk. However, for the PBB products this was largely the result of fortification (see ingredient lists in Supplementary material). Phytate, an antinutrient found in plant-based foods and beverages, reduces mineral absorption from plant-based foods, motivating advice to fortify and combine these with animal-sourced foods and vitamin C-rich foods in situations where nutrition is a priority (37).

The results presented here also caution assuming that nutrients are equally distributed throughout PBB containers. While the impact of shaking product containers was only analyzed for calcium and protein, the trends suggest that similar results would be found for other nutrients. The observed reduced nutrient content of unshaken products matches previous results for calcium. Eight soy PBB products tested for their calcium content, were found on average to have 31% of the calcium content stated of the label when unshaken, due to sedimentation (8). Upon shaking, this increased to 59% of the label stated value, with the remaining calcium content found in solid residue at the bottom of the containers. Our own results described here identified not only discrepancies between the nutritional content of shaken versus unshaken PBB products, but also between the nutritional contents described on their labels versus the content found upon laboratory analysis of shaken samples (Supplementary material).

The discussion of bioavailability must also extend to protein quality. The Digestible Indispensable Amino Acid Score (DIAAS) captures the digestibility of the indispensable amino acids in a food, as well as their ratio in comparison to human requirements (15). DIAAS scores above 1 are considered excellent sources of protein, able to meet the complete amino acid requirements of the consumer, while scores between 0.75 and 1 are good sources of protein, and scores below 0.75 can make no nutritional claim on protein quality. Milk protein concentrate has a DIAAS score of 1.18, compared to 0.94–0.97 for soy protein isolate, 0.54 for cooked rolled oats, 0.4 for almonds, and 0.37 for rice protein concentrate (38, 39). No value was found for coconut. Thus, most PBB types can make no nutritional claim on protein quality, except soy, which is a good source of protein. Moreover, the soy product analyzed here was the only PBB type with a reactive lysine proportion similar to (and exceeding) that of milk. However, it should be noted that this is only a proxy measure for amino acid bioavailability, and that after adjustment for reactivity, the lysine content of the soy PBB remained lower than milk.

Previous work has recommended a blending of legume and grain proteins in PBB to achieve higher overall protein quality (22, 25, 29). While the combination of complementary proteins will address some of the deficits of indispensable amino acids in the products containing only one protein source, the total protein content of products should also be considered.

Some consumers choose PBB over milk for perceived reductions in the environmental impacts of their diets. Indeed, it has been found that milk has roughly twice the carbon footprint of soy PBB by mass on the Italian market (40). In a broad review of life cycle analyses, milk had on average three times the greenhouse gas emissions (CO₂-equivalents), more than ten times the land use, and higher terrestrial acidification, eutrophication, and scarcity-weighted freshwater withdrawals than soy PBB per liter (41). Life cycle analysis data for other PBB is rare and highly variable, due to their more recent emergence as product categories and their smaller production volumes. However, recent reports suggest GHG emissions between 35% less (oat) and 70% more (rice) than soy PBB per serve (25). Consistent global data on other footprints was only found for soy.

It is important to understand the context of these footprints. Food and non-alcoholic beverages accounted for 24% of New Zealand household consumption-based emissions in 2019 (42). Using data from two analyses of the climate impact of the New Zealand diet, we calculated that New Zealand milk consumption (approximately 200 g per person per day) accounted for around 4.7% (0.3 kg CO₂-equivalents) of an individual’s emissions attributable to diet (43, 44). Combining these percentages, removal of milk from the diet would reduce an individual’s total consumption-based emissions by around 1.1%. This is without considering the emissions related to foods added to the diet to replace milk. For example, using the mean nutrient content values presented here and carbon footprints from Singh-Povel et al. (25), if one were to replace the protein content of milk with an almond, coconut, or rice PBB, this would result in a net increase in emissions. This reflects the results of Singh-Povel et al. (25), who showed that meeting nutritional requirements for amino acids with milk incurred GHG emissions of 312 g CO₂-equivalents, with higher emissions for all other PBB except soy (160 g CO₂-equivalents).

While the GHG emissions from milk production are significantly higher than those of PBB per serve, milk’s high nutrient density relative to soy and oat PBB resulted in equal scores on a combined nutrition and climate impact metric (45). Elsewhere, using a recently developed Nutrient-Rich Food Index combined with an Environmental Impact metric, milk outperformed an unfortified oat beverage twofold, but a calcium-fortified oat beverage outperformed milk (46). The combination of life cycle analysis data with nutritional indices is a nascent field without defined standards for calculation, so such scores must be interpreted with caution (47, 48). However, it is essential when considering the environmental impact of two food products that their respective nutritional value and function in the diet also be taken into account.

Given the results presented here and previously by other authors, soy PBB appear the nearest nutritional substitute for milk, with several caveats pertaining to sedimentation, calcium bioavailability, protein quality, and price. While individual consumers will consider price, nutritional value, and environmental impact differently or not at all in purchasing decisions, it is important that the scientific and regulatory community understand the implications of milk and PBB consumption.

This research adds to the international consensus that PBB should in general not be considered as nutritional substitutes for milk (21, 22). Indeed, recommendations exist from physicians’ societies that PBB and milk are not interchangeable, particularly in the diets of infants and young children, due to the reduced nutritional value of PBB (49).

While PBB can certainly be of dietary value to those unable (due to health constraints) or unwilling to consume milk, the nutritional contribution of these products should be more widely understood to ensure consumption of nutrient adequate diets. This is particularly relevant for children and pregnant women. In the future, regulations that drive production of PBB products with nutritional contents meeting proposed standards would help to achieve this goal.

The original contributions presented in this study are included in the article/Supplementary material, further enquiries can be directed to the corresponding author.

JH and WM conceived the idea for the work. AD oversaw the sample collection and analysis. NS and AD analyzed the data and wrote the manuscript. All authors contributed to review of the manuscript and approved its submission for publication.