An Overview on Nutritional Aspects of Plant-Based Beverages Used as Substitutes for Cow’s Milk

2.1.1. Inclusion and Exclusion Criteria

The inclusion criteria were scientific studies referring to plant-based beverage used as an alternative to cow’s milk; have been published in English; present data on the serving size, ingredients, and nutritional composition, containing at least data on energy (kcal) and macronutrients (carbohydrates, protein, and lipids) of plant-based beverages.

2.1.2. Collected Information

The data collected from scientific studies were authors; country of origin; year of publication; types of plant-based beverages presented; serving size of the beverages analyzed; nutritional composition; ingredients; specifications on the origin of the beverages, that is, if the beverage was prepared and analyzed for the study or if it is a beverage available on the market and had its nutritional values removed from the label, among other information. Regarding nutritional composition, the values collected from plant-based beverages were energy value; macronutrients (carbohydrates, protein, and lipids); if available, dietary fiber, calcium, iron, magnesium, and sodium.

The nutrient values were converted to the equivalent of 100 mL using Microsoft Excel^®. For the serving sizes in grams, a density of 1.027 g/mL was considered, based on the soy-based beverage values, and the calculations were made [27]. When available, salt values were converted into the equivalent in sodium, given that 1 g of salt presents 400 mg of sodium [28]. Microsoft Excel^® was used to standardize data.

4.1.1. Processing Performed

The sapucaia nut-based beverage (the sapucaia nut (Lecythis pisonis) is a Brazilian species found in the Amazon and Atlantic Forest) was subjected to crioconcentration in block (method of total freezing followed by partial thawing of the solution, under gravitational separation), capable of concentrating solid matter by removing water in ice form [47]. This process concentrates nutritional compounds, such as protein, carbohydrate, calcium, and magnesium, influencing the beverage’s nutritional content [47]. This concentrated water-soluble extract can be used as an ingredient for other food products to improve their nutritional content as selenium, in which the concentrated extract could reach 10,037 μg/g [47].

The hot grinding method—capable of inactivating the lipoxygenase enzyme of the water-soluble soy extract that causes its typical “beany” flavor—[63] and the cold grinding method (traditional oriental method) were performed to obtain water-soluble soy extract [44]. The cold-extracted beverages had a higher moisture content and, consequently, lower concentrations of proteins and total solids than the hot-extracted beverages [44].

A study analyzed the effect of physical and antioxidant treatments on the lipoxygenase enzyme activity in a soy-based beverage [43]. The author observed that the protein and lipid content of BRS-213 cultivar’s beverages subjected to physical treatments (irradiation—5.00 kGy; thermal—80 °C) with tocopherol supplementation were higher than the control sample. The study showed that adequate heat treatment increases lipids and proteins content, as well as their solubility and digestibility [43].

The physical treatments (irradiation—5.00 kGy; thermal—80 °C) with tocopherol supplementation in BRS-213 cultivar’s beverages also increased the macronutrient concentration compared to the control sample due to lower moisture content [43]. Furthermore, the beverages produced with the EMB-48 soy cultivar subjected to heat treatment had a significant increase in lipid and protein content [43]. The hydrothermal processing of the soy-based beverage caused a rupture in the soy cell wall, allowing the passage of lipids and proteins, which was responsible for increasing the content of these nutrients [43].

As for irradiation (conservation technique) to which soy-based beverages were subjected, a study [42] verified a significant reduction in the protein content when increasing the dose of gamma radiation. Deamination (release of the amine group from the rupture of the peptide bonds of the amino acid, forming ammonia) was mentioned as a possible cause [42]. However, this process may have improved the protein quality since deamination makes it more hydrophilic, increasing its solubility and digestibility [42].

Another aspect in producing plant-based beverages capable of influencing its nutritional content is the raw material:water ratio. A study [48] found higher macronutrient and energy concentration in the soy-based beverage with a 1:8 ratio (soy:water) than in those with a 1:10 and 1:12 ratio. These results were expected since water dilution implies nutrients dilution in the final product.

4.1.2. Added Ingredients

In the production of plant-based beverages, the addition of other ingredients may improve the nutritional profile, the functional or sensory properties of the beverage [22,64]. Salt, sugar, syrups, flavorings, vanilla essence, cocoa, apple juice concentrated, and others are incorporated to improve sensory aspects, mainly the flavor [42,64]. In addition to enhancing flavor, salt and sugar are usually added in beverages and foods to improve texture or shelf-life [65].

Cow’s milk presents a mild and typical flavor, neither sweet nor salty, characterized mainly by the balance between lactose and salt [4]. Therefore, it is common to find salt in plant-based beverages, as well as ingredients for a sweet flavor (sugar, maltodextrin, apple juice, agave syrup, vanilla extract). It is important to highlight that the use of ingredients like sucrose, maltodextrin, and fructose might negatively impact the glycemic index and salt also might impair the nutritional quality. The consumption of foods with low (<55) and medium (56–69) glycemic index is recommended, especially to control blood glucose levels [20,23]. A low glycemic load diet is related to a lower risk of diabetes, cardiovascular disease, and obesity [66].

Sugar is often used to improve sensory quality but influences the nutritional quality negatively. In the studies by Barros and Venturini Filho [44] and Karimidastjerd and Kilic-Akyilmaz [60], the plant-based beverages with added sugar are more caloric and with higher amounts of carbohydrate than those without added sugar. In the sesame-based beverages studied by Reis [34], the carbohydrate amount of the sample added with maltodextrin is almost twice the amount of the pure sesame-based beverage. Consequently, the sample with maltodextrin is more caloric [34].

Other ingredients commonly found in plant-based beverages are vegetable oils, such as sunflower oil. Martínez-Padilla et al. [53] pointed out that the addition of these oils can provide a smooth mouthfeel similar to that of cow’s milk, and Aydar et al. [64] mentioned its use in order to improve the silky aspect.

A study [22] showed that it is possible to add starch in plant-based beverages as a plant-derived thickening agent and pectin or locust bean gum to improve the texture. Reis [34] used maltodextrin to improve the stability of the beverage and Sethi et al. [19] referred to the use of sodium bicarbonate as an alkalizing agent, which might prevent destabilization by sedimentation of solid particles in the beverage.

A study [39] used enzymes in the quinoa-based beverage preparation, with the addition of the Termamyl enzyme for the dextrinization process and the amyloglucosidase enzyme for saccharification. In food industry, inulin can be used as a texture modifier, sugar or fat substitute, and it also has a prebiotic effect on the human organism [67].

Due to the nutritional composition of most plant-based beverages (not similar to that of cow’s milk—high in protein and calcium) and nutritional losses during the processing of the raw material, in plant-based beverages the addition of vitamins (e.g., A, D, E, B2, folic acid, B12), minerals (e.g., calcium, zinc) and proteins (usually isolated or extracted from sources, for example, peas or soy) is frequent, trying to achieve a similar composition to cow’s milk [68]. However, other vitamins and minerals are added with different functions. Barros [43] added tocopherol (vitamin E) with the function of antioxidant treatment of beverages.

Zinc gluconate, zinc oxide, calcium carbonate, tricalcium phosphate and monocalcium phosphate are some of the micronutrient compounds used as food fortifiers [69]. Algae Lithothamnium calcareum is mentioned by Scholz-Ahrens et al. [54] as another source of calcium added to plant-based beverages. Although these beverages are often fortified, the added nutrients are not always bioavailable as those naturally present in milk [68].

Tricalcium phosphate can be used for several functions as an acidity regulator, buffer, anticaking agent, clouding agent, emulsifying, firming agent, flour treatment agent, humectant, moisture-retention agent, raising agent, stabilizer and texturizing agent; calcium carbonate can be used as an acidity regulator, anticaking agent, surface colorant, firming agent, dough conditioner, and stabilizer [70]. Some of these functions are important in plant-based beverages, but they were not discussed in the studies that use them.

The function of gums as food additives can also be used in plant-based beverages. In this sense, gellan gum is used as a gelling agent, stabilizer, and thickener; locust (or carob) bean gum and guar gum are used as an emulsifier, stabilizer, and thickener; xanthan gum as an emulsifier, foaming agent, stabilizer and thickener; gum arabic (acacia gum) is used as a bulking agent, carrier, emulsifier, glazing agent, stabilizer and thickener [70].

The technological purposes of other food additives that appeared in the beverages ingredients lists are carrageenan (bulking agent, carrier, emulsifier, gelling agent, glazing agent, coating agent, humectant, stabilizer and thickener); lecithin (antioxidant and emulsifier); ascorbic acid (acidity regulator, antioxidant, flour treatment agent and sequestrant); citric acid (acidity regulator, antioxidant, color retention agent, and sequestrant); sodium carboxymethyl cellulose (bulking agent, emulsifier, suspension agent, firming agent, gelling agent, glazing agent, coating agent, humectant, stabilizer and thickener); sodium potassium hexametaphosphate (acidity regulator; emulsifier, moisture-retention agent, raising agent, sequestrant, stabilizer and texturizing agent); sodium metabisulfite (antioxidant, bleaching agent, flour treatment agent and preservative); potassium citrate (acidity regulator, emulsifying salt, sequestrant and stabilizer); potassium phosphate (acidity regulator, buffer, emulsifier, emulsifying salt, humectant, moisture-retention agent, sequestrant, stabilizer and texturizing agent); magnesium phosphate (acidity regulator, anticaking agent, emulsifying salt, raising agent, stabilizer and thickener); sucrose esters of fatty acids (emulsifier, foaming agent, glazing agent and stabilizer); mono- and di-glycerides of fatty acids (antifoaming agent, emulsifier, glazing agent, surface-finishing agent and stabilizer) [70].

4.2.1. Energy

The energy value comes from macronutrients (carbohydrate, protein, and lipid) [23]. Considering the energy value of the cow’s milk mentioned above converted to the standard serving size of this study (66 Kcal/100 mL), most plant-based beverages (86.07%, n = 105) are less caloric than the cow’s milk using the same portion. Only one almond-based beverage [36], the baru almond-based beverage [40], two cashew nut-based beverages [23,33], three coconut-based beverages [23,54], the groundnut-based beverage [49], one rice-based beverage [57], the safflower-based beverage [49], two sapucaia nut-based beverages [47], both sesame seed-based beverages [34], two soy-based beverages [44,54], and the spelt-based beverage [54], presented a total energetic value ranging from 66 to 183 Kcal/100 mL equal or higher than the cow’s milk.

4.2.2. Carbohydrate

Almost 27.87% (n = 34) of the studied beverages were higher in carbohydrate content than the cow’s milk (4.78 g/100 mL). Regarding differences in composition, the carbohydrate in cow’s milk is mostly lactose—contributes to the use of vitamin D and the absorption of calcium, phosphorus and magnesium in the intestine—while plant-based beverages are lactose-free [4,21,71] and flavor lactose substitutes most used are sugar, maltodextrin, apple juice, and agave syrup.

Regarding glycemic index (GI), Jeske et al. [66] evaluated the GI of bovine milk and commercial milk substitutes produced with almonds (Prunus dulcis), cashews (Anacardium occidentale), coconut (Cocos nucifera), hazelnut (Corylus avellana), hemp (Cannabis sativa), macadamia (Macadamia spp.), oat (Avena sativa), quinoa (Chenopodium quinoa), rice (Oryza spp.), and soy (Glycine max). The plant-based beverages GI ranged from 47.53 (Organic soya drink from Provamel) to 99.96 (Organic brown rice drink from Rude Health), while cow’s milk (Clona Dairy Product Ltd., Clonakilty, Ireland) had GI equal to 46.93 [66]. Among the beverages analyzed by Jeske et al. [66], eight based on almond (Alpro), carob/almond, cashew, macadamia, quinoa and soy (Provamel, Sojade and Alpro—whole-bean) presented low GI as well as bovine milk, and six other based on almonds, hazelnut, hemp, oat, and soy had medium GI. The analyzed beverages based on coconut and rice, which contained mostly glucose, had a high GI [66].

The GI value is usually influenced by the type of sugar, with each type having a GI value [66]. Jeske et al. [66] presented the GI of maltose (105), sucrose (61), fructose (19), and lactose (46). Some of the plant-based beverage samples mentioned above had added sugar or sweeteners, such as agave syrup (present in cashew, macadamia and quinoa samples), apple concentrate (present in the soy sample from Provamel), sucrose (present in hazelnut, almond and soy original from Alpro) and maple syrup (present in the carob/almond sample) [66]. Agave syrup and apple concentrate are high in fructose, while sucrose and maple syrup contributed to high sucrose values [66]. Additionally, products that have ingredients rich in starch are high in glucose and/or maltose. Rice-based samples presented high maltose and glucose content and sample based on oat, which contains β-glucan capable of reducing GI, was high in maltose [66].

4.2.3. Protein

Of the plant-based beverages studied, 16.39% (n = 20) have a higher amount of protein than the cow’s milk (3.37 g/100 mL). Regarding protein quality, the Digestible Indispensable Amino Acid Score (DIAAS) is the recommended measure for analyzing it [73]. From the DIAAS cut-off values, the food can be characterized as “excellent/high” (value equal to or greater than 100) and “good/source” (between 75 and 99) [73].

The DIAAS method is indicated to replace the Protein Digestibility Corrected Amino Acid Score (PDCAAS) based on some considerations, such as using a single value of fecal crude protein digestibility in the PDCAAS method for correction for digestibility, while the DIAAS use “true ileal amino acid digestibility for the dietary indispensable amino acids” [73]. It is also pointed out an overvaluation of the protein quality of foods that contain antinutritional factors and an inadequate estimate of the protein quality of high-quality proteins due to a non-attribution of extra nutritional value by the PDCAAS method [73].

Chalupa-Krebzdak et al. [23], Scholz-Ahrens et al. [54], and Sousa and Kopf-Bolanz [65] showed DIAAS values for milk proteins and some plant-proteins (soy (Glycine max), rice (Oryza spp.), oats (Avena satina) and almond (Prunus dulcis)). In these studies, cow’s milk has a higher DIAAS value than the plant-based proteins. Among the plant-proteins, soy presented DIAAS values (84.00–90.60) closest to cow’s milk [23,54,65]. The DIAAS values of the other proteins presented were oats (54.00) [54,65], almond (40.00) [54] and rice (37.00–59.00) [23,54,65], not considered good nor excellent [73] as soy and cow’s milk.

Proteins provide amino acids that perform essential functions in the body, such as structural, defense, transport, and regulatory [23,74]. The deficiency of essential amino acids, which must be ingested in the diet, can reduce protein synthesis and physiological and biochemical changes [74]. Thus, attention is needed when replacing milk with a plant-based beverage regarding protein, and a diet needs to be planned to guarantee an adequate aminogram.

4.2.4. Lipid

The percentage of plant-based beverages studied in which lipid content is higher than cow’s milk (3.76 g/100 mL) is 13.11% (n = 16). The lipid in cow’s milk is mainly composed of saturated fatty acids, while plant-based beverages tend to have a higher content of unsaturated fatty acids and are cholesterol-free [4,6,20,23,53]. However, there may be exceptions, as mentioned by Chalupa-Krebzdak et al. [23], Craig and Fresán [20] and Vanga and Raghavan [6] the case of coconut-based beverage that has a high content of saturated fatty acids.

The high consumption of foods rich in saturated fatty acids and cholesterol is associated with an increased risk of developing cardiovascular diseases, while the consumption of polyunsaturated fatty acids corresponds to a risk reduction factor for these diseases [74]. Despite that, studies have shown that the consumption of dairy products does not negatively affect human cardiovascular health [23,53,75]. Chalupa-Krebzdak et al. [23] mentioned as possible cause that “many nutrients in dairy products that may offset the effects of potentially harmful levels of dietary saturated fatty acids”.

The isocaloric replacement of saturated fatty acids for polyunsaturated has collaborated to reduce LDL and total cholesterol in humans [23,74]. In this sense, the lipid composition of the plant-based beverages does not have to be the same as that of cow’s milk regarding the nutritional aspect [23] but is necessary to evaluate its need considering sensory and technological aspects. Chalupa-Krebzdak et al. [23] pointed out that replacing milk with plant-based beverages, except for some coconut-based beverages, can decrease the intake of saturated fatty acids in the diet.

Although coconut-based beverage has a high content of saturated fatty acids [6,20,23], it contains medium-chain fatty acids (MCFAs) that can be converted into ketone compounds, which are favorable in brain functioning [14]. In addition, Vanga and Raghavan [6] report that lauric acid, which mainly contributes to raise high-density lipoprotein (HDL) cholesterol levels and, consequently, reduce levels in the bloodstream of low-density lipoprotein (LDL) cholesterol, is present in coconut fats.

4.2.5. Dietary Fiber

The consumption of dietary fiber might contribute to intestinal regulation, the reduction of blood cholesterol and glucose, and it is also associated with a lower incidence of diabetes, cardiovascular disease, gastrointestinal disorders and colon cancer [74,76]. Among the plant-based beverages that present dietary fiber data, most (81.82%, n = 18) have a higher dietary fiber content than cow’s milk reference (0.00 g/100 mL). In this sense, plant-based beverages have an advantage. Unfortunately, due to the studies’ lack of data, it was not possible to link the fiber content and GI in the samples analyzed.

4.2.6. Micronutrients

Calcium is a nutrient that stands out in milk and is essential for bone and dental structure, muscle function, and nerve conduction [54,74]. The calcium values of plant-based beverages ranged from 0.00 to 1252.94 mg/100 mL and 44.44% (n = 24) of the plant-based beverages were greater than the cow’s milk (122.21 mg/100 mL). These beverages with a higher calcium content (except for the beverages based on sapucaia nut, which went through crioconcentration as previously mentioned), were all fortified with calcium.

As mentioned earlier about fortification, many commercial plant-based beverages are fortified with calcium to achieve cow’s milk’s amount [21]. Despite this, there are plant-based beverages that are not fortified. The substitution of milk for these non-fortified beverages when the diet is not balanced, calcium and other nutrients may be deficient [21].

Moreover, the bioavailability of the fortifier, and not only the amount of the nutrient, should also be taken into account [54]. As an example of calcium, Craig and Fresán [20] mention that calcium absorption from tricalcium phosphate is considerably less than milk, while calcium carbonate is equivalent to milk.

Magnesium is another essential micronutrient contained in milk [4]. Considering the studied beverages in which the magnesium data were provided (ranging from 0.84 to 10,178.60 mg/100 mL), most of them (87.50%, n = 14) have higher magnesium content than cow’s milk (13.35 mg/100 mL). The sapucaia nut-based beverages have a very high magnesium content per 100 mL, exceeding the Tolerable Upper Intake Level (UL) for this nutrient [77]. Therefore, as previously mentioned, these beverages can be used as ingredients in other food products for nutritional purposes [47].

Iron is not naturally contained in appreciable amounts in cow’s milk [71]. Considering iron content of the beverages that present these data (ranging from 0.04 to 1.40 mg/100 mL), only a rice-based beverage (12.50%, n = 1) [46] presented lower amount, however close, than the whole cow’s milk (0.05 mg/100 mL). With that, plant-based beverages have a certain advantage in terms of quantity, mainly considering a vegetarian diet that, in general, lacks iron [78].

Sodium is a component of salt and it is also found in milk [28]. Craig and Fresán [20] pointed out that consumers are generally concerned about the content of this mineral in plant-based beverages for health reasons. The high consumption of this nutrient is associated with noncommunicable diseases [28]. Among the plant-based beverages that present sodium data that ranged from 0.00 to 343.43 mg/100 mL, 53.57% (n = 15) of the beverages have higher sodium values than cow’s milk (50.32 mg/100 mL). These beverages with a higher sodium content (except for the beverages based on sapucaia nut, which went through the process of crioconcentration as previously mentioned [47]), are commercial beverages that have salt as an ingredient [52]. Despite this, other beverages contain salt as an ingredient that has a lower sodium content than this cow’s milk [52,55].

Unfortunately, the function of salt in these beverages that present sodium information and have salt as an ingredient has not been reported. However, Karimidastjerd and Kilic-Akyilmaz [60] reported adding salt to the beverage to balance the flavor, and Pinelli et al. [79] used salt to produce a quinoa-based beverage to increase the protein content.