Composition, Properties, and Beneficial Effects of Functional Beverages on Human Health

Abstract

Functional beverages comprise a special category of drinks free of alcohol that contain bioactive components from plant, animal, marine, or microorganism sources that contribute to the reinforcement of human health. Functional beverages are mainly divided into the following basic categories: (i) dairy-based beverages and (ii) non-dairy-based beverages. Functional beverages have several positive functional properties such as the rehydration of the body, recovery of lost energy, the increase of athletic performance, the prevention of pain in joints, the improvement of heart health, the improvement of immunity and the digestive system, and the creation of the feeling of satiety and boosting mood. However, according to health experts, there are also functional beverages that induce obesity and heart diseases because of their high content of sugars, sweeteners, and other components such as caffeine, taurine, taurine combined with caffeine, creatinine, etc. The scope of this review was to highlight the main components and the functional properties of energy drinks along with the effects of functional beverages on human health. Limited review articles address this overall hypothesis in the recent literature, thus comprising the significance of the current study.

1. Introduction

The functional beverage sector of the beverage industry in the US and several developed and developing countries have been flourishing on account of the easy choice of a healthier beverage compared to the choice of a food and the easier supply of healthy additives in comparison with foods [1]. A functional beverage is any drink free of alcohol that contains bioactive components from plant, animal, marine, or microorganism sources that contribute to the reinforcement of the health situation of humans [2]. In the category of functional beverages there are dairy drinks, sports and performance drinks, energy drinks, ready-to-drink teas, kombucha, “smart” drinks, fortified fruit drinks, plant milks, and enhanced water [1,3]. Beverages contribute to the hydration of the body and to the rapid regain of energy. However, there are also some functional beverages such as kombucha that have no good clinical findings associated with the maintenance of a good health situation [4].

The purchase of functional beverages by consumers depends on the factors of <<convenience>> and <<health>>. According to some scientists, functional drinks improve heart health, immunity, digestion, and joint health, while other scientists have claimed that functional drinks create the feeling of satiety and boost the mood [1,3,4,5]. Health experts believe that the consumption of functional beverages is associated with the appearance of obesity and heart diseases on account of their high content of sugars and sweeteners [3,4,5]. Some of the components that are contained in energy drinks are taurine, caffeine, B vitamins, guarana, ginseng, ginkgo biloba, L-carnitine, sugars, yerba maté, and creatine. Although these components have obtained the approval by the United States Food and Drug Administration, health experts recommend that consumers have knowledge about every constituent of a functional beverage [3]. In energy drinks, the quantity of caffeine can range from 50 to 200 milligrams per serving [6]. According to Health Canada, beverage products that contain caffeine may have a toxicological effect to children [6].

Functional beverage products are categorized into the following categories:

(1)

Dairy beverages (e.g., fermented milk, enriched yogurt with probiotics, functional milk fortified with extra calcium, omega-3, vitamins, etc.)

(2)

Non-dairy beverages (e.g., fruit and vegetable-based beverages fortified with vitamins and omega-3 unsaturated fatty acids, ready-to-drink teas, fortified bottled water, dairy substitutes, energy, isotonic, hypertonic, and hypotonic drinks referred to as functional waters) [7].

Probiotics are foods containing living microorganisms (mainly bacteria) that possess several benefits for health [8,9,10,11,12]. Probiotics prevent oxidative stress, improve the regular function of the colon and stomach, and are ranked into the category <<add well to your life>>. The growth of functional drinks is due to the demand for high-functional drinks in sports. These functional sports drinks contribute to rehydration, recovery of lost energy, the increase of athletic performance, and prevention of pain in joints. The reason for the development of energy drinks was due to the loss of electrolytes such as sodium, potassium, chloride, calcium, phosphate, and magnesium that happen by perspiration during any intense physical activity [13]. The presence of salt in sports drinks takes part in fluid retention and energy provision. Amino acids aim to slow tiredness and improve muscle function, while vitamin B helps boost metabolism and the generation of energy. Energy drinks containing simple carbohydrates (CHO) are appropriate for a quick energy burst, while the complex CHO sustains the energy [14]. For the production of plant-based beverages, fruits, vegetables, and herbs alone or combined with other ingredients like fiber, vitamins, and minerals are commonly used.

Functional beverages contain components such as vitamins, minerals, phytochemicals, and phenolic antioxidants that have additional health benefits [15]. The consumption of functional beverages can improve the human health situation and control the progression of degenerative diseases connected with changes in lifestyle and environmental pollution. It must be emphasized that the use of these functional beverages for disease prevention should be at the premonitory stage [16]. A functional beverage must not be used as a pill or capsule, it must be used as a part of a normal diet and must be consumed in amounts corresponding to these of exhibitions of beneficial effects. However, the addition of some ingredients has a negative impact on the quality of functional beverages. For example, the addition of calcium gives a bitter taste, and the addition of proteins containing branched-chain amino acids cause a loss of smooth taste. Effect on texture and stability of functional beverages may also reduce fat or sugar content and the presence of gums/hydrocolloids and emulsifiers. The stability of functional beverages also depends on the ionic chemical compounds (acidulants, salts, bases, and amphoteres) that interact with each other.

Carbonated and dilutable drinks are two species of soft drinks. Carbonates may be an important part of the functional drink sector shortly. In the soft drink category, superfruits can also be enlisted, with the addition of vitamins and minerals for the cheaper production and easier to use in-home functional drink varieties [17].

2. Dairy-Based Beverages

Milk-based drinks or beverages are products that are consumed by all consumer groups, but special types of milk or milk-based beverages are consumed by specific consumer groups. For example, skim milk or toned milk is consumed by people suffering from obesity or diseases related to fat consumption. In the last decade, the fortification of these beverages has been applied. The fortificants that are used in these beverages are prebiotic, probiotic, dietary fiber, phytosterols, proteins, minerals, vitamins, etc. The main ingredients used in the production of these beverages are skim milk or skim milk powder (SMP), sugar, preservatives, colors, flavors, acids, functional ingredients, fruit mixes/ juices/concentrates, and water. The milk-based beverages segment is one of the most growing segments in the dairy market. The main processes for the production of high-quality standard milk-based beverages are homogenization, heat treatment, acidification, enzymatic processing, stabilization, etc.

Milk beverages can be subjected to some modifications. The most common types of modified milk beverages are low-sugar functional milk beverages, low-fat functional milk beverages, functional milk beverages with altered fat composition, and functional milk beverages with altered protein composition. Low-sugar functional milk beverages can be produced by the following process: (a) substitution of milk sugar with fruit sugar, (b) blending of beverages with milk sugar, and (c) substitution of sugar by artificial sweeteners of high relative sweetness [18]. The increase of sweetness of milk beverages can also be achieved by enzymatic hydrolysis of lactose by enzyme lactase. These hydrolyzed lactose-milk beverages can be consumed by lactose-intolerant people. In milk-based beverages of high fat content (i.e., 3–5%), the fat is removed. This removal has a beneficial effect on people suffering from certain diseases such as heart disease. Another method of fat content reduction is the substitution of saturated and trans fatty acids by unsaturated fatty acids. The unsaturated fatty acids that are contained in vegetables and marine oil have high beneficial effects on human health [19]. The only problem of unsaturated fatty acids is their high sensitivity to oxidation. This problem can be solved by the addition of antioxidants, the reduction of head space, and the use of packaging materials of low permeability to oxygen and low transparency. From the family of unsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) exhibit more interesting characteristics on account of their ability to prevent diseases [20,21,22,23,24]. Dairy proteins can be modified in order to cover some nutritional requirements or the increase of their functional properties [25]. Additionally, non-dairy protein sources such as proteins from rice, oat, and soya can alter the protein composition of milk [26]. The only factor that can reduce the acceptability of dairy beverages containing vegetable proteins is the activity of inherent enzymes present in tissues that lead to the formation of various chemical compounds with undesirable tastes.

The addition or fortification of new ingredients can enhance the functionality of a beverage more compared to the modification of fat and protein composition. The fortificants that can be used in functional milk beverages are conjugated linolenic acid (CLA), eicosapentaenoic acid, docosahexaenoic acid, probiotics, prebiotics, dietary fiber, vitamins, minerals, polyphenols, phytosterols, etc. [27,28,29,30]. Vitamins and minerals are also used in the fortification of dairy-based and fruit-mixed beverages. The main disadvantage of water-soluble vitamins is their high sensitivity to oxidation, which leads to the formation of discoloration and undesirable taste. Minerals used for fortification are divided into soluble and insoluble mineral salts. Soluble mineral salts have high bioavailability but undesirable taste, while insoluble mineral salts have good taste, but they have a high tendency towards sedimentation. It must also be noted that some mineral ions act as catalysts in the oxidation of unsaturated fatty acids. Other chemical compounds that are used in the fortification of dairy-based beverages are polyphenols, fiber, prebiotics, and phytosterols. Polyphenols relate to the enhancement of antioxidant properties of a product and the protection of health. Furthermore, polyphenols cause unsteadiness to produce after the formation of an ionic complex due to their conjugation with proteins. In fiber fortification, concentration should be taken into account because of the negative textural changes caused by fibers. Prebiotics are non-digestible carbohydrates that enable the growth of lactic acid bacteria in the colon. The addition of phytosterols in dairy beverages can reduce the levels of low-density lipoprotein (LDL) in blood [31].

Important nutritional and functional properties for human health and diet also have the ingredients of whey such as immunoglobulins, lactoferrin, lactoperoxidase, and certain growth factors. Whey is used in the production of beverages due to the increase of nutritional value and the reinforcement of functional properties of whey [32,33]. Whey proteins are used to produce functional beverages because of their high digestibility. Whey-based functional beverages are very useful for sportspersons and bodybuilders. The addition of probiotics, dietary fiber, vitamins, minerals, etc., can increase the functional properties of whey-based beverages [34]. Based on the use of other ingredients and processing operations for making beverages, whey-based functional beverages are separated into three types. These types are as follows:

(i)

Dairy-based;

(ii)

Fruit-juice-based; and

(iii)

Thirst-quenching type.

2.1. Liquid Yogurt, Buttermilk, and Other Functional Dairy Beverages

For the production of dairy-based beverages such as liquid yogurt, whey or whey components can be utilized as functional ingredients. These types of beverages are divided into two categories: (i) fermented, and (ii) non-fermented-type beverages. In fermented-type beverages, cultured dairy beverages are included such as buttermilk, sour milk, etc., and non-fermented-type beverages include milk smoothies, flavored milk, etc. Both types contain whey or a portion of whey. For the production of fermented-type dairy beverages and non-fermented-type dairy beverages, acid whey and sweet whey are used, respectively. The stabilization and prevention of precipitation of casein micelles at pH 4.6 in fermented-type dairy beverages is required. The stabilization of casein micelles can be achieved by the addition of hydrocolloids. Denaturation and insolubility of whey proteins can be done by the heating of beverages, so the use of non-thermal processing is needed. For the fortification of this type of product, whey protein isolates and whey protein concentrates can be utilized [31].

Buttermilk is a product that, because of its high content of protein, phospholipids, and minerals, plays a significant role in the prevention of diseases such as heart disease, diabetes, cancer, etc. [29]. Therefore, buttermilk possesses an important thesis in the development of the functional beverages sector. The action of sphingolipids has been connected with diminished LDL levels. The preventive action of sphingomyelin in colon cancer has been also declared. Both liquid and powdered buttermilk have remarkable antioxidant activity. Today, fermented skim milk is used as a functional beverage that is also called cultured buttermilk on account of their common functional properties. Buttermilk can also be mixed with soy protein isolate for the production of functional beverages. Every functional dairy beverage that has a similar protein content to that of milk can be manufactured without having negative sensory characteristics [30]. The physicochemical and sensory characteristics of cultured buttermilk presented were improved after the addition of soluble dietary fiber such as hydrolyzed guar gum, which exhibits beneficial effects in heart diseases, diabetes, and digestion-related diseases [28]. The use of Aloe vera in the enrichment of nutritional value is also very important. The addition of Aloe vera in cultured buttermilk completes the nutrients of cultured buttermilk due to the content of various bioactive ingredients [29]. In the production of functional buttermilk probiotics bacteria also can be utilized for the improvement of gut health level [27]. Prebiotics, which are added to buttermilk as the main source for the growth of probiotics bacteria, can enhance the functional properties of buttermilk and the gut health levels. For the prevention of several diseases, buttermilk from butter production and cultured buttermilk can also be utilized for the development of functional beverages with important health benefits.

It has been reported that all the added ingredients of functional dairy beverages have profound effects on the overall health of people [31]. These added ingredients are probiotics, prebiotics, phytosterols, antioxidants, bioactive peptides from milk, dietary fiber, minerals, vitamins, and colostrum immunoglobulins. The consumption of functional dairy beverages rich in probiotics has many benefits to the health such as the reduction of cholesterol levels, alleviation of lactose-intolerance symptoms, prevention of intestinal tract infections, prevention of diarrhea, prevention of colon cancer, and improvement of the immune system [35,36,37]. Additionally, the addition of prebiotics such as fructo-oligosaccharides (FOSs) and gluco-oligosaccharides (GOSs) along with probiotics synthetized a dairy beverage of many health benefits. Prebiotics increase the growth and activity of probiotics, and as a result, increases of improvement rate of people [38]. The addition of some important bioactive ingredients of Colostrum, such as lactoperoxidase, lactoferrin, and lysozyme in milk contributes to the improvement of immunity, prevents diarrhea, stomach cancer, and ulcers, and at the same time shows protection against infections [39]. The fortification of milk or dairy products with phytosterols such as campesterol β-sitosterol and stigmasterol causes a reduction in the absorption of cholesterol from the gut and in the LDL cholesterol levels [40]. A reduction of 10% in LDL has been observed after the intake of 2 g phytosterol esters per day [41]. Phytosterols have the property of reducing the absorption of cholesterol. Because of this, phytosterols exhibit high effectiveness in the prevention of cardiovascular diseases. Phytosterols have also been proposed for the therapy of patients with high blood cholesterol level by the American Heart Association and the European Current Dietary Guidelines [42].

The role of omega-3 fatty acids is also important for the reinforcement of dairy products’ functional properties. The main omega-3 fatty acids of high functional properties are eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and ALA (α-linolenic acid). Omega-3 fatty acids offer several benefits on human health, such as the prevention of cardiovascular diseases, abnormal clotting of blood, reduction of triglyceride levels, regulation of the immune system, and improvement of brain function [23,43,44,45,46]. The only disadvantage of the presence of omega-3 fatty acids into the dairy product is low oxidative stability [19]. The addition of dietary fibers into dairy products also plays an important role. The soluble dietary fibers decrease the cholesterol levels and prevent the increase of glucose levels [47]. Insoluble dietary fibers are not absorbed and keep the pH of the intestine stable as a result of the prevention of constipation, the faster removal of toxic waste through colon, and the prevention of colon cancer by the prevention of cancerous substances production by colon microorganisms [48,49]. A daily dose of 20–35 g of dietary fiber for the adults is recommended by the American Dietetic Association [50].

The functional properties of dairy beverages can be enhanced by the addition of several antioxidants, minerals, and vitamins [31,51]. The most common antioxidant compounds that are added to dairy functional beverages are vitamin C, vitamin E, and vitamin A, as well as enzymes such as catalase, glutathione peroxidase, glutathione reductase, and superoxide dismutase [52,53,54,55,56,57,58,59,60,61]. Antioxidants act against cancer, coronary heart disease, neurological disorders, and neurodegenerative diseases, and they can also boost the immune system and delay aging. The minerals with high functional properties are calcium, iron, copper, magnesium, manganese, and zinc. Calcium is essential for the maintenance of bone and teeth health [62], and copper is necessary for the normal function of the heart and arteries, protection of red blood cells against oxidation, and the prevention of osteoporosis and osteoarthritis [63,64,65]. Iron is an important mineral for the prevention of anemia and the production of hormones and connective tissue [66,67]. Magnesium promotes the synthesis of proteins, regulates blood pressure and sugar levels in the blood, and contributes to the normal function of muscles and nerves [68,69,70]. Manganese takes part in the activation of enzymes for bone reproduction and growth [62], and zinc takes part in the metabolism of cells, the prevention of osteoporosis, the function of the immune system, protein synthesis, synthesis of DNA, and wound healing [64,71,72,73,74]. Vitamin D helps the metabolism and absorption of calcium, the maintenance of bone growth, and boosting of the immune system [62,75,76]. Vitamin A contributes to the normal function of vision, immune reactions, and gene transcription [77,78,79,80,81,82,83,84]. Furthermore, the bioactive peptides of milk have been favored for their high and valuable functional properties. Bioactive peptides in milk can stimulate the immune system, assist with digestion and absorption of nutrients in the body, prevent obesity, and prevent the exhibition of metabolic disorders [85].

2.2. Fruit-Juice-Based

The production of fruit-juice-based whey beverages can be performed by mixing fruit juice and pulp with whey (with or without deproteinization). These products are characterized by high nutritional value on account of their additional nutrients such as whey, fruit juice/pulp/concentrate, flavor, color, sweetener, and preservatives [32]. Fruit-whey-based beverages may also be subjected to fortification with minerals and vitamins. The advantage of these beverages is the denaturation of whey proteins during heating, which results in the formation of sediment. The sedimentation can be avoided by adjusting the pH (around 3.6) of the beverage before the heating treatment. Sedimentation can also be observed in low pH due to the interaction between whey proteins and pectin from fruit pulp or juice. This sedimentation can be avoided by using pectinolytic enzymes before mixing with whey or by utilizing fruits that have very low quantities of pectin.

2.3. Thirst-Quenching-Type Beverages

The thirst-quenching beverage category comprises carbonated-type beverages. Carbonated beverages consist of water and minor ingredients such as sweeteners, colorants, flavoring agents, and carbon dioxide. The water can be substituted by clarified and deproteinated liquid whey. The carbonation of these beverages is difficult without the removal of proteins on account of the foaming properties of whey proteins [34]. The functional activity of these beverages is mainly attributed to the addition of vitamins, minerals, and other functional fortificants.

Table 1. The beneficial effects of the added constituents.

Constituents	Beneficial Effect	References
Probiotics	Reduction of cholesterol levels; alleviation of lactose-intolerance symptoms; prevention of intestinal tract infections; prevention of diarrhea; prevention of colon cancer; improvement of the immune system.	[35,36,37]
Ingredients of colostrum (lactoperoxidase, lactoferrin, and lysozyme)	Improvement of immunity; prevention of diarrhea, stomach cancer, and ulcers; protection against infections.	[39]
Phytosterols (campesterol β-sitosterol, and stigmasterol)	Reduction in the absorption of cholesterol from the gut and low-density lipoprotein cholesterol levels; prevention of cardiovascular diseases.	[40]
Omega-3 fatty acids (eicosapentaenoic acid, docosahexaenoic acid, and α linolenic acid)	Prevention of cardiovascular diseases; abnormal clotting of blood; reduction of triglyceride levels; regulation of the immune system; improvement of brain function.	[23,43,44,45,46]
Soluble dietary fibers	Decrease of cholesterol levels and prevention of the increase of glucose levels.	[47]
Insoluble dietary fibers	Prevention of constipation; faster removal of toxic waste through colon; prevention of colon cancer by prevention of cancerous substances producted by colon microorganisms.	[48,49]
Antioxidants (catalase, glutathione peroxidase, glutathione reductase, and superoxide dismutase)	Protective action against cancer, coronary heart disease, neurological disorders, and neurodegenerative diseases. Boosting of immune system and delay of aging.	[52,53,54,55,56,57,58,59,60,61]
Calcium (Ca)	Maintenance of bones and teeth health.	[62]
Iron (Fe)	Prevention of anemia; production of hormones and connective tissue.	[66,67]
Copper (Cu)	Normal function of the heart and arteries; protection of red blood cells against oxidation and prevention of osteoporosis and osteoarthritis.	[63,64,65]
Magnesium (Mg)	Synthesis of proteins; regulation of blood pressure and sugar levels in blood; normal function of muscle and nerves.	[68,69,70]
Manganese (Mn)	Activation of enzymes for growth of bones and reproduction.	[71]
Zinc (Zn)	Metabolism of cells; function of the immune system; protein synthesis; synthesis of DNA; and wound healing.	[64,72,73,74]
Vitamin D	Metabolism and absorption of calcium; maintenance of bone growth; boosting of the immune system.	[62,75,76]
Vitamin A	Normal function of vision; immune reactions; and gene transcription.	[77,78,79,80,81,82,83,84]

lists the beneficial effects of the added constituents in functional beverages.

3. Functional Milk and Juices

3.1. Functional Milk: The Case of Kefir

In various developing countries, consumers are getting used to changing their diet habits from a high-energy diet to a diet that combines health benefits and the prevention of diseases [86]. Probiotics play a key role in the functional food market as these are solutions to numerous gastrointestinal problems. Probiotics are living microorganisms that improve the health of the gastrointestinal system, stimulate and activate the immune system, reduce the LDL cholesterol levels, and manage the lactose intolerance; they have also anti-mutagenic and anti-carcinogenic properties [87,88,89]. One of the most popular products in the functional food sector is kefir. Kefir is produced by adding kefir grains to sheep milk or a sugar solution. There are several recipes with different components in kefir production. The use of cow milk in kefir production is done on a smaller scale. Kefir grains originate from the Caucasus mountains and are produced commercially for the manufacturing of products sold in local supermarkets. Grains contain a mixture of lactic acid bacteria, acetic acid bacteria, and yeasts within a water-soluble branched glucogalactan kerifan [90,91,92,93,94,95]. In the microflora of kefir grains there are Lactobacillus brevis, L. helveticus, L. kefir, Leuconostoc mesenteroides, Kluyveromyces lactis, K. marxianus, and Pichia fermentans [96,97]. Kefir as a fermented beverage is known for its antioxidant, antimicrobial, and anti-inflammatory properties [98]. The antioxidant properties of kefir depend on the substrate sources, the fermentation time, and storage time [99,100,101]. The produced exopolysaccharides from milk kefir fermentation protect proteins from oxidation [102]. It has been also stated that the supernatant of kefir also has the ability to reduce the damage of DNA. In addition, the supernatant exhibited higher antioxidant activity than milk [103].

Kefir has also exhibited in vitro antimicrobial effects against various pathogens. A reduction was achieved in total viable counts of the Salmonella enterica subspecies (Arizonae and Typhimurium) after their culture in Kefir compared to milk as a control sample [104]. Additionally, a reduction was exhibited in the growth of enteric pathogens by the kefir grain milk cultures in supernatants and by the action of the added strain of Lactobacillus kefiri into the culture [105,106]. An inhibition to the cytotoxicity of Clostridium difficile was observed after the culture supernatant of kefir isolates on Vero cells and S-layer proteins isolated from Lactobacillus kefiri [107,108]. The pre-incubation of yeasts and bacteria isolated from kefir with Caco-2 and HT-29 cells induces a reduction in Shigella flexneri invasion and proinflammatory cytokine production [109].

Several studies, both ex vivo and in situ, have demonstrated the anti-inflammatory and immunomodulatory capabilities of kefir [110,111,112,113]. Isolated organisms from kefir can promote the anti-inflammatory cytokines Th-2 response and inhibit the pro-inflammatory Th-1 response [114]. The consumption of kefir by mice for 7 days induces an increase in Th1 cytokine production in the small intestine and both Th1 and Th2 cytokine production in the large intestine [115,116]. Kefir can achieve the reduction of glycemia and the increase of the equilibrium between pro- and anti-inflammatory cytokines [117]. In another in vitro study, a mitigation of the lipopolysaccharide-induced secretion of IL-6 was recorded by kefir exo-polysaccharides (KEPS) and kefiran (KE). Additionally, both KEPS and KE suppressed the expression of related-inflammatory molecules (IL-6 and phosphorylated mitogen-activated protein kinase p-MAPK), indicating their efficiency in the treatment of inflammatory disorders [118]. Furthermore, Kefir mitigated the inflammatory cascade and increased the levels of acetate and propionate while reducing the intestinal damage of dextran sodium sulfate, which causes colitis [119]. Another research showed that kefir peptides (KP) suppress the phospho-IkappaB (p-IkB), NF-kB, phospho P38 (pp38), and p-JNK activation and reduce the tumor necrotic factor (TNF-α) expression.

Moreover, an alleviation in synovitis was recorded by decreasing the responsibility for rheumatoid arthritis inflammatory signaling molecules (TNF-α, Il-1β, and Il-6). In total, KP modulates the NF-kB pathway and reduces the expression of macrophage-related inflammatory signaling molecules [120]. According to recent research, kefir reduced the expression of proinflammatory cytokines TNF-α, IL-6, and IL-Iβ, and elevated IL-10 expression as a result of the decrease of alveolar bone loss [121]. A reduction on TNF-a, tumor size, volume, and a number of metastatic tumor cells was exhibited after the consumption of kefir by mice [122,123,124]. An increase in IL-10 gene expression in the ileum and mesenteric lymph nodes of healthy Swiss mice was achieved after the consumption of kefir fermented by the strain of Lactobacillus kefiri CIDCA 8348 for 21 days [125]. Studies indicated an increase in the production of IgA cells and the function of macrophage in both the intestinal and bronchial tissue [126,127]. The consumption of kefir reduced the concentration of proinflammatory cytokines TNF-α and IL-1β in colonic tissue, increased the concentrations of IL-10, and improved the histological situation in mice [128,129]. The concentration of serum IgE was decreased, and the concentration of Th1 cytokines in splenocytes was increased after the provision of heat-inactivated Lactobacillus kefiranofaciens M1 in mice [130,131].

Unfortunately, probiotics also have some drawbacks. The low resistance to high acidity in the stomach and to bile salts and bile acids are two of the main drawbacks of probiotics [132]. Research studies are carried out for the increase of stability of probiotics during the processing and storage of products as well as the increase of their resistance in acidic environments [133]. The most common and efficient way to protect probiotic bacteria from acidic environments during manufacture and storage is encapsulation. The protection of probiotic bacteria during processing and storage can be achieved by the application of microencapsulation. The most popular and effective microencapsulation techniques are chilling, emulsion, extrusion, and spray drying [134]. The materials that have been used as encapsulating materials are plant-based cellulose, carboxymethyl cellulose, and chitosan [135,136,137]. Generally, most probiotic bacteria cannot survive in an acidic environment (pH 2) except for a few strains such as Lactobacillus reuteri [138]. According to recent studies, a number of viable probiotic bacteria in the level of 10⁸ colony-forming units must colonize in the gut in order to be able to offer health benefits [139].

3.2. Functional Fruit and Fortified Juices

The nutritional value of fruits and vegetables is very high, which is attributed to the high content of vitamins, minerals, and dietary fibers. The minimum recommended consumed quantity of fruits and vegetables by the World Health Organization (WHO) is 400 g per day, while in other countries such as Sweden and Finland, the minimum recommended consumed quantity is equal to 500 g per day [140].Functional fruit juices are produced by the addition of some functional components to common fruit juices such as carotenoids, phenolic acids, flavonoids, fatty acids, probiotics, prebiotics, minerals, and vitamins. Antioxidants are the first compounds that are added to oils and fats for the prevention of oxidative damage [141]. Antioxidants are utilized in both food additives and supplements [142]. The categories of chemical compounds that are considered antioxidants are phenolic compounds (e.g., flavonoids, phenolic acids, stilbenoids, coumarins, lignins, and tannins), carotenoids (e.g., carotenes and xanthophylls), and terpenoids (e.g., monoterpenes, triterpenes, and some sesquiterpenes). Fruit juices such as “superfruits”, which contain various bioactive compounds, can be ranked as functional beverages [143]. “Superfruits” is a mixture of wild fruit species such as blueberries, goji berries, acerola, acai, camu-camu, and others. The bioactivity of functional fruit juices can be increased by mixing different types of juices (e.g., cranberry juice and pear juice) in different ratios [144]. The incorporation of probiotic bacteria to non-dairy products such as fruit juices has been investigated. Fruit juices are considered the best medium for the delivery of probiotic bacteria because of their high content in polyphenols, vitamins, minerals, and other nutritive compounds [145,146,147,148,149].

The addition of probiotics improves the nutritive value of fruit juices and contributes to the stability of the product [150]. Because of the low concentration of proteins and amino acids, the presence of phenolic compounds, flavonoids, and organic acids in probiotic bacteria cannot always be applied in fruit juices [151]. However, the presence of saccharides, organic acids, and ascorbic acid can help the growth and viability of probiotics [152,153]. Additionally, the presence of cellulose in fruit juices can act protectively during manufacturing and storage [154]. Generally, the factors that can affect the viability and stability of probiotic bacteria in fruit substrates are the bacterium strain, the composition of juice, the oxygen levels, the antimicrobial compounds, the artificial dyes and flavors, and the production processes and handling [155]. The methods that can be applied for the maintenance of the stability of probiotics in fruit juices are the fortification by prebiotics, cellulose, β-glucans, the storage at low temperatures in a modified atmosphere enriched by carbon dioxide, the addition of antioxidants, and the probiotics encapsulation [146,152,156,157,158,159,160,161]. The most common probiotic bacteria that are utilized in fruit beverages are the strains Lactobacillus plantarum, Lactobacillus acidophilus, Lactobacillus helveticus, Lactobacillus casei, Lactobacillus paracasei, Lactobacillus rhamnosus, Lactobacillus reuteri, Bifidobacterium breve, Lactobacillus gasseri, Lactobacillus crispatus, and some strains of Bacillus, Clostridium, Enterococcus, Lactococcus, Leuconostoc, Bifidobacterium, Pediococcus, Propionibacterium, Streptococcus, Sporolactobacillus, and Saccharomyces species [161]. The selection of a suitable strain is very important for the forming of the desirable sensory characteristics of fruit beverages. Additionally, the conditions of fermentation are a very important and crucial factor for the maintenance of probiotic bacteria in a good situation during fermentation and storage [162].

Table 2. List of used probiotic bacteria species in the food and beverage industry [163].

Lactobacillus Species	Bifidobacterium Species	Others
Lactobacillus acidophilus	Bifidobacterium adolescentis	Bacillus coagulans
Lactobacillus amylovorus	Bifidobacterium animalis	Bacillus cereus
Lactobacillus brevis	Bifidobacterium breve	Clostridium botyricum
Lactobacillus casei	Bifidobacterium bifidum	Enterococcus faecalis
Lactobacillus rhamnosus	Bifidobacterium infantis	Enterococcus faecium
Lactobacillus crispatus	Bifidobacterium lactis	Escherichia coli
Lactobacillus delbrueckii subsp. Bulgaricus	Bifidobacterium longum	Lactococcus lactis subsp. Cremoris
Lactobacillus fermentum		Lactococcus lactis subsp. Lactis
Lactobacillus gasseri		Leuconostoc mesenteroides subsp. Dextranicum
Lactobacillus helveticus		Pediococcus acidilactici
Lactobacillus johnsonii		Propionibacterium freudenreichii
Lactobacillus lactis		Saccharomyces boulardii
Lactobacillus paracasei
Lactobacillus plantarum
Lactobacillus reuteri
Lactobacillus rhamnosus
Lactobacillus salivarius
Lactobacillus gallinarum

lists the probiotic bacteria used in the food and beverage industry.

Prebiotics have the property of the selective promotion of the activity of one of a select categories of bacteria in the intestine. This leads to the promotion of the fermentation of a particular category of beneficial bacteria [164]. Components that are used as prebiotics are inulin, fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), non-digestible polysaccharides, polyphenols, dietary fibers, and flavoring agents. Prebiotics can avoid small-intestinal digestion and reach the colon where they are fermented by Lactobacillus and Bifidobacteria spp. bacteria. [165]. Intestinal bacteria convert polysaccharides to monosaccharides via a variety of metabolic processes. The main products of fermentation are the short-chain fatty acids (SCFAs) acetate, propionate, and butyrate [166]. The products of gut bacteria metabolism act as substrates for the growth of other bacteria. For example, the by-products lactate and acetate can be used for the growth of Eubacterium, Roseburia, and Faecalibacterium, which produce butyrate [165]. Butyrate is the main SCFA that is used for energy. Additionally, propionate can be used for glucose synthesis or it can be used as a substrate for glucose synthesis in the liver. The SCFAs are metabolized by the microorganisms of the intestine if they are absorbed by the intestine. Prebiotics prevent the attack of epithelium by microbes or pathogens [167].

Fruits act as a beneficial prebiotic on account of a mixture of useful characteristics such as buffering capacity, inulin, fiber, and antinutritional factors [168]. In a study, a prebiotic effect is exhibited by the biotransformation of phenolic compounds during fermentation and gastrointestinal digestion, which enables the survival of Lactobacillus and Bifidobacterium spp. in fermented pomegranate juices [164]. The dragon fruit oligosaccharides intake at a dosage of 4 g/kg per day for two weeks can produce SCFAs in the colon system, which can regulate the intestinal microflora [169]. In another study, extracts of apple peel and sweet-lime peel exhibit a prebiotic effect for Lactobacillus casei, Lactobacillus rhamnosus, and Lactobacillus plantarum [170]. Apple peel and sweet-lime peel exhibited the higher prebiotic index for Lactobacillus plantarum and Lactobacillus rhamnosus, respectively, while the prebiotic index for the Lactobacillus casei was almost comparable both in apple peel and sweet-lime peel.

Generally, most dietary deficiencies come from the insufficient consumption of fruits and vegetables [171]. The danger of myocardial infarction is reduced by 15% after the daily consumption of at least five servings of fruits and vegetables. Moreover, a reduction of coronary heart disease and ischemic stroke by 31% and 19%, respectively, has been observed after the consumption of 600 g of fruits and vegetables [172]. The consumption of the same amount of fruits and vegetables also reduces stress and fatigue [173].

4. Functional Waters

Functional waters are a category that include sports and energy drinks (isotonic, hypertonic, and hypotonic drinks), vitamin and mineral-fortified drinks, herbal drinks, and in general, health and wellness drinks.

4.1. Sports Drinks

The performance and health of an athlete are linked with sports nutrition and nutrients such as carbohydrates, proteins, electrolytes, vitamins, and other nutrients [174,175]. One of the limiting factors of athletic performance is hydration [176]. The reduction of dehydration can be achieved by the provision of electrolytes (i.e., magnesium, calcium, potassium, sodium) and carbohydrates that are contained in sports drinks. Generally, higher hydration levels are attained by the consumption of sports drinks compared to the consumption of water [177]. A previous study reported that the consumption of sports drinks containing sodium during a ride for 3 h in warm temperatures maintained the plasma levels of sodium and produced less urine [178]. The addition of carbohydrates in a sports drink such as glucose polymers and maltodextrins can increase the content of carbohydrates in a sports drink without the excessive increase of sweetness [178]. Poor diet and weight gain are the main disadvantages of the excessive consumption of sports drinks containing carbohydrates [179].

4.2. Energy Drinks

Energy drinks are ranked in the category of functional beverages, and they can improve concentration, durability, and performance [175,180]. Energy drinks are mainly consumed by young people, college students, and athletes [181,182]. The most common ingredients in energy drinks are caffeine, B vitamins, glucuronolactone, ginseng, and guarana [175,177]. Related to caffeine, it is considered that caffeine harms human health. Other ingredients in energy drinks can change the total amount of bioavailable caffeine, such as guarana, which contains a significant quantity of caffeine and methylxanthines because of the increment of the toxic effect of an energy drink [175,183]. An increase in the behavioral effects of alcohol was recorded by mixing energy drinks and alcohol [184]. According to research, the synergistic effect between alcohol and caffeine or other ingredients is responsible for atrial fibrillation in young people [185]. Moreover, the mix of alcohol and energy drinks can increase the rate of excessive drinking, the possibility of alcohol dependence, and related alcohol incidents [186].

4.3. Herbal Drinks

The use of herbal drinks by consumers has increased. Along with herbal drinks, the consumption of other plant-based beverages such as tea, coffee, and cocoa has also increased. Herbal drinks are produced by several morphological plant parts such as leaves, stems, roots, fruits, buds, and flowers. Herbal drinks contain high quantities of carotenoids, phenolic acids, flavonoids, coumarins, alkaloids, polyacetylenes, saponins, and terpenoids, among others. The high antioxidant, antibacterial, antiviral, anti-inflammatory, antiallergic, antithrombotic, antimutagenicity, anticarcinogenicity, and antiaging effects of these ingredients have been demonstrated [187,188,189].

The tea made from the leaves and buds or twigs of the plant Camellia sinensis is the most consumed beverage in the world. The types of true teas are black tea, oolong tea, green tea, and white tea. Herbal tea/beverage is related to infusions with fruit or other herbs that do not contain Carmellia sinensis. For this reason, herbal beverages have the names tisane, herbal infusion, or botanical infusion. The production of herbal beverages can be performed by the steeping (infusion) or boiling (decoction) of fresh or dried flowers, immature fruits, leaves, seeds, and/or roots. Many consumed herbal beverages have no caffeine at the same detectable levels compared to those of coffee and tea. Herbal beverages may take part in the improvement of antioxidant status and the reduction of oxidative stress [190].

According to Health Canada, herbal beverages are ranked according to natural health products (NHPs) and the consumption of 2–3 cups per day of selected herbal teas (citrus peel, lemon balm, ginger, orange peel, and rosehip) has beneficial effects on pregnancy and breastfeeding [191]. Herbal beverages and herbal teas made from Aegle marmelos (Bael), Cassia auriculata (Ranawara), Aerva lanata (Polpala), and Hemidesmus indicus (Iramusu) have been used in countries with developed traditional medicine such as India, Sri Lanka, and China. Herbal teas are produced by processes such as decoction, infusion, or maceration and are sold in market either in bulk form or in sachets. Herbal products and teas may be sold in commerce in different forms such as whole dried plant parts, dried powder, dried particles within tea bags, as well as granulates and solutions.

The antioxidant ingredients that are contained in herbal beverages are phenolic acids, flavonoids, lignans, lignins, tannins, coumarins, terpenes, carotenoids, and polyacetylenes.

The most popular herbal teas are produced by the herbs Centella asiatica, Aspalathus linearis, Cochlospermum angolensis, Ilex paraguariensis, Chamomilla recutita, Matricaria chamomilla, and Chamaemelum nobile. Centella asiatica is consumed by people in Asian countries and it may be also mixed with garlic, coriander, or ginger. Centella asiatica can stimulate the activity of the enzymes superoxide dismutase, catalase, and glutathione peroxidase, and it contains beneficial bioactive compounds such as alkaloids, terpenoids, saponins, asiatic acid, madecassic acid, asiaticoside, madecassoside, and polyacetylenes [192,193,194,195]. Apoptosis by 63% after the provision of 28 μM of cadiyenol is displayed in mouse lymphoma cells (P388D1) within 24 h [196]. Furthermoe, the nitric oxide production is reduced by 70% in lipopolysacahrride (LPS)-activated mouse macrophages. Aegle marmelos (bael) is a subtropical tree that is cultivated in Southeast Asia and is rich in coumarins, vitamin C, and riboflavin. The leaves, stems, bark, and fruits of this tree act therapeutically in dysentery, diarrhea, and various other intestinal problems.

Bael haw also acts against the consequences of gamma-irradiation, algos, hypelipidemia, dyslipidemia, cancer, and diabetes [197,198,199,200,201,202]. Some of the chemical compounds of several parts of bael are the coumarins marmelosin, marmesin, imperatorin, and the alkaloids aeglin and aegelenine [203]. Different parts of the bael tree have presented protective action against the growth of viruses, funguses, bacteria, and inflammation [204,205]. Coumarins may be responsible for the antidiabetic properties of the fruit extract that stimulates insulin production [206]. However, the intake of bael can present toxicological effects if its quantity overcomes critical limits. Amounts of aqueous extracts of the leaves of bael equal to 50 mg/100 g of body weight did not exhibit any toxicological effects to the liver or kidneys [207]. Additionally, no toxical effect was presented in the heart, liver, kidneys, testis, spleen, and brain after a continuous supply of 50 mg/kg body weight of the extracts of Aegle marmelos for 14 days [208]. Another popular herbal tea that is consumed in India and Sri Lanka is the dried flower buds, flowers, and leaves of the herb Cassia auriculata. The flower and leaf extracts of Cassia auriculata have shown antihyperglycemic effects in experimental diabetes [209,210]. An inhibition in α-glucosidase activity in vivo and in vitro was observed by the action of methanolic extracts of Cassia flowers [211]. Furthermore, an inhibition was also exhibited in lipid peroxidation in the brain of diabetic rats by the action of aqueous extracts of Cassia [212]. The alcoholic extract of Cassia seeds displayed cardiovascular protection and no negative effect in male and female rats [213].

In South Africa, the most popular herbal teas are produced by the herbs African rooibos (Aspalathus linearis), borututu (Cochlospermum angolensis), and honey bush tisanes. Rooibos is used for the alleviation of infantile colic, allergies, asthma, and dermatological problems. The addition of honeybush can help the expectoration and can act as a stimulant for chronic catarrh and pulmonary tuberculosis [214]. Additionally, the antioxidant and antimutagenic activities in vitro of rooibos and honeybush have been proved. The prevention and treatment abilities of rooibos against vascular diseases are attributed to Chrysoeriol, a constituent that can inhibit the transport of smooth muscle cells inside the aorta [215]. Rooibos tea can also significantly reduce the activity of the angiotensin-converting enzyme [216].

In South America, yerba mate is a social and medicinal beverage rich in caffeine; it is produced by the herb Ilex paraguariensis and is consumed by native people. Several studies have demonstrated the hepatoprotective, diuretic, antioxidant, anti-inflammatory, and antimutagenic properties of yerba mate [217,218,219,220]. Yerba mate can also stimulate the central nervous system and induce a reduction in serum lipid levels in the hyperlipidemic hamster model [217,221]. Yerba mate extract retards the expression of genes responsible for adipogenesis, such as Creb-1 and C/EBPα, and stimulates the expression of genes that are responsible for the inhibition of adipogenesis, such as Dlk1, Gata2, Gata3, Klf2, Lrp5, Pparγ2, Sfrp1, Tcf7l2, Wnt10b, and Wnt3a [222]. Another tea that acts as a great inhibitor of α-amylase and lipase activities is kombucha tea [223]. Kombucha tea can also decrease the rate of absorption of LDL-cholesterol and triglycerides, increases HDL-cholesterol and suppresses the increase of glucose levels in the blood. The activities of aspartate transaminase, alanine transaminase, gamma-glytamyl transpeptidase, and creatinine and urea contents are also reduced by kombucha tea [219].

In Europe, chamomile tea is widely consumed. Chamomile is ranked in Asteraceae or Compositae families and there are several varieties such as Chamomilla recutita, Matricaria chamomilla, and Chamaemelum nobile. Chamomile can significantly prevent the aggregation of platelets and exhibits moderate antioxidant and antimicrobial properties as well as high anti-inflammatory, anti-mutagenic, and cholesterol-lowering activities [224]. The antioxidant, hypocholesterolemic, anti-parasitic, anti-aging, and anti-cancer properties of chamomile have been supported by studies [224,225,226]. Chamomile also inhibits COX-2 enzyme activity and the production of LPS-induced prostaglandin E (2) in RAW 264.7 macrophages in vitro [227]. It is worth noting that a small part of people exhibit sensitivity to chamomile and present allergic reactions [228].

In Turkey, ‘Dagcayi’, produced by the infusion of S. condensate, has gained the interest of consumers. The main characteristic of S. condensate is the content of hydroxybenzoic and hydroxycinnamic acids, which are in the flower, leaf, and seed of S. condensate, and their concentration depends on the infusion temperature, time duration, and the part of the plant used for infusion. The phenolic acid p-coumaric acid has also been identified in the flower, leaf, and seed of S. condensate. In Europe and North Africa, peppermint tea, which is brewed from Mentha piperita, is consumed, and has an antioxidant capacity and antibacterial activity against various pathogens [229,230]. According to some research, the herb C. asiatica can induce liver problems, stomach upset, nausea, and drowsiness, and the active constituents of some herbs can also negatively affect metabolic enzyme activity. Furthermore, liver damage, interaction with medications, interaction with metabolic enzymes, and other natural ingredients can be induced by the concentrated form of some herbs such as green tea. It should be noted that there is not much available published information on the safety of herbs and herbal beverages and the interaction between herbs and therapeutic drugs.

5. Conclusions

This systematic review addresses two-hundred and thirty references and highlights the composition, properties, beneficial effects, and even toxic effects of sports and functional drinks on human health. The topic studied herein has not been exhaustively investigated, as new drinks or beverages are produced by the beverage industry in a global zone based on the principles of the production of novel functional drinks. The components are the target factors of these beverages related to human health. Therefore, the main scope of the beverage industry should be to reduce the components that are associated with chronic pathophysiological disorders, such as diabetes, cancer, etc., with natural ingredients such as phenolic compounds, terpenoids, and other phytochemicals found in plants and fruits. This topic is getting more valuable nowadays, as the adulteration of foods and drinks at an international level has drastically increased, thus more action is required by the food sector and the beverage industry for the awareness of consumers.