Energy ingredients included in energy drinks and foods are a "cocktail" of two groups of functional ingredients: those involved in generation of energy or calories and those involved in mental and cognitive alertness and excitement. From the former group, elegant examples include ribose, carnitine and coenzyme Q10. From the latter, we have caffeine, taurine and guarana.
Here, we review major functional ingredients of each group. The fast-metabolized simple sugars (as energy generating fuels or "conventional nutrients") are out of the scope of this review.
Ingredients that build internal energy
D-Ribose, or simply ribose, is an aldopentose (5-carbon monosaccharide with an aldehyde functional group) that is used by all cells of the body. Ribose is an essential structural component of "energy currency" adenosine triphosphate (ATP) as well as several other compounds that are critical to metabolism. Ribose also comprises the backbone of RNA and is related to DNA. Forming ribose in heart and muscle is a slow process that, in turn, delays energy recovery when energy pools have been depleted by disease or exercise. Ribose supplementation restores and maintains depleted energy reserves.
Ribose is often marketed as a supplement for boosting energy and reducing fatigue post exercise (muscle cramping and soreness), as well as for fibromyalgia and chronic fatigue syndrome. Ribose also increases cardiac efficiency, power output and tolerance to stress. Ribose is Generally Recognized as Safe (GRAS) (absorption of ~95 percent with peak blood levels found within 30-45 minutes). The recommended daily dose of ribose depends on the product benefit – up to 1.5g for energy, up to 7g for physical performance and up to 10g for cardiovascular and general health.1-6
L-Carnitine or simply carnitine, is biosynthesized primarily in the liver and kidneys from the amino acids lysine and methionine. Carnitine is required for the transport of fatty acids from the cytosol into the mitochondria so they can be broken down through beta-oxidation for energy production. Carnitine biosynthesis yields approximately 20mg carnitine per day, and a balanced diet can supply an additional 100-300mg of carnitine per day. Carnitine is not metabolized or degraded, but excreted in the urine. Therefore, lost carnitine has to be replenished by biosynthesis, consumption of foods of animal origin or dietary supplements (2-4g/day).
Extensive research has shown the effectiveness of carnitine in applications such as exercise (optimization of performance, delayed onset of fatigue and improved recovery process), heart health, weight management (optimal fat oxidation), brain wellness, infant nutrition (not fully developed carnitine biosynthesis – fortified infant formula) and healthy aging.7-10
Coenzyme Q10 is known simply as CoQ10 (also as ubiquinone) where Q refers to the quinone chemical group, and 10 refers to the number of isoprene repeats.
CoQ10 is an oil-soluble, vitamin-like substance present primarily in the inner membrane of mitochondria. It is a component of the electron transport chain and participates in aerobic cellular respiration, generating energy in the form of ATP. Because 95 percent of the human body's energy is generated this way, organs with the highest energy requirements (heart, liver and kidney) have the highest CoQ10 concentrations. Meat and fish are the richest source of dietary CoQ10 (daily intake about 3-6 mg).
Absorption of CoQ10 is similar to lipids where emulsification (via bile salts) and micelle formation is required. Water-soluble CoQ10 offers easier formulation of energy drinks and higher bioavailability. Fully reduced CoQ10 (ubiquinol) is more polar and shows enhanced bioavailability.
CoQ10 may be beneficial in treatment of patients with congestive heart failure. It also has the potential in hypertensive patients to lower systolic and diastolic blood pressure. CoQ10 has been shown to reduce progression of Parkinson Disease and has been found to have a beneficial effect on the condition of some sufferers of migraine headaches. It is used in treatment for those disorders where patients are not capable of producing enough CoQ10. It also acts as an important antioxidant in the body as exogenous CoQ10 protects cells from oxidative stress by conversion into its reduced form by cellular reductases.11-19
Ingredients for alertness
Caffeine is the most important functional ingredient of energy drinks and foods. Caffeine is a bitter, white crystalline xanthine alkaloid found in many plants such as coffee, tea and, to a lesser extent, chocolate derived from cocoa beans. Less commonly used sources of caffeine include the guarana and yerba mate plants.
Caffeine content in coffee is in the range of 40-100mg/cup. Soft drinks typically contain about 10-50mg/240 ml and energy drinks such as Red Bull have 80mg/250ml. The disparity in experience and effects between the various natural caffeine sources could be because plant sources of caffeine also contain widely varying mixtures of other xanthine alkaloids – theobromine, theophylline and polyphenols – that can form insoluble complexes with caffeine.
Caffeine from coffee or other beverages is absorbed by the stomach and small intestine within 45 minutes of ingestion. In humans, caffeine is a central nervous system stimulant, having the effect of temporarily warding off drowsiness and decreased fatigue, increasing awareness/alertness/attentiveness and elevating one's mood. With these effects, caffeine is an ergogenic, as it increases a person's capability for mental or physical labor.
Caffeine's principal mode of action is as a nonselective antagonist of adenosine receptors in the brain. Caffeine is metabolized in the liver into three primary dimethylxanthine metabolites: paraxanthine (84 percent), theobromine (12 percent) and theophylline (4 percent), which also contribute to caffeine's effects. In healthy adults, caffeine's half-life is about four to five hours. Caffeine is the most widely consumed legal and unregulated psychoactive substance but overdose (>300mg/day) should be avoided.20-55
Taurine is a major constituent of bile and is present in many tissues at higher concentrations than any of the other amino acids. Taurine is a derivative of the amino acid cysteine and is one of the few known naturally occurring sulfonic acids. Taurine is conjugated via its amino terminal group with bile acids (e.g., cholic acid) to form the bile salts with surfactant properties. Taurine occurs naturally in food, especially in seafood and meat (consumption is estimated at 40-400mg/day). Nearly all commercially available taurine is chemically synthesized.
Taurine crosses the blood-brain barrier and has been implicated in several physiological mental phenomena. Taurine shows feedback inhibition of neutrophil/macrophage respiratory burst (i.e., "antioxidant") and prevents oxidative stress induced by exercise. Taurine reduces the secretion of apolipoprotein B100 (an essential structural component of VLDL and LDL, which are major risk factors of atherosclerosis and coronary heart disease). Taurine is possibly beneficial for reducing blood pressure in adults with hypertension. Taurine has also been shown to help people with congestive heart failure by increasing the force and effectiveness of heart-muscle contractions. Taurine has shown hypocholesterolemic effect and weight reduction in young overweight adults. It regulates adipose tissue and possibly prevents obesity and exerts a beneficial effect in preventing diabetes-associated microangiopathy.56-63
Guarana is a climbing plant in the maple family, native to the Amazon basin and especially common in Brazil. Guarana is best known for its fruit, which is about the size of a coffee bean. As a dietary supplement, guarana is an effective energy booster: It contains about twice the caffeine found in coffee beans (about 2-4.5 percent caffeine in guarana seeds compared to 1-2 percent for coffee beans). As with other plants producing caffeine, the high concentration of caffeine is a defensive toxin that repels pathogens from the berry and its seeds. The guarana fruit's color ranges from brown to red and contains black seeds that are partly covered by white arils.
The main polyphenols found in guarana are catechin and epicatechin. Because guarana is rich in caffeine, it is of interest for its potential effects on cognition. Guarana is used in sweetened or carbonated soft drinks (especially in Brazil and Peru). Guarana is also used in energy drinks and foods.
A human pilot study assessed acute behavioral effects to four doses (37.5mg, 75mg, 150mg and 300mg) of guarana extract. Memory, alertness and mood were increased by the two lower doses, confirming previous results of cognitive improvement following 75mg guarana. The findings suggest that the effects cannot be attributed to caffeine alone. Guarana is also used as an ingredient in herbal tea or contained in capsules. Studies on guarana extract in laboratory animals have indicated reduced aggregation of platelets, decreased platelet thromboxane formation from arachidonic acid and fat cell reduction when combined with conjugated linoleic acid.64-69
Other energy ingredients
Other functional ingredients involved in generation of energy (calories) or alertness and excitement may also be found in energy drinks and foods:
B vitamins are eight water-soluble vitamins that play important roles in support and increase the rate of cell metabolism. Supplements containing all eight B vitamins are referred to as a vitamin B complex.
Creatine helps to supply energy to all cells in the body, primarily muscle, by increasing the formation of ATP.
Ginseng is any one of 11 distinct species belonging to the Panax genus in the family. It grows in the Northern Hemisphere in eastern Asia (mostly northern China, Korea, and eastern Siberia), typically in cooler climates and is commercially cultivated in North America. Panax ginsengs are considered adaptogenic (natural herb products that are believed to increase the body's resistance to stress, trauma, anxiety and fatigue) and stimulant. Ginseng is characterized by the presence of ginsenosides.
Glucuronolactone is a popular ingredient in energy drinks with claims that it detoxifies the body. Its role is not well established.
Malic acid, a carboxylic diacid, is found mostly in unripe fruits. The salts and esters of malic acid are known as malates. The malate anion is an intermediate in the Krebs cycle.
Pyruvate, made from glucose through glycolysis, supplies energy to living cells in the citric acid cycle (Krebs cycle), and can also be converted to carbohydrates via gluconeogenesis, and to fatty acids or energy through acetyl-CoA.
Yerba mate (literally, "cup herb") is native to subtropical South America. The flavor of brewed yerba mate is strongly vegetal, herbal and grassy, reminiscent of some varieties of green tea. Mate contains three xanthines: caffeine, theobromine and theophylline, the main xanthine being caffeine. Caffeine content varies between 0.7 percent and 1.7 percent of dry weight (compared to 0.4-9 percent for tea leaves, 2.5-7.6 percent in guarana and up to 3.2 percent for ground coffee); theobromine content varies from 0.3-0.9 percent; and theophylline is present in small quantities, or can be completely absent.
Studies of mate, though very limited, have shown preliminary evidence that the mate "xanthine cocktail" is different from other plants containing caffeine, most significantly in its effects on muscle tissue, as opposed to those on the central nervous system. The three xanthines present in mate have been shown to have a relaxing effect on smooth muscle tissue and a stimulating effect on heart tissue.
Editor's ingredient picks
Ribose: Originally a heart-healthy ingredient for congestive heart failure, it's finding a home in energy drinks and athletes' supplements boxes.
CoQ10: Mitochondrial dysfunction is arguably the underlying disease state of aging because cells require healthy mitochondrial activity to perform life-sustaining metabolic processes. The Q fuels mitochondria – the cell's power plant – better than anything.
Venti Coffee: Starbucks-speak for "super-sized." Sometimes you just gotta give in.
Next-gen energy product tips
In developing the next generation of energy drinks and foods, the following three topics deserve close attention:
Novel, value-added ingredients and processes.
In the future, we will see more juice- and dairy-based energy drinks and foods. We will also witness energy drinks and foods with sustainable energy. In this regard, it is important that both groups of functional ingredients are used in a balanced way. Despite the bitterness of caffeine, high sensory attributes of new energy drinks and foods are a prerequisite for success in the market. Patent protection of novel ingredients also needs close attention.
Safety and potential adverse events of energy ingredients.
Caution is the name of the game. Overdosing of energy ingredients should be avoided. Synergistic and antagonistic effects of functional ingredients in energy drinks and foods should not be ignored. It has been indicated that excessive consumption of energy drinks containing caffeine, taurine and/or guarana may provoke onset of seizures in some people. The recent compulsory withdrawal of caffeinated alcoholic beverages is a mentionable example.
The next generation of energy drinks and foods will need to substantiate their declared claims by conducting clinical trials based on Good Clinical Practices (GCP).
Reza Kamarei, Ph.D., provides R&D/management consulting services to help companies bring to market science-based, clinically proven, nutraceuticals, nutritional foods and beverages, supplements and medical foods. He has worked with Nestlé, Baxter, National Starch and Coca-Cola North America. www.kamareiconsulting.com
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