9.7: Popular Beverages- Caffeine, Alcohol, Sports Drinks

Beverages that Affect Hydration

In this last section, we will discuss three beverage types that affect hydration: caffeinated drinks, alcohol, and sports drinks. We will examine the effects of these beverages on fluid levels and nutrition within the body so that you will be better able to make wise decisions about your beverage choices.

Caffeinated Drinks

Caffeine is a chemical found in the seeds, leaves, and fruit of many plants, where it acts as a natural pesticide. Coffee, tea, and chocolate are the most common natural sources of caffeine found in the diet, but sodas and other beverages can have caffeine added during processing. Caffeine is the most widely consumed psychoactive drug and is such an important part of many people’s lives that they might not even think of it as a drug. A psychoactive drug is any substance that crosses the blood-brain barrier, primarily affecting the functioning of the brain, be it altering mood, thinking, memory, motor control, or behavior.

Typical Doses and Dietary Sources

Up to 90 percent of adults around the world use caffeine daily, and the average adult in America consumes about 135 mg of caffeine each day.¹ According to the FDA, caffeine can be part of a healthy diet. Up to 400 mg of caffeine, or 3 to 4 cups of coffee, each day is not generally associated with negative health outcomes.² However, much higher doses of caffeine can have adverse health effects such as anxiety, restlessness, and insomnia. If high doses greater than 10,000 milligrams are consumed in a short amount of time, caffeine can be fatal.¹ It would take 75-100 cups of standard coffee to reach this dose, and cases of caffeine fatalities have been primarily reported in individuals who consume caffeine supplements or energy drinks with high caffeine content.

Pure caffeine has a bitter taste, which adds to the flavor of many caffeinated drinks. In a survey of Americans age 35-49 years of age, coffee accounted for 65% of total caffeine intake. Tea and soft drinks were equally popular, each contributing to about 16% of total caffeine intake.³ Some individuals who consume caffeine regularly can develop a tolerance to the effects of caffeine, so one cup of coffee may no longer provide a boost of energy. On the other hand, some individuals are more sensitive to the effects of caffeine and may feel anxiety and restlessness after a small dose of caffeine.¹

Just how much caffeine is in a cup of coffee? It varies. The caffeine content of an average cup of coffee can range from 80-100 milligrams, and the range for tea is 30-50 milligrams. Table \(\PageIndex{2}\) provides the range of caffeine found in common beverages.² When estimating your total caffeine consumption, remember it's not only in beverages but also in some foods and medicines.

Table \(\PageIndex{2}\): Caffeine Content in Various Beverages and Foods

Beverage/Food	Caffeine (milligrams)
12 oz. Soft Drinks (12 oz.)	30-40 mg
Green or Black Tea (8 oz.)	30-50 mg
Coffee (8 oz.)	80-100 mg
Energy Drink (8 oz.)	40-250 mg

Source: https://www.fda.gov/consumers/consum...feine-too-much

Coffee and hydration status

A diuretic refers to any substance that elevates the normal urine output above that of drinking water. Caffeinated beverages are commonly believed to be dehydrating due to their diuretic effect, and there is evidence that acute doses of highly caffeinated coffee increase urine output.⁴ However, drinking coffee does not seem to increase the risk of dehydration. In a cross-over study, individuals who regularly consumed both water and caffeinated coffee showed the same hydration level as determined by urine analysis and body weight.⁵ Overall, a systematic review of the scientific studies concluded that coffee with high amounts of caffeine has an acute diuretic effect, but tolerance is developed if individuals regularly consume coffee.⁶ Coffee and teas are, therefore, often considered a source of hydration rather than a diuretic that can contribute to dehydration.

Health Benefits

The most renowned effects of caffeine on the body are increased alertness and delay of fatigue and sleep. How does caffeine stimulate the brain? Caffeine is chemically similar to a chemical in our brains called adenosine. Caffeine blocks the actions of adenosine and affects the levels of signaling molecules in the brain, leading to an increase in energy metabolism. At the molecular level, caffeine stimulates the brain, increasing alertness and causing a delay of fatigue and sleep. At high doses, caffeine stimulates the motor cortex of the brain and interferes with the sleep-wake cycle, causing side effects such as shakiness, anxiety, and insomnia. People’s sensitivity to the adverse effects of caffeine varies, and some people develop side effects at much lower doses. Caffeine's effects on the brain do not diminish with habitual drinking of caffeinated beverages.

Many studies have aimed at determining the health consequences of consuming caffeine, but the results of these studies have several limitations. Because caffeine tolerance can build up over time, it can be difficult to conclude long-term health effects from short studies. Second, drawing conclusions about the health effects of caffeine can be difficult because people may engage in other behaviors, such as smoking, while participating in studies. Third, many studies of caffeine intake focus on coffee and tea, both of which contain phytochemicals called polyphenols. These compounds can have strong antioxidant properties that may impact health. It is also important to consider that many caffeinated drinks contain excess sugars, which can have negative health consequences.

Despite these challenges, some consistent health benefits have been observed. A recent review in the New England Journal of Medicine reports that caffeine intake may be associated with lower long-term weight gain, reduced risk of liver damage, and a lower risk of Parkinson's disease.¹ Parkinson’s disease is an illness of the central nervous system causing many movement disorders. One study demonstrated that men who did not consume coffee had a five times more likely chance of Parkinson’s disease than men who consumed more than 3 cups of coffee daily. In this study, other caffeine sources, such as soft drinks and tea, were also associated with a reduced risk of Parkinson’s disease.⁷

Health Consequences

The acute adverse health effects of caffeine ingestion are anxiety, shakiness, and sleep deprivation. On a more chronic basis, some scientific reports suggest that higher caffeine intake is linked to negative effects on heart health and increased cardiovascular disease, although at this point, most data suggest caffeine does not significantly increase either. A comprehensive review published in the American Journal of Clinical Nutrition reports that caffeine induces a modest increase in blood pressure lasting less than three hours in people with hypertension, but there is no evidence that habitual coffee consumption increases blood pressure long-term or increases the risk for cardiovascular disease.⁸ There is limited evidence that chronic caffeine exposure increases blood pressure chronically in people without hypertension.

Alcohol

Alcohol is both a beverage providing some sustenance and a drug. For thousands of years, alcohol has been consumed in a medicinal, celebratory, and ritualistic manner. In America, it is estimated that more than half of adults consumed an alcoholic drink in the past 30 days.⁹ Like caffeine, alcohol is a psychoactive drug. Alcohols in chemistry refer to a group of similar organic compounds, but in beverages, the only alcohol consumed is ethanol, a simple molecule consisting of two carbons, one oxygen, and six hydrogen atoms.

Typical Doses

Chronic alcohol use occurs when individuals consume alcohol regularly over an extended period. The health consequences of chronic alcohol use are dependent on the amount of alcohol consumed or the dose. Alcohol doses vary depending on the type of alcoholic drink. Some alcoholic drinks, such as beer and wine, have less alcohol content per drink, so standard drink sizes have been established to help define the actual alcohol intake. According to the Dietary Guidelines for Americans, one alcoholic drink equivalent is defined as containing 14 grams or 0.6 fluid ounces of pure alcohol. Based on this definition, 12 fluid ounces of regular beer containing 5% alcohol, 5 fluid ounces of wine containing 12% alcohol, or 1.5 fluid ounces of 80-proof distilled spirits containing 40% alcohol are all standard drink equivalents. The Dietary Guidelines for Americans recommend no more than one alcoholic drink per day for women and no more than two alcoholic drinks per day for men to avoid the negative health effects of alcohol.¹⁰ It is important to note that women who are pregnant and individuals who are under the age of 21 or have a history of certain medical conditions, including substance abuse, should avoid drinking alcohol altogether.

Alcohol Absorption and Metabolism

Alcohol is a hydrophilic or water-loving molecule, is easily absorbed into the bloodstream and distributed throughout the body. The higher the concentration of alcohol in the small intestines, the faster the absorption. so drinks with high alcohol content will cause more rapid absorption. Food in the stomach can slow down alcohol absorption because it slows down the release of stomach contents into the small intestines, where most of the alcohol is absorbed.

More than 90 percent of ingested alcohol is metabolized in the liver. The remaining amount stays in the blood and is eventually excreted through the breath, urine, saliva, and sweat. Blood alcohol concentration, or BAC, measures the amount of alcohol present in the blood and is associated with mental and physical intoxication effects of alcohol (Table \(\PageIndex{1}\)). BAC values, measured in milligrams percent, can be determined using breath tests or breathalyzers, which compare units of alcohol to units of blood. BAC is a measurement used legally to assess intoxication and the impairment and ability to perform certain activities, such as driving a car.

Table \(\PageIndex{1}\): Mental and Physical Effects of Different BAC Levels

BAC Percent	Typical Effects
0.02	Some loss of judgment, altered mood, relaxation, increased body warmth
0.05	Exaggerated behavior, impaired judgment, some loss of muscle control (focusing eyes), feeling of well-being, lowered alertness, release of inhibition
0.08	Poor muscle coordination (balance, speech, vision, reaction time), difficulty detecting danger, and impaired judgment, self-control, reasoning, and memory
0.10	Clear deterioration of muscle control and reaction time, slurred speech, poor coordination, slowed thinking
0.15	Far less muscle control than normal, major loss of balance, vomiting

As a general rule, the liver can metabolize one standard drink per hour. Drinking more than this, or more quickly, will cause BAC to rise to potentially unsafe levels. Giving the liver enough time to metabolize the ingested alcohol fully is the only effective way to avoid alcohol toxicity. Drinking coffee or taking a shower will not help. The legal limit for intoxication in many states is a BAC of 0.08. Taking into account the rate at which the liver metabolizes alcohol after drinking stops and the alcohol excretion rate, it takes at least five hours for a legally intoxicated person to achieve sobriety. In addition to the one-drink-per-hour guideline, the rate at which an individual’s BAC rises is affected by the following factors:

• Sex: BAC levels rise faster in women than men who have consumed the same amount of alcohol.
• Weight: BAC levels rise faster in individuals with lower weights.
• Genetics: Some individuals may not metabolize alcohol quickly, which leads to higher BAC levels.
• Length of time as a heavy drinker: Individuals who are heavy chronic drinkers may metabolize alcohol faster.
• Type of alcohol consumed: Higher alcohol content will lead to faster absorption.
• Amount of alcohol consumed: More alcohol increases BAC levels faster.
• Consumption rate: Fast consumption increases BAC levels faster.
• Consumption before or after a meal: Food in the stomach slows down absorption.
• Mixture: Carbonated drinks can increase absorption.
• Medications: Some medications may affect the absorption and metabolism of alcohol.

Figure \(\PageIndex{1}\). Alcohol and food. Drinking alcohol with food will slow the absorption of the alcohol. Source: "Beer and chicken wings" by Leonid Mamchenkov is licensed under CC BY 2.0.

Health Benefits

Moderate alcohol intake has been shown to provide some health benefits, but it is important to remember that these findings may not apply if an individual has a risk of substance abuse or other underlying health conditions. Studies have consistently shown that moderate alcohol intake reduces the risk of heart disease in middle-aged and older people. A review of twenty-nine studies concluded that moderate alcohol intake reduces the risk of coronary heart disease by about 30% in comparison with those who do not consume alcohol.¹¹ Several other studies demonstrate that moderate alcohol consumption reduces the incidences of stroke, heart attack, and death caused by cardiovascular and heart disease. The drop in risk for these adverse events ranges between percent. Moreover, there is some scientific evidence that moderate alcohol intake reduces the risk of metabolic syndrome, type 2 diabetes, and gallstones.¹² It has not been clearly demonstrated that moderate alcohol consumption benefits younger populations, and the risks of any alcohol consumption do not outweigh the benefits for pregnant women, those who are taking medications that interact with alcohol, and those who are unable to drink in moderation. According to the Dietary Guidelines for Americans, individuals who do not drink alcohol should not start drinking. Drinking less is healthier than drinking more.

Health Consequences

Alcohol consumption can lead to a variety of health problems if consumed in excess. According to the CDC, excessive alcohol use is the leading cause of preventable death in the United States.¹³ Several patterns of drinking are considered excessive alcohol use. First, any alcohol consumption during pregnancy or under the age of 18 is considered excessive. Second, binge drinking is defined as consuming 4 or more drinks on an occasion for a woman or 5 or more drinks on an occasion for a man. According to the National Survey on Drug Use and Health, approximately 10-30% of adults over the age of 18 reported binge drinking in the past 30 days.⁹ Finally, heavy drinking is defined as 8 or more drinks per week for a woman or 15 or more drinks per week for a man. Any form of excessive alcohol use can increase the risk for several chronic diseases.

Because alcohol provides calories, excessive alcohol consumption has been suspected of causing weight gain. One alcoholic drink equivalent contains 100-150 calories, so even moderate drinking can substantially increase calorie intake. Distilled spirits have exceptionally few nutrients, but adding sugary mixers will increase the calorie content of the drink. Beer and wine do provide some nutrients, vitamins, minerals, and beneficial phytochemicals along with calories. Research studies have not consistently shown an association between alcohol consumption and weight gain. For example, a prospective study of nearly 15,000 men showed a slightly increased risk of weight gain with higher alcohol intake.¹⁴ However, light-to-moderate consumption of wine has been associated with less weight gain in some studies.¹⁵ The contradictory results of these studies may be partly because alcohol contributes calories to the diet, but when drunk in excess, it reduces the secretion of pancreatic juice and damages the lining of the gastrointestinal system, impairing nutrient digestion and absorption. Alcohol is also a diuretic, a substance that increases urine output. Heavy alcohol consumption results in dehydration because alcohol suppresses the release of antidiuretic hormone and decreases the kidneys' water reabsorption. Drinking alcohol in excess can lead to a “hangover,” the majority of whose symptoms are the direct result of dehydration.

Effects of Alcohol Abuse on the Brain

Alcohol can adversely affect nearly every area of the brain. When BAC rises, the central nervous system is depressed. Alcohol disrupts the way nerve cells communicate with each other by interfering with receptors on certain cells. The immediate impact of alcohol on the brain can be seen in the awkwardly displayed symptoms of confusion, blurred vision, slurred speech, and other signs of intoxication. These symptoms will go away once drinking stops, but abusive alcohol consumption over time can lead to long-lasting damage to the brain and nervous system. This is because alcohol and its metabolic byproducts kill brain cells. Excessive alcohol intake has the following effects on specific areas of the brain:

1. Medulla. This area controls automatic functions, such as heart rate. When alcohol first limits its functioning, people feel sleepy. With greater BAC levels, unconsciousness, comas, and death can result.
2. Cerebellum. This is where conscious movement is coordinated. With too much alcohol, balance and motor skills are impaired.
3. Cerebral cortex. Senses and thoughts are processed here, and this is where action is initiated. When BAC levels increase, the ability to think, exercise good judgment, and feel pain decreases.
4. Hypothalamus and pituitary gland. Alcohol increases sexual desire but decreases sexual performance. It also prompts signals that increase urine production.
5. Limbic system. When alcohol affects this area, individuals may become very emotional and lose memory function.

Effects of Alcohol Abuse on the Liver

The liver is one of the body’s main filtering organs and is severely stressed by alcohol abuse. The term alcoholic liver disease, or ALD, is used to describe liver problems linked to excessive alcohol intake. ALD can be progressive, with individuals first suffering from a fatty liver and going on to develop cirrhosis. It is also possible to have different forms of ALD simultaneously.

The three most common forms of ALD are

• Fatty liver. A rather benign disorder that develops after excessive alcohol consumption; however, it can progress to more fatal diseases. Fatty liver is reversible if alcohol use is brought under control.
• Alcoholic hepatitis. The symptoms of this alcohol-induced liver inflammation are a swollen liver, abdominal pain, nausea, fever, jaundice, and vomiting. Although linked to alcohol use, even people who drink moderately can sometimes develop this condition, and not all alcohol abusers do. If a person stops drinking alcohol, the liver damage can be reversed. But if they continue, cirrhosis may develop, and death can result.
• Cirrhosis. This serious and sometimes fatal form of ALD develops when liver cells die and form scar tissue, which blocks blood flow and causes wastes and toxins to build up in the system. Strictly speaking, cirrhosis cannot be cured. It can, however, be stopped with medical treatment; and complications can be managed if the individual stops drinking, and many do survive. Not all cases of cirrhosis are strictly due to alcoholism, and not all alcoholics develop the disease. Symptoms of cirrhosis include the buildup of abdominal fluid (ascites), abdominal pain, fever, thirst, confusion, and fatigue.

Figure \(\PageIndex{2}\): Liver cirrhosis. Excessive alcohol consumption destroys liver cells. In an attempt to repair itself, the liver initiates an inflammatory and reparation process, causing scar tissue to form. In the liver’s attempt to replace the dead cells, surviving liver cells multiply. The result is clusters of newly formed liver cells, also called regenerative nodules, within the scar tissue. This state is called cirrhosis of the liver. Source: "Liver Cirrhosis" by BruceBlaus is licensed under CC BY-SA 4.0.

 

Sports Drinks

Sports drinks contain carbohydrate and electrolytes such as sodium and potassium with the goal of replenishing hydration during exercise to enhance performance. Some studies support these claims, but these findings are not consistent.¹⁶ The primary source of water loss during intense physical activity is sweat. Perspiration rates are variable and dependent on many factors including body composition, humidity, temperature, and type of exercise. The hydration goal for obtaining optimal endurance and performance is to replace what is lost. Individuals can replenish lost fluids, energy and electrolytes used during exercise by drinking plain water and eating a sports bar or snack that contains carbohydrates, protein, and electrolytes. If solid food is not tolerated before or during exercise, sports drinks can serve as a convenient was to refuel. Athletes or persons involved in physical activity over an extended period of time, in the heat, or at a frequency in which they can't make up a fuel deficit such as in tournament play, may value from using a sports drink.¹⁷ However, casual exercisers are not likely to need a standard electrolyte-replacing, fuel-providing sports drink.

Although sports drinks are often advertised and perceived as healthy sources of hydration, unnecessary use of sports drinks can lead to weight gain due to excess added sugars and calories, especially in children. In a 7-year study of over 7,000 adolescents, individuals who consumed more sports drinks were more likely to experience weight gain and obesity.¹⁸ It is important to note that excess weight gain is associated with several chronic diseases, including diabetes and cardiovascular disease. Ultimately, the best source of hydration for most people is water.

Attributions

• Zimmerman, "An Introduction to Nutrition (Zimmerman)," CC BY-NC-SA 3.0. The original material was reorganized and updated. New references were added.

References

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