Chapter 9: Alcohol Nutrition, Metabolism, and Health Effects

Alcohol: Nutrition, Metabolism, and Health Effects

What Is Alcohol and How Is It Made?

Alcohol, specifically ethanol, is the type of alcohol found in beverages and is not an essential nutrient. It is produced by the fermentation of yeast and natural sugars in grains (for beer) and fruits (for wine). Liquor is made by distillation, which concentrates the alcohol. Other types of alcohol, such as methanol and isopropanol, are toxic to humans.

• Ethanol: Safe for consumption in moderate amounts, but toxic in excess.

• Fermentation: Yeast converts sugars into ethanol and carbon dioxide.

• Distillation: Process to increase alcohol concentration in liquors.

Why Do People Drink Alcohol?

Alcohol is consumed for various social and psychological reasons, including relaxation, celebration, and socialization. Social drinking refers to patterns of alcohol use considered acceptable by society. Moderate alcohol consumption may offer some health benefits, such as a reduced risk of heart disease, but these benefits are age-dependent and not observed in younger individuals.

• Moderate consumption: Up to one drink per day for women, two for men.

• May increase HDL cholesterol and reduce blood clot risk.

• Health benefits are only seen in women ≥55 years and men ≥45 years.

Standard Drink Sizes

A standard drink contains about 0.5 ounces of pure alcohol. Examples include:

• 12-ounce beer

• 1.5-ounce shot of liquor

• 5-ounce glass of wine

Moderate drinkers should monitor both the size and frequency of their drinks. Binge drinking (abstaining for several days, then overdrinking) is not considered moderate drinking.

How Is Alcohol Absorbed and Metabolized?

Alcohol is a toxin, and the body works quickly to metabolize and eliminate it. Absorption begins in the stomach and continues in the small intestine. The enzyme alcohol dehydrogenase in the stomach metabolizes some alcohol before absorption, but women have less of this enzyme, making them more susceptible to alcohol's effects. Food in the stomach slows absorption.

• About 20% of alcohol is absorbed in the stomach, 80% in the small intestine.

• Alcohol is primarily metabolized in the liver at a rate of about one standard drink every 1.5 to 2 hours.

• Alcohol dehydrogenase converts alcohol to acetaldehyde, which is further metabolized to carbon dioxide and water.

• The microsomal ethanol-oxidizing system (MEOS) is activated with chronic high intake.

• Alcohol circulates in the blood until metabolized; blood alcohol concentration (BAC) correlates with breath alcohol levels.

Blood Alcohol Concentration (BAC)

BAC is a measure of grams of alcohol per deciliter of blood. It is influenced by the number of drinks, body weight, sex, and time.

Drinks per Hour	Body Weight (Women)	Body Weight (Men)
1	0.04–0.05	0.03–0.04
2	0.09–0.10	0.06–0.08
3	0.13–0.15	0.09–0.12
4	0.17–0.20	0.12–0.16
5	0.22–0.25	0.15–0.20
6	0.26–0.30	0.18–0.24
7	0.31–0.35	0.21–0.28
8	0.35–0.40	0.24–0.32
9	0.40–0.45	0.27–0.36
10	0.45–0.50	0.30–0.39

Harmful Effects of Alcohol

Alcohol acts as a depressant on the central nervous system, slowing nerve impulse transmission and impairing thoughts, actions, and behavior. The more consumed, the more areas of the brain are affected, and high doses can suppress vital functions, leading to death.

• Disrupts sleep and causes hangovers (headache, fatigue, nausea, dehydration).

• Acts as a diuretic, causing dehydration and electrolyte imbalances.

• Interferes with hormones (insulin, glucagon, parathyroid hormone, estrogen, reproductive hormones).

• May increase risk of osteoporosis and breast cancer.

• Contributes to both overnutrition (weight gain, abdominal fat) and malnutrition (displacement of nutritious foods, impaired absorption of nutrients such as protein, zinc, magnesium, thiamin, folate, and vitamins B12, A, D, E, K).

• Thiamin deficiency can lead to Wernicke-Korsakoff syndrome.

Calories in Alcoholic Drinks

Alcohol provides 7 kcal/g, which can contribute significantly to daily caloric intake and weight gain.

Effects on Organs

• Can cause inflammation and cancers of the esophagus, mouth, and throat.

• May lead to gastritis, stomach ulcers, hypertension, and heart tissue damage.

• Increases endotoxin production, harming the liver.

• Alcoholic liver disease progresses through three stages: fatty liver, alcoholic hepatitis, and cirrhosis.

Alcohol and Pregnancy

Alcohol consumption during pregnancy can cause fetal alcohol spectrum disorders (FASDs), with fetal alcohol syndrome (FAS) being the most severe form. These disorders cause permanent physical, mental, and behavioral abnormalities. The only safe amount of alcohol during pregnancy is none.

Alcohol Use Disorder (AUD)

Alcohol Use Disorder (AUD) is characterized by continued alcohol consumption despite negative social, psychological, or physical consequences. Binge drinking, drinking and driving, and underage drinking are forms of alcohol abuse.

• Binge drinking: 5+ drinks for men, 4+ for women in about two hours.

• Associated with increased risk of injuries, accidents, violence, and health problems.

• Chronic drinking leads to tolerance and dependence.

• Withdrawal symptoms may occur when not drinking.

Diagnostic Criteria for AUD

The presence of at least 2 of the following symptoms in the past year indicates AUD:

• Drinking more or longer than intended

• Unsuccessful attempts to cut down

• Spending a lot of time drinking or recovering

• Interference with responsibilities

• Continued use despite problems

• Giving up important activities

• Risky behaviors while drinking

• Continued use despite mental/physical health issues

• Increased tolerance

• Withdrawal symptoms

Severity: Mild (2–3 symptoms), Moderate (4–5), Severe (6+).

Prevention and Treatment

• Support from healthcare providers can help reduce consumption in mild cases.

• Severe cases may require counseling, medical support, and ongoing programs such as Alcoholics Anonymous (AA).

Who Should Avoid Alcohol?

• Women who are or may become pregnant

• Children and adolescents

• Individuals taking medications that interact with alcohol

• People with certain medical conditions (e.g., liver disease)

• Those engaging in activities requiring attention or coordination

• Anyone unable to restrict intake

Summary Table: Progressive Effects of Alcohol

Blood Alcohol Concentration	Changes in Feelings and Personality	Brain Regions Affected	Impaired Functions
0.01–0.05	Relaxation, sense of well-being, loss of inhibition	Cerebral cortex	Alertness, judgment
0.06–0.10	Minor impairment of reasoning, memory, attention, mood swings, exaggerated emotions	Cerebral cortex, forebrain	Coordination, depth perception, reasoning, balance
0.11–0.20	Mood swings, reduced sensation, mania	Cerebral cortex, forebrain, cerebellum	Speech, balance, temperature regulation
0.21–0.35	Aggression, reduced sensations, confusion, stupor	Cerebral cortex, forebrain, cerebellum, brain stem	Speech, balance, temperature regulation, breathing
0.36 and greater	Unconsciousness, coma, death possible	Entire brain	Heart rate, breathing

Key Equations

• Alcohol Metabolism: $\text{Ethanol} \xrightarrow{\text{Alcohol Dehydrogenase}} \text{Acetaldehyde} \xrightarrow{\text{Aldehyde Dehydrogenase}} \text{Acetate} \rightarrow \text{CO}_2 + \text{H}_2\text{O}$

• Calories from Alcohol: $\text{Calories from alcohol} = \text{grams of alcohol} \times 7$

Additional info:

• Alcohol is not stored in the body and is prioritized for metabolism over other nutrients.

• Chronic alcohol use can lead to addiction, liver disease, and increased risk of several cancers.