Alcohol
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A food, a drug, and a toxin
Alcohol as a Food
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Provides energy--7 Calories per gram
Is not required by the body for any essential functions
Is not stored in the body
Alcohol as a Drug
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Depresses the central nervous system
Can cross the blood-brain barrier, unlike many other compounds
Is addictive
Alcohol as a Toxin
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Alcohol metabolism in the liver takes first priority over other functions,
including gluconeogenesis and detoxification of other drugs
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Fetal alcohol syndrome can occur when pregnant women drink even modest
amounts
How alcoholic beverages are made
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Yeast metabolize glucose to alcohol, carbon dioxide, and water
Yeast die when alcohol concentration reaches 16-18%
Distillation produces higher alcohol concentrations
Other compounds are distilled with alcohol that provide color and flavor to
beverage
Alcoholic Content of Beverages
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Beer ~ 5%
Wine ~ 12.5%
Vodka, gin, whisky, rum 35-45%
– Usually measured in proof, which is calculated as 2 x % alcohol
– Everclear is 190 proof
Alcohol Absorption & Metabolism
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Alcohol is absorbed throughout the gastrointestinal tract, even in the mouth
and esophagus
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Most is absorbed in the upper small intestine and goes to liver for metabolism
Some alcohol is metabolized in the stomach
Alcohol metabolism is a two-step process
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Step one (moderate drinkers) is alcohol dehydrogenase (a zinc-dependent
enzyme)
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EtOH + NAD+
acetaldehyde + NADH
NADH can be subsequently used for energy
Step One (Heavy drinkers)
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MEOS (microsomal ethanol-oxidizing system)--an enzyme in the liver that
also detoxifies other drugs
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EtOH + NADPH
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Acetaldehyde is toxic, so aldehyde dehydrogenase is needed
acetaldehyde + NADP+
An energy-consuming reaction
MEOS is an inducible enzyme
Step Two (all drinkers)
Acetald. + NAD+CoA
AcetylCoA + NADH
Both acetylCoA and NADH can be metabolized for energy
Antabuse (disulfiram)
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A drug used in aversion therapy for drinkers
Antabuse inhibits aldehyde dehydrogenase, so acetaldehyde builds up in
body and person feels very sick if he/she drinks while taking this drug
Alcohol metabolism is a rate-limited process
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One drink can be dealt with in 1-2 hours
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Drinking on an empty stomach increases the risk of high blood alcohol levels
Multiple drinks at once (e.g., the beer funnel) take longer to remove from
system
Alcohol excretion
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Some is excreted via breath and urine
Police breathalyzer tests take advantage of the fact that breath alcohol is
directly proportional to blood alcohol
Women are at greater risk for alcohol-related disease
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Lower lean body mass and less body water to dilute EtOH
Have lower activity of alcohol dehydrogenase in the stomach
Some evidence indicates they may be more prone to addiction
Long-Term Consequences
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Damage to gastrointestinal tract
Neurologic problems
Fetal alcohol syndrome
Liver disease
Stages of Alcoholic Liver Disease
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Fatty Liver
Alcoholic Hepatitis
Cirrhosis--permanent damage
– Liver becomes nodular
– Circulation through liver becomes backed up
– Can result in brain damage, kidney failure and death
Nutritional abnormalities in alcohol abuse
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Lousy diet leads to multiple nutrient deficiencies
– Bone disease due to poor vitamin D and calcium status
– Wernicke’s encephalopathy-a dementia related to thiamin deficiency