Notes on Alcohol

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Food Science and Human Nutrition
HUN 2201
All Professors

• Focus on: alcohol o Any molecule that contains a hydroxyl group o Usually refers to ethanol, or grain alcohol. o Alcoholic beverages hardly contain any protein, vitamins and minerals o 5 fl oz wine, 12 fl oz beer, 1.5 fl oz distilled spirits contain 12-14 grams of alcohol, about 7kcal/gram o The amount of energy contributed by carb depends on type of beverage • Alcohol absorption and excretion o Absorbed in GI tract via simple diffusion o Small amounts absorbed in stomach; most absorbed in duodenum and jejunum of small intestine  Occurs quickly, although food reduces contact with stomach lining and slows stomach emptying, thus decreasing the rate at which alcohol enters the small intestine o Once absorbed, enters bloodstream  Small water-soluble molecule  Blood alcohol level depends on difference between rates of absorption and elimination  Peak blood concentrations = 1 hour after ingestion • B.A.C. determined by weight, gender, speed of consumption, kind and quantity of beverage, food consumed with it • Alcohol metabolism o 2 primary metabolic pathways o Alcohol dehydrogenase ADH pathway [cytosol]  ADH: enzyme found primarily in liver and stomach that helps break down alcohol into acetaldehyde, then converted to acetyl-coa  Acetaldehyde is a toxic compound  Reactions release high-energy electrons, form NADH…derived from niacin. • Although these processes produce ATP, high levels of NADH slow the citric acid cycle. Acetyl CoA from alcohol, carb, and fat metabolism is used to synthesize fatty acids that accumulate in the liver • Constant rate of breakdown o Microsomal ethanol-oxidizing system [microsomes of smooth ER]  Important when greater amounts of alcohol are consumed  Requires oxygen and energy….occurs in mitochondria • In addition to forming acetaldehyde and water, reactive oxygen molecules are generated, can contribute to liver disease. • Rate of breakdown increases when more alcohol is consumed • Also metabolizes other drugs • Adverse effects of alcohol consumption o Acute effects?  Depending on body size, previous drinking, food intake, and general health, liver can break down about 0.5 g alcohol per hour. If amount exceeds, then excess will be stored in bloodstream until liver enzymes can metabolize it.  In brain, acts as a depressant • First, affects reasoning • Then, affects vision and speech • Then, affects control • Alcohol poisoning slows breathing, heart rate, and gag reflex. Abuse involved in 40% of all traffic fatalities  Blackout drinking: amnesia o Chronic effects?  Alcoholism: risk of addiction greater at younger age; genetic and environmental component  Why alcohol abuse contributes to malnutrition • When alcohol exceeds 30% of calories, nutrient-dense sources have been replaced • Also, secondary malnutrition by interfering with absorption o Inflammation of the stomach, pancreas, and intestine  Decreased absorption of B vitamins and vitamin C  Thiamin deficiency in particular  Mucosal damage also increases ability of large molecules to cross the mucosa, so toxins from gut lumen can enter portal blood, increasing liver’s exposure to them and risk of liver injury by altering the storage, metabolism, and excretion of vitamins and minerals  Increased risk of obesity and abdominal fat, associated with risk of CVD, cancer, diabetes  How alcohol affects the liver • Causes liver damage through both malnutrition and toxic effects • Metabolism via ADH produces excessive NADH, which inhibits the citric acid cycle and affects the metabolism of lipids, carbs, and proteins o High levels of NADH favor fat synthesis and inhibit fat breakdown • Metabolism by MEOS generates free radicals and oxidative stress, damaging membranes and altering enzyme activities o When broken down by ADH, alcetaldehyde is formed, binds to proteins and inhibits reactions of the mitochondria, allowing accumulation • Chronic consumption leads to alcoholic liver disease: o First phase: fatty liver o Second phase: alcoholic hepatitis: inflammation • Both of these are reversible! But if consumption continues, cirrhosis may develop o Irreversible’ scars develop and interfere with metabolic function  Alcohol and cancer • Associated with increased risk of cancer in several organs • Production of acetaldehyde, a carcinogen o Colon cancer: acetaldehyde produced by bacterial metabolism o Alcohol consumed in the diet is absorbed before it reaches the colon, but can pass from blood to lumen, where it may accumulate and contribute to mucosal injury or cancer  Acetaldehyde absorbed back into blood contributes to liver damage  No true “safe” level that does not promote cancer • Benefits of alcohol consumption and safe drinking o May be one drink per women and 2 per men. o With meals, alcohol can stimulate appetite and improve mood. Relaxing social interactions, reduce risk of heart disease and stroke  Increases HDL cholesterol, reduces platelet stickiness and blood clotting protein fibrinogen  Reduces inflammation, increases insulin sensitivity  Benefit one wlll gain from moderate alcohol consumption depends on background, health, gender, etc  Children, adolescents, pregnant women should avoid  No more than 1 drink every 1.5 hours. • Focus on: Eating Disorders o
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