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NUTR 250 Human Nutrition & Metabolisms Chapter 8 Alcohol Dr. Keting Li, FDST, UNL Chapter Overview 1. 2. 3. 4. 5. Sources of alcohol, standard serving sizes Alcohol absorption and metabolism Heath risks and benefits Effects of chronic alcohol use Alcohol abuse and dependency Sources of alcohol 1. Th...

NUTR 250 Human Nutrition & Metabolisms Chapter 8 Alcohol Dr. Keting Li, FDST, UNL Chapter Overview 1. 2. 3. 4. 5. Sources of alcohol, standard serving sizes Alcohol absorption and metabolism Heath risks and benefits Effects of chronic alcohol use Alcohol abuse and dependency Sources of alcohol 1. The form of alcohol we consume is chemically known as ethanol (CH3CH2OH). 2. Sources??? Alcoholic beverages like wine, beer, distilled spirits Alcohol Production Basic principle: yeasts ferment sugar into alcohol and carbon dioxide under anerobic condition C6H12O6 → 2 CH3CHOH + 2 CO2 Source of sugar:  Cereals (barley, wheat, rye, sorghum and millets), fruits, potatoes  Simple sugars or “malts” before fermentation  During malting, the grain seeds sprout, and enzymes are produced to break starches into simple sugars. Barley Malt Wine Production Traditionally carried out with Saccharomyces cerevisiae Beer Production Required ingredients: malt, hops, water and yeast Bottom yeasts: aggregate and settle to the bottom (S.pastorianus) Used for lager-type beers Top yeasts: clump together and trap gas (S.cerevisiae) Used for ale-type beers Fermentation may take from 5 to 9 days to complete Read Beer Labels U.S. % Alcohol by volume China % Alcohol by volume & Original malt extract concentration (Plato degree) Distilled Spirits Distillation Purification of alcohol Ethanol is boiled off and condensates Read Hard Liquor (Distilled Spirits) Labels U.S. Proof = 2 × alcohol% by volume China alcohol% by volume Different distilled spirits Absorption & Distribution Alcohol requires no digestion Alcohol requires no specific transport mechanism or receptors to enter cells Absorbed by simple diffusion (rapid) 20% is absorbed in stomach 80% is absorbed in small intestine Absorption is slowed when food is consumed with alcohol Once absorbed: Enters into blood stream Distribution throughout the whole body (body water) Passes through cell membranes Discussion Age-old rule about drinking: “Always fill up on food before filling up on alcohol.” “Drinking on an empty stomach makes you drunk faster.” Why is it? Alcohol Metabolism Alcohol can not be stored in the body Metabolized as fuels source is a priority Liver: Chief site for alcohol metabolism 3 Pathways: 1. Alcohol dehydrogenase (ADH) pathway 2. Microsomal ethanol oxidizing system (MEOS) pathway 3. Catalase pathway Metabolize nearly all the alcohol consumed. Only 2-10% of is excreted unmetabolized through the lungs, urine, and sweat. Alcohol Metabolism 1. Alcohol dehydrogenase (ADH) Pathway At low to moderate intakes Liver & Stomach Metabolize 90% of alcohol consumed Two enzymes: 1. Alcohol dehydrogenase alcohol  acetaldehyde 2. Aldehyde dehydrogenase acetaldehyde  acetyl-CoA Acetyl-CoA used for: o Energy o Fatty acid synthesis Alcohol Metabolism 2. Microsomal ethanol oxidizing system (MEOS) Moderate to excessive intakes Liver (chief site) Produce same intermediates as the AHD pathway but energy required MEOS adapts to intake: o Efficient metabolism o Greater tolerance MEOS also metabolizes drugs Discussion Why should one not drink excessive alcohol while taking some medications? Alcohol Metabolism 3. Catalase Pathway Minor contribution to alcohol metabolism Liver and other cells (e.g. brain) Factors Affecting Alcohol Metabolism Production and activity of enzymes in the alcohol dehydrogenase pathway 1. Ethnicity: Asians have lower aldehyde dehydrogenase activity Build up of acetaldehyde (toxic); cause flushing, dizziness, nausea, headaches, rapid heartbeat and breathing 2. Biological sex: Women produce less alcohol dehydrogenase. Women have smaller body size and less body water, more concentrated of alcohol in blood 3. Age: Enzyme activity; water distribution volume 4. Other factors Alcohol content, the amount of alcohol consumed, the individual’s usual alcohol intake Rate of Alcohol Metabolism A drinker who weighs 70 kg with normal liver function can metabolize 5-7g of alcohol per hour (1/2 alcoholic equivalent) When alcohol consumption >> metabolic capacity Blood alcohol levels increase Alcohol intoxication: Symptoms appear as the brain and central nervous system Blood alcohol concentration (BAC): BAC is determined by measuring the amount of alcohol excreted through the lungs as BAC is strongly related to alcohol content of exhaled air. Breathalyzer to test BAC Alcoholic drink equivalent In the United States, one "standard" drink (or one alcoholic drink equivalent) is defined as 0.6 US fluid ounce of ethanol per serving, which is about 14 grams of alcohol E.g., 16 fl oz beer with 7% ABV = 1.9 drink equivalent Moderate alcohol intake is: Women: no more than 1 alcoholic drink equivalent/day Men: no more than 2 alcoholic drink equivalent/day Figure 8-1. Examples of 1 standard-size drink Blood Alcohol Concentration (BAC) In U.S., : Alcohol intoxication (BAC ≥ 0.08%) – illegal Rules and Regulations at UNL Don’t drink or possess alcoholic beverages on campus! Some states have more stringent laws 0.02% is equivalent to 1 standard drink. https://nudirections.unl.edu/laws_policies https://housing.unl.edu/movein/rules/index.shtml https://police.unl.edu/drug-free-campus-policy Blood Alcohol Concentration (BAC) In China, 饮酒后驾驶机动车 (酒驾) vs 醉酒后驾驶机动车 (醉驾) 酒驾：20mg/100ml ≤ BAC