Alcohol Metabolism Explained | Ethanol, Acetaldehyde, NADH, and Fatty Liver

Welcome back to the Pre-Health Science Explainers series for pre-health science students, including future nursing students, pre-med students, pre-dental hygiene students, pre-radiology students, pre-EMS students, pre-chiropractic students, and other allied health professionals. In this lesson, we continue our energy metabolism playlist by examining alcohol metabolism. Instead of looking at alcohol as a beverage, this video looks at ethanol as a molecule that the body treats very differently from carbohydrates, fats, and proteins. You will learn why alcohol provides 7 kilocalories per gram but is not considered a nutrient. This video explains what a standard drink means, how ethanol is absorbed rapidly through the stomach and small intestine, and why the liver becomes the main processing site for alcohol detoxification. We also explore the two major alcohol metabolism pathways: the alcohol dehydrogenase pathway and the microsomal ethanol oxidizing system, or MEOS. You will learn how ethanol is converted into acetaldehyde, why acetaldehyde is highly toxic, and how alcohol metabolism creates a major NADH overload that disrupts glycolysis, gluconeogenesis, and the citric acid cycle. Finally, this lesson connects alcohol metabolism to long-term health effects, including alcoholic fatty liver, alcoholic hepatitis, cirrhosis, cancer risk, brain changes, heart damage, and impaired vitamin absorption. In this video, you will learn: • Why alcohol provides calories but is not a nutrient • What ethanol is • What counts as one standard drink • Why beer, wine, and liquor can deliver the same alcohol dose • How alcohol is absorbed into the bloodstream • Why food can slow alcohol absorption • Why carbonation can speed alcohol absorption • What blood alcohol concentration means • How the liver metabolizes alcohol • How the alcohol dehydrogenase pathway works • Why acetaldehyde is more toxic than ethanol • What the MEOS pathway does during heavy alcohol intake • How alcohol metabolism disrupts the NAD+ to NADH ratio • Why alcohol can impair gluconeogenesis and energy metabolism • How alcohol contributes to fatty liver, hepatitis, and cirrhosis This video is ideal for students taking Human Nutrition, Biology, Healthcare Science, Public Health, Nursing prerequisites, Allied Health coursework, and nutrition science courses. It is also helpful for students preparing for the TEAS, HESI, ATI, MCAT, and other healthcare entrance exams. If you are looking for clear and student-friendly explanations of nutrition science, metabolism, digestion, healthcare research, and human biology, subscribe for future explainers in this series. This video is intended for educational purposes only and does not provide medical advice, diagnosis, or treatment. Please consult a qualified healthcare professional for guidance related to your individual health, medications, or supplement use. Timestamps 0:00 Introduction to alcohol metabolism 0:20 Alcohol calories and why alcohol is not a nutrient 0:44 Lesson roadmap 1:07 What is ethanol? 1:36 What is a standard drink? 2:01 Alcohol absorption 2:31 Liver processing and blood alcohol concentration 2:52 Alcohol metabolism in the liver 3:02 Alcohol dehydrogenase pathway 3:27 Acetaldehyde toxicity 3:49 MEOS pathway 4:19 Alcohol and the metabolic traffic jam 4:32 NAD+ and NADH imbalance 5:00 Metabolic domino effect 5:26 Alcoholic fatty liver 5:52 Long-term alcohol-related liver damage 6:05 Fatty liver, alcoholic hepatitis, and cirrhosis 6:28 Acetaldehyde as a carcinogen 6:46 Alcohol effects beyond the liver 7:07 Alcohol calories and metabolic cost 7:22 Final question: alcohol as a metabolic poison Hashtags #AlcoholMetabolism #Ethanol #Acetaldehyde #FattyLiver #NutritionScience