Physiology of Digestion and Absorption Vitamins and Trace Elements lecture from Physiology and Pathophysiology I 25. 10. 2022 M. Chalupová GIT Functions • oral cavity • esophagus • stomach • small intestine – liver – pancreas • large intestine • rectum, anus Gastric Secretion Small Intestine Pancreas Secretion Liver Secretion – Bile Bilirubin – Metabolism and Excretion Lipid Digestion Lipid Absorption Carbohydrate Digestion and Absorption Protein Digestion and Absorption Vitamins • essential, non-caloric nutrients needed in small amounts from the diet • help regulate cell processes and functions • fat soluble (A, D, E, K) • water soluble (B vitamins, vitamin C) Fat Soluble Vitamins • fats and oils of foods • deficiency of these vitamins is rare though can occur with a fat-free diet over long periods • excess stored in the liver and body fat – possible to build up to a toxic level – toxicity is a greater risk if these vitamins are taken as supplements daily Vitamin A (retinol) Vitamin A (retinol)  beta-carotene is converted into vitamin A  vitamin A: ◦ vision ◦ promotes healthy mucous membranes and skin ◦ growth and maintenance of bones, teeth, and cell structure ◦ immunity ◦ reproduction  RDA: 900 ug for males; 700 ug for females Vitamin A in Vision Vitamin A Food Sources • Foods – Only animal products • Liver • Eggs • Milk, butter and cheese • Carotenoids – Orange/Yellow fruits and vegetables • Cantaloupes, carrots, sweet potatoes, winter squash – Leafy green vegetables • Spinach, broccoli Vitamin A Deficiency • not common in the western world but very common in developing countries • blindness, keratinization (hardening and thickening of the skin) • stunted growth, impaired immunity, poor appetite and death Toxicity of Vitamin A • not common unless large amounts of liver eaten • more common from supplements providing several times the recommended level – occurs because vitamin A is stored in the liver and adipose tissue and accumulates – toxicity from beta-carotene does not occur because conversion to retinol is inefficient • excess beta-carotene turns people yellow, but is reversible • abdominal pain, hair loss, joint pain, stunted growth, bone and muscle soreness,nausea, diarrhea, rashes, enlargement of spleen and liver damage Vitamin D • 1,25-dihydroxycholecalciferol – precursor is the body’s own cholesterol • hormone • raises blood calcium by acting on the skeleton, kidneys and the digestive tract to release calcium • cell maturation and immune system stimulation • RDA: 5 micrograms until age 50 – 10 micrograms / day until 70; 15 mcg 70+ Vitamin D Synthesis • ultraviolet light shines on a cholesterol compound in human skin, the compound is transformed into a vitamin D precursor and is absorbed directly into the blood • over 1 1/2 days, the kidneys and liver finish converting the precursor to active vitamin D • kidney or liver disease may affect this process Vitamin D Sources • significant sources – fortified milk, margarine, butter, cereals, and chocolate mixes – veal, beef, egg yolks, liver, fatty fish (herring, salmon, sardines) and their oils Vitamin D Deficiency • children – inadequate calcification, resulting in misshapen bones (bowing of legs) – enlargement long bones ends (knees, wrists) – deformities of ribs (bowed, with beads or knobs) – delayed closing of fontanel, resulting in rapid enlargement of head – lax muscles, muscle spasms • adults – soft, brittle, deformed bones Vitamin D Toxicity • most toxic of all the vitamins – elevated blood calcium – calcification of soft tissues (blood vessels, kidneys, heart, lungs, tissues around joints) – frequent urination Vitamin E (tocopherol) • antioxidant (stabilization of cell membranes, regulation of oxidation) • red blood cells, neurons • deficiency and toxicity are rare – hemolysis, nerve damage • sources: vegetable oils, salad dressings, whole grain cereals, green leafy vegetables, nuts, seeds, peanut butter, egg yolks Vitamin E (tocopherol) Copyright 2005 Wadsworth Group, a division of Thomson Learning Vitamin K • synthesis of blood-clotting proteins and bone proteins that regulate blood calcium Vitamin K • sources: – bacterial synthesis in the digestive tract – liver – leafy green vegetables, cabbage-type vegetables – milk • deficiency symptoms: hemorrhage Water-Soluble Vitamins  Vitamins Bs and C  B vitamins: ◦ Thiamin (B1) ◦ Riboflavin (B2) ◦ Niacin (B3) ◦ Pyridoxine (B4) ◦ Cobalamin (B12) ◦ Folic acid ◦ Pantothenic acid ◦ Biotin B vitamins • act as co-enzymes, involved in energy metabolism – coenzyme is a small molecule that combines with an enzyme to make it active B vitamins • thiamin, riboflavin, niacin, pantothenic acid and biotin participate in the release of energy from carbohydrates, proteins and lipids • vitamin B6 helps the body use amino acids to make protein. Folate and B12 help cells to replicate Vitamin B1 (thiamin) • helps converting carbohydrates to energy • deficiency: – fatigue, nausea, depression, nerve damage • sources: – pork, beef, liver, peas, seeds, legumes, wholegrain products, and oatmeal B2 Vitamin (riboflavin) • key to metabolism and red blood cells • deficiency: – dry, scaly skin • sources: – milk, yogurt, cheese, whole-grain breads, green leafy vegetables, meat, and eggs B3 Vitamin (niacin) • involved with energy production, skin, nerves and digestive system • deficiency: – rare: diarrhea, dermatitis, dementia and death • sources: – meat, poultry, liver, eggs, brown rice, baked potatoes, fish, milk, and whole-grain foods B6 Vitamin (pyridoxine) • involved in chemical reactions of proteins and amino acids • deficiency: – skin changes, dementia, nervous system disorders and anemia • sources: – lean meats, fish, legumes, green leafy vegetables, raisins, corn, bananas, mangos B12 Vitamin (cobalamin) • helps red blood cells production • maintains the myelin sheaths • helps to break down some fatty acids and amino acids • absorption – HCl – pepsin – intrinsic factor required for activation • sources: – only found in animal products (meat, fish, poultry, shellfish, milk, cheese, eggs) B12 Vitamin (cobalamin) • deficiency of folate or B12 produces pernicious anemia (macrocytic, large-cell type) and fatigue, degeneration of peripheral nerves progressing to paralysis • toxicity symptoms: none reported B9 Vitamin (folic acid) • key role in red blood cell formation and cell division • activation – vitamin B12 • deficiency: – anemia (large-cell type), digestive disorders – weakness, mental confusion, fatigue • sources: – leafy, dark green vegetables – liver, beans, peas, asparagus, oranges, avocados B5 Vitamin (pantothenic acid) B7 Vitamin (biotin) • help with metabolism and formation of some hormones • deficiencies are rare • sources: – almost any food, plant-based or animal-based Vitamin C • main functions in the body – collagen synthesis • Strengthens blood vessel walls, forms scar tissue, provides matrix for bone growth – antioxidant – thyroxin synthesis – amino acid metabolism – strengthens immune system – helps in absorption of iron Vitamin C • significant sources – citrus fruits – cabbage-type vegetables, dark green vegetables (such as bell peppers and broccoli) – cantaloupe, strawberries – lettuce, tomatoes, potatoes – papayas, mangoes • easily destroyed by heat and oxygen Vitamin C • deficiency disease: scurvy • deficiency symptoms – anemia (microcellular) – atherosclerotic plaques in the vessels – pinpoint hemorrhages, bone fragility, joint pain – poor wound healing, frequent infections, bleeding gums, loosened teeth – muscle pain and atrophy, depression, rough skin, blotchy bruises Vitamin C • toxicity symptoms – nausea, abdominal cramps, diarrhea – headache, fatigue, insomnia – hot flashes, rashes – aggravation of gout symptoms, urinary tract problems, kidney stones Body Minerals • major (macrobiogenic) – carbon, oxygen, hydrogen, nitrogen, sulphur, phosphorus – sodium, potassium, calcium, chlorine, magnesium, iron • microbiogenic and trace – copper, zinc, molybdenum, cobalt, fluorine, iodine – selenium, manganese, chromium, arsenic, nickel, silicon, boron, cobalt Calcium • the most abundant mineral in your body – 99% is stored in the bones and teeth • integral part of bone structure (serves as a calcium release place) • calcium in body fluids regulates transport of ions across cell membranes • particularly important in nerve transmission and muscle contraction • role in blood clotting Calcium • blood calcium is regulated by hormones sensitive to blood calcium and not by dietary intake • inadequate intake of calcium in early life results in poor bone mass and can lead to osteoporosis • adolescents: 1300 mg/day • adults 19 -50, 1000 mg/day • adults over 51, 1200 mg/day • food sources: milk and dairy products best source, small bones of fish like salmon and sardines, dark green vegetables like broccoli, kale, and spinach Calcium Calcium Absorption Factors that enhance Ca absorption: • stomach acid • vitamin D • lactose • growth hormones Factors that inhibit Ca absorption: • lack of stomach acid • vitamin D deficiency • high phosphorus intake • high- fiber intake • phytates (seeds, nuts, grains) • oxalates (beet greens, rhubarb, spinach) Sodium • the principle cation in the extracellular fluids of the body • helps to maintain acid-base balance • essential to muscle contraction and nerve transmission • 40% of body’s sodium thought to be stored on surface of bone crystals where body can easily draw it into blood • deficiency would be harmful but few diets lack sodium • sodium/water ratio delicately balanced by kidneys • vomiting, diarrhea, and excessive sweating can deplete sodium Sodium • Deficiency symptoms – Muscle cramps, mental apathy, loss of appetite • Toxicity symptoms – Edema, acute hypertension • Significant source – Table salt, soy sauce – Moderate amounts in meats, milks, breads, and vegetables – Large amounts in processed foods Potassium • principal cation within the body’s cell • chief functions in the body – Maintains normal fluid and electrolyte balance – Facilitates many reactions – Supports cell integrity – Assists in nerve impulse transmission and muscle contractions Potassium • deficiency symptoms – muscular weakness – paralysis – confusion • toxicity symptoms – muscular weakness – vomiting – heart arrest after intravenous application Potassium • significant sources – all whole foods – meats, milks, fruits, vegetables, grains, legumes Magnesium • chief functions in the body – bone mineralization – proteosynthesis – enzyme activity – muscle contraction – nerve impulse transmission – maintenance of teeth – immune system functions Magnesium • deficiency symptoms – weakness – confusion – if extreme, convulsions, bizarre muscle movements (especially of eye and face muscles), hallucinations, and difficulty in swallowing – in children, growth failure • toxicity occurs in older people abusing magnesium based laxatives, antacids and other medications Symptoms severe: diarrhea, acid-base imbalance, kidney impairment, confusion, coma, death Magnesium • significant sources – nuts, legumes – whole grains – dark green vegetables – seafood – chocolate, cocoa