Chapter 6: Vitamins PDF

Chapter 6: Vitamins Dr. Zainab Zueter © McGraw Hill, LLC 1  Learning Objectives 1. Compare and contrast fat- and water-soluble vitamins. 2. Describe the general functions and uses of vitamins. 3. Judge when vitamin supplements may be necessary. 4. Evaluate a vi...

Chapter 6: Vitamins Dr. Zainab Zueter © McGraw Hill, LLC 1  Learning Objectives 1. Compare and contrast fat- and water-soluble vitamins. 2. Describe the general functions and uses of vitamins. 3. Judge when vitamin supplements may be necessary. 4. Evaluate a vitamin supplement label. 5. Give examples of food sources for individual vitamins. 6. identify characteristics to look for when choosing a vitamin supplement. © McGraw Hill, LLC 2  What are Vitamins? 1. Organic compounds containing carbon, hydrogen, oxygen, and sometimes nitrogen or other elements. 2. Essential organic compounds. 3. Individual molecules (not long chains). 4. Needed in small amounts (micronutrients). 5. Don't provide energy but are crucial for energy metabolism. 6. Susceptibility to Destruction: ❑ Vulnerable to heat, light, oxidation, acid, and alkalis. ❑ Specific examples: 1. Thiamin sensitive to heat. 2. Riboflavin destroyed by light. 3. Folate often lost during food processing. 4. Vitamin C destroyed by heat and air. © McGraw Hill, LLC 3  What are Vitamins? 7. Free Radical Production: ✓ Free radicals can damage cells and DNA, contributing to aging and diseases like cancer and heart disease. ✓ Free radicals arise from normal metabolism and external factors like UV radiation, pollution, and smoking. 8. Role of Antioxidants: ✓ Antioxidants neutralize free radicals by undergoing oxidation themselves, protecting cells from damage. ✓ Found in many fruits and vegetables, antioxidants prevent oxidative damage. ✓ Key Antioxidant Vitamins: ✓ Vitamin C: Water-soluble, acts within cells. ✓ Vitamin E: Fat-soluble, protects within fat tissue. ✓ Beta-carotene: Provides antioxidant benefits; roles differ among types. © McGraw Hill, LLC 4  What are Vitamins? What are Vitamins? 9. Used as food additives to enhance nutrition content (e.g., vitamin D in milk) and preserve quality (e.g., vitamin C in meats). 10. In megadoses, some act as drugs, not just nutrients, treating specific conditions (e.g., Niacin to lower cholesterol, retinoic acid for acne). © McGraw Hill, LLC 5  Vitamin Classification: A. Fat-soluble vitamins: A, D, E, and K B. Water-soluble vitamins: C and B vitamins (thiamin, riboflavin, niacin, folate, B6, B12, biotin, and pantothenic acid) © McGraw Hill, LLC 6  Vitamin A ✓ Exists as retinol, retinaldehyde, and retinoic acid; found in animal sources (liver, whole milk). ✓ Exists as provitamin A carotenoids from fruits and vegetables (e.g., beta-carotene). ✓ Beta-carotene, a major carotenoid, is a potent antioxidant. ✓ The body stores significant amounts ✓ Deficiency symptoms may take time to appear. ✓ Severe deficiency is rare. © McGraw Hill, LLC 7  Vitamin A ✓ Only preformed vitamin A is toxic in high doses; can be teratogenic during pregnancy. Beta- carotene is not toxic. ✓ Hypercarotenemia (yellowish skin) can occur from high beta-carotene intake, but it's harmless. Functions: Vision, reproduction, growth, immune function; relatively poor antioxidant. Toxicity: risk with high doses of preformed vitamin A; beta-carotene is nontoxic. Deficiency: mostly affects developing countries, causing blindness and increasing infection risk. © McGraw Hill, LLC 8 © McGraw Hill, LLC 9 © McGraw Hill, LLC 10  Vitamin D Vitamin D Production: ✓ The body can produce vitamin D with optimal sunlight exposure and normal liver and kidney function. ✓ Synthesis starts in the liver, converting cholesterol to a vitamin D precursor. ✓ Sunlight on skin converts this precursor to vitamin D3. ✓ Liver and kidneys further process vitamin D3 to its active form. © McGraw Hill, LLC 11  Vitamin D Unique Features of Vitamin D: Acts like a hormone Primary Functions: 1. Maintains normal blood calcium and phosphorus levels by: a) Stimulating absorption from the GI tract b) Mobilizing from bones when needed c) Stimulating kidney retention © McGraw Hill, LLC 12  Vitamin D Potential Additional Benefits: may protect against cancer, metabolic syndrome, diabetes, hypertension, multiple sclerosis, and depression. Vitamin D Sources: 1. Sunlight exposure (15-minute daily walk under optimal conditions) 2. Few natural food sources (liver, fatty fish, egg yolks) 3. Fortified foods (milk, cereals, some orange juices, yogurts, margarines) ✓ RDA is 15 μg/day (600 IU/day) for most adults ✓ Deficiency: leads to bone malformation, rickets (children), osteomalacia (adults) © McGraw Hill, LLC 13 © McGraw Hill, LLC 14  Vitamin D ✓ Increased risk for vitamin D deficiency in elderly: 1. Inadequate dietary intake 2. Limited sun exposure 3. Skin becomes thinner with age, reducing vitamin D production capacity 4. Impaired gastrointestinal (GI) absorption 5. Liver and kidney function may decline with age, affecting vitamin D activation © McGraw Hill, LLC 15  Vitamin D ✓ Toxicity: hypercalcemia and hypercalciuria © McGraw Hill, LLC 16  Toxicity Toxicity : hypercalcemia and hypercalciuria © McGraw Hill, LLC  Vitamin E ✓ Vitamin E : Alpha-tocopherol is the most biologically active form ✓ Primary Functions: 1. Main fat-soluble antioxidant in the body 2. Protects PUFAs and LDL cholesterol from oxidative damage 3. Maintains cell membrane integrity 4. Protects red blood cells against hemolysis 5. Enhances immune system functioning 6. Inhibits platelet aggregation 7. Suppresses tumor angiogenesis © McGraw Hill, LLC 18  Vitamin E ✓Dietary Sources: Found in vegetable oil, nuts and seeds, whole grains, and leafy green vegetables ✓Deficiency: 1. Rare 2. likely due to fat malabsorption syndromes cystic fibrosis: lead to hemolytic anemia and neurologic disorders. 3. Premature infants at risk for red blood cell hemolysis © McGraw Hill, LLC 19  Vitamin E ✓ Toxicity ✓ none, but supplements contra-indicated with anticoagulation drugs (warfarin)increasing the risk of hemorrhage ✓Supplements Risks: 1. High-dose supplements may increase all-cause mortality risk 2. May increase prostate cancer risk in healthy men © McGraw Hill, LLC 20  Vitamin K ✓ Forms of Vitamin K: 1. Phylloquinone: Found in plants (e.g., spinach, broccoli). 2. Menaquinones: Synthesized by bacteria in the intestinal tract. ✓ Functions: 1. Coenzyme for synthesis of prothrombin and at least 6 other blood clotting proteins 2. Essential for activating proteins that help build and maintain bone health. 3. Deficiency can lead to severe bleeding, even from minor wounds. © McGraw Hill, LLC 21  Vitamin K Newborns and Vitamin K: ✓ Newborns are at risk for deficiency due to a sterile gut that can't produce vitamin K initially. ✓ A prophylactic intramuscular dose of vitamin K is given at birth to prevent hemorrhagic disease. ✓Deficiency: 1. Rarely 2. Hypoprothrombinemia (increased prothrombin time) 3. occur due to malabsorption syndromes ✓Medication Interactions: Anticoagulants (e.g., warfarin) Antibiotics can kill vitamin K-producing intestinal bacteria. © McGraw Hill, LLC 22  Water-soluble vitamins Thiamin (vitamin B1) ✓ Function: 1. Coenzyme in carbohydrate and branched-chain amino acid metabolism 2. Important for nervous system functioning ✓ Sources: a variety of foods that include enriched bread, cereals, and processed meats ✓ Deficiency: 1. (beriberi) is rare in developed countries due to food enrichment 2. Alcoholism is the most common cause of thiamine deficiency, leading to Wernicke-Korsakoff syndrome. https://www.osmosis.org/learn/Wernicke- Korsakoff_syndrome:_Year_of_the_Zebra © McGraw Hill, LLC 23 © McGraw Hill, LLC 24  Thiamine Deficiency Water-soluble vitamins Thiamin (vitamin B1) Wernicke-Korsakoff syndrome is an unusual type of memory disorder due to a lack of thiamine (vitamin B1) requiring immediate treatment. © McGraw Hill, LLC  Water-soluble vitamins Riboflavin (Vitamin B2): ✓Function: 1. Integral part of the coenzymes FAD (flavin adenine dinucleotide) and FMN (flavin mononucleotide). 2. Functions in energy release from nutrients in all body cells. 3. Involved in the synthesis of some vitamins 4. the conversion of homocysteine to methionine. ✓sources: Unique in that milk and dairy products are major dietary sources ✓Deficiency risk: higher in elderly and adolescents © McGraw Hill, LLC 26  Water-soluble vitamins Riboflavin (Vitamin B2): Deficiency Symptoms: 1. Sore throat 2. Cheilosis (cracks at corners of mouth) 3. Stomatitis (inflammation of mouth lining) 4. Glossitis (inflammation of tongue) 5. Dermatitis(skin inflammation) © McGraw Hill, LLC 27  Water-soluble vitamins Niacin (Vitamin B3) ✓ Exists as nicotinic acid and nicotinamide ✓ Sources: Found in protein foods, whole grains, and fortified cereals ✓ Can be synthesized from tryptophan (60 mg tryptophan = 1 mg niacin) ✓ Function: Coenzymes NAD and NADP play a role in energy metabolism of glucose, fat, and alcohol. ✓ Deficiency: Severe deficiency leads to pellagra (rare in the U.S., more common in corn-based diets) ✓ Therapeutic Use: Large doses (1–6 g/day) used to manage cholesterol levels; side effects include flushing, liver damage, and gout; UL for general use is 35 mg but not for clinical use. © McGraw Hill, LLC 28  Water-soluble vitamins Vitamin B6 ✓ Forms: pyridoxine, pyridoxal, pyridoxamine ✓ Functions: 1. Amino acid metabolism and transport 2. Conversion of tryptophan to niacin 3. Formation of heme for hemoglobin 4. Converts tryptophan to niacin and forms heme for hemoglobin. 5. Supports the synthesis of myelin sheaths and neurotransmitters. 6. Aids in DNA synthesis and regulation of blood glucose levels by releasing stored glucose from glycogen. 7. Active form is pyridoxal phosphate, involved in nearly 100 enzymatic reactions © McGraw Hill, LLC 29  Water-soluble vitamins Vitamin B6 ✓ Homocysteine Levels: 1. Low levels of vitamin B6, folic acid, and vitamin B12 are linked to elevated blood homocysteine, associated with increased risks of stroke, coronary heart disease, and cognitive decline. 2. Some studies show that B6, B12, and folic acid may lower homocysteine levels in people with vascular disease. ✓ Deficiency related to alcohol abuse. © McGraw Hill, LLC 30  Water-soluble vitamins Folate Source : 1. food source (green leafy vegetables, legumes, liver, orange juice) 2. synthetic folic acid from supplements and fortified foods. 1.Functions: 1. Essential for DNA synthesis and cell division, working alongside vitamin B12. 2. Involved in homocysteine metabolism. 3. Crucial for new cell formation and transmission of genetic traits. © McGraw Hill, LLC 31 © McGraw Hill, LLC 32  Water-soluble vitamins Folate ✓ Gut Health: 1. Folate is recycled in the gastrointestinal tract; a healthy GI tract is vital for folate uptake. 2. Malabsorption syndromes can lead to folate due to impaired absorption. ✓ Deficiency Risks: 1. causes megaloblastic anemia 2. Risk groups: alcoholics, the elderly, fad dieters 3. Increased needs during growth periods (infants, adolescents, pregnant women). © McGraw Hill, LLC 33  Water-soluble vitamins Folate ✓ Supplementation Guidelines: o Tolerable Upper Intake Level (UL) for synthetic folic acid is 1000 µg/day from fortified foods or supplements. o High folic acid intake can mask vitamin B12 deficiency, leading to neurological issues ‫مهم‬. o Cardiovascular Health: folic acid supplements could reduce homocysteine levels or cardiovascular disease risk by up to 25% in certain populations. © McGraw Hill, LLC 34 ❖ Pregnancy and Neural Tube Defects: Neural Tube Adequate folate intake before conception Defects and during early pregnancy reduces the risk of neural tube defects (e.g., spina bifida). ❖ Neural Tube Defects (NTDs): 1. These are serious birth defects affecting the brain and spinal cord. 2. The most common types are spina bifida and anencephaly. 3. They occur very early in pregnancy, often before a woman knows she's pregnant. ❖ Folate's Role in NTDs : Adequate folate intake before conception and during early pregnancy significantly reduces the risk of NTDs. The mechanism of the folate role for rapid cell division and DNA synthesis during early fetal development. Recommends: 400 µg of synthetic folic acid daily. ❖ Impact of Fortification: Studies have shown a significant decrease in the incidence of NTDs since the implementation of folic acid fortification. © McGraw Hill, LLC 35  Water-soluble vitamins B12 Vitamin B12 is the only water-soluble vitamin that does not occur naturally in plants, and must be obtained from animal sources or fortified products. © McGraw Hill, LLC 36  Water-soluble vitamins B12 ❖ Functions: 1. Coenzyme Role: B12 functions as a coenzyme in homocysteine metabolism, similar to folate. 2. folate activates ❖ Sources: ✓ B12 is only naturally found in animal-based foods, not in plants. ✓ Some plant-based fermented foods may contain B12, but it is in an inactive form. ✓ The microflora in the large intestine produce vitamin B-12. ❖ Absorption Mechanism: ✓ B12 must be released from food proteins by Stomach acid ( pepsin and gastric acid) before binding to intrinsic factor. (Stomach acidity) ✓ Vitamin B12 needs an intrinsic factor (a stomach protein) to be absorbed in the lower part of the small intestine (terminal ileum). © McGraw Hill, LLC 37  Water-soluble vitamins B12 1.Interdependent Relationship with Folate: 1. Vitamin B12 activates folate, which is essential for DNA synthesis and maturation of red blood cells. 2. Functions as a coenzyme in homocysteine metabolism. 1.Nervous System Health: 1. Maintains the myelin sheath around nerves; B12 is crucial for neurological health. However, only B12 maintains the myelin sheath around nerves. High folic acid can mask B12 deficiency anemia but not neurological impairments ‫مهم‬ © McGraw Hill, LLC 38  Water-soluble vitamins B12 ❖Deficiency: 1. strict vegan diet 2. Pernicious Anemia: Lack of intrinsic factors prevents absorption, Requires B12 injections. ✓ Inadequate Gastric Acid Secretion: Prevents release of B12 from food proteins; this is a common cause, particularly affecting older adults (6-15% deficient, 20% marginally deficient). ✓ Other Risk Factors: Gastric resection, medications suppressing gastric acid, and H. pylori infection. © McGraw Hill, LLC 39  Water-soluble vitamins B12 ❖ Deficiency 1. strict vegan diet 2. lack of intrinsic factor (pernicious anemia) 3. inadequate gastric acid production. 4. Older adults have a higher risk of B12 deficiency (most of they drug use ), Inadequate gastric acid secretion is a common reason for deficiency, affecting 6% to 15% of older adults. 5. Risk increases with gastric surgery, medications that suppress gastric acid, and infections (e.g., Helicobacter pylori). Recommendations: People over 50 should get B12 from fortified foods or supplements because they may not absorb it well from food due to less stomach acid. © McGraw Hill, LLC 40 © McGraw Hill, LLC 41  Other B Vitamins ✓Pantothenic Acid: 1.Part of coenzyme A (CoA), involved in forming acetyl-CoA. 2.Participates in over 100 metabolic reactions. 3.Best dietary sources: meat, fish, poultry, whole-grain cereals, dried peas, and beans. ✓Biotin: 1. Functions as a coenzyme in the TCA cycle, gluconeogenesis, and fatty acid synthesis. 2. Involved in reactions managing carbon dioxide in compounds. 3. Present in nature and synthesized by gut bacteria ✓Choline: Important for cell metabolism and function. ✓Substances like inositol and carnitine are sometimes labeled as B vitamins, but research is needed to confirm their essentiality. © McGraw Hill, LLC 42  Water-soluble vitamins Vitamin C (Ascorbic Acid) ✓ History and Importance: Found mainly in citrus fruits; famous for preventing scurvy, a disease that historically affected sailors. ✓ Sources: fruits (particularly citrus) and vegetables ✓ Functions of Vitamin C: 1. collagen formation, vital for connective tissue, bones, skin, and tendons. 2. wound healing 3. facilitates iron absorption 4. Metabolic Functions: Involved in neurotransmitter formation, thyroxine synthesis, amino acid metabolism, and immune system function. 5. Acts as a water-soluble antioxidant, protecting vitamins A, E, polyunsaturated fatty acids (PUFAs), and iron from damage. 6. Cold Prevention ???? No strong evidence that high doses prevent colds. © McGraw Hill, LLC 43 © McGraw Hill, LLC 44  Water-soluble vitamins Vitamin C (Ascorbic Acid) ✓Deficiency: 1. scurvy (the deterioration of collagen and connective tissues in the body.) 2. weakened bones, poor wound healing, bleeding gums ✓Recommended Intake: Vitamin C Recommendation (Men: 90 mg, Women: 75 mg) Smokers should add 35 mg/day due to increased oxidative stress and vitamin C turnover. © McGraw Hill, LLC 45  Water-soluble vitamins Vitamin C (Ascorbic Acid) © McGraw Hill, LLC 46  Phytochemicals ✓ Definition and Function: 1. Phytochemicals are non-nutritive compounds produced by plants to protect against viruses, bacteria, and fungi. 2. They enhance the color, taste, aroma, and other characteristics of foods. ✓ Health Benefits: When consumed in fruits, vegetables, whole grains, or nuts, phytochemicals work alongside nutrients and fiber to promote health by: 1. Acting as antioxidants 2. Supporting detoxifying enzymes 3. Stimulating the immune system 4. Regulating hormones 5. Inactivating bacteria and viruses. © McGraw Hill, LLC 47 © McGraw Hill, LLC 48 © McGraw Hill, LLC 49 © McGraw Hill, LLC 50  Dietary guidelines key Recommendations for Specific Population Groups Regarding Vitamins 1.Individuals Age 50 Years and Older: o Consume foods fortified with vitamin B12, such as fortified cereals, or dietary supplements o May not adequately absorb vitamin B12 from protein-bound food sources 2.Women Capable of Becoming Pregnant: o Consume 400 μg daily of synthetic folic acid from fortified foods and/or supplements o Women who consume folic acid-fortified cereal do not need a supplement, as they may risk excessive folic acid intake © McGraw Hill, LLC  Tips For Boosting Fruit And Vegetable Intake 1.Daily Servings Goal: ✓ Aim for at least five servings of fruits and vegetables daily; more is beneficial. ✓ Five servings may provide over 200 mg of vitamin C, exceeding the RDA. 2.Variety and Color: ✓ Focus on variety; include at least one serving each of green, orange, red, citrus, and legumes daily. © McGraw Hill, LLC 52  Tips For Boosting Fruit And Vegetable Intake 3. Preserving Nutrients: ✓ Store vegetables in the refrigerator (except onions, tomatoes, winter squash, and potatoes). ✓ Minimize peeling and cook vegetables for a short time in minimal water; microwaving is preferable to boiling. 4. Incorporate Salads: Start at least one meal each day with a fresh salad. 5. Healthy Snacks: Choose raw vegetables or fresh fruits as snacks. © McGraw Hill, LLC 53  Tips For Boosting Fruit And Vegetable Intake 6. Add Vegetables to Meals: ✓ Incorporate vegetables into dishes (e.g., zucchini in spaghetti sauce, grated carrots in meatloaf, spinach in lasagna). 7.Increase Portion Sizes: ✓ Double the usual portion size of vegetables. 8.Try New Produce: ✓ Buy and try a new fruit or vegetable during grocery shopping. © McGraw Hill, LLC 54  Tips For Boosting Fruit And Vegetable Intake 9. Order Vegetables When Dining Out: ✓ Ensure to order a vegetable with meals at restaurants. 10.Choose 100% Fruit Juice: ✓ Taking 100% fruit juice at breakfast and throughout the day instead of sugary drinks. 11.Fruits as Dessert: ✓ Use fruit as a healthy dessert option. 12.Increase Visibility: ✓ Keep a bowl of fruit on the table and place fresh vegetables prominently on the top shelf of the refrigerator for easy access. © McGraw Hill, LLC 55  Who May Benefit from Supplements: Who May Benefit from Supplements: 1. person on a very low-calorie diet (under 1200 calories). 2. Vegans (need vitamin B12 and possibly vitamin D). 3. Picky Eaters 4. Older Adults (51 years and older): Many in this group may lack adequate nutrient intake due to limited budgets, dietary restrictions, or health issues. Low-dose multivitamin-mineral supplements can help meet intake levels. 5. Alcoholics: Alcohol can impair the intake and absorption of various vitamins, particularly thiamin, riboflavin, niacin, folic acid, and pantothenic acid. 6. Food Insecure Individuals: Those who have inconsistent access to sufficient food resources. 7. Individuals with chronic illnesses or taking medications affecting nutrient absorption or metabolism. © McGraw Hill, LLC 56  Are Supplements a Good Idea? ✓ Supplements should "add to" a healthy diet, not replace it. ✓ The FDA requires a standardized “Supplement Facts” label on all supplements for better consumer information. Safety Concerns: ✓ While multivitamins are generally safe, excessive intakes of certain vitamins can be harmful. ✓ Data indicates a higher prevalence of excessive intakes for vitamins A and folic acid among supplement users. 1. Excess vitamin A can cause headaches, liver damage, and reduce bone strength. 2. Excess folic acid can mask signs of vitamin B12 deficiency, delaying diagnosis and leading to irreversible neurological damage. Conclusion: More is not always better when it comes to vitamins; moderation and balance are key. © McGraw Hill, LLC 57  HOW DO YOU RESPOND? ✓ Is it better to take vitamin supplements with meals or between meals? It is generally better to take vitamin supplements with meals, as food can enhance the absorption of some vitamins. ✓ Should I choose vitamin-fortified foods over those that are not fortified? Choose fortified foods wisely. Fortified milk and cereals can be beneficial sources of nutrients like vitamin D and iron. However, avoid fortified junk food, as it's still less healthy than nutrient-rich whole foods. © McGraw Hill, LLC 58  HOW DO YOU RESPOND? ✓ I am under a lot of emotional stress. Should I take stress vitamins? While significant physical stress (like trauma or thermal injuries) increases the need for certain vitamins, mental stress does not increase vitamin requirements. This misconception is often perpetuated by misleading advertising. © McGraw Hill, LLC 59  KE Y C O N C E P T S 1. Required in small amounts (micrograms or milligrams). 2. Essential, Cannot be adequately produced by the body, so they must come from the diet. 3. Fat-Soluble Vitamins: A, D, E, and K; stored in the liver and body fat, so they don’t need to be consumed daily. Large doses can be toxic. 4. Water-Soluble Vitamins: B-complex and vitamin C; not stored, requiring daily intake. Generally considered nontoxic but can cause side effects in megadoses. 5. Phytochemicals, Plant compounds that help protect plants from diseases and add flavor and color to foods. © McGraw Hill, LLC 60  KE Y C O N C E P T S 6. Antioxidants: Found in foods, but high-dose supplements haven’t been proven beneficial and might even pose health risks. 7. Women of childbearing age should take 400 µg of folic acid daily. 8. Adults over 50 should get most of their vitamin B12 from supplements or fortified foods. 9. Vegans may need supplemental vitamin D and B12. © McGraw Hill, LLC 61