23F-Energy Metabolism Notes.pdf

FNH 250: Nutrition Concepts & Controversies ENERGY METABOLISM Chapter 10 I. B-VITAMINS & ENERGY METABOLISM — Thiamin, Riboflavin, Niacin............................................. 3 A. CO-ENZYME FORMS & ROLES............................................................................................

FNH 250: Nutrition Concepts & Controversies ENERGY METABOLISM Chapter 10 I. B-VITAMINS & ENERGY METABOLISM — Thiamin, Riboflavin, Niacin............................................. 3 A. CO-ENZYME FORMS & ROLES............................................................................................................................... 3 B. DEFICIENCY.............................................................................................................................................................. 3 C. TOXICITY ................................................................................................................................................................... 4 D. RECOMMENDATIONS ............................................................................................................................................ 4 E. FOOD SOURCES ...................................................................................................................................................... 4 2. B-VITAMINS & ENERGY METABOLISM — Vitamin B6, Folate, Vitamin B12 ..................................... 5 A. INTRODUCTION ...................................................................................................................................................... 5 B. CO-ENZYME FORMS & ROLES............................................................................................................................... 7 C. DEFICIENCY.............................................................................................................................................................. 8 D. TOXICITY ................................................................................................................................................................... 9 E. RECOMMENDATIONS ............................................................................................................................................ 9 F. FOOD SOURCES .................................................................................................................................................. 110 3. B-VITAMINS & ENERGY METABOLISM — Pantothenic Acid, Biotin................................................ 11 A. INTRODUCTION, CO-ENZYME FORMS & ROLES ............................................................................................. 11 B. DEFICIENCY............................................................................................................................................................ 11 C. TOXICITY ................................................................................................................................................................. 11 D. RECOMMENDATIONS .......................................................................................................................................... 11 4. VITAMIN-LIKE COMPOUND – Choline .............................................................................................. 12 5. TRACE MINERALS & ENERGY METABOLISM — Iodide, Chromium, Manganese .......................... 12 A. INTRODUCTION .................................................................................................................................................... 12 B. ROLES ...................................................................................................................................................................... 13 C. DEFICIENCY............................................................................................................................................................ 13 D. TOXICITY ................................................................................................................................................................. 14 E. RECOMMENDATIONS .......................................................................................................................................... 14 F. FOOD SOURCES .................................................................................................................................................... 15 6. MAJOR MINERAL & ENERGY METABOLISM — Sulphur .................................................................. 15 A. INTRODUCTION .................................................................................................................................................... 15 B. ROLES ...................................................................................................................................................................... 16 C. DEFICIENCY............................................................................................................................................................ 16 D. TOXICITY ................................................................................................................................................................. 16 E. RECOMMENDATIONS .......................................................................................................................................... 16 F. FOOD SOURCES .................................................................................................................................................... 16 FNH 250 Nutrition Concepts & Controversies Page 2 of 16 Energy Metabolism WATER-SOLUBLE VITAMINS ASSOCIATED WITH ENERGY METABOLISM The B-Vitamins B-VITAMINS — Thiamin, Riboflavin, Niacin, Pantothenic Acid, Biotin, B6, Folate, B12 -function as an integral part of COENZYMES in chemical reactions in the body -many B-vitamin coenzymes are required by enzymes that catalyze chemical reactions to release energy from the macronutrients (see Figure 10-16, p. 337) -do not directly supply energy to cells, but have key roles in aiding the release of energy from the macronutrients and in maintaining healthy blood and nervous systems -compromised B-vitamin intake can decrease energy required for normal cell function that sustains life and supports physical activity -rich sources found in germ, bran & husk layers of grains which are removed in the milling of grains -often B-vitamins are found in same foods, therefore, a low dietary intake of one B vitamin may mean a low intake of another B-vitamin -to return these nutrients to the diets of North Americans, grain products (e.g., flour, breakfast cereals) are enriched with thiamin, riboflavin, niacin, folate (all B-vitamins) and the mineral iron -the amino acid, tryptophan, from dietary protein can be converted to niacin, one of the eight B-vitamins ABSORPTION/TRANSPORTATION/STORAGE -after B-vitamins are consumed, they are released from their coenzyme forms (protein-bound) into free vitamins in the stomach and small intestine, then enter the body as free vitamins -free water-soluble vitamins, often associated with a protein, travel to the cells from liver -once inside cells, the coenzyme forms are re-synthesized for active use -generally, no long term storage of water-soluble vitamins B-VITAMINS: PEOPLE AT RISK -alcoholics: reduced intake, reduced absorption, reduced metabolic use, low “stores”, increased excretion -elderly, malnourished, homeless: decreased intake of food in general, and nutrient-dense foods in particular; can increase risk of deficiency Learning Objectives Name the 8 B-vitamins that act as coenzymes. Describe how coenzymes function to activate enzymes. FNH 250: Nutrition Concepts & Controversies FNH 250 Nutrition Concepts & Controversies Page 3 of 16 I. B-VITAMINS & ENERGY METABOLISM — THIAMIN, RIBOFLAVIN, NIACIN A. CO-ENZYME FORMS & ROLES THIAMIN (old name vitamin B-1) -coenzyme form called Thiamin PyroPhosphate, TPP -aids in the release of energy from carbohydrate (aerobic glycolysis) and from branched chain amino acids (leucine, isoleucine, valine) -aids in the synthesis of DNA, RNA, and neurotransmitters; helps regulate normal nerve impulse transmissions (e.g., to the muscles) RIBOFLAVIN (old name vitamin B-2); flavus = Latin for yellow -coenzyme forms: Flavin MonoNucleotide (FMN) and Flavin Adenine Dinucleotide (FAD) -both forms aid in the release of energy from macronutrients -FMN needed to convert vitamin B6 to its active co-enzyme form (pyridoxal phosphate. PLP); PLP, in turn, is needed to synthesize niacin (a B-vitamin) from the amino acid, Tryptophan -FMN and FAD assist glutathione peroxidase antioxidant enzyme system -unique B-vitamin because 60 mg Tryptophan (an essential amino acid) can be converted to 1 mg niacin = 1 NE (niacin equivalent) NIACIN (old name vitamin B-3) -coenzyme forms: Nicotinamide Adenine Dinucleotide, NAD(H) and the phosphate form of NAD, NADP(H) -both forms aid in the release of energy from macronutrients -both forms needed for the synthesis of new compounds (e.g., fatty acids, glucose, amino acids) -phosphorylated form required for replicating DNA and for cell differentiation B. DEFICIENCY THIAMIN -deficiency disease called BERI-BERI which means "I can't, I can't" in Sinhalese (problems with walking); neural damage; muscle wasting; edema -this disease became prevalent when polished rice became popular in Asia -because thiamin participates in glucose metabolism and the nervous system relies on glucose for fuel, body functions associated with the brain and nerves quickly show symptoms of thiamin deficiency RIBOFLAVIN -deficiency disease called ARIBOFLAVINOSIS, relatively rare -stomatitis (inflammation of the tongue), cheilosis (cracking at the corners of the mouth), glossitis (smooth inflamed tongue), dermatitis (rough skin) -people at risk include alcoholics – poor diets, poor riboflavin use & retention in the body; people who don't regularly consume milk and milk products, which can account for 50% of intake in a mixed, balanced diet -alternatives: enriched breakfast cereals or breads or fortified plant-based beverages (e.g., soy milk) -deficiency symptoms shared with those of thiamin, B6, and folate NIACIN -most metabolic pathways use NAD(H) and NADP(H), therefore, we see widespread symptoms when there is a deficiency of niacin -disease called PELLAGRA (“rough skin” in Italian) -early symptoms: weakness, fatigue, loss of appetite, inflammation of mouth, tongue and intestine -final symptoms are the "4 D’s": dermatitis, diarrhea, dementia, death -first nutritional deficiency epidemic in the USA, occurred in the early 1900s and led to fortification of grains FNH 250: Nutrition Concepts & Controversies FNH 250 Nutrition Concepts & Controversies Page 4 of 16 C. TOXICITY THIAMIN -no toxicity cases known with taking thiamin supplements; no UL RIBOFLAVIN -no toxicity cases known with high riboflavin intakes; no UL NIACIN -pharmacological doses of nicotinic acid can have a drug-like effect on the nervous system causing dilation of blood capillaries in skin that results in the skin reddening – “niacin flush” -can experience painful tingling, especially in the extremities (e.g., finger tips, toes) -advantage – pharmacological doses used in the management of atherosclerosis – can decrease LDL cholesterol and increase HDL cholesterol -disadvantage – may damage liver and cause ulcers D. RECOMMENDATIONS THIAMIN RDA: Males: 1.2 mg/day; females 1.1 mg/day -usual intakes adequate: Canadian adult males, ~1.9 mg/day; females, ~1.5 mg/day UL: none RIBOFLAVIN RDA: Males: 1.3 mg/day; females 1.1 mg/day -usual intakes adequate: Canadian adult males, ~2.2 mg/day; females, ~1.7 mg/day UL: none NIACIN RDA: Males: 16 mg/day; females 14 mg/day -usual intakes adequate: Canadian adult males, ~46 mg/day; females, ~34 mg/day UL: 35 mg/day from supplemental sources only; no evidence of adverse effects from the consumption of naturally occurring niacin in foods E. FOOD SOURCES THIAMIN *denotes rich food sources PLANT FOODS *enriched grains & products (flours, breakfast cereals) sunflower seeds, peanuts, legumes whole grains, wheat germ, bran Losses During Food Preparation -prolonged cooking in water &/or adding baking soda to water ® losses of thiamin -microwave, steaming = good preparation methods ANIMAL FOODS *pork, ham organ meats FNH 250: Nutrition Concepts & Controversies FNH 250 Nutrition Concepts & Controversies Page 5 of 16 RIBOFLAVIN -milk and milk products are rich sources of riboflavin (up to ~50% of intake on a mixed diet) ANIMAL FOODS PLANT FOODS *milk & milk products enriched grains & products meat, fish, poultry (e.g., flours, breakfast cereals, breads) (e.g., ground beef, liver, oysters) dark green vegetables, mushrooms whole grains fortified plant-based beverages Losses During Food Preparation -riboflavin is stable to heat, but destroyed by light and irradiation -opaque milk containers protect riboflavin from degradation NIACIN ANIMAL FOODS *beef liver *chicken tuna halibut salmon PLANT FOODS whole grains, wheat bran *enriched grains and products (e.g., breakfast cereals, flours, crackers) mushrooms, nuts asparagus, green leafy vegetables Losses During Food Preparation -lost into cooking water, little lost to heat ~50% from diet and ~50% from obtained from endogenous conversion of excess Tryptophan 2. B-VITAMINS & ENERGY METABOLISM — VITAMIN B6, FOLATE, VITAMIN B12 A. INTRODUCTION FOLATE (also called folacin) -Latin name from "folium" meaning foliage (i.e., green leafy vegetables = good source) -folate in foods is ~50% absorbed -folate found in foods; folic acid found in supplements and fortified foods -folic acid is ~1.7 times more bioavailable than folate in foods Absorption & Activation -folate is found in foods in polyglutamate form; digestion cleaves off all but one glutamate unit and adds a methyl group (methylated form) before absorption -water-soluble nutrient – travels in bloodstream, first to liver then to other cells -once inside cells, the methylated form of folate is inactive -vitamin B12 accepts the methyl group from folate and in the process both vitamins (i.e., unmethylated folate and methylated B12) become active coenzymes FNH 250: Nutrition Concepts & Controversies FNH 250 Nutrition Concepts & Controversies Page 6 of 16 VITAMIN B12 -unique absorption, normally ~30-70% of vitamin B12 absorbed -failure at any point in the chain of absorption events will result in only ~1-2% absorbed -very large molecule with a cobalt centre -needed in very small amounts (few µg/day) -*only naturally-occurring source is from animal foods (produced by microorganisms) -efficiently recycled in the body; some storage in the liver -each day we lose up to ~2% of vitamin B12 from the body in bile excreted in the feces -bacteria in colon can synthesize B12, but not much of it is absorbed Mouth Stomach vitamin B12 in food (extrinsic factor) food—B12 R-PROTEIN produced by salivary glands acid (pepsin) releases B12 from protein in food food B12 B12—R-PROTEIN stomach releases INTRINSIC FACTOR (IF) Small Intestine TRYPSIN enzyme released from pancreasà small intestine which frees B12 from the R-protein R-PROTEIN IF B–12 IF—B12 Ileum IF ileum absorbs B12 only IF links with B12 special receptor sites for IF–B12 complex, then complex is split apart -in bloodstream: B12 is transferred to a special blood transport protein (transcobalamin) that carries it to the liver, bone marrow, and other tissues FNH 250: Nutrition Concepts & Controversies FNH 250 Nutrition Concepts & Controversies Page 7 of 16 B. CO-ENZYME FORMS & ROLES VITAMIN B6 -coenzyme forms Pyridoxal, Pyridoxine, and Pyridoxamine are all forms of vitamin B6 that can be converted to the most active co-enzyme form, Pyridoxal Phosphate (PLP) -PLP needed in over 100 enzyme systems involving macronutrient (mostly protein) metabolism a. Generating Energy from the Macronutrients i. needed to release glucose from glycogen stores ii. needed for interconversions of amino acids that can feed into the Krebs Cycle b. Reducing Homocysteine Levels in the Blood – reduces risk of heart attack c. Transamination of Amino Acids i. production of non-essential amino acids in body ii. without B6, all amino acids would become essential d. Synthesis of White Blood Cells (WBC) – helps fight infection e. Synthesis of Hemoglobin in RBC – needed to transport oxygen to the cells to allow for the production of energy inside cells f. Conversion of Tryptophan à Niacin g. Synthesis of Glucose (gluconeogenesis), Neurotransmitters (e.g., Serotonin, Dopamine), Steroid Hormones and Bile Acids FOLATE -coenzyme form called TetraHydroFolate acid (THF) needed for: a. Generating Energy from the Macronutrients -needed for inter-conversion of amino acids and other compounds that feed into the Krebs Cycle b. Reducing Homocysteine (HCys) Levels in the Blood -leads to a reduced risk of heart disease (e.g., heart attack and stroke) -elevated levels of blood HCys increases blood clotting and may damage lining of blood vessels to increase plaque formation c. Synthesis of DNA -cells with a fast turnover are actively reproducing DNA and are most affected by folate status (e.g., embryonic development, red blood cells, intestinal cells, healing of burns) d. Activating Vitamin B12 Inside Cells -vitamin B12 is needed to activate THF by accepting a methyl group from the proactive form of THF Other Roles (you are not responsible for learning these roles; not presented in slides) Synthesis Reactions -supplementation with folic acid can improve depression in some cases of mental illness, perhaps related to neurotransmitter synthesis VITAMIN B12 -coenzyme forms – Methylcobalamin and Adenosylcobalamin – needed for: a. Activating the Folate Coenzyme (THF) Inside Cells – to synthesize DNA b. Reducing Homocysteine (HCys) Levels in the Blood -reduces risk of heart disease (e.g., heart attack and stroke; see notes above) c. Synthesis and Maintaining the Integrity of the Myelin Sheath -insulation around nerve fibres; prevention of nerve damage and paralysis FNH 250: Nutrition Concepts & Controversies FNH 250 Nutrition Concepts & Controversies Page 8 of 16 C. DEFICIENCY VITAMIN B6 -rare in adults, except with alcoholics – when alcohol is metabolized, PLP is displaced from its enzyme leading to an increased breakdown and loss of PLP from the body FOLATE a. Macrocytic Anemia -red blood cell (RBC) synthesis occurs in the bone marrow, immature RBC cannot divide and mature because they cannot make new DNA without adequate folate, but they can increase in size, so they are large but still immature cells = MACROCYTIC (big cell) ANEMIA -these immature RBC cannot efficiently carry oxygen in the blood to the cells -observable symptoms of anemia (e.g., fatigue, weakness, paleness, shortness of breath, cool body temperature, intestinal upset) -anemia = lack of adequate oxygen carrying capacity in blood to meet body needs b. Elevated Homocysteine (HCys) Levels in the Blood -increased risk of heart disease c. Neural Tube Defects Developing During Early Pregnancy -high need of folate for rapid cell division especially with multiple birth pregnancies -closure of neural tube (developing brain and central nervous system) occurs in first 28 days of pregnancy -many women are unaware of their pregnancy until after this critical time -improper neural tube closure may cause neural tube defects (spina bifida) or anencephaly (absence of brain) in babies born to mothers of poor folate status d. People at Risk -women taking oral contraceptives may be at increased risk for folate deficiency -chronic users of antacids or aspirin, smokers, alcoholics -burn victims, any individual with GI tract damage (i.e., replacing intestinal cells) e. Symptoms -anemia, diarrhea, GI tract damage, inflammation of tongue, irritability, depression, problems with nerve function VITAMIN B12 Causes a. Lack of Dietary Intake of B12 (least likely cause for deficiency, except for vegans) -because of extremely efficient recycling in the body, it can take many years of inadequate/no dietary intake of B12 before symptoms appear b. Absorption Problems -deficiency symptoms appear much more rapidly when absorption is inhibited -inadequate stomach acid production (atrophic gastritis) – limited release of B12 from protein in food, therefore, cannot bind to IF – can contribute to deficiency -more often due to lack of adequate production of IF -symptoms most often seen in people who are unable to absorb/reabsorb B12 Results a. Patchy Myelin Sheath -incomplete myelin sheath causing neurological damage, which can lead to paralysis b. Macrocytic (Pernicious) Anemia – Secondary Folate Deficiency Inside Cells PERNICIOUS ANEMIA = genetic disorder -caused by a defective gene that results in inadequate production of Intrinsic Factor, therefore, B12 absorption impaired FNH 250: Nutrition Concepts & Controversies FNH 250 Nutrition Concepts & Controversies Page 9 of 16 -inability to absorb B12, not due to decreased dietary intake of B12 -lack of adequate B12 absorption leads to impaired DNA synthesis (folate interaction) and neurological damage -large, immature RBC appear in blood = a form of MACROCYTIC ANEMIA -treatment: monthly injection of B12, to bypass normal process of absorption -symptoms: -Anemia -fatigue, weakness, pale skin, shortness of breath, cool body temperature, intestinal upset -Neurological problems -tingling in extremities, abnormal gait, dementia, depression, insomnia -populations at risk: elderly, vegans, non-absorbers of B12, infants exclusively breastfed by vegan mothers, people with damage to parietal cells in the stomach where intrinsic factor is produced D. TOXICITY VITAMIN B6 -first reported in 1983 when treating PreMenstrual Syndrome (PMS) -women taking supplements of vitamin B6 at 2g/day for 2 months -symptoms = loss of neurological coordination; numb feet, hands & mouth -supplementation needs to be supervised by a health care professional and is a questionable treatment of PMS FOLATE -very rare, folate can exit from body in bile excretion -likeliest cause – supplement use VITAMIN B12 -no symptoms noted -supplements: appear non-toxic -excess excreted in bile E. RECOMMENDATIONS VITAMIN B6 RDA: Adults (19-50 yr): 1.3 mg/day -usual intakes adequate: Canadian adult males, 2.2 mg/day; females, 1.6 mg/day UL: 100 mg/day FOLATE RDA: Adults: 400 µg/day; pregnancy = 600 µg/day; lactation = 500 µg/day -usual food intakes adequate for Canadian men, 520 mg/day; marginal for Canadian women, 405 mg/day (not including supplemental forms) -women capable of pregnancy should consume 400 µg/day of folate from supplements, fortified foods or both – in addition to the folate they consume in their usual daily diet UL: 1000 µg/day VITAMIN B12 RDA: Adults: 2.4 µg/day -pregnancy 2.6 µg/day; lactation 2.8 µg/day -usual intakes adequate: Canadian men, 5.1 µg/day; women, 3.8 µg/day UL: none FNH 250: Nutrition Concepts & Controversies FNH 250 Nutrition Concepts & Controversies Page 10 of 16 F. FOOD SOURCES VITAMIN B6 IN FOODS -beef liver, turkey, pork, fish, Brewer’s yeast -legumes, whole grains, green leafy veggies, fruit (e.g., banana, cantaloupe, watermelon), seeds, potatoes, squash Losses During Food Preparation -vitamin B6 decreases with milling of grains and exposure to light, oxidation, high temperatures BIOAVAILABILITY -animal sources more readily absorbable than plant sources FOLATE IN FOODS -beef liver, fish, fortified grain products, legumes, fresh dark green leafy vegetables (e.g., spinach, broccoli, asparagus, parsley, chard), dark orange vegetables (e.g., squash), fresh fruits, orange juice, Brewer’s yeast Losses During Food Preparation -very susceptible to heat, oxidation, prolonged storage, food processing methods, ~1/2 lost in food preparation -choose raw salads, fresh vegetables and fruits as good sources of folate FOLATE IN SUPPLEMENTS -folic acid found in supplements and fortified foods -folic acid is ~1.7 times more bioavailable than folate in foods; to account for this difference we use µgDFE (micrograms of Dietary Folate Equivalents) as units of measure -as of January 1997, flours in Canada have been fortified at a level of 150 µg folic acid/100 g flour VITAMIN B12 IN FOODS -only found in animal foods, or, bacterial or soil contamination of plant foods -most nutrient-dense sources: clams, oysters, organ meats, beef, eggs -yeast – depends on type of medium grown on -fortified sources (e.g., fortified soy or other plant-based drinks, meat analogues) -fermented soy products (e.g., miso, tempeh) & spirulina blue-green algae do not provide B12 in bioavailable form Losses During Food Preparation -microwaves destroy vitamin B12 Learning Objectives Explain the importance of adequate folate intake for women of childbearing age. Describe the association between folate, vitamin B12, vitamin B6, and homocysteine, a marker for cardiovascular disease. Describe the absorption process for vitamin B12, the most common problem associated with the absorption process, and the effects of reduced vitamin B12 status. FNH 250: Nutrition Concepts & Controversies FNH 250 Nutrition Concepts & Controversies Page 11 of 16 3. B-VITAMINS & ENERGY METABOLISM — PANTOTHENIC ACID, BIOTIN A. INTRODUCTION, CO-ENZYME FORMS & ROLES PANTOTHENIC ACID -"pantos" = Greek for everywhere (widespread in the food supply) -coenzyme form called Coenzyme-A (CoA) is needed to synthesize: -acetyl-CoA which holds the central position in transforming energy from CHO, FAT and PRO through the Krebs cycle and electron transport chain to produce ATP -fatty acids, neurotransmitters, steroid hormones and hemoglobin BIOTIN -*intestinal synthesis by bacteria -coenzyme form called Biocytin and is needed for: -releasing energy from CHO -synthesis reactions – e.g., glucose, fatty acids, DNA B. DEFICIENCY PANTOTHENIC ACID -very rare, seen in alcoholics; symptoms: fatigue, headache, nausea, "burning foot", numbness, tingling (neurological symptoms) BIOTIN -very rare -people on long-term antibiotics (due to bacterial synthesis in GI tract) -artificially induced with AVIDIN - a protein in raw egg whites (need ~24 raw eggs; high risk of salmonella) -symptoms: depression, lethargy, dermatitis, hair loss, loss of appetite C. TOXICITY PANTOTHENIC ACID -no cases of toxicity BIOTIN -no cases of toxicity D. RECOMMENDATIONS PANTOTHENIC ACID RDA: Adults: 5 mg/day Adequate intake UL: none BIOTIN RDA: Adults: 30 µg/day Adequate intake UL: none FNH 250: Nutrition Concepts & Controversies E. FOOD SOURCES PANTOTHENIC ACID -pantothenic acid is found in many foods -“pantos” is Greek for everywhere ANIMAL FOODS PLANT FOODS eggs, poultry mushrooms, avocados meat, liver many vegetables (e.g., broccoli) milk and milk products whole grains fish legumes (e.g., peanuts) Losses During Food Preparation – unstable to heat BIOTIN -present in most foods in one of 2 forms: free biotin or biocytin, usually bound to a protein Losses During Food Preparation – resistant to heat and light destruction FNH 250 Nutrition Concepts & Controversies Page 12 of 16 Learning Objectives Describe the primary functions and 3 common food source for each of the 8 B-vitamins. Name and describe the symptoms of deficiency diseases associated with each of the B-vitamins. Describe the potential for toxicity caused by supplemental intakes of B-vitamins. 4. VITAMIN-LIKE COMPOUND – CHOLINE CHOLINE -serves as coenzyme, but is not essential in the diet -used to synthesize neurotransmitters and phospholipids -aids in reducing blood homocysteine levels -made in the liver from amino acids + folate + vitamin B12 -found in many common foods: eggs, soybeans, milk, liver; often consumed as lecithin -deficiencies rare -increased intake may alter the fluidity of cell membranes which may lead to changes in function of the cell membranes, may lower blood pressure, cause diarrhea, and cause fishy body odour -typical intake 400-900 mg/d in addition to what is synthesized by the liver -it has been thought that at certain times in life, endogenous synthesis may not meet requirements, therefore, a new DRI-AI was recommended -however, it is still not considered an essential nutrient for adults -DRI-AI adults: males 550 mg/d females 425 mg/d -DRI-UL all adults: 3500 mg/day 5. TRACE MINERALS & ENERGY METABOLISM — IODIDE, CHROMIUM, MANGANESE A. INTRODUCTION IODIDE (I-) -iodide ion is an essential nutrient found in foods -added to salt (potassium iodide) to prevent production of a GOITER = enlarged thyroid gland -'fortified salt' = iodized salt -very efficient absorption ~95% CHROMIUM (Cr3+) -like Iron, Chromium exists in different oxidation states 3+ -Cr is best absorbed and used in the body -vitamin C enhances absorption; antacids decrease absorption -very low absorption ~0.4-2.5% of intake FNH 250: Nutrition Concepts & Controversies FNH 250 Nutrition Concepts & Controversies Page 13 of 16 MANGANESE (Mn2+) -body contains ~20mg Manganese -mostly in bone, glands and metabolically active organs such as liver, pancreas, kidneys -low need, plentiful in the diet B. ROLES IODIDE Thyroid Function (~80% of body Iodide in thyroid gland) -integral component of 2 thyroid hormones (triiodothyronine, T3; thyroxine, T4) which control the rate at which cells use oxygen to produce energy and regulate: -BMR (basal metabolic rate) -body temperature -nerve and muscle function -reproduction, growth and development -the thyroid gland (neck area) captures Iodide from the bloodstream -selenium needed for deiodinase enzyme – removes an iodide ion from T4 to form T3 – T3 is the most biologically active thyroid hormone CHROMIUM Maintenance of Blood Glucose Level -Chromium is a cofactor needed to help insulin receptors facilitate GLU uptake into cells Other Roles (you are not responsible for learning these roles; not presented in slides) -metabolism of DNA and RNA; needed for growth -immune function MANGANESE Cofactor for many different enzymes in metabolic reactions, for example… -arginase – urea synthesis -superoxide dismutase antioxidant enzyme system in mitochondria -pyruvate carboxylase – CHO metabolism (pyruvate à oxaloacetate) Cartilage production – cushion for joints between bones Other Roles (you are not responsible for learning these roles; not presented in slides) -protein matrix of bone -prevention of lipid oxidation by free radicals C. DEFICIENCY IODIDE a. Goiter -one of the world's most common and preventable disorders -thyroid hormone levels decrease and the body responds by increasing the size of the thyroid gland to try to increase I- uptake from the blood = futile attempt -SIMPLE GOITER appears as a large lump in the neck area and cannot be reversed through diet alone, but can be surgically removed -TOXIC GOITER appears from overconsumption of raw foods from the cabbage family which contain GOITROGENS (e.g., raw turnip, raw cauliflower, raw broccoli, raw rutabaga, raw cassava), substances that can inhibit thyroid uptake of Iodide FNH 250: Nutrition Concepts & Controversies FNH 250 Nutrition Concepts & Controversies Page 14 of 16 -observed in Northern Italy, Africa, Latin America, SE Asia -not usually of clinical importance unless coexisting with Iodide deficiency b. Cretinism -severe Iodide deficiency during the early months of pregnancy causes irreversible mental and physical disabilities in the baby that is often born mute, deaf and/or blind; does not grow to full potential c. Weight Gain -reduced levels of thyroid hormones may lead to slower metabolism, weight gain and a feeling of lethargy and fatigue CHROMIUM -seen in people on long term intravenous feeds not supplemented with Chromium (rare) -malnourished children -may see impaired insulin action resulting in high BGL and high blood insulin levels due to lack of GLU uptake by cells MANGANESE -rare -symptoms: impaired growth, staggering gait, impaired CHO metabolism -Calcium supplements and Iron supplements may inhibit Manganese absorption D. TOXICITY IODIDE >2000mg/day (i.e., supplement use) -see increase in size of thyroid gland (like goiter) – can impede breathing potentially leading to suffocation CHROMIUM -extremely low risk MANGANESE -rarely observed (e.g., miners exposed to high manganese environments) -excess Mn may aggravate Iron deficiency E. RECOMMENDATIONS IODIDE IN FOODS RDA: Adults: 150 µg/day (~1/2 teaspoon salt) -pregnancy: 220 µg/day; lactation: 290 µg/day Adequate intake ~200-500 µg/day (due to iodized salt; processed foods) UL: 1100 µg/day CHROMIUM IN FOODS AI: Adult (19-50 yr) males: 35 µg/day; females: 25 µg/day Typical intakes ~30 µg/day UL: none FNH 250: Nutrition Concepts & Controversies FNH 250 Nutrition Concepts & Controversies Page 15 of 16 CHROMIUM IN SUPPLEMENTS -Chromium-picolinate supplements claim to increase muscle mass, lose body fat, and prevent diabetes, heart disease and aging -no conclusive scientific evidence to support claims based on action of Chromium alone -if taking a supplement, best to use multivitamin and mineral type MANGANESE IN FOODS AI: Adult males: 2.3 mg/day; females: 1.8 mg/day Adequate intake UL: 11 mg/day F. FOOD SOURCES IODIDE -most reliable source is iodized table salt -fast foods, processed foods, baked goods (iodized salt) -oceans are a major source of Iodide -saltwater fish, seafood, kelp CHROMIUM -Chromium concentrations in foods linked with levels in soil (true for many trace minerals) -the more refined foods are, the lower they are in Chromium ANIMAL FOODS PLANT FOODS egg yolks *whole grains liver legumes, nuts (e.g., peanuts) cheeses mushrooms, onions dark chocolate MANGANESE -plant foods: nuts, seeds, whole grains, fruits, vegetables, legumes, coffee, tea Learning Objectives Identify at least 3 trace minerals that function as cofactors in energy metabolism, and describe their respective roles. Describe effects of severe iodide deficiency both in adulthood and in pregnancy. 6. MAJOR MINERAL & ENERGY METABOLISM — SULPHUR SULPHUR or SULFUR (S) A. INTRODUCTION -not consumed and not used in body as the element (ion) itself -found in S-containing amino acids of proteins and as part of the B-vitamins thiamin and biotin FNH 250: Nutrition Concepts & Controversies FNH 250 Nutrition Concepts & Controversies Page 16 of 16 B. ROLES a. Amino Acids -Sulphur is an essential component of 2 amino acids: Cys & Met -disulfide bonds stabilize 3-D configuration and function of proteins (e.g., insulin) b. Liver Pathways: Sulphur used in drug detoxifying pathways in liver C. DEFICIENCY -not observed except with severe protein deficiency D. TOXICITY -not observed E. RECOMMENDATIONS -none -consumed in proteins FOOD SOURCES -plant and animal proteins supply Sulphur ANIMAL FOODS PLANT FOODS milk & milk products whole grains meat legumes (e.g., tofu) fish poultry -sometimes sulfites used to preserve foods (e.g., apricots, papaya, mango) and beverages (e.g., wine) to keep their flavour and extend their shelf life Learning Objectives You are working on a nutrition team studying the micronutrient status of women in Vietnam. Your team found severe iodide deficiency in adult women. What physical signs of iodide deficiency do you see? Explain why these signs are present. Your grandfather has been feeling low energy and you suspect he has low vitamin B12 status. What do you think are appropriate strategies to increase his vitamin B12 levels back to normal? Your cousin Ellen is 26 years old and engaged to be married. What would you tell her about folic acid supplements? Explain why. FNH 250: Nutrition Concepts & Controversies