Minerals.docx

1、MineralsMineralsIntroduction Conception: minerals are nutritionally important chemical elements obtained from the macronutrients excluding C, H, N, and O. They are considered essential. If their source of exposure were removed, there would be a consistent and reproducible impairment of some physiolo

2、gical activity.Inorganic elemental atoms that are essential nutrients, but not changed by digestion or metabolism.Minerals are found in many different chemical forms including: complexes, chelates and free ions (especially group 1 and 17 elements). Minerals are essentially indestructible since they

3、are not affected by heat, light, oxidizing agents or extremes in pH. ClassificationMacro or Major minerals minerals 钾（K，potassium） 钠（Na，sodium） 钙（Ca，calcium） 磷（P，phosphorus） 镁（Mg，magnesium） 氯（Cl，chlorine） 硫（S，sulfur）Present in body tissues at concentrations 0.01%Micro or Trace minerals (body needs r

4、elatively less) iodine碘I、 zinc锌Zn、 selenium硒Se、 copper铜Cu、 molybdenum钼Mo、 chromium铬Cr、 cobalt钴Co、 iron铁Fe manganese, fluoride, silicon, tin, arsenic, nickelPresent in body tissues at concentrations 0.01%Essential microminerals(8):iodine碘I、 zinc锌Zn、 selenium硒Se、 copper铜Cu、 molybdenum钼Mo、 chromium铬Cr、

5、 cobalt钴Co、 iron铁Fe Potential toxic micro-minerals:铝Al、锡Sn、锂Li、铅Pb、镉Cd、汞Hg、砷As Function of Minerals1 part of the rigid body structure and soft body tissue 如钙、磷、镁是骨骼和牙齿的重要成分，磷、硫是构成组织蛋白的成分。bone is Ca3(PO4)2, CaCO3 and Mg3(PO4)2 are the major ingredients of bone, teeth; phosphorus and sulfur are the co

6、mponents of protein. Soft tissue includes skin, fibrous tissues, fat(which are connective tissue), and muscles, nerves and blood vessels (which are not connective tissue). 2part of body fluids (fluids outside of cells); Na+ ,K+, and Cl- (chlorine) are present as ions and preserve the electrolyte bal

7、ance in our bodies. 3Keep balance of fluids pH value 酸性、碱性无机离子的适当配合，加上重碳酸盐和蛋白质的缓冲作用是维持机体酸碱平衡的重要机制。 4Keeping neuron, muscles exciting 在组织液中的各种无机离子，特别是保持一定比例的钾、钠、镁、钙离子是维持神经、肌肉兴奋性，细胞膜通透性以及所有细胞正常功能的必要条件。 5Part of important physiological bioactive components in body 无机元素是构成某些具有特殊生理功能的物质的重要成分。如血红蛋白和细胞色素系统

8、中的铁，甲状腺素中的碘和谷胱甘肽氧化物酶中的硒。 6.Some participate with enzymes in metabolic processes (cofactors) 无机离子是很多酶系统的活化剂、辅因子或组织成分。如盐酸之于胃蛋白酶原，氯离子之于唾液淀粉酶，镁离子之于氧化磷酸化的多种酶类，以及很多其他含金属的酶类。 Absorption & Regulation of MineralsAbsorptionSmall intestine & large intestineRegulationKidneys & small intestineThe bioavailability

9、 of a mineral may be influenced by a variety of factors:1.The chemical form will determine how readily our bodies absorb the mineral. A highly stable chelate form would be poorly absorbed compared to free ions that are readily absorbed. Phytate(植酸盐) and oxalate (草酸盐), found in some foods, reduce the

10、 absorption of calcium, iron and zinc. Iodine absorption may be hindered by nitrates （硝酸盐）. But, ligands配位体that form soluble chelates with metals will enhance absorption. In contrast, iron absorption may be increased when vitamin C is consumed during the same meal.2. Interactions with other minerals

11、 In high concentrations, some minerals may actually inhibit the absorption of another mineral. The absorption of iron is inhibited by high concentrations of calcium, and too much iron itself may lead to poor zinc absorption.3. Requirement, The amount of a mineral people actually absorb can vary, and

12、 will depend upon their own needs, and how much they already have of that nutrient in the body. Minerals are fairly stable in normal food processing conditions. CalciumMost abundant mineral in animal tissues99% Ca in bone and teeth skeleton Ca(PO4)2 85% ; CaCO310% 1% present in Blood & other tissues

13、 Called miscible calcium pool (混溶钙池) Lots of functionsBone， teeth structureNerve functionMuscle contractionBlood clottingDecrease penetration of capillary vessel and membrane Food Sources1.Milk and dairy products High amounts High bioavailability (fortified with vitamin D)2. Green leafy vegetables P

14、oor absorption3. Fish bones4. Fortified juice/cerealCalcium AbsorptionDependent on Vitamin DCa binding protein in intestinal epithelial cellAbsorption depends on needParticularly high during growth, pregnancy and lactationBioavailability decreased byPhytates (grains)OxalatesWheat bran higher fiberLo

15、w estrogen雌激素levels (postmenopausal women)Calcium RegulationThree hormones involved in regulation1. Vitamin D3 from kidney2. Parathyroid hormone (PTH) from parathyroid gland3. Calcitonin from thyroid glandPTH and Vitamin D3 act to increase plasma Ca, while calcitonin acts to decrease plasma CaHormon

16、al Control SystemsMaintaining normal blood calcium and phosphorus concentrations is managed through the concerted action of three hormones that control fluxes of calcium in and out of blood and extracellular fluid:Parathyroid hormone serves to increase blood concentrations of calcium.1. Increases bo

17、ne resorption by activating osteoclastic activity2. Increases renal calcium reabsorption by the distal renal tubules3. Increases the formation of 1,25-dihydrocholecalciferol by increasing the activity of alpha-hydroxyls in the kidney Vitamin D acts also to increase blood concentrations of calcium. I

18、t is generated through the activity of parathyroid hormone within the kidney. 1. Enhances calcium absorption from the intestine2. Facilitates calcium absorption in the kidney3. Increases bone calcification and mineralization4. In excess, mobilizes bone calcium and phosphate Calcitonin is a hormone t

19、hat functions to reduce blood calcium levels Calcitonin is a 32 amino acid polypeptide secreted by the parafollicular cells in the thyroid gland. It tends to decrease serum calcium concentration and, in general, has effects opposite to those of PTH. Suppression of renal tubular reabsorption of calci

20、um. In other words, calcitonin enhances excretion of calcium into urine.Inhibition of bone resorption, which would minimize fluxes of calcium from bone into blood.Responses to Low Blood CalciumParathyroid hormone (PTH) releasedStimulates conversion of inactive form of vitamin D to calcitrol Increase

21、s in blood calciumSmall intestineResorption at kidneys & bloodCalcium Deficiencies1. Rickets in growing children2. Osteomalacia (osteoporosis) in adult Calcium and OsteoporosisAround age 40, bone breakdown exceeds formation.Ideally, want very high bone mass when this begins.By age 65, some women hav

22、e lost 50% of bone mass.Calcium Toxicity1. About 90% of all hypercalcemia cases are the result of hyperparathyroidism, a condition in which parathyroid hormones are produced in excess.2. Increase the risks of kidney stone肾结石 3. Milk-Alkali Syndrome, MAS(乳碱综合症):symptoms include hypercalcemia (高钙血)、al

23、kalosis (碱中毒)和renaldysfunction (肾功能障碍)。 乳碱综合症是指因长期进食大量牛奶或钙剂，并服用大量可吸收的碱剂引起的高钙血症、碱中毒及不同程度的肾功能损害等一组临床症候群。过去多发生在消化性溃疡患者的内科治疗中，因治疗方案的改进，如服用不溶性碱性药物，本征现已罕见。 4. Overtake of calcium can disturb the intake of other minerals. Iron,zinic, magnasium, and phosphorusPhosphorous人体内第二大元素，在成人体内含量为400-500g左右，占体重1左右，占体

24、内无机盐总量的14Functions1.Component of bone, teeth skeleton2. Component of protein, DNA and RNA 3. Vitally important in energy metabolismATPcreatine phosphate磷酸肌酸 磷酸肌酸是在肌肉或其他可兴奋性组织（如脑和神经）中的一种高能磷酸化合物，是高能磷酸基的暂时贮存形式，能在肌酸激酶的催化下，将其磷酸基转移到ADP分子中。当一些ATP用于肌肉收缩，就会产生ADP。这时，通过肌酸激酶的作用，磷酸肌酸很快供给ADP以磷酸基，从而恢复正常的ATP高水平。由于肌

25、肉细胞的磷酸肌酸含量是其ATP含量的34倍，前者可贮存供短期活动用的、足够的磷酸基团。在活动后的恢复期中，积累的肌酸又可被ATP磷酸化，重新生成磷酸肌酸，这是同一个酶催化的相反的反应。因为细胞中没有其他合成和分解磷酸肌酸的代谢途径，此化合物很适合完成这种暂时贮存的功能。 4. As a coenzyme in metabolic system (TPP, FAD, NAD+) 5. Maintenance of blood pH (phosphate buffer)Metabolism & Regulation of Phosphorus in the BodySmall intestineV

26、itamin D-dependent active transportSimple diffusionConcentrations controlled by: Calcitriol, PTH, calcitonin Excreted by kidneyBioavailability could be improved if phytate P can be reduced. Fermentation of flour could reduce phytate P content. 食物中的磷以有机磷和无机磷两种形式存在，有机磷主要是蛋白质和磷脂类，无机磷主要是谷类和蔬菜中以植酸形式存在的磷，

27、不易被人体吸收。 Main source of P in grainDeficiencies includeRickets or osteomalacia Pica异食癖(depraved appetite) chewing of wood, bones Low fertility or growthPhosphorus ToxicityOvertake of phosphorus can cause hyperphosphatemia高磷血症是慢性肾脏病(CKD)的常见并发症,是肾功能衰竭排磷困难引起继发性甲状旁腺功能亢进、钙磷乘积变化、维生素D代谢障碍 三、钾（potassium）Func

28、tions of Potassium in the Body1. Fundamental for normal nerve and muscle function especially critical in the right amount for regulating nerve transmissions and muscle contractions, which involves the interchange of potassium and sodium in and out of nerve and muscle cells 2. Needed for metabolism o

29、f carbohydrates and proteins. . Essential for protein and nucleic acid synthesis involved in synthesis of protein from amino acids Converts glucose into glycogen (muscle fuel) needed for metabolism and storage of carbohydrates for use as energy by the muscles 3. Regulates heart function needed for h

30、eart function and rhythm, and helps treat heart disorders. a diet comprising high potassium foods lowers risk of stroke and heart attack by up to 40%. 4. Required for normal fluid balance acts with sodium to control the bodys water balance 5. maintain acid/alkali balance helps regulate the bodys ele

31、ctrolyte and acid-alkaline (pH) balance 6. Reduces blood pressure helps the body handle sodium and so reduce risk of high blood pressure7. prevents osteoporosis studies also show a correlation between bone mineral density and intake of potassium-rich foods that help to maintain the bodys pH (acid al

32、kaline) balance so that less calcium needs to be mobilized from bone to do so, which preserves bone strength and prevents osteoporosis. 8 Important role in kidney function potassium citrate is known to dissolve calcium and so help prevent formation of kidney stones and calcification of soft tissues. large scale studies have shown that those who follow the RDA and t