Chapter 12 The Trace Elements

Copyright 2010, John Wiley & Sons, Inc. Trace Elements Talk The trace elements include iron, zinc, copper, manganese, selenium, iodine, fluoride, chromium and molybdenum. They are required in amounts less than 100 mg per day. Trace elements have been difficult to study, as they are difficult to remove from the diet. Rate of bioavailability is a concern for trace elements. Copyright 2010, John Wiley & Sons, Inc. 2

Copyright 2010, John Wiley & Sons, Inc. Iron in the Diet Copyright 2010, John Wiley & Sons, Inc. 3

Copyright 2010, John Wiley & Sons, Inc. Iron Talk Hemoglobin is the iron-containing component of the blood. Iron from animal products is heme iron. Iron from plant products is nonheme iron. Iron cookware can be a source of nonheme iron in the diet. Heme iron is more efficiently absorbed than nonheme iron. Iron from the diet is absorbed into the intestinal mucosal cells. Copyright 2010, John Wiley & Sons, Inc. 4

Copyright 2010, John Wiley & Sons, Inc. Heme Iron Absorption Copyright 2010, John Wiley & Sons, Inc. 5

Copyright 2010, John Wiley & Sons, Inc. Iron in the Body Ferritin is the major iron storage protein. Transferritin is an iron transport protein in the blood. Hemosiderin is an insoluble iron storage compound produced by the body when iron exceeds the storage capacity of ferritin. Iron is essential for the delivery of oxygen to cells. Two oxygen-containing proteins, hemoglobin and myoglobin, contain iron. Most of the iron in the body is part of hemoglobin. Copyright 2010, John Wiley & Sons, Inc. 6

Copyright 2010, John Wiley & Sons, Inc. DRIs for Iron Copyright 2010, John Wiley & Sons, Inc. 7

Copyright 2010, John Wiley & Sons, Inc. Iron Deficiency When iron is deficient, hemoglobin cannot be produced. When there is insufficient hemoglobin, red blood cells are microcyctic and hypochromic and unable to deliver sufficient oxygen to the tissues. This is known as iron deficiency anemia. It is estimated that as much as 80% of the world’s population may be iron deficient and 30% suffer from iron deficiency anemia. Copyright 2010, John Wiley & Sons, Inc. 8

Iron Toxicity and Overload Iron is essential for cellular metabolism, but too much can be toxic. A UL has been set at 45 mg/day from all sources. Iron poisoning can be life-threatening. It can damage the intestinal lining and cause abnormalities in body pH, shock and liver failure. Iron overload can happen over time and accumulates in tissues such as the heart and the liver. The most common form of iron overload is hemochromatosis. Copyright 2010, John Wiley & Sons, Inc. 9

Copyright 2010, John Wiley & Sons, Inc. Zinc in the Diet Copyright 2010, John Wiley & Sons, Inc. 10

Copyright 2010, John Wiley & Sons, Inc. Zinc Talk Zinc is essential in the diet for growth and development. Zinc from animal sources is better absorbed than zinc from plant sources. Zinc can be bound by phytates, affecting bioavailability. Zinc is the most abundant intracellular trace element. Zinc is involved in the functioning of over 300 different enzymes, including superoxide dismutase, important for protecting cells from free radical damage. Zinc can be toxic if taken in excess. Copyright 2010, John Wiley & Sons, Inc. 11

Copyright 2010, John Wiley & Sons, Inc. Copper Talk Copper may be important in helping to prevent certain types of anemia. The richest dietary source of copper is organ meat. Seafood, chocolate, nuts, seeds and whole-grain foods are also good sources. Zinc can decrease the bioavailability of copper. The RDA for copper for adults is 900 micrograms per day. Copyright 2010, John Wiley & Sons, Inc. 12

Copyright 2010, John Wiley & Sons, Inc. Manganese Talk The best sources of manganese are whole grains and nuts. Manganese is a constituent of some enzymes and an activator of other enzymes. Manganese-requiring enzymes are involved in amino acid, carbohydrate and cholesterol metabolism, cartilage formation, urea synthesis and antioxidant protection. Manganese, like copper and zinc, is needed for the activity of a form of superoxide dismutase. Copyright 2010, John Wiley & Sons, Inc. 13

Copyright 2010, John Wiley & Sons, Inc. Selenium in the Diet Copyright 2010, John Wiley & Sons, Inc. 14

Copyright 2010, John Wiley & Sons, Inc. Selenium Talk The selenium content of plant foods, such as grains and seeds, depends on the selenium content of the soil in which they are grown. Selenium deficiency can lead to Keshan disease, affecting the heart muscle. Symptoms of selenium deficiency include muscular discomfort and weakness. There may be a connection, still being researched, between diets low in selenium and higher incidences of cancer. Copyright 2010, John Wiley & Sons, Inc. 15

Copyright 2010, John Wiley & Sons, Inc. Iodine Talk The iodine content of food depends on the soil where plants are grown or where animals graze. Soil near the ocean or sea is higher in iodine than soil inland. Most of the iodine in the diet comes from iodized salt. Iodized salt is salt fortified with iodine. “Natural” sea salt may be very low in iodine. More than half the iodine in the body is found in the thyroid gland. Iodine is an essential component of thyroid hormones, including thyroxine. Copyright 2010, John Wiley & Sons, Inc. 16

Copyright 2010, John Wiley & Sons, Inc. Thyroid Hormones Copyright 2010, John Wiley & Sons, Inc. 17

Iodine and Thyroid Hormones Copyright 2010, John Wiley & Sons, Inc. 18

Copyright 2010, John Wiley & Sons, Inc. Iodine Talk When the supply of iodine is adequate, the body can produce the needed thyroid hormones. The RDA for iodine for adult men and women is 150 micrograms per day. The RDA for iodine is higher during pregnancy and lactation. Consuming diets high in goitrogens, such as cabbage, cassava and millet, limits the bioavailability of iodine. Iodine deficiency may result in hereditary cretinism. The UL for adults is 1100 micrograms of iodine per day. Iodine toxicity is possible. Copyright 2010, John Wiley & Sons, Inc. 19

Copyright 2010, John Wiley & Sons, Inc. Chromium Talk Dietary sources of chromium include brewer’s yeast, liver, nuts and whole grains. Cooking in stainless steel can increase food’s chromium content. Chromium is involved in carbohydrate and lipid metabolism. Copyright 2010, John Wiley & Sons, Inc. 20

Copyright 2010, John Wiley & Sons, Inc. Fluoride Talk Fluoride is important for dental health. Fluoride is present in small amounts in almost all soil, water, plants and animals. The most common sources of fluoride are fluoridated water, tea, marine fish eaten with their bones, such as canned salmon or sardines, and topical toothpaste. Calcium-rich foods reduce the bioavailability of fluoride. Copyright 2010, John Wiley & Sons, Inc. 21

Copyright 2010, John Wiley & Sons, Inc. Fluoride Toxicity Copyright 2010, John Wiley & Sons, Inc. 22

Summary of Trace Elements Copyright 2010, John Wiley & Sons, Inc. 23

Summary of Trace Elements Copyright 2010, John Wiley & Sons, Inc. 24

Benefits and Risks of Trace Element Supplements Copyright 2010, John Wiley & Sons, Inc. 25

Copyright 2010, John Wiley & Sons, Inc. Chapter 12 Copyright 2010 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information herein. . Copyright 2010, John Wiley & Sons, Inc. 26