Chapter 12 The Trace Minerals

Chapter 12 The Trace Minerals
Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.
Trace Minerals Include iron, zinc, copper, manganese, selenium, iodine, fluoride, chromium and molybdenum Required in amounts less than 100 mg/ day Difficult to study because they are difficult to remove from the diet Rate of bioavailability is a concern for trace elements Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 2

Iron Hemoglobin is the iron-containing component of the blood Heme iron—from animal products Nonheme iron—from plant products 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 © 2016 John Wiley & Sons, Inc. All rights reserved. 3

Iron Absorption and Transport
Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 6

Iron in the Body Ferritin—the major iron storage protein Transferrin—an iron transport protein in the blood Hemosiderin—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 © 2016 John Wiley & Sons, Inc. All rights reserved. 7

Progression of Iron Deficiency

Iron Deficiency When iron is deficient, hemoglobin cannot be produced Iron deficiency anemia—when there is insufficient hemoglobin, red blood cells are microcytic and hypochromic and unable to deliver sufficient oxygen to the tissues 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 © 2016 John Wiley & Sons, Inc. All rights reserved. 9

Those at Risk for Iron Deficiency

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 Hemochromatosis—the most common form of iron overload Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 11

Zinc Essential in the diet for growth and development Animal sources are better absorbed than zinc from plant sources Can be bound by phytates, affecting bioavailability Most abundant intracellular trace element Involved in the functioning of over 300 different enzymes, including superoxide dismutase Important for protecting cells from free radical damage Toxic if taken in excess Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 12

Regulation of Zinc Absorption

Copper 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 Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 15

Inhibition of Copper Absorption

Manganese The best sources are whole grains and nuts 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 © 2016 John Wiley & Sons, Inc. All rights reserved. 18

Selenium The selenium content of plant foods, such as grains and seeds, depends on the selenium content of the soil in which they are grown Symptoms of selenium deficiency include muscular discomfort and weakness Selenium deficiency can lead to Keshan disease, affecting the heart muscle Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 20

Glutathione Perioxidase

Iodine Iodine content of food depends on the soil where plants are grown or where animals graze Soil near the ocean 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 © 2016 John Wiley & Sons, Inc. All rights reserved. 23

Iodine When the supply of iodine is adequate, the body can produce the needed thyroid hormones 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 © 2016 John Wiley & Sons, Inc. All rights reserved. 27

Chromium Dietary sources include brewer’s yeast, liver, nuts and whole grains Cooking in stainless steel can increase food’s chromium content Involved in carbohydrate and lipid metabolism Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 28

Fluoride Important for dental health 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 © 2016 John Wiley & Sons, Inc. All rights reserved. 29

Chapter 12 Copyright 2016 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 © 2016 John Wiley & Sons, Inc. All rights reserved. 31

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