chapter 12 the trace elements. trace elements talk the trace elements include iron, zinc, copper,...
TRANSCRIPT
Chapter 12THE TRACE ELEMENTS
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 2012, John Wiley & Sons Canada, Ltd.
Iron in the Diet
Copyright 2012, John Wiley & Sons Canada, Ltd.
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 2012, John Wiley & Sons Canada, Ltd.
Heme Iron Absorption
Copyright 2012, John Wiley & Sons Canada, Ltd.
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 2012, John Wiley & Sons Canada, Ltd.
DRIs for Iron
Copyright 2012, John Wiley & Sons Canada, Ltd.
DRIs for Iron
Copyright 2012, John Wiley & Sons Canada, Ltd.
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 2012, John Wiley & Sons Canada, Ltd.
Iron and Zinc in the Canadian Diet
Copyright 2012, John Wiley & Sons Canada, Ltd.
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 2012, John Wiley & Sons Canada, Ltd.
Zinc in the Canadian Diet
Copyright 2012, John Wiley & Sons Canada, Ltd.
Zinc in the Canadian Diet CCHS suggests that a number of Canadians are
not meeting their zinc requirements. The richest sources of zinc are found in animal products
Copyright 2012, John Wiley & Sons Canada, Ltd.
Zinc in the Diet Vegetarians are more vulnerable to having
inadequate zinc intakes. Vegans my be 50% more vulnerable due to the lower bioavailability of zinc from vegan sources. Wise food choices are necessary.
Canadian regulations also require some foods, such as simulated meat products and beverages derived from legumes, nuts, cereal grains and potatoes, to be fortified with zinc. This information will be listed in the Nutrition Facts Table.
Copyright 2012, John Wiley & Sons Canada, Ltd.
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 2012, John Wiley & Sons Canada, Ltd.
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 2012, John Wiley & Sons Canada, Ltd.
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 2012, John Wiley & Sons Canada, Ltd.
Selenium in the Diet
Copyright 2012, John Wiley & Sons Canada, Ltd.
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 2012, John Wiley & Sons Canada, Ltd.
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 2012, John Wiley & Sons Canada, Ltd.
Thyroid Hormones
Copyright 2012, John Wiley & Sons Canada, Ltd.
Iodine and Thyroid Hormones
Copyright 2012, John Wiley & Sons Canada, Ltd.
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 2012, John Wiley & Sons Canada, Ltd.
Iodine Talk All salt sold for household use in Canada,
including sea salt, must be iodized (trace element iodine added).
Since the introduction of iodized salt in Canada, iodine intake has been adequate and iodine deficiency rare.
Copyright 2012, John Wiley & Sons Canada, Ltd.
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 2012, John Wiley & Sons Canada, Ltd.
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 2012, John Wiley & Sons Canada, Ltd.
Fluoride Talk (continued) 43% of the Canadian population receive fluoridated
water, but there are substantial regional differences. Fluoride intake has also increased due to the
widespread use of fluoride toothpaste and fluoridated water in foods and beverages that are distributed in nonfluoridated areas.
Dental caries remain a public health problem. However, increased fluoride intake and advances in dental care have dramatically improved the dental health of the public.
Copyright 2012, John Wiley & Sons Canada, Ltd.
Fluoride Talk (continued)
Copyright 2012, John Wiley & Sons Canada, Ltd.
Fluoride Talk (continued)
Copyright 2012, John Wiley & Sons Canada, Ltd.
Fluoride Toxicity
Copyright 2012, John Wiley & Sons Canada, Ltd.
Summary of Trace Elements
Copyright 2012, John Wiley & Sons Canada, Ltd.
Summary of Trace Elements (continued)
Copyright 2012, John Wiley & Sons Canada, Ltd.
Benefits and Risks of Trace Element Supplements
Copyright 2012, John Wiley & Sons Canada, Ltd.
Benefits and Risks of Trace Element Supplements
Copyright 2012, John Wiley & Sons Canada, Ltd.
Copyright
Copyright © 2012 John Wiley & Sons Canada, Ltd.
All rights reserved. Reproduction or translation of this work beyond that permitted by Access Copyright (The Canadian Copyright Licensing Agency) is unlawful. Requests for further information should be addressed to the Permissions Department, John Wiley & Sons Canada, Ltd. The purchaser may make back-up copies for his or her own use only and not for distribution or resale. The author and the publisher assume no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information contained herein.
.
Copyright 2012, John Wiley & Sons Canada, Ltd.