17.11: Summary
- Page ID
- 58207
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The trace minerals are those that we require in very small amounts, and include iron, zinc, iodine, selenium, copper, manganese, fluoride, chromium, and molybdenum.
Iron deficiency is one of the most common mineral deficiencies in this country and throughout the world. Iron is critical for carrying oxygen in the hemoglobin of red blood cells, and deficiency leads to anemia. Deficiency can be caused by dietary deficiency, increased need, blood loss, or decreased absorption. Deficiencies are common in children and women of childbearing age. Iron deficiency can also result in increased lead absorption; lead is particularly toxic for children and the developing fetus.
Dietary iron is found in two forms—heme iron (almost exclusively from animal tissue) and non-heme iron (from some animal tissue, but mostly from plant foods). Heme iron is better absorbed than non-heme iron. Other dietary constituents (e.g., vitamin C, oxalic acid) can affect the absorption of non-heme iron.
Iron toxicity can be a problem, particularly in people at risk for the genetic disease hemochromatosis, which results in excess iron being deposited in body tissues. Iron supplements and/or habitually eating foods heavily fortified with iron are ill-advised for these people, as well as for men and postmenopausal women in general.
Zinc is critical for growth, particularly during pregnancy and childhood. A deficiency can result in birth defects, slow growth, changes in taste, and reduced immune function and wound healing. Toxicity is rare.
Iodine is an essential part of thyroid hormone, and deficiency causes goiter (an enlargement of the thyroid gland), Other conditions can cause goiter, but goiter caused by iodine deficiency is the most common kind and is called simple goiter. In the fetus, severe iodine deficiency can cause severe physical and intellectual disability.
Iodine is found in iodized salt, foods from the sea, and in processed foods in which iodine-containing compounds are added.
Selenium is a part of an antioxidant enzyme. Large excesses can be very toxic.
Copper is required for many enzymes and hemoglobin production. Copper deficiency is usually only found in the genetic disease Menkes’ steel hair disease, although zinc supplements may also lead to deficiency through competition for absorption.
Figure 17-7: Key functions of minerals.
Manganese is important for many enzymes, and deficiency and toxicity are rare.
Molybdenum is also needed for many enzymes, and it’s difficult to become deficient in this trace mineral.
Fluoride increases the hardness of tooth enamel and bone, and is found in adequate amounts in the water supply of about three-fourths of the U.S. population. Fluoridation of water should be considered where it’s lower than the recommended level of 0.7 ppm (parts per million).
Chromium promotes insulin action.
There are other minerals which haven’t yet been proven to be essential for humans, but it’s very unlikely that we’d become deficient in any of these.
For continually updated fact sheets on individual minerals, go to the website of the Office of Dietary Supplements. ods.od.nih.gov/factsheets