Zinc - Toxicology of Metals - page 906

found mean Zn intakes of 10.7 ± 5.75 mg, in men and
7.9 ± 3.54 mg in women (Offi ce of National Statistics,
2002), and a survey of boys and girls aged 15-18 years
had intakes similar to those of adults, although 11-14-
year-olds had intakes of 7.7 mg and 6.7 mg, respec-
tively (Thane et al ., 2004).

common among children, aged 1-5 years, older
adults, and individuals with more education and
income. By current standards (Trumbo et al ., 2001),
among US adults older than 60 years of age, 35-41%
of men and 36-45% of women have “low” dietary
intakes of Zn that can be improved by Zn supple-
mentation (Ervin et al ., 2002). In contrast, a survey
of German young persons, aged 2-18 years, found
approximately 6% consumed supplemental minerals
(Sichert-Hellert and Kersting, 2004).

5.4.1 Plants

Pulses and cereals are the major sources of dietary
Zn for most people (Gibson 1994). In contrast, in the
United States pulses and cereals provide approxi-
mately 30% of dietary Zn (Walsh et al ., 1994). The effect
of processing on the Zn content of some plant-derived
foods is shown in Table 1. For example, the Zn content
of yellow whole grain cornmeal is 2.2 mg/cup (122 g)
and of yellow degermed corn meal is 1.0 mg/cup (138
g); the Zn content of cooked long grain brown rice is
1.2 mg/cup (195 g), and of cooked long grain white
rice is 0.5 mg/cup (175 g). Pulses are usually richer in
Zn than refi ned cereals. For example, the Zn content
of beans ranges from 1.9 mg/cup (172 g) in cooked
mature black beans to 2.5 mg/cup (164 g) in boiled
chickpeas.
Indigestible plant ligands such as phytate, some die-
tary fi bers and lignin, and products of nonenzymatic
Maillard browning formed during cooking inhibit
intestinal Zn absorption (Sandstead and Smith, 1996).
Removal of Zn-binding ligands by milling and/or
fermentation improves Zn bioavailability (Sandstrom
and Sandberg, 1992; Larsson et al ., 1996).

5.5 Work Environment
5.5.1 Inhalation

Exposure to metallic Zn and Zn compounds occurs
during Zn mining, smelting, welding, and other
uses of Zn compounds (Simon-Hettich et al ., 2001).
Zinc-oxide fume and dust are regulated in many
countries at 5-10 mg/m 3 consistent with guidelines
of the International Labor Organization (ILO) to pre-
vent respiratory illness. Data from several European
countries and the United States suggest this goal is
being achieved.

6 BIOLOGICAL MONITORING

6.1 Direct Indicators of Zn Status

6.1.1 History

Dietary history is a key indicator of risks to Zn nutri-
ture. A focused history of the frequency of consumption
of fl esh foods, foods rich in nondigestible Zn-binding
ligands, and Zn supplements can provide qualitative
insights (Yokoi et al ., 2003). A detailed quantitative his-
tory will provide deeper understanding of Zn intake
and factors that can affect Zn use (e.g., Ca [Wood and
Zheng, 1997], Fe [Solomons, 1986], Cu [Sandstead,
1995], Cd [Brzoska and Moniuszko-Jakoniuk, 2001;
Reeves and Chaney, 2002], Pb [Godwin, 2001; Basha
et al ., 2003], phytate [Sandstrom and Sandberg, 1992],
dietary fi ber [Knudsen et al ., 1996], Maillard browning
products [Lykken et al ., 1986], and folate [Milne et al .,
1984; Simmer and Thompson, 1985]). High dietary
phytate × Zn and phytate × Ca/Zn molar ratios are
indicative of increased risk of low Zn bioavailability
(Gibson et al ., 2003).

5.4.2 Flesh Foods

Animal fl esh is the best source of readily bioavailable
Zn. In the United States, meat provides approximately
50% of dietary Zn (Walsh et al ., 1994). Red meat is the
richest common source compared with fowl and fi sh
(Table 1). Preferential consumption of poultry, fi sh, and
dairy products instead of red meat increases the risk of
Zn defi ciency (Yokoi et al ., 1994; Yokoi et al ., 2003).

5.4.3 Dairy Products

Cow milk products provide approximately 20% of
the daily Zn intake in the United States (Walsh et al .,
1994). Adult absorption of 65 Zn tracer added to cow's
milk was 28% compared with 31% from “humanized”
cow's milk infant formula, 41% from human milk, and
14% from soy formula (Sandstrom et al ., 1983).

6.1.2 Plasma/Serum Zinc

Plasma/serum Zn is the least sensitive indicator of
Zn status. Concentrations may (or may not) decrease
with Zn defi ciency (Pekarek et al ., 1979) and may (or
may not) increase with toxicity (Kumar and Jazieh
2001). Many factors affect plasma Zn concentration:

5.4.4 Nutritional Supplements

A national survey in the United States found that
approximately 40% of the population takes nutritional
supplements (Ervin et al ., 1999). Consumption is