Minerals and Trace Elements 227possibly as a result of inhalation rather than inges-
tion, “manganic madness,” manifested by psychosis,
hallucinations, and extrapyramidal damage with
features of parkinsonism.
In 2001, the US Food and Nutrition Board set the
tolerable UL for manganese at 11 mg/day for adults
(19 years and older). Elevated blood manganese con-
centrations and neurotoxicity were selected as the
critical adverse effects on which to base their UL for
manganese.
Assessing status
Progress in the fi eld of manganese nutrition has been
hampered because of the lack of a practical method
for assessing manganese status. Blood manganese
concentrations appear to refl ect the body manganese
status of rats fed defi cient or adequate amounts of
manganese, but consistent changes in blood or plasma
manganese have not been observed in depleted or
repleted human subjects. Researchers are actively
investigating whether the activities of manganese-
dependent enzymes, such as manganese-SOD in
blood lymphocytes and blood arginase, may be of use
in detecting low manganese intake; however, there is
evidence that these enzymes can be infl uenced by
certain disease states.
Requirements and dietary sources
Relatively high concentrations of manganese have
been reported in cereals (20–30 mg/kg), brown
bread (100–150 mg/kg), nuts (10–20 mg/kg), ginger
(280 mg/kg), and tea (350–900 mg/kg dry tea). Con-
centrations of manganese in crops are dependent on
soil factors such as pH, whereby increasing soil pH
decreases plant uptake of manganese. Products of
animal origin such as eggs, milk, fi sh, poultry, and red
meat contain low amounts of manganese (Table 9.20).
Many multivitamin and mineral supplements for
adults provide 2.5–5.0 mg of manganese.
There is currently no RDA set for dietary manga-
nese; instead, there is an AI value [these values were
established by the US Food and Nutrition Board in
2001]: infants 0.003 mg (fi rst 6 months), 0.6 mg (7–
12 months), children 1.2 and 1.5 mg (1–3 and 4–8
years, respectively), teenage boys 1.9 and 2.2 mg (9–13
and 14–18 years, respectively), adult men 2.3 mg (19
years and older), teenage girls 1.6 mg (9–18 years),
adult women 1.8 mg (19 years and older), pregnant
women 2.0 mg, and lactating women 2.6 mg. The AI
was set based on median intakes reported from the
US Food and Drug Administration Total Diet Study.Micronutrient interactions
Iron–manganese interactions have been demon-
strated whereby iron defi ciency increased manganese
absorption, and high amounts of dietary iron inhibit
manganese absorption, possibly by competition for
similar binding and absorption sites between nonheme
iron and manganese.9.13 Molybdenum
Molybdenum does not exist naturally in the pure
metallic state but rather in association with other ele-
ments, or predominantly in solution as the molybdate
anion. Insoluble molybdenum compounds include
molybdenum dioxide and molybdenum disulfi de.
The metal has fi ve oxidation states (2–6), of which
+4 and +6 are the predominant species. Major
molybdenum-containing ores are molybdenum sul-
fi tes and ferric molybdenum ores, usually produced
as by-products of copper mining operations, while
other molybdenum salts are by-products of uranium
mining. Molybdenum is used mostly in metallurgical
applications such as stainless steel and cast iron
alloys, and in metal–ceramic composites. Molyb-
denum compounds have anticorrosive and lubricant
properties and can act as chemical catalysts.
Molybdenum uptake into plants and hence into the
food chain occurs mostly from alkaline or neutral
soils. Water usually contains little molybdenum except
near major mining operations.Absorption, transport, and
tissue distribution
Molybdenum is readily absorbed (40–100%) from
foods and is widely distributed in cells and in the ECF.
Some accumulation can occur in liver, kidneys, bones,Table 9.20 Dietary sources of manganese
Rich sources
(>20 mg/kg)
Intermediate sources
(1–5 mg/kg)Poor sources
(<1 mg/kg)Nuts Green leafy
vegetables
Animal tissueWholegrain cereals Dried fruits Poultry
Dried legumes Fresh fruits Dairy products
Tea Nonleafy vegetables Seafood