conspectus of researchon copper metabolism and requirements

2032 KARL E. MASON
cant changes in copper requirements occur.
Considering the rather bizarre food intakes
and eating habits of this segment of popu
lations, there is real need for copper bal
ance studies on pre-college teenagers.
Except for the inconclusive observations of
Dawson et al. ( 152 ), no consideration has
been given to the special nutritional re
quirements, including those of copper, in
teen-age pregnancies. Considering that in
such situations there is need to meet
growth requirements of the adolescent
mother as well as those of the developing
fetus, it may be assumed that requirements
are appreciably greater than in adult preg
nant women.
Adults
Since adults are past the growing phase
of life, copper requirements are expressed
in terms of mg/day rather than as mg/kg/
day, as in the case of infants and adoles
cents.
Dietary intake. An earlier section (pp.
1998-1999) deals with the wide variation in
copper content of human diets in various
countries and of individuals of different
ages. Table 2 summarizes additional data
from studies in which the daily dietary
intake of copper (often as only one of
many trace elements), exclusive of copper
balance, was of primary concern. Indian
diets, which are predominately vegetarian
in composition, are notably high in copper
content. Analyses of diets of ovovegetarian
and nonvegetarian populations in India by
Soman (727) indicate, by writers's calcu
lation from the data given, intakes of about
5.7 and 7.1 mg/day, respectively. An ex
ceptionally high content of copper in
Indian diets is also reported by De ( 154)
as shown in table 3. These values are con
siderably in excess of those reported from
other countries. Only in the studies of
Guthrie (289, 291) is mention made of the
influence of liver, well known to be much
higher in copper than other food constitu
ents. In other studies in which composi
tion of the diet employed is given, liver has
not been listed as an ingredient. Somewhat
surprising are the low copper levels found
in student diets (White), hospital diets
(Gormican; Brown et al.) and self-selected
diets (Holden et al.). The values reported
are appreciably lower than those for com
parable types of diets in the balance
studies recorded in table 3. The studies
summarized in table 2 merely give some
picture of variations in the copper intake of
small groups of individuals in several dif
ferent countries. They provide no valid in
formation concerning requirements for
copper, since there is no evidence of their
ability to maintain positive balance over
long periods of time. To a certain extent
the same may be said of traditional balance
studies such as recorded in table 3, but
the latter do provide data on copper re
tention, in terms of intake less fecal excre
tion. While they provide data over only a
limited period of days or weeks, they do
represent a measure of daily requirements
somewhat equivalent to that provided by
total parenteral nutrition.
Balance studies. Table 3 summarizes, in
chronological sequence, data pertaining to
balance studies on human adults. In 6 of
the first 10 studies, extending from 1934 to
1954, the estimated requirement ranges
from 2.0 to 2.6 mg/day. These data pro
vided the basis for the wide acceptance of
2.0 or 2.0 to 2.5 mg as the daily require
ment of copper for adult man. However,
Cartwright and Wintrobe (106) later state
that at lower levels of intake adjustments
may be made to reduce copper excretion
such that the daily requirement would be
less than 2 mg and might even be negli
gible. Presumably, a major factor in this
adjustment would be a call upon copper
stores in the liver and other organs.
The levels of copper intake reported by
Holt and Scoular (349) are truly excessive
and the investigators, noting the much
lower values recorded by Leverton and
Binkley (452) for college students fed
similar diets, somewhat naively attribute
this difference to "a regional effect upon
the composition of food." Considering also
the unreasonably low fecal and urinary
loss and high retention values (calculated
from tabular data reported but not com
mented upon in the report) the atypical
results recorded suggest unknown defects
in methodology. The somewhat high cop
per content of Indian diets of De ( 154) is
in accord with the observations of Soman
(727), table 1. Whether the predominantly
Downloaded from
jn.nutrition.org
by guest on February 27, 2013