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Cortical bone formation and diet among protohistoric iroquoians.

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 6023-28 (1983)
Cortical Bone Formation and Diet Among Protohistoric
lroquoians
SUSAN PFEIFFER AND PATRICIA KING
School ofHumon Biology, Uniwnrity of Guelph, Guelph,Ontario, C m d a
KEY WORDS
Cortical bone, Paleonutrition, Ca intake, Ca:P ratio,
Huronia
ABSTRACT
Two samples of protohistoric Iroquoians are found to show low
values for bone formation indicators. Two southern Ontario ossuary samples,
Kleinburg (1600 AD, N = 561) and Uxbridge (1490 2 80 AD, N = 457) are
examined. Mean values for the cortical index (Barnett and Nordin, 1960) and
percent cortical area (Garn, 1970)are consistently below expected normal values.
Some of the lowest values may reflect the presence of a disease state. Nevertheless,
it is argued that the results may indicate chronic dietary insufficiencies. Both
absolute calcium intake and the calcium to phosphorous ratio are discussed as
possible causative factors.
Past researchers have frequently noted differences in adult cortical bone remodeling
among prehistoric skeletal samples (Cassidy,
1972;Perzigian, 1973;Eriksen, 1976;Richman
et al., 1979).Differences in the amount of cortical bone have been tentatively attributed to
dietary differences among groups.
It has been recognized that the nutritional
influenceson cortical remodeling cannot easily
be differentiated from genetic and biomechanical influences. Furthermore, there is no simple relationship between calcium intake and
bone formation or maintenance (Garn et al.,
1969b). Although calcium intake may influence the incidence of senile osteoporosis (Matkovic et al., 19791,other factors such as meat
protein and phosphorus intake complicate the
relationship (cf. Chinn, 1981;Draper and Bell,
1979).
One reason for the inability to assess accurately the influence of dietary factors on bone
kinetics is that researchers must base their
observations on generalized dietary reconstructions. We rarely have accurate dietary information and skeletal material from the same
population. A general lack of energy intake or
a specific dietary deficiency may be postulated,
but the data do not facilitate the testing of
hypotheses.
Documents from the period of historic European contact in southern Ontario furnish relatively thorough dietary information for certain Amerindian groups. The Huron Indians,
0002-9483/83/6001-0023$02.00
0 1983ALAN R. LISS, INC.
especially, were the subject of ethnographic
documentation by explorers, Recollet and Jesuit missionaries from 1615 to their defeat and
dispersal by the Iroquois in 1649-50. These
various accounts have fiumished a basis for numerous ethnographic reconstructions (cf.
Tooker, 1964; "rigger, 1969, 1976). Heidenreich (1971)approached the records from a cultural geographer's perspective, and established a tentative profile of probable food sources
and preferences (see Table 1).
It is within this context that two large Iroquoian samples were examined for their relative amount of adult cortical bone.
MATERIALS AND METHODS
Skeletal samples from two Iroquoian 08suaries were examined. The Kleinburg Ossuary, excavated in 1970 by F. J. Melbye, has
been dated by trade goods to ca. 1600 AD. The
Uxbridge Ossuary, excavated in 1975-77 by P.
Cook, is radiocarbon dated to 1490 2 80 AD.
Both sites were located north of Toronto, Ontario, not far from historic Huronia.
An Iroquoian ossuary sample consists of the
thoroughly mixed skeletal remains of everyone
who had died during the 8-12 years preceding
ossuary construction. According to ethno-
Received March 22,1982;aceepted August 16,1982.
24
S. PFEIFFER AND P. KING
TABLE 1.Recommended duilv intake of nutrients compared with Humn intake
~~~~
~~~
~
Protein
Calories
Recommended intake
Daily food
3,000
Huron intake
Corn
1,950
Squash
50
Beans
400
300
Fish
Meat
150
Fruit
150
Totals
3,000
gm
70
55.0
1.4
6.0
40.0
25.0
1.6
129.0
~
Calcium
mg
Iron
mg
800’
10
120
38
38
14.0
0.6
2.0
1.8
3.2
2.3
23.9
11
34
230
Vitamin A
Ascorbic
acid
Thiamine
mg
Riboflavin
mg
Niacin
mg
5,000
1.2
1.7
19
70
3,000
9,723
220
240
2.25
0.05
0.14
0.24
0.06
0.06
2.80
0.7
12.0
0.9
1.0
14.7
4.5
0.8
33.9
-
IU
10
224
13,417
0.8
0.1
0.1
0.2
1.0
2.9
mg
8
14
-
-
32
54
‘Represents Canadian and American RDA. The FAOiWHO (1962)suggests 400-500 mgiday for adults on cereal diets.
Reproduced from Heidenreich (1971)with permission
graphic sources, exceptions to universal inclusion may be newborn infants and males killed
in battle. Infants are, indeed, underrepresented in most ossuary samples, but there is
no evidence that adult males are consistently
underrepresented. The Kleinburg sample includes a minimum of 561 individuals, of whom
28% are immature. Most adults died prior to
age 40, based on pubic symphysis assessment.
The adult sex ratio is approximately balanced.
The Uxbridge sample includes a minimum of
457 individuals, of whom 31% are immature.
Here, too, most adults died prior to age 40, and
there is no pelvic evidence for an unbalanced
sex ratio. Analysis of Uxbridge adult age and
sex is currently preliminary. From the Kleinburg sample, 96 left femoral midshafts, 22
lumbar vertebrae, and 130 second left metacarpals were examined. From the Uxbridge
sample, 90 second left metacarpals were examined.
The Kleinburg material was assessed by two
separate, but closely correlated, techniques.
Followingthe technique of Barnett and Nordin
(1960),measurements were taken from metacarpal radiographs and femoral cross sections to assess their relative cortical thickness
(the femoral and metacarpal scores), and radiographs of the lumbar vertebrae were used
to calculate the relative anterior body height
(the lumbar score). The scores are essentially
indices of medial and lateral cortical thicknesses over total midshaft breadth, or posterior
over anterior body height. These three measurements taken together were proposed by
Barnett and Nordin (1960)to be a technique
for the diagnosis of osteoporosis. Although this
assessment is no longer considered very useful
for that purpose (Nordin et al., 1970), i t is still
a valuable technique for quantification of cortical bone. Reference values for nonosteopo-
rotic Britons are useful for comparison. The
technique has been used for previous studies
of prehistoric samples (cf. Cassidy, 1972;Cook,
1979),and it correlates well with measures of
percent cortical area (r > 0.90)(Garn, 1970).
Barnett and Nordin (1960)used the third lumbar vertebra to calculate their lumbar score.
We were unable to identify third lumbar vertebrae with certainty, so we used fifth lumbar
vertebrae.
The second technique used to quantify cortical bone status is the calculation of Garn’s
(1970)percent cortical area. The second left
metacarpals from both the Kleinburg and
Uxbridge samples were measured to this end.
All measurements were taken from radiographs, using a Helios needlepoint caliper.
Indeed, the same measurements are used to
calculate both Barnett and Nordin’s score and
Garn’s percent cortical area. The difference between the two measures is that the score is
one-dimensional and the area measurement is
two-dimensional (Garn, 1970,p 65).The Barnett and Nordin scores are included here because they offer an indication of bone status
from multiple skeletal sites, from the trunk as
well as appendages.
RESULTS
A comparison of the ossuary-derived Barnett
and Nordin scores with those of normal Britons
is displayed in Figures 1-3. Each of the three
Kleinburg distributions is skewed to the left.
Using Barnett and Nordin’s original cutoff values for the determination of osteoporosis, 24%
of the femora, 21.5% of the metacarpals, and
36% of the vertebrae would be classified as “osteoporotic.”
The mean values derived for percent cortical
areas for Kleinburg and Uxbridge metacarpals
are 75.9% (s = 8.22)and 74.5% (s = 10.431,
25
CORTICAL BONE AND DIET
FEMORAL SCORE
METACARPAL SCORE
30.
25-
N.125
25
%
N.125
20-
20.
1510.
10.
5.
5
SCOR
5-
5-
10-
%
10.
15
15
20-
20.
25-
N = 96
3oJ
25
4
Fig. 1. Femoral cortex scores for Barnett and Nordin’s
British reference sample, all over 50 years of age (above),
as compared to Kleinburg Ossuary femora (below). A low
score indicates a low amount of cortical bone per unit
of area.
Fig. 2. Second left metacarpal cortex scores for Barnett
and Nordin’s British reference sample, all over 50 years of
age (above),as compared to Kleinburg Ossuary metacarpals
(below). A low score indicates a low amount of cortical bone
per unit of area.
respectively.These are substantially lower than
the population means summarized by Garn
(1970), which range from 84.2% (Costa Rican
males) to 91.0% (El Salvador females). Garn’s
weighted pooled means are 85.7% for males,
and 89.7%for females. One proposed statistical
limit of osteoporosis is a percent cortical area
value that is 2 SD below the mean. Using the
lowest population mean (84.2, s = 6.8) the osteoporosis cutoff is 70.6%. The cortical area
values of 25.6% of the Kleinburg metacarpals
and 26.7% of the Uxbridge metacarpals fall at
or below this value.
The distributions of metacarpal cortical areas
for Kleinburg and Uxbridge are plotted in Figure 4. The plot of the Uxbridge values is markedly bimodal, with approximately 10%of the
area values lying below 60. This group of low
values explains the lower mean value for
Uxbridge as compared to Kleinburg. It has been
argued elsewhere that the Uxbridge material
shows strong evidence of tuberculosis or some
similar condition (Pfeiffer, 1981). Evidence of
premortem vertebral destruction and sacroiliac deterioration has been used to estimate that
a minimum of 20-26 adults, or 6.5-8%, were
affected. Similar cases of premortem deterioration are not present at Kleinburg, at least
not in substantial numbers. The lowest area
values from the Uxbridge sample are therefore
likely to be linked to a disease state. Figure 4
also illustrates that the modal class for the two
samples is around 80, a value much closer to,
but still below, Garn’s range of population
means.
DISCUSSION
The two protohistoric Iroquoian populations
examined here demonstrate low values for
amounts of cortical bone, as expressed by Barnett and Nordin scores or the calculation of
percent cortical area.
Results have been expressed in terms of osteoporosis not because we wish to argue that
a disease state is present, but because we wish
to emphasize the general trend toward low values for amounts of cortical bone. Finer levels
of analysis are not possible using these ossuary
samples, because the age and sex of the individual specimens are unknown. The sex of
complete Kleinburg femora has been estimated using discriminant function analysis
S.PFEIFFER AND P. KING
26
LUMBAR SCORE
30
N=125
%
sco
%
N=22
25
Fig. 3. Lumbar body scores for Bamett and Nordin’s
British reference sample, all over 50 years of age (above),
aa compared to Kleinburg os~uaryvertebrae (below).A OW
score indicates some degree of anterior body wedging.
%
1
(Pfeiffer, 1979).This represents only a fraction
of the total sample, however. We also tried to
discriminate the sexes statistically by comparing Mexican-American metacarpal measurements (Garn et al., 1973), but, because of
their gracility, results were unrealistically
skewed toward females. We can only say that
the samples are composed primarily of young
adults, and probably include approximately
equal representation of males and females.
Given these demographic characteristics, cortical remodeling appears to be markedly deficient.
Heidenreich argued that the Huron diet (Table 1)was likely to have been adequate in both
energy content and nutrients. Intake of calcium and vitamin C appears to have been below current recommended allowances, but “additional calcium was probably obtained by
gathering calcium-rich foods such as clams,
nuts, and crabs.” Furthermore, “the water supply in Huronia is high in calcium carbonate”
(Heidenreich, 1971, p 165). Meat protein intake was probably low, and exposure to sunlight was adequate. Both these factors reduce
the need for dietary calcium. There are no docIUnented Ca8es Of
faders
Heidenreich to conclude that dietary calcium
intake was marginally adequate.
10
5
0
4i-4‘5
5b
$5
40
45
o;
7’5
s’o
s’5
do
915
id0
PCA (Percent Cortical Area)
Fig. 4. Distrihution of percent cortical area values, second left metacarpals from the Kleinburg and Uxhridge
ossuaries.
27
CORTICAL BONE AND DIET
It is now recognized, however, that availability of calcium for bone tissue formation depends not only on dietary calcium but also the
ratio of phosphorus to calcium in the diet (cf.
Draper and Scythes, 1981). The optimal ratio
varies according to the absolute calcium content, but generally, as the amount of phosphorus increases beyond a Ca:P ratio of 1:1, there
is a rise in plasma phosphorus, a decline in
plasma calcium, and a consequent increase in
parathyroid hormone synthesis and bone resorption. A 6-month study on adult pigs (whose
bones undergo cortical remodeling) demonstrated that a Ca:P ratio of 1:3, with moderate
calcium intake, was associated with decreased
rib ash, decreased femoral bone formation, and
increased lumbar vertebral marrow width
(DeLuca et al., 1976). Such effects are most
marked when calcium concentration in the diet
is high. Because the efficiency of calcium absorption decreases at high intakes and the efficiency of phosphorus absorption remains unchanged, both absolute and relative calcium
intake must be considered when evaluating the
possible effects of the Ca:P ratio.
By all accounts, the staple food in the Huron
diet was corn. Corn is relatively low in calcium
and high in phosphorus. Using a standard table of food composition values (Health and
Welfare Canada, 19711, the reconstructed Huron diet shows a calculated Ca:P ratio of 1:3.8,
due mainly to the corn component. However,
nearly half the phosphorus in corn is contained
in insoluble phytin. This means that the ratio
of available nutrients may be closer to 1:2. The
effect of this ratio on bone formation, assuming
low absolute calcium levels, should not be very
great for adults. Animal experimentation indicates that the effect on rapidly growing juvenile bone could be marked, however.
Protein-calorie malnutrition in the growing
child has been shown to result in low percent
cortical areas (Garn et al., 1964,1969a). Childhood differences in the cortical index have been
used to try to discriminate paleonutrition among
prehistoric Illinois Valley groups (Cook, 1979).
We know of no evidence, however, that such
childhood cortical deficiencies are normally retained into adulthood.
The low values for adult bone formation in
the Kleinburg and Uxbridge samples are not
clearly explained by any single dietary variable. A number of chronic factors may, however, be implicated. These include low calcium
intake, excess phosphorus relative to calcium,
and protein-calorie malnutrition. Genetic and
biomechanically based hypotheses are less at-
tractive. Although it is clear that there are
differences in bone dynamics among major racial groups, there is thus far no evidence for
genetic differences at the more local level. We
also have no reason to believe that the Iroquoian horticulturists were markedly inactive.
Further work should compare corn-baaed
horticulturists with related groups depending
on other dietary regimes. This approach may
differentiate any unique bone formation characteristics associated with a corn-based, low
meat diet from those possibly associated with
protein-calorie insufficiency.
ACKNOWLEDGMENTS
We wish to thank Dr.F. J. Melbye of Erindale College, University of Toronto, for access
to the Kleinburg sample. Radiography was
kindly provided by Mr. Carl Basiano and Mr.
Alex Nelson of the Ontario Veterinary College,
University of Guelph. We thank Dr. H. H.
Draper for his review of the manuscript. Funding for this research was partially furnished
by a grant from the Social Sciences and Humanities Research Council of Canada.
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