289
Asia Pac J Clin Nutr 2004;13 (3):289-291
Original Article
Comparison of the dietary cobalt intake in three
different Australian diets
Bevan Hokin PhD1, Michelle Adams PhD1, John Ashton PhD2 and Honway Louie PhD3
1
School of Applied of Sciences, University of Newcastle.
Sanitarium health food Company, Research Laboratories, Coorabong, NSW, Australia
3
Australian Government Analytical laboratories, Pymble, NSW, Australia
2
Differences in the dietary intake of cobalt were assessed for vegans, lacto-ovo-vegetarian and non-vegetarian
Australians using food intake logs, and daily or average trend recall over three months. A significant decrease
in cobalt intake was observed for the lacto-ovo-vegetarian population compared with the intake in vegans and
omnivores. There is no RDI for cobalt, however, the cobalt intake of Australians was similar to that reported in
other countries. Microflora above the terminal ileum have been shown to produce significant amounts of
biologically available vitamin B12. This study was unable to demonstrate a correlation between elemental
cobalt intake and serum vitamin B12 concentrations in humans, as has been shown in vitro.
Key Words: cobalt, lacto-ovo-vegetarian, vegan, Australia
Introduction
Little is known about the role of dietary cobalt, other than
as a component of cyanocobalamin, vitamin B12.1-3 Low
levels of cobalt in ruminant diets has been reported to lead
to vitamin B12 deficiency,4 however as humans obtain
their vitamin B12 primarily from animal food sources the
role of cobalt for this purpose seems limited. Previous
studies however, have suggested a role of microbial
fermentation in diet supplementation of vitamin B12, in
particular by bacteria in the oral cavity and small
intestine.5,6 Vitamin B12 produced by colon bacteria is not
absorbed.7
The risk of vitamin B12 deficiency in certain dietary
groups, such as vegetarians, is well-recognised.8
Interestingly, it has been reported that the incidence of
vitamin B12 deficiency is lower in some countries, than in
Australia.9-10 As it is recognised that the cobalt levels in
foods may be influenced by geographical distribution, and
by seasonal variation, it is possible that the vitamin B12
levels in some vegetarian communities may be significantly supplemented by indigenous microflora, and this
supplementation may be cobalt dependent. This hypothesis
has been confirmed in vitro.10 There are no reports of
cobalt levels in Australian foods, so to determine the
dietary intake, one hundred and fifty foods were analysed
by a Finnigan High Resolution Inductively Coupled
Plasma Mass Spectrometer,11 and this data was used to
compare the dietary cobalt intake by Australian vegan,
lacto-ovo-vegetarian and non-vegetarian populations.
Normal daily intake is reported to be in the range
2.5-3.0mg/day.12,13 Toxicity with cobalt has been reported
to occur within the range of greater than 25-30mg cobalt
daily.1
Subjects and methods
Foods were analysed for cobalt11 and daily intake was
calculated from food recall records. Diet history records
using food intake logs for 24 hours, daily recall or average
trend recall over three months, were obtained from
informed volunteers. All procedures were performed in
accordance to Human Ethics guidelines, with approval
given through the University of Newcastle Human
Research Ethics Committee.
Diet history data was obtained from three populations:
vegans (N=10), lacto-ovo-vegetarians (N=10) and nonvegetarians (N=10). All participants were over the age of
eighteen, but results were not stratified for age and gender.
Results were calculated using an Excel database and
spreadsheet, and are shown in Table 1.
Fasting blood samples were collected from participants,
using accepted techniques. Serum vitamin B12 was
estimated using the BioRad radio immunoassay method.14
Estimated elemental cobalt intake was compared with the
measured serum vitamin B12 concentration in vegans and
lacto-ovo-vegetarians, by linear regression and ANOVA
techniques, using the Excel Statistical package.
Correspondence address: Dr Bevan Hokin, Pathology
Department, Sydney Adventist, Hospital, 185 Fox Valley Road,
Wahroonga, NSW 2076
Tel: 02 9487 98511; Fax: 02 9487 9535
Email: bevan@sah.org.au
Accepted 24 October 2003
B Hokin, M Adams, J Ashton and H Louie
290
Table 1. Calculated daily intake of cobalt by selected groups of Australians
Mean daily intake
µg/day
Standard deviation
40.1 a
20.8b
19.8
15.4
17.81 to 81.8
17.81 to 36.1
22.7b
39.7 a
12.2
16.5
6.67 to 37.3
19.6 to 68.5
Vegan
Vegan excluding two
participants consuming large
amounts of potato
Lacto-ovo-vegetarian
Non-vegetarian
Range
µg/day
Values are means (N=10)
Values within a given column with the same superscripts are not significantly different (P>0.05, Student’s t-test, two tailed)
Table 2. Measured serum vitamin B12 concentrations of selected groups of Australians.
Mean serum concentration
pmol/L
Standard error of the
mean
Range
pmol/L
175a
175a
366
6.6
6.2
27
86-296
91-325
166-680
Vegan
Lacto-ovo-vegetarian
Non-vegetarian
Values are means (N=10). Values within a given column with the same superscripts are not significantly different (P > 0.05, Student’s t-test, two tailed)
Results
The average cobalt intakes for the selected population
groups are shown in Table 1. A significant difference in
cobalt intake was observed between the lacto-ovovegetarian group and the other two populations (P<0.05),
with no difference between the vegan and non vegetarian
groups (P>0.05).
The estimated dietary intake of cobalt by each group
was compared with serum vitamin B12 concentration
(Table 2) by linear regression and ANOVA. There was no
correlation by linear regression (R2=0.02), and no
statistical significance by ANOVA (P=0.34).
Table 3. Daily cobalt intake for various nationalities
Country
Mean daily cobalt intake
µg /day
Australia
34.2 (6.6 – 81.8)
15
France
29
Canada16
11
United Kingdom17
18
Unites States
3.4-11.6
19
13.3-44.6
20,21
25
Brazil
Spain
11-28
Discussion
The average daily intake of cobalt by Australians was
found to be comparable with that reported for other
nationalities (Table 3).
The wide range in results from different studies and
countries, partially reflects the different methods and
technology available, with the more recently reported data
15,19
using the same methods as were used in this study.
A major source of cobalt in the Australian diet is from
meat and potatoes, and this is reflected in the dietary
intake results. The cobalt intake of both vegans and non
vegetarians was higher than that of lacto-ovo-vegetarians
(P<0.05).
Vegans generally reported consuming more potatoes
than the other two groups, accounting for most of the
difference. Potatoes contain a high concentration of cobalt
(137 µg/kg). The exclusion of two participants that were
outliers for potato consumption, reduced the mean cobalt
intake of the vegan group to be comparable to that of the
lacto-ovo-vegetarian group. The major sources of cobalt
in the non vegetarian group were red meat (86µg/kg) and
potato (mostly in the form of chips). No clinical significance has been able to be inferred from these differences
in intake of cobalt.
The lack of correlation between serum vitamin B12
concentrations and estimated cobalt intake was not
surprising. Only a very small amount of elemental cobalt
is incorporated into vitamin B12 (0.04µg per 1µg of
vitamin B12). Thus assuming all the dietary cobalt
consumed by the participant with the lowest intake (6.67
µg) was absorbed, 165µg of vitamin B12 could be
manufactured which is far in excess of the RDI of the
vitamin. Further studies examining the dietary intake of
cobalt of vegetarians with low serum vitamin B12 may
provide a better insight into its role in vitamin B12 levels
in non-ruminant animals.
The vitamin B12 concentration of vegans is usually
significantly lower than that of lacto-ovo-vegetarians.10
The gap is closing however, as lacto-ovo-vegetarians are
consuming fewer eggs and less dairy foods, while the
vegans and consuming more foods fortified with vitamin
B12.10 In this study, the vegans were not taking vitamin
B12 tablet supplements or IM injections, but the majority
were consuming foods supplemented with vitamin B12
eg. So Good soy milk alternative. This may account for
the unexpected similarity in the mean serum vitamin B12
concentration in both the vegan and lacto-ovo-vegetarian
groups.
291
Comparison of the dietary cobalt intake in three different Australian diets
Conclusion
Although certain vegetarian diets demonstrated a
significantly lower cobalt intake than that of the nonvegetarian diet, no correlation could be observed between
cobalt intake and serum vitamin B12 levels. This
probably reflects the fact that all diets in this study
provided cobalt at a level that was within the required
range. Overall, the Australian dietary intake of cobalt is
reflective of that observed in other countries.
Acknowledgement
This research was supported by contributions from the
Australian Government Analytical Laboratories, Pymble, NSW,
Australia, and the Sanitarium Health Food Company,
Cooranbong, NSW, Australia.
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