Implementing food-based dietary guidelines for - United Nations ...

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ments, even among countries where omnivorous diets
are habitually consumed. For example, in UK mixed
diets, iron is assumed to have a fixed bioavailability
of 15%, irrespective of age and life-stage group [207],
whereas in the United States and Canada, a factor of
18% is used for the bioavailability of iron in the mixed
diets of both children and nonpregnant adults, but 25%
is used for women in the second and third trimesters
of pregnancy and 10% for those consuming vegetarian
diets [204]. Similarly, the United Kingdom uses a fixed
factor of 30% for zinc, irrespective of age and life-stage
group [207], but the United States and Canada apply
a factor of 41% and 48% for the bioavailability of zinc
from diets of adult (over 19 years) males and females,
respectively, and 30% for preadolescent children [204].
Australia and New Zealand have adopted the US and
Canadian bioavailability adjustments for iron for children
4 years of age or older, nonpregnant adults, and
vegetarians, but the IZiNCG adjustments for zinc [36,
208]. Other expert groups, such as FAO/WHO [181]
and IZiNCG [36], employ several factors to adjust for
the bioavailability of iron and zinc, depending on the
composition of the habitual diet, as noted earlier.
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Adjustments are needed to translate physiological
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protein, folate, and vitamin A. The magnitude of the
adjustments depends on the nutrient and will vary
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