On the subject "where do people who don't use dairy get their calcium
from?", I came across an abstract which says that the calcium absorption
rate from soft-boned Bengali fish is 24%, which is about the same as
the absorption rate from milk. It is concluded that soft fish bones
constitute a good source of calcium.

If we assume that the calcium absorption rate from canned sardines is
similar, considering that the RDA has been calculated assuming that
people get most of their calcium from milk, and knowing from the USDA
figures that canned sardines contain 240 milligrams (Pacific sardine)
- 382 milligrams (Atlantic sardine) of calcium for 100 grams, then about
300-400 grams of canned sardines would be enough to meet a RDA of 1000
mg/day.

Of course, other factors come into play, like the Ca/P ratio, which is
.66 and .78 for Pacific and Atlantic sardine respectively, so it is
hard to know whether 300-400 grams are enough or not. Another issue is
that of cooking: I suspect that calcium is less available from raw
fish bones and/or that fewer people are willing to chew them thoroughly.


--Jean-Louis Tu <[log in to unmask]>


Hansen M et al. Calcium absorption from small soft-boned fish. J Trace
Elem Med Biol 1998 Nov;12(3):148-54

The prevalence of osteoporosis in developing countries is low
compared to most industrialised countries despite an apparent low Ca
intake. It is possible, however, that food surveys have overlooked
important Ca sources in developing countries. Small fish eaten with the
bones can be a rich source of Ca, even though Ca from bone may be
considered unavailable for absorption. In the present study, absorption
of Ca from indigenous Bengali small fish was compared with the Ca
absorption from milk. Ca absorption from single meals was determined
in 19 healthy men and women (21-28 y). Each subject received two
meal types on two separate occasions. Both meals consisted of white
wheat bread, butter and ultra pure water with the main Ca source being
either small Bengali fish (397 mg Ca in total) or skimmed milk (377
mg Ca in total). The meals were extrinsically labelled with 47Ca, and
whole-body retention was measured on day 8, 12, 15 and 19 after
intake of each meal. The labelling procedure was evaluated by an in
vitro method. The calculated absorption of Ca as measured with 47Ca
whole-body retention was 23.8 +/- 5.6% from the fish meal and 21.8
+/- 6.1% from the milk meal (mean +/- SD), which was not
significantly different (p = 0.52). Even after correction for an
incomplete isotope exchange, as indicated by the in vitro study, Ca
absorption was similar from the two meal types. It was concluded that
Ca absorption from small Bengali fish was comparable that from
skimmed milk, and that these fish may represent a good source of Ca.