Everyone is right.  Dark skin is a risk factor for rickets if we are
depending on ultraviolet exposure for vitamin D intake.  But why is dark
skin not a risk factor for rickets in the baby?  Because he gets stores
of vitamin D from the mother during pregnancy.  In South Africa where I
worked, we never saw rickets except in artificially fed babies.  Yet the
mothers covered the babies up except for the tops of their heads when
they took them out.  The mothers got lots and lots of sun exposure and
thus were vitamin D sufficient themselves.  They passed on good stores
to the baby.

Now, if the mother has low stores, the baby may not get adequate stores.
And if he gets little outside exposure, he may develop rickets.  The
typical breastfed baby who is at risk for rickets in Toronto (not *that*
far north) is a child of a Muslim woman, veiled and covered to her eyes
who thus does not get much sunlight exposure even in summer.  In
Toronto, if you don't get it from the sun, you get it from food, the
best source being vitamin D enriched milk.  But women from this culture
often do not drink milk either.  So they often have low vitamin D
stores.  They should get their stores up by taking prenatal vitamins,
however.

Jack Newman, MD, FRCPC