Yes, it's me again (feast or famine)
Perth Western Australia might be a bit isolated, but there is one consolation
(apart from the wonderful weather and lifestyle). We have Prof Peter Hartmann
at the Uni of Western Australia - Peter is a Prof of Biochemistry who does
all his research into lactation (started off with pigs but found humans
much more interesting :). All his postgraduate students do work on human
lactation as well. Peter had two articles in the March 1995 JHL.
Anyway, he is now investigating the changes in the chemistry of milk
during the menstrual cycle. Apparently about 5-6 days before ovulation
and 6-7 days after ovulation there is an increase in concentration of sodium
(from 5mM to 10mM) and chloride (from 11mM to 22mM) and a decrease in
concentrations of lactose (220mM to 170 mM), potassium (from 14mM to 10mM)
and glucose (from 1.7mM to 1.1mM). The cause of these changes is unknown
so far.
He is currently getting volunteers who are breastfeeding and menstruating
 (usually NMAA Members) to collect samples of breastmilk from each breast
before each feed every day for one cycle, and urine samples every day !!
It is interesting to wonder if these chemical changes are picked up in the
flavour of the milk, causing fussiness or refusal in infants. As some
women still ovulate whilst using the minipill, it may still show through
as a reaction in their baby. I'm not sure if non-ovulatory cycles show
these chemical changes, but will keep you posted as his study progresses.

Fiona Coombes
NMAA Breastfeeding Counsellor
Family Physician  IBCLC
Perth Western Australia