Below is a copy of a Lactnet post I sent when I was an active LC.

For some women (I was one) there is a drop in milk supply beginning 
about a week before a menstrual period and continuing a few days into 
the period. I researched this when my babies were feeding and found 
that from mid-cycle until a couple of days into the period, there is 
a steady decrease in blood calcium levels.  Obviously the decrease 
varies among women, as some women never experience this drop in milk. 
This lower blood calcium level is also the cause of uterine cramping 
before and in the first days of the period.

I began to take a calcium/magnesium supplement from mid-cycle until 3 
days into my period. The milk supply was maintained. When my 
daughters began menstruating, I had them follow the same plan and 
they were able to have little or no uterine cramping.

I recommend supplementation for mothers who call me with this supply 
problem. The amount of added ca/mag is variable, of course.  I 
suggest that she add 500mg-1000mg supplement of calcium with half as 
much magnesium. The more meat that we eat the more Ca/Mag we need. 
Usually it takes the higher doses to accomplish the desired goal. The 
added ca/mag has resolved the problem in all of my clients who have tried it.

It can even be effective if they call me with the decrease in supply 
and say that a period is due.  I suggest that they begin immediately 
with 1000mg of ca/mag a day, and there is usually an increase in 
supply within 24 hours.

One problem is to determine when "mid-cycle" is with a mother just 
resuming menses.  I suggest that she take the supplement throughout 
the month until she sees a pattern of cycling.

One shouldn't take calcium without magnesium in a 2/1 ratio (the 
ratio that is found in foods and is usually found in supplements). 
And dissuade someone's taking Tums for their calcium.  It is not an 
adequate dietary supplement and it is an antacid, while calcium needs 
an acidic gastric environment for assimilation.

Hey, I wonder if the 4-month supply drop, or those illusive "growth 
spurts," could be related to calcium levels in the blood related to 
pending or active menses? I'll try ca/mag supplementation the next 
time a client calls with a sudden drop in supply.

Patricia Gima,Retired LC
Milwaukee, Wisconsin, USA 

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