Re: How long between eating food and when the proteins show up in breast milk?

Aloha, Thomas,

     Proteins, or at least parts of them, can do some interesting things 
in the body.  First, my congratulations on your new baby...and my 
encouragement to your wife for breastfeeding.  I tell my introductory 
nutrition students here at the University of Hawaii/Manoa that 
nutritionally-speaking 'breast IS best.'

     The problem that your baby/wife seem to be having may or may not be 
caused by proteins in the food that your wife eats.  My educated guess is 
probably not, though.  Proteins are made of amino acids (20 different 
ones)...and the human digestive tract does a quite good job of breaking 
protein down into individual amino acids before anything is absorbed into 
the body.  The individual amino acids generally do not cause any problems 
(like allergic reactions).  However, the lining of the digestive tract (in 
the small intestine) does allow some short chains of amino acids to be 
absorbed directly into the blood, also.  These are called peptides.  Also, 
apparently some whole proteins can get through between the cells.  In 
milk, casein is one of the proteins that causes an allergic response in 
some people.  However, for the casein to survive all the metabolic changes 
that happen for breast milk to be produced is not probable.

     Do the dairy products cause your wife any problems?   Does the baby's 
problem develop with just milk in your wife's diet?  Other dairy foods?  
If you/she are certain that it is really cow's milk, then she might try 
other sources of calcium (cheese, yogurt, cottage cheese, calcium 
supplements).  I really hesitate to suggest that your wife stop using 
dairy products, if it causes her no problems, since milk, in particular, 
is such a nutrient-rich food...for both her and for her producing breast 
milk.  Soy milk and other soy products can be substitutes, but you really 
need to check the nutrition label to make sure that the product is 
fortified with calcium, vitamin B12, and riboflavin.  Also, the protein 
content may not be as high...and the type of protein is different.  
Lastly, some people have strong allergies to the protein in soy 
products...best to stick with dairy products, if at all possible.  Anyway, 
your wife could eliminate dairy from her diet (and making sure she gets 
enough of the other substitute foods) for a day of two to see if this 
makes a difference in the baby.

     Another possibility is that the baby's problem could be related to 
something else that your wife eats/drinks with the dairy products.  Some 
vegetables (onions, garlic, broccoli)are very strong-flavored, and the 
flavoring compounds can go straight through to the breast milk...kind of 
like when your urine smells strange after eating asparagus...same 
principle (it's the flavors getting in the body fluids). Sometimes, too, 
it can be just a fussy baby.  I had one (daughter) who was crabby whenever 
I nursed her, regardless of what I ate;  my other child (son) was a great 
baby and no problems in nursing.  Babies are strange little critters and 
VERY individual. 

     In many of these cases, the problem is temporary and seems to go 
away.  If it is severe and the baby seems to be in distress, of course it 
is best to talk with your pediatrician and/or a dietitian to see if 
changing your wife's diet for the rest of the time she nurses might help.