(1, 2) This can be through direct effects on the nervous system, as well as through more general effects on quality of digestion. (naturopathiccurrents.com)
In general the effect of very poor nutrition on a lactating woman is to reduce the quantity rather than the quality of breastmilk.» (lllc.ca)
Serotonin, meanwhile, appeared to have a more general effect on aversion to harm, not just a heightened concern for another person. (sciencemag.org)