Breastfeeding research tells us that short-term fasting (not eating) will not decrease milk supply, but that severe dehydration can decrease milk supply. Fasting does affect the biochemical/nutrient content of breastmilk to a certain extent.
There have been a few studies on fasting and breastfeeding (see the references below). Zimmerman et. al. (2009) tested the milk of Israeli women before and after religious fast days and found a number of biochemical changes in the milk associated with fasting 24+ hours. Studies in the United States by Neville et. al. (1993), Neville & Oliva-Rasbach (1987) and Tigas et. al. (2002) likewise showed no significant decrease in milk supply after a short fast (the women in these studies did drink water during the fast). The breastfeeding woman’s body appears to make several metabolic adaptations during short-term fasting to ensure that milk production is not affected.
Rakicioğlu et. al. (2006) studied mothers with babies aged 2-5 months who fasted during Ramadan (no food or fluids between 5:00 am and 7:30 pm). They found that although infant growth and macronutrient content of breastmilk was not affected, levels of several nutrients in breastmilk (zinc, magnesium and potassium) decreased and the nutritional status of the breastfeeding mothers was affected. These authors noted that “it would seem prudent to excuse lactating women from fasting during Ramadan.” Prentice et. al. (1983) studied women in West Africa who were fasting for Ramadan and found that milk volume was not affected but milk composition did change to a certain extent. The researchers noted that the women appeared to superhydrate themselves overnight when fluids were allowed to lessen daytime dehydration.
Mothers may want to err on the safe side, and drink water even if they are not eating. There are two risks to not drinking all day: (1) mom gets dehydrated, and (2) if the dehydration is severe enough milk supply can decrease. Mom’s dehydration is comparatively easy to deal with — if she feels thirsty (or urine gets very yellow, or she feels dizzy or ill) she needs to drink. The decrease in milk supply related to dehydration may be a bigger issue for some fasting mothers – some mothers have a hard time getting supply back up (this is often seen in mothers who don’t eat or drink due to illness). When a mother does not drink fluids for a day, baby generally nurses as usual the day of the fast, but often needs to nurse more often the next day or two.
Some mothers have found that drinking water on fast days is more of a need during the first six months when baby is exclusively breastfed (not taking any food or drink other than breastmilk); once baby is older and taking other foods, it may be feasible to neither eat nor drink during the fast.
Keep in mind that mothers who have sugar metabolism problems (diabetes or hypoglycemia) or other health problems, fasting could be risky (for mom). Consult both your doctor and your religious advisor if you feel that you might have health issues that preclude fasting.
Jewish law exempts from fasting anyone whose health might be even a little harmed by it – this would include pregnant and nursing women whose health (or the health of her baby or fetus) might suffer from fasting. There may be ways of eating and drinking small increments that are still compatible with fasting. However, a local competent Orthodox rabbinic authority should be consulted so that the method and amounts of eating and drinking will be done within the correct guidelines.
Muslim women who are pregnant or breastfeeding may be exempt from fasting if they feel that their health or the baby’s health would be negatively affected by the fasting. The mother may be expected to compensate for the missed fasting at a later time or pay some expiation for not fasting. Consult a scholar or a book of fiqh to determine the appropriate guidelines.
Additional information and references
Fascinating research on Ramadan fasting gives breastfeeding mothers ‘food for thought’ from the Sharjah Baby Friendly Emirate Campaign (2012)
Ramadan and breastfeeding from BabyCenter Arabia
Fasting on Yom Kippur During Pregnancy by Hannah Katsman
Breastfeeding and Jewish Law from the Nishmat Women’s Online Information Center (includes some Q&As on fasting)
Eidelman AL. Fasting and the Nursing Mother: A Jewish Law (Halachic) Perspective. ABM News and Views. 1998;4(3).
Straight from the Heart: A Torah Perspective On Mothering Through Nursing by Tehilla Abramov
Kridli SA. Health beliefs and practices of Muslim women during Ramadan. MCN Am J Matern Child Nurs. 2011 Jul-Aug;36(4):216-21; quiz 222-3.
Zimmerman DR, Goldstein L, Lahat E, Braunstein R, Stahi D, Bar-Haim A, Berkovitch M. Effect of a 24+ hour fast on breast milk composition. J Hum Lact. 2009 May;25(2):194-8.
Rakicioğlu N, Samur G, Topçu A, Topçu AA. The effect of Ramadan on maternal nutrition and composition of breast milk. Pediatr Int. 2006 Jun;48(3):278-83.
Tigas S, Sunehag A, Haymond MW. Metabolic adaptation to feeding and fasting during lactation in humans. J Clin Endocrinol Metab. 2002 Jan;87(1):302-7.
Ertem IO, Kaynak G, Kaynak C, Ulukol B, Gulnar SB. Attitudes and practices of breastfeeding mothers regarding fasting in Ramadan. Child Care Health Dev. 2001 Nov;27(6):545-54.
Neville MC, Sawicki VS, Hay WW Jr. Effects of fasting, elevated plasma glucose and plasma insulin concentrations on milk secretion in women. J Endocrinol. 1993 Oct;139(1):165-73.
Hamosh M, Dewey KG, Garza C, et al: Nutrition During Lactation. Institute of Medicine, Washington, DC, National Academy Press, 1991, p. 92. This book is available free from the HRSA Information Center.
Neville M, Oliva-Rasbach J. Is maternal milk production limiting for infant growth during the first year of life in breast-fed infants? p. 123-133 in Goldman AS, Atkinson SA, Hanson LA, eds. Human Lactation 3: The Effects of Human Milk on the the Recipient Infant. Plenum Press 1987, New York.
Prentice AM, Lamb WH, Prentice A, Coward WA. The effect of water abstention on milk synthesis in lactating women. Clin Sci (Lond). 1984 Mar;66(3):291-8.
Prentice AM, Prentice A, Lamb WH, Lunn PG, Austin S. Metabolic consequences of fasting during Ramadan in pregnant and lactating women. Hum Nutr Clin Nutr. 1983 Jul;37(4):283-94.