Water intakes of lactating women

Extra fluids for breastfeeding mothers for increasing milk production

BACKGROUND

Breastfeeding is known to be the biological norm. Despite this, many women wean their babies because of perceived insufficient breast milk production. Mothers are sometimes advised to increase their fluid intake in the hope that this could improve breast milk production. The effect of extra fluid on human breast milk production is not well established, however.

OBJECTIVES

To assess the effect of extra fluid for breastfeeding mothers on milk production/supply and infant growth.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (27 April 2014), MEDLINE (1966 to 27 April 2014), African Journals Online (27 April 2014) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials and quasi-randomised controlled trials on extra fluids for breastfeeding mothers.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the potential studies for inclusion and assessed trial quality.

MAIN RESULTS

Five trial reports were retrieved using the search strategies. Four trials were excluded. We did not identify any randomised controlled trials for inclusion but we included one quasi-randomised study (involving 210 women) that evaluated the effect of extra fluid for breastfeeding mothers on breastfeeding outcomes. The study was considered to be at a high risk of bias. Only one of this review's primary outcomes was reported (breast milk production (as defined by the trialist)) but data were not in a suitable format for analysis (no standard deviations or standard errors were reported). The trialist reported that advising women to drink extra fluids did not improve breast milk production. No data were reported for the review's other primary outcomes: satisfactory weight gain in the infant (as defined by the trialists) and duration of exclusive breastfeeding (months). Similarly, no data were reported for any of this review's secondary outcomes: duration of any breastfeeding; mother's satisfaction with breastfeeding; hydration in mother; dehydration in the infant; or episodes of gastrointestinal illness.

AUTHORS' CONCLUSIONS

This review only identified one small quasi-randomised controlled trial of low quality and high risk of bias. The study provided limited data on only one of this review's primary outcomes, breast milk production, but the data were not reported in a format that permitted further analysis. The trialist reported that extra fluids did not improve breast milk production. However, this outcome was measured by using test feeds (also known as test weighing). In the 1950s, when the study was conducted, it was common for babies in developed countries to be weighed before and after a feed, known as test weighing or test feeding. However, this practice is not now routinely practiced for term infants due to concerns about lack of precision as a measure of breast milk production. The included study did not report on this review's other primary outcomes (satisfactory weight gain in the infant or duration of exclusive breastfeeding) nor any of the review's secondary outcomes.The effect of additional fluids for breastfeeding mothers remains unknown, due to a lack of well-conducted trials. However, because the physiological basis for any such improvement remains unclear, the conduct of further clinical trials may not be a priority. There is not enough evidence to support an increased fluid intake beyond what breastfeeding mothers are likely to require to meet their physiological needs.

Assessing the exposure of pregnant women to drinking water disinfection byproducts

BACKGROUND

To evaluate associations between exposure to disinfection byproducts in drinking water and adverse birth outcomes, personal exposure to disinfection byproducts must take into consideration multiple routes of exposure.

METHODS

We assessed the reproducibility and validity of a questionnaire measuring water consumption, showering and bathing habits, use of chlorine-based products, and swimming pool attendance in 237 pregnant Italian women enrolled between June and December 1999. The questionnaire was completed during the last trimester of pregnancy (preQ) and again a few days after delivery (postQ). Data from postQ were compared with a 7-day diary completed during the last trimester.

RESULTS

According to postQ, total water intake was 2.6 liters per day, whereas tap water intake was 0.6 liters per day. Intraclass correlation coefficients of postQ compared with preQ were 0.85 for tap water daily intake and 0.77 for duration of showering and bathing. Pearson's correlation coefficients were 0.84 for tap water daily intake, 0.81 for frequency of showering, and 0.94 for bathing. The kappa statistics were 0.76 (95% confidence limits = 0.68, 0.85) for use of domestic chlorine-based products and 0.82 (0.70, 0.94) for indoor swimming. Pearson's coefficients for postQ compared with the diary were 0.78 for tap water daily intake, 0.62 for frequency of showering, and 0.64 for bathing. Compared with the diary, the sensitivity and specificity of postQ in assessing indoor swimming were 75% and 90%, respectively.

CONCLUSIONS

The questionnaire appears to be a valid and reliable method for assessing exposure to disinfection byproducts in the last trimester of pregnancy.

Another look at: fuel + O2 --> CO2 + H2O. Developing a water-oriented perspective

Water plays many vital roles which must be maintained despite constant threat of water stress from the environment. Mechanisms to maintain these roles over the long-term involve intermediates of many metabolic pathways, such as glycerol, sucrose, free amino acids and their derivatives. In addition to viewing metabolic products as intermediates along energy-related pathways, nutrition researchers and epidemiologists should consider them as determinants of intracellular fluid maintenance. Satiety processes, oxidative-fuel selection, hormonal control, and intracellular-signaling processes can all be interpreted in terms of water-oriented metabolism. Water intake and hydration status can vary considerably, and may be inadequate for a sizeable proportion of Western adults. Due to the metabolic adaptations required to compensate for perpetually inadequate water, chronic sub-optimal water intakes may be highly relevant to chronic disease etiology. Preliminary evidence links water-oriented metabolism to obesity, diabetes, cardiovascular disease, hypertension and cancer. Development of a water-oriented perspective may reveal an important new area of research in human nutrition and epidemiology.

The diuretic effects of alcohol and caffeine and total water intake misclassification

Data from the 1994 USDA nationwide survey (CSFII) on 190 non-smoking males (aged 20-29) were used to propose a method for adjusting total water intake for the diuretic effects of caffeine and alcohol, and evaluate the potential for related misclassification bias. The data were processed on a per meal basis. Under the assumption that subjects were in water balance at the start of the survey day, water losses due to caffeine (1.17 ml/mg caffeine) and alcohol (10 ml/g alcohol) were subtracted from crude intake estimates. If water intake for one meal was inadequate for excretion of the associated osmotic load at 750 mosmol/l, water losses for the subsequent meal were reduced by 32%. Unadjusted and adjusted mean total water intakes differed by 321.5 g. Misclassification appeared worst at higher water intakes. Linear regression models, each with a water intake variable as an independent variable and body mass index as the outcome, were fit to evaluate the potential for alcohol- and caffeine-related misclassification bias. Misclassification resulted in large changes (all >10%) in linear regression estimates of effect. Future studies of water-disease relationships, especially those intending to compare extremes of total water intake, should consider caffeine- and alcohol-related misclassification bias.

Hydration as a limiting factor in lactation

A relatively untapped area of research concerning lactation and hydration exists for bioanthropologists interested in the ecology of breastfeeding. This review details current limited knowledge on the topic with recommendations about relevant research questions for human biologists. On average, lactating mothers produce >750 ml/day milk for their infants. Breastfeeding thus promotes a powerful thirst stimulus in the lactating mother, resulting in a 12-16% increase in fluid intake among Western women. Thirst during lactation may be mediated by oxytocin release, since this hormone is structurally similar to the antidiuretic hormone, vasopressin. Prolactin also may be involved. A few studies among Western women concluded that moderate dehydration does not affect milk production, but it is not known how lactating women in hot and/or dry climates respond to chronically limited water supplies. Lactating women in such environments may use both physiological and behavioral adaptations to conserve fluid requirements, such as reducing activities during breastfeeding and carrying extra fluid supplies while travelling. Given the limited state of knowledge on lactation and hydration, future field studies should incorporate research to determine the importance of adequate fluids in maintaining milk production and the health of both mothers and infants. Am. J. Hum. Biol. 10:151-161, 1998. © 1998 Wiley-Liss, Inc.

Thirst induced by a suckling episode during breast feeding and relation with plasma vasopressin, oxytocin and osmoregulation

OBJECTIVE

There have been anecdotal reports of increased maternal thirst during breast feeding, but the physiological mechanisms remain obscure. We have assessed and quantified the stimulation of maternal thirst during breast feeding (suckling), and correlated the changes with plasma oxytocin and vasopressin levels.

DESIGN

A within subject design was used with each subject acting as her own control. Each subject participated in a suckling period and a control non-suckling period the order of which was counterbalanced.

SUBJECTS

Ten healthy breastfeeding women ranging from 28 to 52 days post partum.

MEASUREMENTS

Thirst (assessed by a visual analogue scale), plasma vasopressin, plasma oxytocin (pOT), plasma osmolality and haematocrit, blood pressure, volume of milk transferred to baby, volume of water drunk immediately following each experimental period.

RESULTS

Thirst increased significantly more over a suckling period than over a comparable control period (P = 0.013). The peak level of thirst correlated with the volume of water consumed to satiety following the suckling period (r = 0.7, P = 0.024). As expected, pOT levels rose significantly in response to suckling (P < 0.001). Six women demonstrated a close relation between thirst and oxytocin response during the suckling period. Despite significant changes in thirst during suckling there was no increase in plasma vasopressin or in osmoregulatory parameters.

CONCLUSIONS

This study confirms that suckling is a potent stimulus to thirst in the mother, and is not associated with vasopressin release or dependent on any measurable alterations in osmoregulation. What actually stimulates thirst during breast feeding remains unknown, but there are two potential explanations for these observations: (1) suckling sends nerve impulses to the paraventricular and supraoptic nuclei in the hypothalamus which may have afferents within the central nervous system which stimulates a thirst response simultaneous with oxytocin release; (ii) a learned anticipation of thirst may be occurring in a situation associated with expectant fluid loss to preserve homeostasis.

Intake of tapwater and total water by pregnant and lactating women

BACKGROUND

Despite theoretically higher requirements for water due to physiologic demands of pregnancy and lactation, little is known of actual ranges of intake in pregnant and lactating women.

METHODS

Population-based estimates of total water and tapwater intake in women of reproductive age were derived using data from the 1977-78 USDA Nationwide Food Consumption Survey. Three-day average intakes were calculated for 188 pregnant women, 77 lactating women, and 6,201 non-pregnant, non-lactating control women.

RESULTS

Total water intake (mean +/- SD) was 1,940 +/- 686 g/day (median 1,835) for control women, 2,076 +/- 743 g/day (median 1,928) for pregnant women and 2,242 +/- 658 g/day (median 2,164) for lactating women. Tapwater intake was 1,157 +/- 635 g/day (median 1,065) for control women, 1,189 +/- 699 g/day (median 1,063) for pregnant women, and 1,310 +/- 591 g/day (median 1,330) for lactating women. Total water intake was equal to or greater than 3,000 g/day among 7 percent of control women, 11 percent of pregnant women, and 13 percent of lactating women. Tapwater intake was equal to or greater than 2,000 g/day among 10 percent of control women, 15 percent of pregnant women, and 8 percent of lactating women.

CONCLUSIONS

These results should be useful in estimating amounts of nutrients and toxic substances that women of reproductive age obtain through the water supply.