Breast feeding and fluid intake in a hot climate

A systematic review of hot weather impacts on infant feeding practices in low-and middle-income countries

BACKGROUND

Increased rates of exclusive breastfeeding could significantly improve infant survival in low- and middle-income countries. There is a concern that increased hot weather due to climate change may increase rates of supplemental feeding due to infants requiring fluids, or the perception that infants are dehydrated.

OBJECTIVE

To understand how hot weather conditions may impact infant feeding practices by identifying and appraising evidence that exclusively breastfed infants can maintain hydration levels under hot weather conditions, and by examining available literature on infant feeding practices in hot weather.

METHODS

Systematic review of published studies that met inclusion criteria in MEDLINE, EMBASE, Global Health and Web of Science databases. The quality of included studies was appraised against predetermined criteria and relevant data extracted to produce a narrative synthesis of results.

RESULTS

Eighteen studies were identified. There is no evidence among studies of infant hydration that infants under the age of 6months require supplementary food or fluids in hot weather conditions. In some settings, healthcare providers and relatives continue to advise water supplementation in hot weather or during the warm seasons. Cultural practices, socio-economic status, and other locally specific factors also affect infant feeding practices and may be affected by weather and seasonal changes themselves.

CONCLUSION

Interventions to discourage water/other fluid supplementation in breastfeeding infants below 6 months are needed, especially in low-middle income countries. Families and healthcare providers should be advised that exclusive breastfeeding (EBF) is recommended even in hot conditions.

24-h hydration status: parameters, epidemiology and recommendations

Hydration of individuals and groups is characterised by comparing actual urine osmolality (Uosm) with maximum Uosm. Data of actual, maximum and minimum Uosm in infants, children and adults and its major influencing factors are reviewed. There are remarkable ontogenetic, individual and cultural differences in Uosm. In the foetus and the breast-fed infant Uosm is much lower than plasma osmolality, whereas in children and adults it is usually much higher. Individuals and groups may show long-term differences in Uosm. In industrialised countries, the gender difference of Uosm is common. There are large intercultural differences of mean 24-h Uosm ranging from 860 mosm/kg in Germany, 649 mosm/kg in USA to 392 mosm/kg in Poland. A new physiologically based concept called 'free-water reserve' quantifies differences in 24-h euhydration. In 189 boys of the DONALD Study aged 4.0-6.9 y, median urine volume was 497 ml/24-h and median Uosm 809 mosm/kg. Considering mean-2 s.d. of actual maximum 24-h Uosm of 830 mosm/kg as upper level of euhydration and physiological criterion of adequate hydration in these boys, median free-water reserve was 11 ml/24-h. Based on median total water intake of 1310 ml/24-h and the third percentile of free-water volume of -156 ml/24-h, adequate total water intake was 1466 ml/24-h or 1.01 ml/kcal. Data of Uosm in 24-h urine samples and corresponding free-water reserve values of homogeneous groups of healthy subjects from all over the world might be useful parameters in epidemiology to investigate the health effects of different levels of 24-h euhydration.

Sociocultural factors and the promotion of exclusive breastfeeding in rural Yoruba communities of Osun State, Nigeria

Child survival strategies include prolonged and intensive breastfeeding, together with its early initiation, and breastmilk only for the first six months of life. This paper reports on local knowledge and attitudes of breastfeeding and the sociocultural factors that shape its practice in poor rural Yoruba communities of Southwestern Nigeria. The study has conducted 10 focus group discussions among homogeneous groups of grandmothers, pregnant women, lactating mothers, husbands, and community health workers, and a questionnaire survey of 256 third trimester pregnant women. All women in these communities breastfeed their infants on demand, and for up to two years, because breastmilk is universally accepted as the best food for babies, and breastfeeding spaces births. Prelacteal feedings of water herbal infusions and ritual fluids are the norm, and breastmilk is supplemented, from birth, with water and teas. Exclusive breastfeeding is considered dangerous to the infant: the baby has an obligatory requirement for supplementary water to quench its thirst and promote its normal development, and for herbal teas which serve as food and medicine. Colostrum is discarded because it is dirty, "like pus", and therefore potentially harmful to the infant, although 24% of the survey sample would give it to their babies. Expressed breastmilk is suspect as it can get contaminated, poisoned or bewitched. Complementary foods are introduced as early as two months because of perceived lactation insufficiency. The commonest supplement is a watery maize porridge of low nutrient density. Breastfeeding can also be dangerous, as toxins and contaminants can be passed to the infant through breastmilk. The most serious conflict with the WHO/UNICEF recommendations is the lack of local credibility of exclusive breastfeeding. According to local knowledge, the early introduction of water, herbal teas, and of complementary foods is designed to enhance child survival, while these are supposed to do the exact opposite by the WHO/UNICEF rationale, by exposing the infant to contaminants early, thereby increasing diarrheal morbidity and mortality. Child survival interventions need to address this conflict.

Weaning recommendations: the scientific basis

Current weaning recommendations are based on nutritional need, physiologic maturation, and the behavioral and developmental aspects of infant feeding. Inadequate energy and protein intake and deficiencies of iron, zinc, vitamin A, and vitamin D are the most commonly observed nutrient deficiencies during infancy and weaning recommendations have focused on their prevention. This article reviews the data and summarizes implications for infant weaning in both developed and developing countries. Current published recommendations for infant feeding are outlined and major concerns are highlighted.

Water supplementation in exclusively breastfed infants during summer in the tropics

This study was designed to determine the need for water supplementation to maintain water homoeostasis in exclusively breastfed infants during summer in a tropical country. A prestudy questionnaire revealed that 97% of 34 nurses and 63% of 70 doctors advocated such supplementation. 45 healthy, male, exclusively breastfed babies, aged 1-4 months, were recruited from a well-baby clinic. 9 who had never received supplemental water plus a random selection of 14 others were allocated to group I (breastmilk only); the remaining 22 infants were allocated to group II (breastmilk plus supplemental fluid according to the mother's usual practice). The babies were studied at the hospital for 8 h; breastmilk intake was measured by weighing the infant before and after each feed, water intake by calibrated bottles, and urine output by accurate collection and measurement. The maximum room temperatures were 34-41 degrees C and relative humidities 9-60% (below 50% in all but 3 infants). In group II the mean water intake was 11% (95% confidence interval 7-16%) of the total fluid intake. Both breastmilk intake (274 vs 210 ml) and total fluid intake (274 vs 233 ml) were higher in group I than in group II (p = 0.003, p = 0.073, respectively), after adjustment for age, weight, length, room temperature, and humidity. However, there were no significant differences between the groups in urine output, urine or serum osmolality, weight change, or rectal temperature whether or not the factors adjusted for included total fluid intake. Thus, exclusively breastfed infants do not need supplemental water to maintain water homoeostasis; a reduced breastmilk intake is a potential disadvantage of this practice.

Cereal-based oral rehydration therapy. II. Strategic issues for its implementation in national diarrheal disease control programs

Field studies in Bangladesh demonstrated that after proper training, village mothers were able to prepare and use rice-based, salt-enriched oral rehydration solutions containing safe concentrations of sodium, and were capable of achieving significantly fewer treatment failures and a reduction in the duration of diarrhea than with glucose-based oral rehydration solutions (ORS). An additional longitudinal study showed that improved growth and weight gain occurred with the consistent use of ORS; the effect was greater when rice-based ORS were used. In addition, the following possible limitations and benefits of cereal-based oral rehydration therapy, which are relevant to the strategies for its implementation in national diarrheal disease control programs, are discussed: safety, osmolarity, hypernatremia, spoiling, effectiveness, rehydration ability, reduction in diarrhea volume and duration, nutritional effects, effect on food intake, acceptance and usage by care givers, training of health workers, self-reliance of families, effect on other child survival activities, costs, potential problems in changing to cereal-based ORS, and the role of industrial production in packaged cereal-based ORS.

Do ambient temperature and humidity influence the breast-milk intake of babies?

This study explored the possible effect of ambient temperature and humidity on the breast-milk intakes of Australian infants (n = 35) aged 6-12 weeks. Over a 24 h period, each baby was fed only on milk from the breast; milk intakes, temperature and humidity were monitored. Milk intakes--determined by test-weighing the baby, with a correction for evaporative losses during feeds--showed a mean of 830 g/24 h, with median 818 and s.d. 152. The mean correction for evaporative losses was 46 g/24 h; omission of this correction would have led to an average underestimate of 5.5% in 24 h intakes. Ambient conditions varied substantially between subjects: 24 h mean temperatures ranged from 14 to 28 degrees C, and humidities from 48 to 97%. Over these ranges, breast-milk intakes did not appear to be significantly influenced by ambient temperature or ambient humidity; however, the rate of evaporative losses increased by 0.008 g/min for each 1 degree C rise in ambient temperature.

No need for water supplementation for exclusively breast-fed infants under hot and arid conditions

This study was conducted in 4 villages in India during the hottest and driest season of the year to determine whether exclusively breast-fed infants need additional water under extremely hot and dry climatic conditions. The ambient temperature was 35-40 degrees C and the relative humidity 10-35%, except during the early morning hours. 63 urine samples were collected from 31 infants below 6 months of age and 28 samples from 13 infants aged 6-10 months, all of whom were receiving nothing but breast milk. Specific gravity (and corresponding osmolality) of urine samples from the younger group ranged from 1.004 (66 mosmol/litre) to 1.036 (1234 mosmol/litre), with a mean of 1.011 (322 mosmol/litre). For the older group the range was 1.005 (103 mosmol/litre) to 1.029 (978 mosmol/litre) and the mean was 1.015 (468 mosmol/litre). These values are well below levels of urine concentrations known to be attainable by infants of corresponding ages. Thus, even under hotter and drier climatic conditions than have previously been studied, healthy exclusively breast-fed infants do not require additional water. Exclusive breast feeding for the first 4-6 months is therefore a reasonable public health recommendation; it is imperative in areas where contaminated drinking water may contribute to infant morbidity, diarrhoeal disease in particular.

Relative density of urine: methods and clinical significance

The physical properties and chemical composition of urine are highly variable and are determined in large measure by the quantity and the type of food consumed. The specific gravity is the ratio of the density to that of water, and it is dependent on the number and weight of solute particles and on the temperature of the sample. The weight of solute particles is constituted mainly of urea (73%), chloride (5.4%), sodium (5.1%), potassium (2.4%), phosphate (2.0%), uric acid (1.7%), and sulfate (1.3%). Nevertheless, urine osmolality depends only on the number of solute particles. The renal production of maximally concentrated urine and formation of dilute urine may be reduced to two basic elements: (1) generation and maintenance of a renal medullary solute concentration hypertonic to plasma and (2) a mechanism for osmotic equilibration between the inner medulla and the collecting duct fluid. The interaction of the renal medullary countercurrent system, circulating levels of antidiuretic hormone, and thirst regulates water metabolism. Renin, aldosterone, prostaglandins, and kinins also play a role. Clinical estimation of the concentrating and diluting capacity can be performed by relatively simple provocative tests. However, urinary specific gravity after taking no fluids for 12 h overnight should be 1.025 or more, so that the second urine in the morning is a useful sample for screening purposes. Many preservation procedures affect specific gravity measurements. The concentration of solids (or water) in urine can be measured by weighing, hydrometer, refractometry, surface tension, osmolality, a reagent strip, or oscillations of a capillary tube. These measurements are interrelated, not identical. Urinary density measurement is useful to assess the disorders of water balance and to discriminate between prerenal azotemia and acute tubular necrosis. The water balance regulates the serum sodium concentration, therefore disorders are revealed by hypo- and hypernatremia. The disturbances are due to renal and nonrenal diseases, mainly liver, cardiovascular, intestinal, endocrine, and iatrogenic. Fluid management is an important topic of intensive care medicine. Moreover, the usefulness of specific gravity measurement of urine lies in interpreting other findings of urinalysis, both chemical and microscopical.

Milk consumption and hydration status of exclusively breast-fed infants in a warm climate

To assess the hydration status of 40 exclusively breast-fed Peruvian infants, their milk intake and urinary volume and concentration were measured during 8-hour daytime observations. Maximum home temperatures ranged between 26 degrees and 33 degrees C; environmental relative humidity ranged between 49% and 96%. The infants consumed between 105 and 528 gm milk during the observation period; the standardized intakes ranged between 4.0 and 12.1 gm/kg body weight per hour (mean +/- SD 7.5 +/- 1.7 gm). The infants voided between 0.9 and 6.3 ml urine per kilogram of body weight per hour (mean +/- SD 3.4 +/- 1.3 ml). The maximum urinary specific gravity in each infant ranged between 1.003 and 1.017. We conclude that healthy infants can maintain adequate hydration status while exclusively breast-fed under these environmental conditions.

Supplementary water for breast-fed babies in a hot and dry climate--not really a necessity

Urine osmolarity under hot and dry climatic conditions remains within the expected physiological ranges and thus shows that supplementary water for breast-fed infants is not necessary.