Hormones and growth factors in milk.

Research dealing with hormones/growth factors in milk has progressed rapidly during the last 10 yr from their identification in milk to their regulation of various functions in the maternal organism and in the neonate. Many hormones, growth factors, and bioactive substances present in the maternal organism are present in colostrum and milk, often exceeding concentrations that occur in maternal plasma. Some appear in milk in different, sometimes multiple, forms from that found in maternal serum, reflecting to some extent synthesis and posttranslational processing by mammary tissue. Recent research has indicated that many milk hormones/growth factors survive the environment of the gut of the neonate, become absorbed into the neonatal circulation, and exert important functions in the neonate.

Bioactive and immunoreactive prolactin variants in human milk.

Human milk from mothers of term (T) and preterm (PT) infants was collected during early (days 2-7), mature (2-16 weeks), or late (> 16 weeks) lactation. PRL-like bioactivity (B) was measured by Nb2 cell proliferation, and PRL immunoreactivity (I) was determined by RIA. PRL activity is reported in PRL equivalents (1 PRL equivalent = 1 ng NIDDK reference material). Milk from early lactation contained significantly greater PRL-like B compared to I (T:B, 132.5 +/- 13.0; I, 83.43 +/- 12; PT:B, 195.8 +/- 56; I, 74.45 +/- 13.7). PRL-like B and I declined as lactation progressed (T mature: B, 41.74 +/- 8.9; I, 27.19 +/- 5.5; T late: B, 17.84 +/- 5.5; I, 27.33 +/- 1.8; PT mature: B, 59.85 +/- 16; I, 45.16 +/- 4.3). Milk PRL B to I ratios were consistently greater than serum B to I ratios during early lactation (milk: T, 1.4 +/- 0.3; PT, 3.6 +/- 1.3; serum: T, 1.0 +/- 0.2; PT, 0.58 +/- 0.12). During early lactation, high PRL-like B was widely distributed among several (n = 4-6) bioactive forms differing in molecular mass [8 to > 66 kilodaltons (kDa)] in T milk, but the majority of B in PT milk was detected in two or three forms. During mature and late lactation, lower PRL-like B was associated with two or three peaks (20 to > 66 kDa). A large fraction of PRL-like B (67%-84%) was associated with the phosphorylated (P-) fraction of human milk. Four immunoreactive forms (24, 30, 32, and 40 kDa) of P-PRL were identified by immunoblot analyses. Alkaline phosphatase treatment converted the 40-kDa immunoreactive P-PRL to 24-kDa PRL, increased the B of the P-fraction by 2-fold, but did not change total PRL I detected. PRL in the Concanavalin-A-retained fraction accounted for 59-69% of PRL in milk based on RIA results. No PRL-like B was detected in the Concanavalin-A-retained fraction of human milk; however, treatment of the glycosylated fraction of milk with peptide-N-glycosidase F increased thymidine incorporation by Nb2 cells 1.67-fold compared to that in controls. The results of this study show that human milk contains considerably greater PRL-like activity than previous reports based on RIA detection. The appearance and regulation of multiple bioactive PRL variants in milk throughout the course of lactation may serve as a mechanism by which milk PRL influences neonatal development.

Influence of maternal selenium status on human milk selenium concentration and glutathione peroxidase activity.

This study assessed whether relationships existed between maternal indices of selenium (Se) nutrition and milk content of Se and activity of glutathione peroxidase (GSH-Px). Samples of milk (n = 72) collected at 4, 8, 12, and 16 wk postpartum and blood from lactating (n = 10) and control (n = 8) women were analyzed. Plasma and erythrocyte Se concentrations and plasma GSH-Px activity were significantly lower in lactating than in control women. Maternal plasma Se concentration was positively correlated with plasma GSH-Px activity (r = 0.53, p less than 0.01) and with milk Se content (r = 0.61, p less than 0.01) and GSH-Px activity (r = 0.51, p less than 0.01). Stage of lactation did not influence either milk or blood values. Milk Se concentration was positively correlated with milk GSH-Px activity (r = 0.81, p less than 0.001). Results indicate that human milk Se content and GSH-Px activity are directly influenced by maternal Se nutrition.

Maternal folate status during extended lactation and the effect of supplemental folic acid.

BACKGROUND: Folate requirements during lactation are not well established. OBJECTIVE: We assessed the effects of dietary and supplemental folate intakes during extended lactation. DESIGN: Lactating women (n = 42) were enrolled in a double-blind, randomized, longitudinal supplementation trial and received either 0 or 1 mg folic acid/d. At 3 and 6 mo postpartum, maternal folate status was assessed by measuring erythrocyte, plasma, milk, and dietary folate concentrations; plasma homocysteine; and hematologic indexes. Infant anthropometric measures of growth, milk intake, and folate intake were also assessed. RESULTS: In supplemented women, values at 6 mo for erythrocyte and milk folate concentrations and for plasma homocysteine were not significantly different from those at 3 mo. In supplemented women compared with unsupplemented women at 6 mo, values for erythrocyte folate (840 compared with 667 nmol/L; P < 0.05), hemoglobin (140 compared with 134 g/L; P < 0.02), and hematocrit (0.41 compared with 0.39; P < 0.02) were higher and values for reticulocytes were lower. In unsupplemented women, milk folate declined from 224 to 187 nmol/L (99 to 82 ng/mL), whereas plasma homocysteine increased from 6.7 to 7.4 micromol/L. Dietary folate intake was not significantly different between groups (380+/-19 microg/d) and at 6 mo was correlated with plasma homocysteine in unsupplemented women (r = -0.53, P < 0.01) and with plasma folate in supplemented women (r = 0.49, P < 0.02). CONCLUSIONS: A dietary folate intake of approximately 380 microg/d may not be sufficient to prevent mobilization of maternal folate stores during lactation.

Copper, iron, and zinc contents of mature human milk.

Daily, weekly, and within-day variations in copper, iron, and zinc contents of human milk were investigated in order to determine whether one sample from an individual is representative of these elements. Total solids, fat, and protein contents were also measured. Fifty women in their 6th to 12th week of lactation each provided seven milk samples consisting of five consecutive daily samples and two additional samples collected either within a single day or at weekly intervals. Fat varied the most of all constituents and total milk solids reflected this variability. Values ranged from 0.2 to 10.4 g/100 ml for fat and from 8.58 to 17.49 g/100 ml for total solids. Protein varied from 0.76 to 2.04 g/100 ml among individuals, with little variation within an individual. Copper content varied considerably among women and within the same woman. With a large proportion of low values, the range was 0.09 to 0.63 mug/ml. Iron content was also found to vary within women as well as among women. Values ranged from less than 0.1 to 1.6 mug/ml with a preponderance of low values. Zinc content was more evenly distributed over the range of 0.14 to 3.95 mug/ml,and within an individual it did not vary widely. A representative estimate of copper and iron contents would therefore require multiple samples, whereas only one sample may provide a representative estimate of zinc content. Comparison of morning, midday, and evening values showed that copper and zinc are higher in the morning and iron is lower at this time. Increased amounts of copper, iron, and zinc were found in multiparous women whether or not they had previously lactated. Milk from older women had lower iron and higher copper and zinc contents than that from younger women. No differences were found in milk of women receiving dietary mineral and vitamin supplements. Calculations indicated that fully breast fed infants under 3 months of age receive approximately 0.35 mg/kg per day of zinc and 0.05 mg/kg per day of both copper and iron.

Distribution of selenium in human milk.

The present studies were designed to characterize selenium distribution in human milk. These studies reveal that most selenium in human milk is protein bound. Percentage dialyzable selenium varied proportionally with total selenium content of milk but not with stage of lactation. Neither rate of freezing nor frozen storage of samples for one month influenced distribution profiles. At least nine selenoproteins were detected in dialyzed milk samples following molecular sieve (Sephadex) chromatography. Glutathione peroxidase accounted for approximately 15-30% of selenium found in milk. Approximately half of peroxidase activity in human milk was associated with selenium dependent glutathione peroxidase activity.

Manganese intake and serum manganese concentration of human milk-fed and formula-fed infants.

Manganese (Mn) status was determined in 24 infants exclusively fed either human milk (n = 8) or formula (n = 16) from birth to 3 months. Mn intakes were estimated from test weighings , dietary records, and direct analyses of human milk and formula via graphite furnace atomic absorption spectrophotometry. Mean human milk Mn concentrations significantly decreased (p less than 0.05) with the progression of lactation, from 6.6 micrograms/L during the 1st month of lactation, to 3.5 micrograms/L by the 3rd month of lactation. Infant formulas were observed to contain considerably higher levels of Mn (70.0 to 1289.0 micrograms/L) than either human milk (means = 4.9 micrograms/L) or cows' milk (means 25.2 micrograms/L). At 3 months, human milk-fed infants consumed a smaller volume of milk (689.0 ml) than formula-fed infants (894.0 ml), and also received significantly less Mn (0.42 micrograms/kg/day) than formula-fed infants (183.22 micrograms/kg/day). Mean sera Mn concentrations of infants receiving human milk or formula were similar, with mean values of 4.4 and 4.7 micrograms/L, respectively. Manganese intakes of human milk-fed infants were found to be linearly correlated (r = 0.78) with the respective serum Mn concentration at 3 months of age.

Pteroylpolyglutamates in human milk.

Considerable variation exists in reported values for total folate content and the pteroylpolyglutamate (PteGlun) content of human milk. We investigated possible methodological sources of this variation. In two laboratories, milk folate content (with and without folate conjugase) was determined microbiologically. No differences in total milk folate or PteGlun (n greater than 3) content were found between laboratories. PteGlun was found to comprise a significant fraction of total milk folate (28%). Use of rennin did not alter total folate content nor the percent of PteGlun in human milk. Heating (121 degrees C for 5 min) increased folate concentrations (190%, P less than 0.0001), indicating that release of folate from binding protein is necessary for folate utilization by Lactobacillus casei. Although human milk folate conjugase, (FC) activity was approximately one-twentieth that of plasma FC activity, it was not sufficient to autolyze endogenous PteGlun. Thus, microbiological protocols that do not use folate conjugase and do not release folate from binding proteins will seriously underestimate milk folate values.

Selenium intakes and status of human milk and formula fed infants.

Selenium status was assessed in 28 infants receiving either human milk (n = 8) or a proprietary formula (n = 20) as their sole nutritional source from birth to 3 months. Infants' selenium intakes were determined from dietary records, "test weighings," and direct analysis of human milk and formula. Fore milk samples (n = 72) collected from group I mothers had a mean selenium concentration (ng/ml) of 16.3 +/- 4.9, whereas the selenium content of proprietary formula was 8.6 +/- 0.9. The selenium concentration of hind milk was significantly greater (p less than 0.05) than that of fore milk. At 3-months selenium intakes as well as serum selenium concentrations for human milk fed infants were significantly greater than those for formula fed infants. A significant positive correlation (r = 0.42; p less than 0.05) was found between infants' selenium intakes and their serum selenium concentrations. The results indicate that feeding practice directly affects selenium status during infancy.

Folate intake and blood concentrations of term infants.

Folate nutrition of 67 full-term infants was studied longitudinally from birth to 1 year. Infants were grouped according to type of milk consumed during early infancy: group I (n = 14) received human milk; group II (n = 31), a standard cow-milk infant formula; and group III (n = 22), the same formula with added iron (12.3 mg/L). Solid foods were introduced after 3 months. Folate status, as indicated by serum and red blood cell folate concentrations, and folate intake were measured periodically. Blood folate concentrations of all groups were higher than or similar to adult control values. No differences in indices of folate status were observed between formula-fed groups at any time frame. At 6 weeks and 3 months formula-fed infants had folate intakes and blood concentrations significantly greater than human milk-fed infants. With the introduction of solid foods, decreases in blood folate concentrations paralleled decreases in milk folate intake within each group. Serum folate concentrations correlated with both total folate intake and milk folate intake, whereas RBC folate concentrations correlated with only milk folate intake. The results indicate that milk, regardless of type (human milk, formula, and cow milk), is an important dietary source of folate during the first year of life and that both human milk and proprietary formula feeding during early infancy provide more than sufficient folate to maintain blood folate concentrations well above acceptable limits.

Milk selenium of rural African women: influence of maternal nutrition, parity, and length of lactation.

The selenium content of milk samples from rural Gambian women (n = 55) was evaluated as a function of parity, stage of lactation, and maternal nutrition. Samples were collected during periods of relative food abundance (dry season) and food scarcity (rainy season). Milk selenium was lower (p less than 0.01) in the rainy than in the dry season (208 vs 256 nmol/L, respectively). Milk selenium was similar in samples from women in early (1-6 mo postpartum) and late (13-19 mo postpartum) lactation. During late lactation, parity, which ranged from 1 to 11, was negatively correlated with milk selenium regardless of plane of maternal nutrition (p less than 0.02). Measures of protein, glutathione peroxidase, and total peroxidase were not affected by stage of lactation or parity. Glutathione peroxidase activity accounted for 38% of the peroxidase activity in milk. Results show that although length of lactation alone had little impact, milk selenium secretion was influenced by both maternal nutritional adequacy and parity of rural Gambian women.

Selenium status of infants is influenced by supplementation of formula or maternal diets.

Plasma selenium of infants fed proprietary formula was significantly less than that in infants fed human milk. Addition of selenite to the formula (0.253 mumol Se/L) increased plasma selenium and activities of glutathione peroxidase (GPx) and total peroxidase (Px). However, erythrocyte selenium decreased significantly during the 12-wk study in infants receiving human milk or formula with or without supplemental selenite. Infants fed human milk from women receiving 0 or 200 micrograms supplemental selenium as selenomethionine or selenium-enriched yeast had plasma selenium that paralleled changes in their selenium intake. Plasma GPx and Px activities were unrelated to human milk selenium intake. Milk from women given either selenium supplement prevented the decline in infant erythrocyte selenium. Results of these studies suggest that the method of feeding modifies the infant's apparent selenium status and that the molecular form of selenium provided and/or its interaction with other milk constituents are determinants of infant selenium status.

Selenium status of lactating women is affected by the form of selenium consumed.

The impact of providing selenomethionine (2.7 mumol Se) or selenium-enriched yeast (2.9 mumol Se) on the selenium status of lactating and nonlactating women with customary intakes of approximately 1.3 mumol Se/d was studied. Plasma selenium declined in unsupplemented lactating women but not in nonlactating women. Selenomethionine increased plasma selenium in both lactating and nonlactating women whereas selenium-enriched yeast increased plasma selenium only in nonlactating women. Erythrocyte selenium concentration was not significantly modified by lactation. Plasma glutathione peroxidase (GPx) activity decreased with duration of lactation in unsupplemented women and selenomethionine or selenium-enriched yeast supplementation prevented the decline. Milk selenium declined markedly for 20 wk after parturition in unsupplemented women. Selenomethionine significantly increased milk selenium concentrations whereas selenium-enriched yeast prevented a decline. These results clearly show that the source of selenium provided to lactating women can significantly influence selected indexes of selenium status, including milk selenium concentration.

Dietary protein source and plasma lipid profiles of infants.

Total cholesterol and triglyceride concentrations were measured in plasma samples taken at 4 and 8 weeks of age from 40 full-term infants who had been fed either human milk or one of three formulas containing casein-to-whey ratios of 82:18, 66:34, or 50:50 to investigate whether dietary protein influenced the development of plasma lipid profiles. Infants fed the formula with the casein-to-whey ratio of 82:18 had significantly higher plasma cholesterol levels at both 4 and 8 weeks of age compared with other groups of infants (P less than .05). Infants fed the high-casein formula also showed an increase in plasma cholesterol levels with time (P less than .001). Plasma triglyceride concentrations decreased as concentration of casein decreased (P less than .05) among the formula-fed groups and increased with time. Infants fed human milk had plasma triglyceride concentrations similar to those infants who had been fed the 82:18 formula at 4 weeks of age; however, triglyceride concentrations eventually fell and were similar to those concentrations in infants who had been fed the 50:50 formula at 8 weeks of age. Results indicate that constituent lipids of human milk or formulas were not determining factors for changes observed in plasma cholesterol levels and triglyceride concentrations among groups. Since formulas differed only in proteins and their constituent amino acids, further investigation of the impact of dietary protein (amino acids) on development of blood lipid profiles in infants is warranted.

Indices of protein metabolism in term infants fed human milk, whey-predominant formula, or cow's milk formula.

Relationships between intakes of amino acids and total nitrogen, and blood indices of protein utilization were studied in 37 term infants fed either human milk, whey-predominant formula, or cow's milk formula as the sole nutritional source for 8 weeks. Biochemical analyses of two-hour fasting blood samples, and intakes calculated using three-day dietary records and direct analyses of milk samples were used to evaluate these relationships. Intakes of total nitrogen were positively correlated with plasma valine, leucine, isoleucine, phenylalanine, and serum urea nitrogen concentrations (r = .46 to .62, P less than .01 to .001). Intakes of the four amino acids whose plasma concentrations were positively correlated with total nitrogen intakes plus four additional amino acids (threonine, tyrosine, histidine, and methionine) were correlated with their respective plasma concentrations (r = .41 to .74, P less than .01 to .001). These relationships have not been previously described in term infants. Compared with values in infants fed human milk, plasma concentrations of valine, phenylalanine, methionine, and serum urea nitrogen were elevated with whey-predominant formula and cow's milk formula feeding. Values for four additional amino acids (threonine, lysine, leucine, and isoleucine) were elevated with whey-predominant formula feeding. Data indicate that altering the whey-to-casein ratio and, thus, the amino acid pattern of formulas will not achieve the desired blood indices characteristic of human milk feeding without a reduction in the total nitrogen content of formulas.

Nutritional guidance is needed during dietary transition in early childhood.

OBJECTIVE: To assess dietary nutritional quality during dietary transition to a modified adult-style diet in the second year of life. DESIGN: A total of 55 children from 12 to 18 months old and their parents were studied. Dietary intake and indices of growth were measured monthly. Dietary data were collected monthly and tabulated using the Minnesota Nutrient Data System. Data were evaluated using repeated-measures analysis of variance, time trend, and correlational analyses. RESULTS: Mean energy intake increased from 12 to 18 months of age (926+/-24 kcal to 1062+/-33 kcal) with contributions from energy-yielding macronutrients remaining relatively constant. Throughout the study, fat intakes were below 30% of energy for 22% to 33% of the sample. Micronutrient intake patterns were diverse with intake for some nutrients (vitamins A, C, B(6), B(12), and D and calcium) remaining above recommended levels despite changes over the course of the study. Folate intakes increased from 79% of the recommended value at 12 months old to approximately 100% at 18 months old. Zinc and vitamin E intakes were well below recommended levels throughout the study, and iron decreased markedly from 96% of the recommended level at 12 months old to 76% at 18 months old. APPLICATIONS/CONCLUSIONS: These data show that intakes of some key nutrients are low during the period of dietary transition in early childhood, and intakes for some nutrients actually decrease despite increases in energy intake. Furthermore, because a considerable portion of children studied were consuming low-fat diets, it is clear that many parents are not following the only pediatric nutrition recommendations that currently exist. These findings argue strongly for the development of dietary guidance that not only addresses fat restriction, but also assists parents in selecting diets that support optimum growth and development in young children.nutrient intake, infants, dietary density.

Feeding and growth characteristics of human milk-fed infants.

Anthropometric measurements, milk intake, and nursing frequency data of 50 exclusively breast-fed infants were analyzed to determine the existence, extent, and nature of relationships among nursing frequency, quantity of milk consumed, and growth characteristics. In comparison with the National Center for Health Statistics growth standards, anthropometric measures for all infants fell within the 10th and 95th standard percentiles for the following growth parameters: Mean lengths ranged from 54 +/- 2.5 cm at 2 weeks to 64 +/- 1.6 cm at 16 weeks; mean weights ranged from 3,735 +/- 526 gm to 6,326 +/- 633 gm; mean head circumferences ranged from 36 +/- 1.2 cm to 41 +/- 1.0 cm. Significant associations were observed for milk intake with weight and length measures. Strength of association, however, was highly variable across age categories, ranging from 0.32 to 0.71 for weight and 0.16 to 0.70 for length. The coefficients indicate that 10% to 50% of the total variance in weight and 3% to 49% of total variance in length could be ascribable to milk intake. Average milk intakes were significantly correlated with infant length and weight at 2, 6, and 12 weeks. Average frequency of nursing was positively associated with infant weight at 12 weeks. Increases in average milk intakes between 2 and 4 weeks were significantly related to increases in length for the same period. Likewise, an increase in average milk intake between 8 and 12 weeks was associated with a corresponding change in mean length.(ABSTRACT TRUNCATED AT 250 WORDS)

Infant feeding practices.

Nutrient intakes of thirty-nine infants were determined by a combination dietary record/recall method at two, four, eight, and twelve weeks of age. Infants were grouped according to feeding method: Formula only formula plus solid foods, human milk only, and human milk plus solid foods. The contribution of various types of solid foods and milk to total energy and nutrient intakes within each feeding regimen was determined. The effect of feeding regimen upon renal concentrating capacity was assessed by determining plasma osmolality, sodium, and urea in blood samples drawn at four and eight weeks of age. Results indicate that milk was the major source of energy and of ten of the thirteen nutrients tabulated at all ages examined. Data also suggest that solid foods replace, rather than supplement, human milk or formula on a caloric basis. The feeding methods examined did not influence plasma osmolality and sodium levels, despite significant differences in dietary renal solute load observed between breast-fed and formula-fed infants. Plasma urea levels were positively correlated with protein intakes at eight weeks of age. Implications of the data for counseling parents are discussed.

PIP: An investigation was undertaken in a university community in Illinois to obtain quantitative data on the types and amounts of food consumed by full-term infants under 3 months of age, to determine the partitioning of energy and nutrient intakes between human milk or formula and other foods, and to determine the effect of feeding method on dietary renal solute load and osmolality, sodium, and urea. The 22 male and 17 female apparently healthy and full-term infants were born between August 1, 1977 and April 15, 1978. The mean age of the 39 mothers was 24.1 years (range, 16-36 years). Infant food intakes were obtained using a combination dietary record/recall method. The mothers kept 3-day dietary records for their infants at ages 2, 4, 8, and 12 weeks. The infants were followed longitudinally and were classified according to the feeding method used at each age. Energy and nutrient intakes (except chloride from solid foods) were tabulated using a computer program based on data provided by infant food manufacturers. 26 of the infants were formula fed; 13 were breast fed. By the age of 8 weeks, 83% of the formula fed infants were receiving solid foods, compared to 31% of the breast fed infants. Infant cereal (rice and oatmeal) was the type of solid food most often introduced first. Strained fruits were offered next most often as a 1st food. Vegetables and vegetable-meat combination dinners were not offered to infants in this investigation as the 1st solid foods. Milk was the major source of energy, protein, carbohydrate, fat, calcium, sodium, chloride, potassium, thiamin, riboflavin and pyridoxine for infants receiving formula only, formula plus solid foods, breast milk only, and breast milk plus solid foods. Solid foods and/or nutritional supplements provided significant amounts of iron, vitamin A, and ascorbic acid. Supplemental foods had the greatest impact on nutrient intakes of breast fed infants. Addition of solid foods and formula to diets of breast fed infants resulted in higher protein, sodium, and iron intakes and increased their dietary renal solute so that it was similar to that of the formula fed infants. The feeding regimens failed to influence plasma osmolality and sodium, despite the significantly higher renal solute load imposed by the diets of formula fed infants compared to totally breast fed infants at 4 and 8 weeks. Plasma urea levels reflected dietary protein at age 8 weeks. Most of the sodium ingested by the formula fed infants was provided by formula. The study findings support delaying solid foods until 5-6 months of age.

Breast-feeding through the first year predicts maternal control in feeding and subsequent toddler energy intakes.

OBJECTIVE: Current recommendations for infant feeding encourage breast-feeding through the first year. This research was conducted to evaluate associations among breast-feeding, maternal control of child feeding, and the dietary intake of toddlers during the second year of life. In particular, we sought to determine whether breast-feeding through the first year and subsequent toddler intake was mediated via maternal control of child feeding. DESIGN/SUBJECTS: Fifty-five white infants and their mothers were monitored longitudinally from age 12 or 13 months to age 18 months. MAIN OUTCOME MEASURES: Breast-feeding through the first year and maternal control in infant feeding were evaluated as predictors of energy intake at age 18 months. STATISTICAL ANALYSES PERFORMED: Regression analysis was used to evaluate predictors of toddler energy intake at age 18 months. A mediation model tested if the relationship between breast-feeding and infant intake was mediated by maternal control in feeding. RESULTS: Breast-feeding through the first year was associated with higher toddler energy intakes at age 18 months through its influence on maternal control in feeding. Mothers who breast-fed their infants for at least 12 months used lower levels of control in feeding. Lower levels of maternal control in feeding were associated with higher toddler energy intakes. The highest energy intakes among children aged 18 months were observed among taller and leaner toddlers. APPLICATIONS/CONCLUSIONS: Our findings suggest that breast-feeding through the first year may have an effect on children's energy intake by shaping mothers' child-feeding practices. These findings may be used by clinicians to assist parents in making informed decisions about choice of infant-feeding method and to provide anticipatory guidance regarding infant-feeding style when initiating dietary diversity.

Self-selected diets of lactating women often fail to meet dietary recommendations.

OBJECTIVE: To assess longitudinally nutrient intakes of lactating women during the postpartum period. DESIGN: Dietary data from lactating women were collected by means of 2-day food records at 3 and 6 months postpartum. Intake of energy and selected nutrients was tabulated and compared with dietary standards. SUBJECTS: The 52 lactating women enrolled in the study lived in a university community, were apparently healthy, had a body mass index within normal range, were successfully nursing a term infant, and planned to nurse for at least 6 months. STATISTICAL ANALYSES PERFORMED: Paired t tests and Stuart-Maxwell chi(2) analyses. RESULTS: Mean energy intakes were below the Recommended Dietary Allowance. Mean intakes of most nutrients met or exceeded recommended standards except for zinc and vitamins D and E at both 3 and 6 months postpartum. Calcium and folate intakes were also below standards at 6 months. Although mean iron intake exceeded the standard at both measurement times, there was a significant decline from 3 to 6 months. Relative frequencies of mothers meeting various percentages of standards differed significantly from 3 to 6 months for calcium; iron; folate; and vitamins E, D, and B-6. At 6 months, significant increases were noted in the number of women reporting calcium, folate, and vitamin B-6 intakes at less than one half of the recommended amounts. APPLICATIONS/CONCLUSIONS: Guidance for lactating women should stress food sources of nutrients likely to be limited in their diets: calcium; zinc; folate; and vitamins E, D, and B-6.