A comparison of intakes of breast-fed and bottle-fed infants during the first two days of life.

OBJECTIVE: In the first days of life, breast-fed infants consume minimal amounts of milk; this may be explained by substrate limitation (limited milk output) and/or by self-limitation (through low appetite and/or suck-swallow competency). The spontaneous milk intake of unrestricted formula-fed infants has not been studied to date. We compared the spontaneous formula intake of unrestricted formula-fed infants to that of breast-fed infants over the first 48 hours of life. We hypothesized that 1) spontaneous formula intake of unrestricted infants is much higher than that of breast-fed infants and 2) spontaneous formula intake correlates positively with gestational age or birthweight. METHODS: We studied 43 healthy, term infants. By maternal choice, 15 infants were exclusively breast-fed and 28 were formula-fed ad libitum every four hours. Breast-fed infants were weighed before and one hour after initiation of feeding, and intake was calculated from the difference between the measurements and corrected individually for the infant's normal postnatal decrease in body weight. Bottles offered to formula-fed infants contained 60 cc, and the remainder was carefully measured. Intakes were expressed as cc/kg/d, and weight changes as % of birthweight. Statistical methods included Student's t tests and stepwise regression analysis. RESULTS: Breast feeding on Day I was 9.6 +/- 10.3 (mean +/- SD) vs. 18.5 +/- 9.6 cc/kg/d in formula-fed infants (p=0.011); on Day 2 it was 13.0 +/- 11.3 vs. 42.2 +/- 14.2 cc/kg/d (p<0.001). Breast-fed infants lost significantly more weight on Day 2 (p=0.015). In multiple regression, when the dependent variable was the second-day intake, the significant independent variables were group (higher intake in the formula-fed group), weight loss (the higher the weight loss, the lower the intake), and first-day intake (the higher the first-day intake, the higher the second-day intake). CONCLUSION: Newborn infants offered formula ad libitum every four hours consumed much larger amounts than breast-fed infants fed according to the same schedule. In addition, weight loss was more marked in breast-fed infants on Day 2 of life.     

Breast milk provides better antioxidant power than does formula

OBJECTIVE: We examined the effect of breast milk on plasma total antioxidant capacity (TAC), total peroxide (TP), and oxidative stress index (OSI), which are biomarkers of oxidative status. METHODS: Fifty-four healthy term infants 3 to 6 mo of age were fed breast milk or a cow's milk modified formula. Plasma TAC, vitamin C, albumin, bilirubin, and uric acid levels were measured as indexes of antioxidative markers. Plasma TP levels were measured as an oxidative stress marker. The OSI was calculated to assess oxidative status. RESULTS: No significant differences were observed between groups with respect to growth or anthropometric measurements. Plasma uric acid, total protein, and albumin concentrations were slightly higher in the breast-fed group than in the formula-fed group. There was a positive correlation between infant's age and serum albumin levels; between TAC and plasma uric acid, albumin, and total bilirubin; and between plasma iron and TP levels in both groups (r > 0.256, P < 0.05). In addition, there was a negative correlation between plasma iron and TAC (r = -0.267, P = 0.01). Plasma TAC and vitamin C levels were significantly higher in the breast-fed group than in the formula-fed group (P < 0.05). Plasma TP levels and the OSI were higher in the formula-fed group than those in the breast-fed group (P < 0.05). CONCLUSIONS: Our data suggest that breast milk provides better antioxidant power than does formula.     

Urinary methylmalonic acid excretion in infants fed formula or human milk

Serum vitamin B-12 and urinary methylmalonic acid (MMA) concentrations were determined in 62 healthy infants aged 1-6 mo. Urinary MMA was inversely correlated with serum vitamin B-12 concentrations (r = -0.550, p less than 0.001); serum vitamin B-12 was higher (p less than 0.001) and urinary MMA concentrations were lower (p less than 0.001) in formula-fed infants than in infants fed human milk (from the breast). Human-milk-fed infants who had received supplemental formula had higher serum vitamin B-12 concentrations than did infants exclusively fed human milk. It is not clear whether the serum vitamin B-12 and urinary MMA concentrations in infants fed human milk reflect biochemical deficiency of vitamin B-12, and the clinical significance of these findings needs to be investigated.     

Protein-degradation products and bacterial enzyme activities in faeces of breast-fed and formula-fed infants

The aim of the present study was to determine the effects of age and diet (breast milk, formula milk and weaning diet) on metabolic activities in faecal samples from infants aged 1 week to 1 year, and to compare these findings with activities found in samples from adults. Such activities can provide valuable information on functional changes in the microbiota that may have significance for the health of the host. Fresh faecal samples were collected from forty-four breast-fed infants (twenty-four males, twenty females) and thirteen formula-fed infants (three males, ten females) throughout the first year of life. The samples were analysed for protein-breakdown products, including the faecal concentrations of NH3, phenol and p-cresol, and faecal bacterial enzyme activities. There was wide individual variation in all variables measured; however, the values in infants were substantially lower then those found in adults. In pre-weaned infants, faecal NH3 concentration and beta-glucuronidase activity were the only endpoints that were significantly different in breast-fed and formula-fed infants (P<0.001 and P<0.05 respectively). This was not apparent after weaning. There was a significant difference between the breast-fed and formula-fed weaned groups and their pre-weaned counterparts only for NH3 (P<0.05). beta-Glucuronidase activity and phenol concentration were significantly (P<0.01) greater in weaned breast-fed infants compared with pre-weaned breast-fed infants. No differences were observed between pre-weaned and weaned formula-fed infants for any of the variables except for NH3 concentration. It can be concluded from the present study that there are significant differences in two faecal characteristics between breast- and formula-fed infants and that changes occur as the infants grow older and are weaned onto solid foods.     

Longitudinal manganese and copper balances in young infants and preterm infants fed on breast-milk and adapted cow's milk formulas

1. Mn and Cu intake and retention in twenty full-term infants and six preterm infants were studied on the basis of 72 h balances. The age of the infants was 2-16 weeks and the gestational age of the preterm infants (triplets) 34 and 36 weeks. Three nutrition schemes were pursued: breast-fed, formula-fed with unsupplemented adapted formula and formula-fed with trace element supplementation. 2. The mean Mn concentration of all breast-milk samples (n 2339) was 6.2 micrograms/l. The two formulas had similar Mn concentrations (77 and 99 micrograms/l) but had different Fe, Cu (121 and 619 micrograms/l), Zn and I contents. The mean Cu concentration in mother's milk was 833 micrograms/l. 3. The following mean daily Mn intakes and retentions (micrograms/kg) respectively were measured: breast-fed full-term 1.06 (SD 0.43) and 0.43 (SD 0.65), formula-fed full-term 14.2 (SD 3.1) and 2.8 (SD 4.8), formula-fed preterm 15.0 (SD 2.2) and 0.06 (SD 5.87). The results for Cu were 114.5 (SD 22.3) and 88.0 (SD 46.5) micrograms/kg in breast-fed, 19.8 (SD 4.2) and 4.6 (-11.5-9.6) in the unsupplemented formula-fed and 106.4 (SD 18.9) and 55.5 (SD 20.3) in the supplemented formula full-term infant group. No significant influence of the trace element contents of the formulas on the relative retention of Mn or Cu was found. 4. Young preterm infants, and to some degree young full-term infants, often had negative Mn balances caused by a high faecal excretion. The formulas with a Mn concentration below 100 micrograms/l gave a sufficient supply of Mn. Preterm infants fed on the unsupplemented formula had a marginal Cu supply and their first balances were negative (-3.8 (SD 1.8) micrograms/kg). 5. In accordance with the estimated safe and adequate daily dietary intakes (recommended dietary allowances), formula-fed infants receive much more Mn than breast-fed infants and their absolute retention is higher. 6. Cu from breast-milk had a significantly better biological availability than that from cow's milk formula. If retentions similar to those in breast-fed infants are intended, we conclude, therefore, that cow's milk formula should be fortified with Cu up to a level of at least 600 micrograms/l.     

The relationship of breast feeding to third-day bilirubin levels

The purpose of this study was to determine the relationship of feeding method to serum bilirubin levels on the third day of life. Two hundred eighty-one apparently healthy full-term neonates had third-day bilirubin levels drawn between 58 and 82 hours of age. Mean serum bilirubin levels were 5.6 mg/dL for formula-fed, 6.9 mg/dL for mixed-fed, and 7.5 mg/dL for breast-fed infants. The difference was statistically significant (P less than .01) between the formula-fed and breast-fed groups. Breast-fed infants lost more weight by the third day than formula-fed infants (mean weight loss 180 g for breast-fed infants, 100 g for formula-fed infants). A third-day bilirubin levels among the feeding groups were then compared using an analysis of covariance with weight loss as the covariate. By this method, type of feeding was still a significant predictor of third-day bilirubin levels (P = .04) as was weight loss (P = .03).     

Effect of prebiotic galacto-oligosaccharide, long-chain fructo-oligosaccharide infant formula on serum cholesterol and triacylglycerol levels

OBJECTIVE: Cholesterol is a nutrient of essential importance in infant feeding because it is necessary in membrane development. In adults with high lipid levels, high doses of inulin (oligofructose) inconsistently decreased levels of serum cholesterol. The aim of the present study was to evaluate cholesterol and triacylglycerol levels in infants receiving a formula with a specific mixture of 0.6 g/100 mL of galacto-oligosaccharides (GOS) and long-chain fructo-oligosaccharides (lcFOS) in a ratio of 9/1, a control formula, or breast milk. Because the level of lcFOS in the infant milk is low, we hypothesized that there would be no differences between the formula groups. METHODS: Two hundred fifteen infants were included in a prospective, randomized, double-blinded, placebo-controlled trial during the first 6 mo of life. Formula-fed infants were randomized to receive a standard infant formula with a specific mixture of 0.6 g/100 mL of GOS/lcFOS, in a ratio of 9/1, or a control formula. Breast-fed infants were randomized to receive one of these two formulas after the mother had decided to discontinue breastfeeding. Serum levels of cholesterol, high-density lipoprotein, low-density lipoprotein (LDL), and triacylglycerol were determined at 8 and 26 wk of age and were provided for infants who received the GOS/lcFOS formula or control formula from birth or after cessation of breastfeeding and for the subgroups that were fully fed with breast milk and formula. RESULTS: One hundred eighty-seven infants completed the study. Total cholesterol and LDL levels at 8 and 26 wk were significantly lower in the formula-fed groups than in the breast-fed infants. There were no significant differences between the formula-fed groups. Levels of triacylglycerols and high-density lipoprotein did not differ between groups. CONCLUSION: Our study demonstrated no differences in total cholesterol and LDL cholesterol in infants receiving an infant formula with GOS/lcFOS from infants receiving a control infant formula. Furthermore, total cholesterol and LDL cholesterol levels were higher in breast-fed infants than in formula-fed infants.     

Vitamin A status of preterm infants: the influence of feeding and vitamin supplements

Consecutive weekly determinations of plasma retinol, alpha-tocopherol, retinol-binding protein, prealbumin, and zinc were performed on a group of 58 infants weighing less than 2000 g at birth in an intensive-care nursery. Data were classified by the feeding regimen of the preceding week: parenteral, premature formula, or own mother's milk. Mean plasma-retinol values were less than 20 mcg/dl, the lower limit of normal for adults, with the highest values in the formula-fed group. Retinol-binding protein and prealbumin values were lowest in the parenterally-fed group. Alpha-tocopherol concentrations were consistently maintained at levels higher than 500 mcg/dl only in infants fed their own mother's milk. Mean zinc concentrations above 70 mcg/dl, the lower limit of normal for adults, occurred only in parenterally fed infants. Doubling the recommended vitamin supplement in formula-fed infants did not produce a significant increase in plasma retinol or tocopherol.     

Phenylalanine kinetics differ between formula-fed and human milk-fed preterm infants

Infants fed casein-dominant formulas have higher plasma phenylalanine and tyrosine concentrations than those fed mother's milk. Conversely, elevated plasma threonine concentrations are observed in infants fed whey-dominant formulas. We recently showed that formula-fed preterm infants have a lower capacity to degrade threonine than do preterm infants fed mother's milk. We hypothesized that these same infants (n = 18) would differ in their catabolism of phenylalanine in response to phenylalanine loads provided by formulas with increasing casein content of formulas (whey:casein 60:40, 40:60, and 20:80) compared with preterm infants fed mother's milk. Plasma phenylalanine concentrations significantly rose (49, 46, 79 micromol . L(-1) for whey:casein 60:40, 40:60, and 20:80, respectively, pooled SD 8, P < 0.05); and plasma phenylalanine concentrations in infants fed mother's milk were low (40 +/- 4 micromol . L(-1)). Using [1-(13)C]phenylalanine tracer and (13)CO(2) production in breath we found that although there was a significant positive relation between phenylalanine oxidation and phenylalanine intake in formula-fed infants (r(2) = 0.43, P = 0.03), these infants were not able to increase their oxidation of phenylalanine enough to prevent a significant rise in plasma phenylalanine when fed the 20:80 formula. Compared to infants fed mother's milk, formula-fed infants had significantly lower phenylalanine oxidation (39.1 vs. 30.7% of phenylalanine intake, respectively, P < 0.05). We conclude that one of the mechanisms for the differences in plasma amino acid concentration between formula-fed and mother's milk-fed preterm infants may be in vivo down-regulated catabolism of 2 important essential amino acids (phenylalanine in addition to threonine) in formula-fed preterm infants.     

Breast-fed and formula-fed infants do not differ in immunocompetent cell cytokine production despite differences in cell membrane fatty acid composition

BACKGROUND: Breast-fed and formula-fed infants differ in the amount and type of polyunsaturated fatty acids consumed. The fatty acid composition of cell membranes is related to dietary fatty acids and, in adults, changes in membrane fatty acid composition are accompanied by changes in monocyte cytokine production and hence a modification of the immunologic response. OBJECTIVE: Our objective was to determine whether production by immunocompetent cells of the proinflammatory cytokines interleukin 1 (IL-1) and tumor necrosis factor (TNF) differs between breast-fed and formula-fed infants. DESIGN: Twenty-six healthy infants (13 breast-fed and 13 fed modified cow-milk formula) aged 2-4 mo were studied. The fatty acid composition of red blood cell (RBC) membrane phospholipids was measured by gas-liquid chromatography and IL-1 and TNF release were measured in whole blood culture in bacterial-endotoxin-stimulated and unstimulated cells. RESULTS: The infants' ages, weights, hemoglobin concentrations, and white blood cell counts did not differ significantly between groups. The percentage of n-3 fatty acids of total RBC phospholipid fatty acids was significantly higher in breast-fed than in formula-fed infants (6.31 +/- 2.5% compared with 2.98 +/- 0.97%); docosahexaenoic acid (22:6n-3) concentrations were also markedly higher in breast-fed infants (5.1 +/- 1.2% compared with 2.2 +/- 0.9%, P: < 0.001), but eicosapentaenoic acid (20:5n-3) and docosapentaenoic acid (22:5n-3) concentrations did not differ significantly between groups. The percentage of n-6 fatty acids was not significantly different between groups. The percentage of oleic acid (18:1) was higher in formula-fed than in breast-fed infants (16.2 +/- 0.7% compared with 20.6 +/- 1.1%; P: < 0.001). IL-1 and TNF release in whole blood culture did not differ significantly between groups. CONCLUSION: The release of proinflammatory cytokines by immunocompetent cells does not differ significantly in breast-fed and formula-fed infants despite differences in cell membrane fatty acid composition.     

Serum T4 level in term newborns: Comparison between breast-fed and formula-fed infants

Serum thyroxine measurement ([¹²⁵I] T₄-RIA) was performed on the third day of life in 1759 normal, full-term infants. The T₄ concentrations were similar in the 680 formula-fed infants (16.32±0.09 μg/dl) and in the 1079 breast-fed infants (16.46±0.08 μg/dl). A male breast-fed infant was discovered to have hypo-TBG-emia. Our findings show that breast feeding from birth will not interfere with neonatal screening for hypothyroxinemia on the third day of life. Additionally, the mean T₄ value in the formulafed males was significantly lower than the breast-fed males, (15.88±0.13 μg/dl vs 16.32±0.11 μg/dl, p<0.01). Also, the formula-fed males has a significantly lower (p<0.01) T₄ concentration when compared with the formula-fed females.     

Continuous nasoenteral feeding: inverse relation between infusion rate and serum levels of bilirubin

The relation between nasoenteric formula caloric infusion rate and the serum bilirubin level was examined in 15 healthy subjects. The study protocol spanned 3 days and included fasting studies on day 1, continuous maintenance nasogastric feeding of a formula diet on day 2, and continuous feeding at a rate twice the maintenance level on day 3. Blood studies were performed in the early morning of each day. Fifteen subjects underwent the fasting measurements and the maintenance infusion, while 11 underwent all 3 days of the protocol. With the maintenance infusion serum bilirubin fell from the fasting value of (X +/- SD) 0.77 +/- 0.53 to 0.63 +/- 0.49 mg/dl for a reduction of 18% (p less than 0.05). For the subgroup of 11 subjects receiving two levels of formula infusion, fasting and maintenance serum bilirubin levels were 0.81 +/- 0.57 and 0.65 +/- 0.47 mg/dl, respectively, (p less than 0.05). With the twice maintenance infusion the plasma bilirubin decreased further to 0.46 +/- 0.29 mg/dl, a decrement of 43% relative to fasting (p less than 0.01). No other significant changes were detected during the protocol in the standard blood chemical and hematologic studies. Thus, the serum level of bilirubin is inversely related to the formula caloric infusion rate during continuous nasoenteric feeding.     

The impact of milk and weaning diet on gastrointestinal permeability in English and Gambian infants

To test the hypothesis that cow's milk formula and weaning diet may damage the gut mucosa, the gastrointestinal permeability of 77 healthy English and Gambian infants was measured from the urinary recovery of the markers lactulose and mannitol included in feeds. All infants were born at term and studied at 6, 12 and 18 weeks of age. No infant developed diarrhoea or failed to thrive. Infants fed on cow's milk formula had higher urinary lactulose: mannitol excretion ratios than breast-fed infants at 6 weeks of life (P less than 0.05). There was no significant difference in the urinary marker excretion ratios of English formula-fed and Gambian breast-fed infants at 12 weeks. An increase in urinary lactulose: mannitol excretion ratios was seen in all infants at 18 weeks. This was more probably due to increasing age than to the introduction of weaning diet. Cow's milk formula feeding was associated with greater intestinal permeability than breast feeding in infants aged 6 weeks. The introduction of weaning diet after 6 weeks did not appear to have an impact on the gastrointestinal permeability of healthy growing infants born in either England or rural Gambia.     

The new "breast from birth" growth charts. An updated version of the paper given at the Primary Care Conference and Exhibition, May 2003

The Child Growth Foundation has published the first weight reference charts specifically designed for the breast-fed infant. Based on a sample of 120 long-term British breast-fed babies, the charts demonstrate the particular growth pattern of breast-fed babies. This differs from formula-fed infants in that breast-fed babies initially gain weight more rapidly, but from two to three months of age their weight gain decreases and they begin to move downwards across centiles. At present breast-fed babies are measured against the standard British 1990 weight reference chart rather than one that reflects the pattern of the long-term breast-fed baby. The author, Tam Fry from the Child Growth Foundation, argues that the new charts will prevent mothers and health professionals from becoming anxious and changing the infant from breast to formula milk when growth begins to slow down. He also suggests that the charts could be used as the reference for all British babies, whatever the means of feeding.     

母乳喂养与代乳品喂养新生儿血中胃泌素及胃动素水平比较

目的比较正常新生儿母乳喂养与代乳品喂养情况下血中胃泌素及胃动素水平的差异。方法应用放射免疫分析技术对100例正常足月新生儿(其中比较组50例由母乳喂养．对照组50例由代乳品喂养)的血清胃泌素、血浆胃动素进行了检测和统计分析。结果比较组胃泌素和胃动素水平明显高于对照组．表明母乳中胃泌素、胃动素进入新生儿体内后与内源性胃泌素、胃动素具有类似的生物活性．能补充新生儿体内的不足。结论从胃肠激素这一角度证明母乳喂养的优越性。     

Immunoglobulin A level in human milk from mothers delivering preterm

Little information is available on immunoglobulin content of milk from mothers of preterm babies. In this study we have measured IgA levels in samples from preterm and term mothers during the 1st month postpartum. The concentration of IgA tended to be constant in the preterm group (about 251 mg/dl) while it showed a decreasing trend in the term group (from 212.8 +/- 19.9 to 171.6 +/- 12.8 mg/dl). From day 10 onward IgA levels in preterm milk were significantly higher than in term milk (p less than 0.002). These findings support the idea that premature infants fed their own mothers' milk would benefit from more stable levels of IgA, at a time when their mucosal immune system is poorly developed.     

Cholesterol metabolism in adult baboons is influenced by infant diet

We tested the hypothesis that preweaning diet alters cholesterol metabolism in adult baboons. Eighty baboons, progeny of 6 sires and 80 dams, were either breast-fed or fed one of three infant formulas containing 2, 30 or 60 mg cholesterol/100 mL. At 16 wk of age the baboons were weaned to one of four diets containing 1.0 or 0.01 mg cholesterol/kcal with 40% of energy from saturated [polyunsaturated fat/saturated fat [P/S) = 0.37] or unsaturated fat [P/S = 2.1] and maintained on these diets until they were necropsied as young adults at 7-8 yr of age. We observed no significant effects of formula cholesterol content on serum lipid or lipoprotein concentrations measured at 6-8 yr of age, but formula cholesterol intake influenced the cholesterol turnover rate and several variables of cholesterol metabolism in the adult. At 6-8 yr, baboons that were breast-fed during infancy, compared with those that were formula-fed, had lower high-density lipoprotein cholesterol (HDL-C) concentrations and higher ratios of very-low-density plus low-density lipoprotein cholesterol (VLDL + LDL-C) to HDL-C. Breast-fed baboons, as adults, had lower cholesterol production rates, masses of the rapidly exchanging cholesterol compartment (pool A) and neutral steroid excretion rates than did those fed formula as infants. Breast and formula feeding differentially influenced the adult metabolic responses to dietary cholesterol or fat saturation. These results demonstrate that breast vs. formula feeding in infancy alters cholesterol metabolism and serum lipoprotein concentrations in adult baboons.     

A randomized trial of different ratios of linoleic to alpha-linolenic acid in the diet of term infants: effects on visual function and growth

BACKGROUND: There are nutritional recommendations that the ratio of linoleic to alpha-linolenic acid (LA:ALA) in formula for term infants be between 5:1 and 15:1. These recommendations were made in the absence of data on functional or clinical outcomes. OBJECTIVE: We compared the fatty acid status, visual evoked potential (VEP) acuity, and growth of term infants fed formula containing an LA:ALA of 10:1 or 5:1 with those of a breast-fed reference cohort. DESIGN: Formula-fed infants were allocated randomly in a double-blind fashion to receive formula with an LA:ALA of either 10:1 (16.9:1.7; n = 36) or 5:1 (16.3:3.3; n = 37) from near birth to 34 wk of age. Increased ALA was attained by replacing soy oil with low-erucic acid cannola oil. A parallel group of breast-fed infants was also recruited. Infant growth and fatty acid status were assessed at 6, 16, and 34 wk of age. VEP acuity was assessed at 16 and 34 wk. RESULTS: Infants fed the 5:1 formula had greater docosahexaenoic acid (DHA) concentrations in plasma and erythrocyte phospholipids than did infants fed the 10:1 formula, but DHA concentrations of infants fed the 5:1 formula remained less than those in breast-fed infants. The VEP acuity of all formula-fed and breast-fed infants was not significantly different at 16 and 34 wk of age. At birth, infants fed the 5:1 formula were heavier, were longer, and had a greater head circumference than infants assigned to the 10:1 formula group; this differential was maintained throughout the trial. The rate of gain in weight, length, and head circumference was not significantly different between the 2 formula-fed groups, although breast-fed infants had lower weight and length gains than did formula-fed infants between 16 and 34 wk of age. CONCLUSION: Lowering the LA:ALA in formula from 10:1 to 5:1 by using low-erucic acid canola oil resulted in a modest increase in plasma DHA but had no effect on VEP acuity or growth rate.     

山东临沂市254名农村婴幼儿血清视黄醇和类胡萝卜素水平及其与相关膳食因素的关系

目的为了解农村婴幼儿血清维生素A(VA)营养状况和血清类胡萝卜素水平,以及两者关系和相关影响因素而开展本研究。方法采用整群抽样方法,对山东省临沂市某镇辖区内254名6～24月龄健康婴幼儿进行健康体检和喂养状况调查。采集足背静脉血样,用高效液相色谱法测定血清视黄醇和β-胡萝卜素、α-胡萝卜素、β-隐黄素及叶黄素+玉米黄素含量。用膳食频率法回顾性调查婴幼儿最近一个月内的各类食物摄入状况,分析喂养状况与血清视黄醇和类胡萝卜素水平的关系。结果被调查婴幼儿血清视黄醇浓度平均为(0.96±0.55)μmol/L,不同月龄段间没有明显差异(P>0.05);血清VA缺乏率为40.6%,边缘性VA缺乏率为32.6%。血清β-胡萝卜素、α-胡萝卜素、β-隐黄素和叶黄素+玉米黄素浓度的平均值分别为(0.056±0.088)μmol/L、(3.3±12.1)nmol/L、(27.0±45.2)nmol/L和(0.22±0.22)μmol/L。不同月龄段儿童血清叶黄素+玉米黄素浓度存在差异(P<0.05),13～18月龄段低于6～12月龄儿童。母乳喂养和配方奶粉是影响婴幼儿血清视黄醇和β-胡萝卜素水平的主要因素。母乳喂养频率与β-胡萝卜素水平呈负相关(P<0.05),而配方粉喂养频率与血清视黄醇和除α-胡萝卜素以外的类胡萝卜素水平呈正相关(均为P<0.05);水果蔬菜喂养频率则只与血清β-胡萝卜素、α-胡萝卜素和β-隐黄素浓度呈正相关。血清视黄醇与类胡萝卜素各组分,以及类胡萝卜素各组分之间,具有显著正相关关系(均为P<0.001)。结论调查的农村婴幼儿血清VA营养状况较差,血清β-胡萝卜素、α-胡萝卜素、β-隐黄素及叶黄素+玉米黄素浓度与母乳、配方奶粉、水果蔬菜添加等喂养状况关系密切。     

Serum leptin concentrations in infants: effects of diet, sex, and adiposity

BACKGROUND: Leptin, the product of the obese (ob) gene, is a regulator of food intake and energy metabolism. Immunoreactive leptin was detected recently in breast milk and it has been hypothesized that leptin may be absorbed and may contribute to differences in body composition between breast-fed and formula-fed infants. OBJECTIVE: The objective was to evaluate whether diet, adiposity, or sex affect plasma leptin in breast-fed and formula-fed infants. DESIGN: Venous blood samples were drawn from healthy, exclusively breast-fed or formula-fed Swedish infants at 1, 4, and 6 mo of age (n = 193) and from 12-mo-old Finnish infants (n = 79). Anthropometric measurements were made and plasma samples were analyzed for leptin, insulin, and glucose. RESULTS: There were no significant differences in plasma leptin between formula-fed and breast-fed infants at 1 and 4 mo of age, whereas formula-fed infants had significantly higher ( approximately 5%) leptin concentrations at 6 mo of age. Similar results were observed after correction for BMI. Plasma leptin was 15-25% higher in female than in male infants at 1, 4, and 12 mo of age (P < 0.05), also after correction for BMI. When all infants were analyzed together, a positive correlation (r = 0.34, P < 0.0001) was found between plasma leptin and BMI. Very low leptin concentrations were found in breast milk after centrifugation and the high concentrations reported previously were likely due to interference in the assay by milk fat. CONCLUSIONS: Plasma leptin concentrations are not higher in breast-fed than in formula-fed infants; however, sex and adiposity affect leptin concentrations even at this early age.