Reflections on infant feeding in the 1970s and 1980s.

In 1985 35% of US infants were breast-fed until at least age 4 mo whereas in 1971 the corresponding figure was only 10%. Breast-feeding is less common among lower income than among higher income groups. In 1985 10% of infants aged 6 mo were fed fresh fluid cow milk--down from 70% in 1971. Most formula-fed infants receive iron-fortified formulas (12 mg Fe/L). Beikost is now commonly fed to infants less than age 2 mo. The Infant Formula Act of 1980 resulted in promulgation of new quality control and labelling requirements for infant formulas. Over the past 15 y, salt and sugar concentrations of commercially prepared beikost items have been decreased, and certain modified food starches are no longer used. There is considerable doubt about the bioavailability of the electrolytic iron powder used to fortify most of the dry infant cereals.

PIP: In 1985, 35% of US infants were breastfed until at least age 4 months whereas in 1971 the corresponding figure was 10%. Breastfeeding is less common among lower income than among higher income populations. In 1985, 10% of infants aged 6 months were fed fresh fluid cow's milk, down from 70% in 1971. Most formula-fed infants receive iron-fortified formulas today (12 mg Fe/liter). Beikost (foods other than milk/formula fed to infants) is now not commonly fed to infants less than 2 months. The Infant Formula Act of 1980 resulted in promulgation of new quality control and labelling requirements for infant formulas. Over the past 15 years, salt and sugar concentrations of commercially prepared beikost items have been decreased, and certain modified food starches are no longer used. There is considerable doubt about the bioavailability of the electrolytic iron powder used to fortify most dry infant cereals. Possible reasons for the increase in breastfeeding and decrease in formula feeding are discussed, and nutrient specifications for formulas are listed.

Methionine fortification of a soy protein formula fed to infants.

Data from study of nine normal full-term infants fed a soy isolate-based formula unsupplemented with methionine were compared with similar data from study of 10 similar infants fed the same formula supplemented with L-methionine and with data from previous studies of larger groups of infants receiving various other feedings. Food intake, growth, and serum chemical values were studied from 8 through 111 days of age. In addition, nitrogen balance studies were carried out. Statistically significant differences were as follows: lesser weight gain per 100 kcal by infants fed the unsupplemented soy isolate-based formula than by infants fed milk-based or other soy isolate-based formulas; lesser serum concentrations of albumin at age 28 days by infants fed the unsupplemented soy isolate-based formula than by breast-fed infants; greater serum concentrations of urea nitrogen by infants receiving the unsupplemented soy isolate-based formula than by those receiving the same formula supplemented with L-methionine. A number of other differences was noted but were not statistically significant. The results suggest that normal infants fed a formula providing 2.25 /100 kcal of a soy protein isolate not fortified with methionine performed less well during the first 6 weeks of life than did breast-fed infants and infants fed milk-based formulas or other soy isolate-based formulas fortified with methionine. The limiting nutrient appears to have been methionine.

What is the safe protein-energy ratio for infant formulas?

Infants eat primarily to satisfy energy needs and the safe amount of protein in infant formulas (ie, the amount adequate for nearly all infants) is therefore expressed as the protein-energy ratio. We studied male infants aged 8-112 d fed milk-based formulas. One group (experimental group) was fed formulas that provided protein-energy ratios of 3.73 g/MJ (1.56 g/100 kcal) from 8 to 27 d of age, gradually decreasing to 2.99 g/MJ (1.25 g/100 kcal) from 84 to 111 d of age. Growth rates and serum albumin and urea nitrogen of these infants were compared with those of a concurrently studied control group and a previously studied large reference group. Gains in weight and concentrations of serum albumin of the three groups were not significantly different. Gains in length were significantly less for the experimental group than for the reference group. Serum urea nitrogen was significantly less in the experimental group than in the control group or reference group. We conclude that the protein-energy ratios of the experimental formula diet were below the safe level. Because the decrease in growth rate of the experimental group was rather small (demonstrable only in comparison with the large reference group), and because serum albumin of the experimental group increased with age as in normally nourished infants, we suspect that the safe protein-energy ratio of infant formulas lies closer to the ratios fed to the experimental group than to the ratio [approximately 5.0 g/MJ (2.1 g/100 kcal)] in currently marketed milk-based formulas.

Nitrogen balance studies with normal children.

A total of 1148 nitrogen balance studies were conducted in 100 boys and 23 girls 1 to 11 years old. Mixed, customary diets supplied between 8.9 and 21.4% of calories from protein. Duration of balance studies ranged from 72 hr in the youngest subjects to 120 hr in older children. Regressions and 95% confidence intervals of nitrogen retention on nitrogen intake are presented. The slope of the regression was significantly greater for children 12 to 18 months old than for children of other age groups. Correlation coefficients between various parameters of nitrogen balance and energy intake are presented. Although variability in results of nitrogen balances within subjects appears to be rather large, a significant difference between subjects was observed.

What are infants fed in the United States?

Estimates of calorie intake from various sources during infancy are presented in relation to age. The estimates, based on published reports and personal communications to the author, concern total calorie intake and its distribution between milk or formula and beikost (i.e., foods other than milk or formula fed to infants), relative prevalence of breast, formula- and milk-feedings, relative popularity of specific commercially prepared formulas, and percentage of calories consumed in the form of commercially prepared strained and junior foods and "table" foods.

Formulas for premature infants: fate of the calcium and phosphorus.

Formulas designed for feeding of premature infants contain minerals added by the manufacturer. Although it is known that these minerals may be poorly suspended in the formula, little is known about concentrations of minerals in formula delivered to the infant under conditions prevailing in premature infant nurseries. In partially empty bottles of Similac Special Care, concentrations of calcium and phosphorus of this residual formula were found to be substantially greater than concentrations in full bottles. Presumably, concentrations of calcium and phosphorus in formula delivered to the infants was relatively low. Enfamil Premature and SMA Preemie infant formulas contain lesser quantities of added calcium and demonstrated less tendency to sedimentation. Substantial decrease in concentration of calcium was observed with all three formulas during continuous infusion, but the decrease was greatest with Similac Special Care. Little or no change in concentrations of calcium and phosphorus were observed with simulated bolus feeding by gavage.

Lack of adverse reactions to iron-fortified formula.

Some physicians are reluctant to recommend feeding of iron-fortified formulas to infants because of a fear of adverse reactions. In crossover studies, parents' records were compared with regard to their infant's behavior (fussiness, cramps, regurgitation, flatus, colic) and stool characteristics during periods when iron-fortified formulas were fed and periods when non-iron-fortified formulas were fed. No statistically significant feeding-related difference was noted except for stool color.

Strategies for the prevention of iron deficiency: iron in infant formulas and baby foods.

Iron deficiency is the most prevalent nutrition deficiency among infants and young children in industrialized as well as developing countries. It is a condition that is preventable through appropriate dietary measures. The infant born at term is endowed with a sizable amount of iron, which allows the infant to be fed a nearly iron-free diet (e.g., breast milk) for 4-6 months without becoming overtly iron deficient. This has led some to conclude that depletion of iron stores in healthy infants is a normal and, hence, innocuous process that usually gives way to gradual repletion of iron stores as dietary diversification leads to greater iron intakes. Preservation of maternal iron stores at the expense of infant iron stores may have offered survival advantages to the human species during evolution. But there is no evidence that depletion of iron stores can offer advantages to infants in industrialized or developing countries. On the contrary, there is ample documentation of shortterm as well as long-term adverse effects from iron deficiency. Prudence therefore dictates that a high priority be assigned to the prevention of iron depletion and deficiency among infants and young children worldwide.

Breast-feeding and evolution.

Several possibilities have been discussed as explanations for the failure of milk of the human species to meet certain nutritional needs of its young under living conditions prevailing in industrialized countries. The thoughts presented are speculative, and, in some instances, more than one explanation has been offered. The welfare of the mother as well as that of the infant must be considered--e.g., the mother's health might be seriously jeopardized if 0.5 to 1.0 mg of iron daily were secreted in milk. Moreover, evolutionary forces may be expected to influence milk production and composition in relation to diets and environmental conditions existing over several hundred thousand years. If we change our diets (e.g., consume less vitamin K) or if we change our environment (e.g., protect infants against sunlight and restrict the infant's contact with iron in dirt), milk that was adequate under prior living conditions may no longer be adequate. Finally, we wish to protect all infants against death or disability, including that resulting from a catastrophic event (e.g., intracranial bleeding as a result of vitamin K deficiency) too rare to be expected to influence evolutionary changes.

Gain in weight and length during early infancy.

Although rate of growth is generally recognized as a valuable indicator of health status, few reference data are available for gain in weight or length during the period of most growth in infancy. We have therefore summarized our data concerning gains in length and weight of 203 breast-fed males, 216 breast-fed females, 380 formula-fed males, and 340 formula-fed females. Seven sets of measurements (at ages 8, 14, 28, 42, 56, 84 and 112 days) were made with each infant. The 5th, 10th, 25th, 50th, 75th, 90th and 95th centile values together with the means and standard deviations are presented for selected age intervals on a feeding-specific (i.e. breast-fed or formula-fed) and sex-specific basis. We believe that these data will be useful as a reference for interpreting results of infant studies.

Fluoride intake by infants.

Many infants are fully or partially breast fed during the early months of life; however, the percentage of such infants decreases to about 30 percent by 4 months of age. The majority of US infants are fed formulas for most of the first 10 months of life. Although fluoride (F) intakes by fully breast-fed infants are low, F intakes by partially breast-fed infants and by formula-fed infants are highly variable, depending primarily on the F content of the water used to dilute concentrated liquid or powdered infant formula products. In communities with F content of the drinking water less than 0.3 ppm, F consumption by many infants will be 30 to 40 micrograms.kg-1.d-1. The addition of a F supplement of 0.25 mg/d for a 4 kg infant would increase the F intake by 63 micrograms.kg-1.d-1, resulting in a total intake of about 100 micrograms.kg-1.d-1, an intake in the range believed to be associated with development of fluorosis of the permanent teeth. However, for the US infant population generally, many fewer infants are exposed to high F intakes from formula plus a supplement (recommended only for communities with water providing less than 0.3 ppm F) than from formula alone in communities with F content of 1 ppm in the drinking water. In assessing the possible effects of F intake during infancy on development of fluorosis, it is important to recognize that infant feeding practices have changed greatly during the past 30 years. In the 1960s, most infants over 4 months of age were fed fresh cow's milk and intakes of F were therefore low. By the mid 1970s a trend toward more extended feeding of formula was evident and this trend has continued into the 1990s. Prolonged exposure to high intakes of fluoride during infancy is much more common now than in the past.

Fluoride intake and prevalence of dental fluorosis: trends in fluoride intake with special attention to infants.

BACKGROUND: Although the predominant beneficial effect of fluoride occurs locally in the mouth, the adverse effect, dental fluorosis, occurs by the systemic route. The caries attack rate in industrialized countries, including the United States and Canada, has decreased dramatically over the past 40 years. However, the prevalence of dental fluorosis in the United States has increased during the last 30 years both in communities with fluoridated water and in communities with nonfluoridated water. Dental fluorosis is closely associated with fluoride intake during the period of tooth development. METHODS: We reviewed the major changes in infant feeding practices that have occurred since 1930 and the changes in fluoride intakes by infants and young children associated with changes in feeding practices. RESULTS AND CONCLUSIONS: Based on this review, we conclude that fluoride intakes of infants and children have shown a rather steady increase since 1930, are likely to continue to increase, and will be associated with further increase in the prevalence of enamel fluorosis unless intervention measures are instituted. RECOMMENDATIONS: We believe the most important measures that should be undertaken are (1) use, when feasible, of water low in fluoride for dilution of infant formulas; (2) adult supervision of toothbrushing by children younger than 5 years of age; and (3) changes in recommendations for administration of fluoride supplements so that such supplements are not given to infants and more stringent criteria are applied for administration to children.