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The bacon chow study: effects of maternal nutritional supplementation on infant mental and motor development

Sandra K. Joos, Ernesto Pollitt, and William H. Mueller
The University of Texas Health Science Center, School of Public Health, Houston, Texas, USA

INTRODUCTION

Over the past 15 years, four large-scale experimental nutritional supplementation studies have been conducted in Guatemala, Bogota, New York City, and Taiwan (1-3). Each of these studies included some control over dietary intake, longitudinal evaluations, and measurements of the effects of maternal supplementation on the behavioural development of infants and children. However, the results of the Taiwan study have not been available because of the death in 1973 of the principal investigator, Dr. Bacon Chow of the Johns Hopkins School of Hygiene and Public Health.

In 1967 Dr. Chow initiated a study in Taiwan to determine whether a protein and calorie supplement to mothers during pregnancy and lactation would have a beneficial effect on the growth and development of their infants. Because experiments with rats indicated that protein deficits in the maternal diet during pregnancy and lactation had the greatest negative effects on physical and behavioural development, the primary aim was to study supplementation of the diets of mothers who had a marginal protein intake rather than of obviously undernourished mothers (4). A rural population in Taiwan with low protein intake but no frank malnutrition was chosen, and the study was conducted over a 6 1/2-year period, from 1967 to 1973.

Associates of Dr. Chow have published preliminary findings (5, 61. Further analyses of dietary and supplement intake, birth weight, growth, and behavioural development have been completed since Dr. Ernesto Pollitt received a copy of the data tapes in 1978 (7-11). A summary of the results of an analysis of the effects of maternal supplementation on the mental and motor development of the Taiwan infants at eight months of age is presented here.

METHODS

Design

The Bacon Chow study was a randomized, controlled, double-blind trial of nutritional supplementation of pregnant and lactating women. Two hundred ninety-four pregnant women were randomly assigned to one of two groups. Group A received a high-calorie and protein supplement (800 kcal, 40 9 protein per day), while group B received a placebo. (Until June 1970 formula B, the placebo, contained only 6 kcal per day; thereafter, it contained 80 kcal, no protein per day.) Both the supplement and the placebo were liquid formulas packaged in 121/2 ounce (375 ml) cans and were similar in taste, texture, and weight. All women also received a multivitamin and mineral tablet daily.

The supplement or placebo was given to each mother beginning three weeks after the delivery of the first infant born to her after the study began. It was continued throughout the lactation of this infant, through the interpregnancy period, and through the pregnancy and lactation of the second infant she delivered during the study. No supplement was provided directly to the infants. Each mother, then, provided two "study" infants and was given supplement or placebo during the gestation of the second, but not the first, infant.

Subjects

The study was conducted in 14 villages in Sui-lin Township, an economically distressed agricultural region about 180 miles south-west of Taipei, Taiwan. The diet of the population was limited mainly to rice, sweet potatoes, and other vegetables, with little animal protein. The 294 women selected for the study were of lowest economic status and were considered to be marginally nourished. A preliminary dietary survey of the women indicated that caloric intake was as low as 1,200 kcal per day, and the daily protein intake (primarily of vegetable origin) was less than 40 9. Lactation in this population continued until infants were about 15 months of age, and all mothers began supplementing the infant diet at around seven months (6).

The criteria for the selection of the study women included the following: married, with one normal male child; in the third trimester of pregnancy; planning to have at least one more child; 19 to 30 years old; and in satisfactory health on physical examination, with normal values for haemoglobin, plasma protein, and haematocrit (5). Of the 294 women recruited, 225 gave birth to two infants within the study period. The 69 women who did not were almost evenly divided between groups A and B.

Procedures

Both supplement and placebo were distributed twice daily by nurses, who measured and recorded the volume remaining in the can after the women had drunk the formulas. The percentage of the total volume consumed was averaged and recorded monthly. Neither the mothers nor the nurses knew whether a can contained supplement or placebo. The mothers' daily food intake was surveyed at approximately three-month intervals. Duplicate samples of three meals were collected in the homes by the nurses and analysed for nitrogen, fat, and carbohydrate content. Between-meal eating was not assessed, and therefore the total daily intake is probably underestimated. Nevertheless, the food survey information does appear to reflect reliably the inter- and intra-group variability in food intake over time (8).

Assessment of mental and motor infant development at eight months of age, using a research version of the Bayley Scales of Infant Development, was begun two years after the study was under way. Only 60 of the first study infants were examined, while all but 14 of the second infants were. The testing was done by two American-trained Chinese psychologists in a specially designed and equipped room located at the central village in Sui-lin Township. We have no quantitative data regarding inter-tester reliability, but one of the original investigators has informed us that it was high (A.M. Hsueh, personal communication, 1980).

The infants were tested on 24 motor items and 50 mental items. Each item was scored as passed or failed. Because of the large number of items that all infants passed or failed, items were selected for this analysis if at least 10 per cent but not more than 90 per cent of the sample passed the item. Seven items in the motor scale and 10 items in the mental scale met this criterion. Scores of 0 to 7 on the motor scale and 0 to 10 on the mental scale are therefore possible.

Because only a small number of first study infants were tested, this analysis is restricted to a between-group comparison of the second study infants. Because of the ordinal nature of the modified mental and motor scales, the statistical analyses were based on non-parametric tests of group differences. However, parametric tests were also calculated, and the results are presented.

Cases were excluded from this analysis for the following reasons: missing information on the Bayley Scales (14 cases), on supplement intake by the mother (2 cases), or on birth measurements- i.e., weight and anthropometry - (1 case); the presence of congenital anomalies (5 cases); extremely low supplement intake by mothers (4 cases); or an extreme age at testing ( 1 case). Twenty-seven cases were thus excluded, leaving 198 cases evenly divided between groups A and B.

RESULTS

There were no significant differences (p < 0.05) between the groups in any moderating variables that could influence the results of the between-group Bayley Scales comparisons (i.e., maternal anthropometry and reproductive characteristics, parents' education and scores on the Raven's Progressive Matrices, and age of the infant at testing). Therefore, none of these variables was controlled in the analysis. Although group-B mothers tended to consume slightly more food at home than group A, because of the contents of the supplement in group A, total intake in group A was substantially above that of group B (about 400 kcal/day, on average) throughout pregnancy and lactation.

Table 1 presents the means and standard deviations of the mental and motor scores of infants of mothers in the two groups, with males and females combined and separated. The mental scores of group-A infants were no higher than those of group-B infants, nor were there any sex differences in either group. The motor scales of group-A infants were, however, higher than those of group-B infants, and the difference is statistically significant.

Chi-square analysis of single items in the motor scales showed that the majority of the difference in infants of group-A mothers is accounted for by only three items: the ability of the infant to raise itself to a sitting position, to pull itself up until standing, and to bring two objects together at midline.

DISCUSSION

Maternal nutritional supplementation during pregnancy and lactation had no effect on the Bayley mental-scale scores attained by infants at eight months of age. There was a modest beneficial effect on the motor scores of infants of mothers who consumed the high calorie and protein supplement, with the majority of effect in only three items. No sex differences in response to the supplement were detected. These findings are consistent with those of the Guatemala (1) and Bogota (2) studies, in which effects of a nutritional supplement were also most evident in motor items or subscales. The findings of these studies are also similar in that the independent effect of nutrition on behavioural development was not large in any of them.

TABLE 1. Mean Mental and Motor Scores of Infants by Group

  Group A Group B
Number Mean (SD) Number Mean (SD)
Mental scores *            
All 99 4.48 (2.27) 99 4.39 (2.06)
Males 53 4.49 (2.11) 52 4.37 (2.67)
Females 46 4.48 (2.47) 47 4.43 (1.84)
Motor scores            
All 99 3.80 (1.90) 99 3.31 (1.71)**
Males 53 3 70 (1.95) 52 3.21 (1.60)***
Females 46 3.91 (1.85) 47 3 43 (1.83)

* No significant differences at p < 0.10.
** One-tail p = 0.02 (Mann-Whitney U test); one-tail p = 0.03 (Student's t-test).
*** One-tail p < 0.10 (Mann-Whitney U test and Student's t-test).

In the Taiwan study, the small impact of the maternal supplement on infant behavioural test performance despite the magnitude of the nutritional intervention may have been caused by several factors. First, the population was probably only marginally malnourished at the outset of the study. Second, mothers who could have been at risk for poor birth outcome were excluded by the selection criteria. Finally, the infants received no direct supplementation from the investigators.

The finding of supplement effects on the motor-scale and not on the mental-scale performance of Taiwan infants, and primarily on motor-scale items in other studies, may have to do with the nature of developmental processes in the first year of life. Infants interact with and experience their environment primarily through the sensorimotor behaviours by which they manipulate and explore their physical surroundings. Improvement in neuromotor and sensorimotor functioning characterizes development at this age and would therefore be most affected by prenatal environment and nutrition in the first year of life.

Overall, the benefit of maternal supplementation on the behavioural performance of Taiwanese infants at eight months of age was small. Even though a statistically significant difference exists between the motor scores of A and B infants, and even if this can be attributed to the different levels of nutritional supplementation of the mothers, the functional significance of this difference is unresolved.

ACKNOWLEDGEMENTS

We gratefully acknowledge the contributions to this study made by Dr. R. Quentin Blackwell and Dr. Janet Hardy.

Dr. Blackwell was the principal co-investigator during the data collection period, and Dr. Hardy directed the assessment of infant development.

The data analysis was supported in part by the Ford Foundation and the Nestlé Coordination Centre in Nutrition, Washington, D.C., USA

REFERENCES

1. R.M. Klein, P, Arenales, H, Delgado, P. Engle, G. Guzmán,, M, Irwin, R. Lasky, A. Lechtig, R. Martorell, V. Pivaral, P. Russell, and C. Yarbrough, "Effects of Maternal Nutrition on Fetal Growth and Infant Development," Bull. PAHO, 10: 301-316 ( 1 976).

2. M. G. Herrera, J.O. Mora, N. Christiansen, N. Ortiz, J. Clement, L. Vuori, D. Waber, B. de Paredes, and M, Wagner, "Effects of Nutritional Supplementation and Early Education on Physical and Cognitive Development," in R. R. Turner and H. W. Reese, eds., Lifespan Psychology: Intervention [Academic Press, New York, 1980), pp. 149-184.

3. D, Rush, Z. Stein, and M, Susser, Diet in Pregnancy: A Randomized Controlled Trial of Nutritional Supplements (Alan R. Liss, Inc., New York, 1980).

4. B. Chow, A.M. Hsueh, and R,Q. Blackwell, "Taiwan Study," in Nutritional Supplementation and the Outcome of Pregnancy (National Academy of Sciences, Committee on Maternal Nutrition, Food and Nutrition Board, Washington, D.C., 1973), pp. 111-128.

5. R.Q Blackwell, B. Chow, K. Chinn, B.N. Blackwell, and S.C. Hsu, "Prospective Maternal Nutrition Study in Taiwan: Rationale, Study Design, Feasibility and Preliminary Findings," Nutr. Rep.. Int, 7: 517532 (1973).

6. R.M. Herriott, A.M. Hsueh, and R. Aitchison, Influence of Maternal Diet on Offspring: Growth, Behavior, Feed Efficiency and Susceptibility (Human) (final report on AID/CSD 2944 contract with Johns Hopkins University, 1977).

7. S.K, Joos, E, Pollitt, W.H. Mueller, and D.L. Albright, "The Bacon Chow Study: Maternal Nutritional Supplementation and Infant Behavioral Development," Child Development (in press).

8. M. K. Lam, E. Pollitt, and A.M. Hsueh, "The Bacon Chow Study: Dietary Supplementation and Food Intake during Pregnancy and Lactation," Amer. J. Clin. Nutr. (in press).

9 E. C. McDonald, E. Pollitt, W. H. Mueller, A.M. Hsueh, and R. Sherwin, "The Bacon Chow Study: Maternal Nutritional Supplementation and Birth Weight of Offspring," Amer J. Clin. Nutr., 34: 2133-2144 (1981).

10. W. H Mueller and E. Pollitt, "The Bacon Chow Sturdy: Effects of Nutritional Supplementation on Sibling-Sibling Anthropometric Correlations," Human Biology (in press).

11. J, Wohlleb, E. Pollitt, W, Mueller, and R, Bigelow, "Maternal Supplementation and Postnatal Growth," paper presented at the 12th International Congress of Nutrition, San Diego, Calif., USA, Aug. 1981.

African Nutrition Congress

The Second African Nutrition Congress will be held 2024 February 1983 in Ibadan, Nigeria. The theme of the congress will be "Food and Nutrition in Africa in the Eighties."

Consisting of symposia, invited lectures, free communications, and poster sessions, the congress will focus on the following subthemes:

- Food Production, Conservation, and Marketing,
- Nutrition and Primary Health Care,
- Nutrient I intake and Requirements,
- Food, Nutrition, and Population,
- Nutrition Training and Education

The organizers- the Department of Human Nutrition of the University of Ibadan, in conjunction with the Nutrition Society of Nigeria, and the International Union of Nutritional Sciences- extend an invitation to scientists and others interested in nutrition research and its applications.

The languages of the congress will be English and French.

The registration fee is US$80 (N 501 if paid before 1 October 1982; thereafter it will be US$160 (N 1001. Payment should be made to: Second African Nutrition Congress, Department of Human Nutrition, University of Ibadan, Ibadan, Nigeria.

Requests for information and all other correspondence should be sent to: Prof. Adewale Omololu, Secretary-General, African Nutrition Congress, Department of Human Nutrition, University of Ibadan, Ibadan, Nigeria.