Should We Restrict Dietary Fat and Cholesterol Early in Life? Idamarie Laquatra PhD, RD, Nutrition Consultant, Pittsburgh, PA. Infants grow and develop rapidly during the first two years of life, explaining their high energy requirements during this time. Fat, an energy-dense nutrient, is a necessary component in the diets of infants and young children because of their extraordinary energy needs and limited stomach capacity 1. In addition, essential fatty acids provide substrates for arachidonic acid and docosahexaenoic acid which accumulate in the central nervous systems of developing children. Deficient amounts of these long-chain fatty acids may adversely affect visual development and intelligence 1. In their Statement on Cholesterol, The American Academy of Pediatrics recognized the importance of fat in the diet of infants and young children. The Academy advised that no restrictions be placed on the fat and cholesterol content of the diet of infants from birth to two years of age 2. The Joint Working Group of the Canadian Paediatric Society and Health Canada stated that science simply cannot support a recommendation for a restricted fat intake for all Canadian infants 3. The Group recommended that from the age of two years to the end of linear growth (after the growth spurt of adolescence), there should be a transition from the high fat diet of infancy to a diet that includes no more than 30% of energy as fat and no more than 10% of energy as saturated fat. Recently, the popular press has picked up on a report of a study in Finland and suggests that lowering dietary fat during late infancy or early childhood may reduce the risk of cardiovascular disease in later life. This article is a critique of the Special Turku Coronary Risk Factor Intervention Project for Babies (STRIP) 4,5. The objective of this long-term coronary prevention project was to evaluate the impact of an individually supervised, low-fat, low-saturated fat and low-cholesterol diet on infants and healthy children. In this prospective trial, 1062 healthy seven-month old-infants were randomized into an intervention or control group. The intervention group met with a pediatrician, nurse and dietitian during visits at one to three month intervals until the age of two years and then twice yearly. At the age of four years, 816 children continued their participation in the study. The following dietary advice was given during the visits: the best diet for the child was one that satisfied the child's hunger, with 30-35% of calories from fat before three years of age, after which the fat content of the diet was to be tapered to 30%; a polyunsaturated:monounsaturated:saturated fatty acid ratio of 1:1:1; daily cholesterol intake of less than 200 mg, 12 - 15% of energy from proteins, and 55 - 58% from carbohydrates. Intervention-group mothers were encouraged to breast feed or formula feed until the infant was one year of age. Fat intake was not to be reduced before the age of 13 months. After one year of age, 0.6 liter of skimmed milk was suggested for daily use, and the addition of vegetable oil or soft margarine was encouraged to reach a fat intake of 30 - 35% of calories from fat until age two. The use of leaner meat products and low-fat cheese was advised. Parents of infants in the control group were not counselled but met with the research team twice yearly from the beginning of the trial. Their dietary advice followed the guidelines used in the Finnish well-baby clinics: parents were advised to continue breastfeeding or formula feeding until the child was one year old; thereafter, cow's milk with at least 1.9% fat was suggested. No other suggestions concerning the quality of fat in the diet were given. Food consumption was evaluated using food records kept on three or four consecutive days at 8, 13, and 18 months of age and at six-month intervals thereafter. Blood samples were drawn to measure serum cholesterol, high-density-lipoprotein cholesterol, and apolipoproteins A1 and B. During the trial, children in both groups continued their regular visits to the well-baby clinics for vaccinations, long-term growth follow-up and health education. In the first publication from the trial, Lapinleimu and colleagues reported on dietary analyses, growth effects and changes in blood chemistries when the infants were eight and 13 months 4. Only formula-fed infants were included in the analyses at eight months because the volume and composition of breast milk could not be adequately estimated. Among infants who received formula as the only milk source, mean energy intakes at eight and again at 13 months were significantly lower in the intervention versus control group. Despite the seven percent lower caloric intake at both time periods, the mean growth did not significantly differ between groups and compared favourably with the growth curves for Finnish children. The researchers did not explain how infants in the intervention group maintained their growth despite consuming significantly fewer calories than the infants in the control group. A lower level of physical activity has been suggested as the reason for the lack of effect of a reduced calorie intake on growth velocity 6. A prospective study of Ugandan children supports this reasoning 7. Despite energy intakes 30 percent below recommended levels, Ugandan children demonstrated growth rates similar to those of healthy English children. These children were able to maintain a virtually normal rate of growth due to a reduction in activity which lowered their energy requirements. Reduced physical activity may have a negative impact on infants and children. Energy for play, physical activity, exploration of the surroundings, learning, and interactions with other children and adults is necessary for normal growth and development 8. Lapinleimu et al. also reported that fat intake in both the intervention and control groups was less than 30% at eight months and 13 months. This was contrary to the initial target of not reducing the fat intake until after 13 months of age. Possibly, the low fat intakes were due to the use of skim milk in the intervention group and 1.9% fat milk in the control group perhaps even before the infants reached 12 months of age. According to the authors, another possible explanation for the low fat intake could be that the studies were not blinded. Bias may have been introduced by parents trying to appease the study personnel and they may have been overly zealous in trying to protect their children from heart disease. Closer examination of the growth data in the STRIP Baby Project indicated an alarming problem in both the intervention and control groups. While the mean growth compared favourably with Finnish growth curves, almost 10% of the infants in both groups were seven percent or more below the average weight for height for healthy Finnish children at age 13 months. The energy and fat intakes and the dietary fat composition of these slow-growing children were similar to the other children in the study who did not exhibit slow growth. No explanation for this observation was presented. It is conceivable that some infants exhibit a greater vulnerability to alterations in calories and fat than others. Alternately, the diet records may have been inaccurate. A number of reports have documented growth failure when calories and fat are restricted in infancy. Pugliese et al. reported on the parental misconceptions and health beliefs which caused failure to thrive in a group of infants seven to 22 months of age 9. Poor growth was secondary to decreased caloric intake due to a low percentage of energy contributed by fat. Lifshitz and Moses reported growth failure in young children associated with unsupervised dietary treatment of hypercholesterolemia 10. The patients who had growth failure were generally older, having consumed the restricted diets for a prolonged period. Finally, Hansen et al. reported a small, but significant growth deficit as a result of dietary intervention in children, ages one to 17 years, with familial hypercholesterolemia 11. The most likely explanation for the less than optimal growth was an inadequate energy supply. In the second report of the STRIP Baby Project, nutrient intakes of children aged eight months to four years were evaluated 5. In addition to the markedly lower fat intakes by the children in the intervention and control groups at and after weaning, the authors noted that intervention resulted in a decreased intake of saturated fatty acids and cholesterol in the one to four-year-old children. Intakes of vitamins, minerals and trace elements by the intervention and control groups of children were similar and adequate throughout the study. They fulfilled the Nordic Nutrition Recommendations, with the exception of vitamin D and iron. Supplementation of these two nutrients was routinely advised for children in both groups. The calorie intakes of children increased with age. No data were reported on growth in the second study. Results from other studies on the effect of a reduced-fat diet on the nutrient intakes of children have been mixed. The effect of variation in percent fat in the diet of a sample of 871 ten-year-olds was investigated in the Bogalusa Heart Study 12. Results indicated that a greater percentage of children in the low fat intake group (< 25% of calories) did not meet the Recommended Dietary Allowances (RDAs) for vitamin B6, vitamin B12, vitamin E, thiamin, riboflavin and niacin, when compared to the high fat group (>40% of calories). Also, the percentage of total sugar intake was higher in the low versus high fat group. A cohort study of preschool children demonstrated that calcium intakes were less than the RDA in the lowest two quintiles of fat intake (27 - 30% of calories). Mean intake of iron was close to the RDA regardless of level of fat intake, and mean intakes of phosphorus, thiamin, riboflavin, niacin and vitamins A and C were above the RDA in all quintiles of fat intake 13. Because both of these studies were observational in design, they do not directly address the effects of intervention on nutrient intake. Given the state of scientific knowledge in the area of heart disease, the reports from the STRIP Baby Project raise a critical issue: Should fat be altered during the first two years of life? The STRIP Baby Project is not the first to show that fat intake during the first two years of life is lower than recommended. This does not mean that the current recommendation for fat intake of infants is overstated. In fact, biochemical and long-term clinical evaluations are needed to address the issues. Should this be the basis for a change in the dietary recommendations as soon as the infant is weaned to reduce the risk of cardiovascular disease in later life? No data exist to support the idea that restriction of dietary fat and cholesterol in infancy modifies the risk of atherosclerosis in adults. What purpose, then, would a restriction serve? The authors of the STRIP Baby Project contend that a low-fat diet would more likely be followed when implemented early in life. No data exist to support this contention. Finally, the parents in the STRIP Baby Project received intensive counselling by a pediatrician, nurse and dietitian at each visit. Although this might be a model for intervention in sick children, it does not represent usual care in a well-baby setting. Close supervision is needed when any alteration in diet occurs during this sensitive time of life; otherwise compromised intake of energy and certain essential nutrients and sub-optimal growth and development may occur. References
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