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Abstract

Human milk is relatively high in cholesterol compared with infant formula (10-15 mg/dL versus 0-1.1 mg/dL respectively). The high intake of cholesterol by breast-fed infants as compared to those fed formula has been shown in the past to result in high circulating levels of cholesterol. It is presently hypothesized that this abundance of cholesterol in the diet inhibits endogenous cholesterol synthesis, resulting in the low rates of cholesterol synthesis seen in breastfed infants, as opposed to formula-fed infants. Continual suppression of cholesterol synthesis in infancy may render the breast-fed infant less able to synthesize cholesterol as an adult. Ideally, when challenged with a high cholesterol diet as an adult, it would be preferable for the body to limit its own synthesis of cholesterol, in order to counterbalance the increased availability of cholesterol in the diet. Infants never having had to make their own cholesterol would have an advantage over those whose metabolism had been imprinted at a young age to synthesize cholesterol. This latter group may not have the same capacity to downregulate endogenous cholesterol synthesis as adults. Three groups of infants were used to examine the effect of cholesterol feeding in the first four months of life on serum lipids and endogenous cholesterol synthesis. Group one was breast-fed. Group two was fed a regular commercially available infant formula. Group three was fed the same formula enriched with cholesterol at a level similar to that found in breast milk (13 mgldL). There was no difference in serum lipids between breast-fed and formula-fed infants, nor between the two different formula groups. Total-cholesterol was 4.33± 0.85, 3.65±0.40, and 3.75±1.06 mmoWL for the breast-fed, modified formula-fed, and regular formula-fed respectively. LDL cholesterol was 2.18±0.81, 1.43±0.56, and 1.64±0,72 mmol/L respectively. HDL-cholesterol levels were 1.17± 0.26, 1.10±0.30, 1.07±0.14 mmol/L respectively. Triglyceride levels were 4.90±1.60, 5.61±2.48, and 5.15±2.20 mmol/L respectively. Fractional synthetic rates of cholesterol (FSR) were significantly (p