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The effect of early feeding on human cholesterol synthesis at four months of age

University of British Columbia

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<O.OO1) different between breast-fed and regular formula fed infants. Values were 2.04±1.21% per day for the breast-fed group (n9) and 8.29±0.77% per day for the regular formula-fed group (n=3). FSR of the modified formula-fed group was 8.53±0.10% per day (n=5). There was no difference in FSR between the two formula-fed groups. Thus, addition. of cholesterol to infant formula did not result in suppression of cholesterol production. Rather, the same rate of cholesterol synthesis as the regular formula-fed group was observed. The number os subjects precluded the confidence level supported by a larger study population, hence resulting in a cautious interpretation of the data. However, from these findings it can be suggested that the form of the added cholesterol (unesterifled cholesterol) was not similar enough to that found in breast milk (partially esterifled cholesterol) to exert a significant effect. As well, one may further speculate that there is some other factor responsible, such as differences in fatty acid position on the triglyceride molecule between breast milk and infant formula. Even though breast milk contains significantly more cholesterol than infant formula, based on results of the present research, there is no advantage of fortifying infant formula with cholesterol.

Thesis/Dissertation

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2009-02-24

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http://hdl.handle.net/2429/5010

Family and Nutritional Sciences

University of British Columbia

UBCV

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