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Dear Sir:
King et al (1) present very intriguing fatty acid profiles from the serum lipids of subjects fed varying amounts of carbohydrate. One of the many points of interest is the elevation in myristic acid (14:0), palmitic acid (16:0), and total saturates in the phospholipids (PLs) and cholesteryl ester (CE) fractions in response to a low-fat (17% of energy), high-carbohydrate diet. Also of interest in this report is the lack of data quantitating the total serum triacylglycerol fraction and its fatty acid composition.
Given the great interest in the atherogenic properties of saturates, particularly palmitic acid (2), the composition of serum total and saturated fatty acids in response to a low-fat diet is important. This is especially true for the serum triacylglycerol fraction, which transports the greatest amount of fatty acids among the serum lipid fractions.
Ruderman et al (3) and Dreon et al (4) reported that the substitution of carbohydrate for fat during a eucaloric diet raises total serum triacylglycerol, which was confirmed by others (5, 6). If, as these prior reports have shown, the low-fat, high-carbohydrate diet raised fasting serum triacylglycerol in the current study by >50%, and assuming that the 14:0 and 16:0 contents in the triacylglycerol fraction increased by 10–20% (as King et al report for the PL and CE fractions), this translates to a near doubling of the circulating mass of 14:0 and 16:0, despite the total dietary fat being cut by 50% in these subjects.
Given the intensified discussion of the health effects of a low-fat diet because of the recent publication of the Women's Health Initiative results (7), it would be of considerable interest to see data from the current study for the serum total triacylglycerol and its saturated fatty acid composition with the transition to the 17%-fat diet in King et al's study. This apparent paradox of markedly increased 14:0 and 16:0 contents in the triacylglycerol fraction despite the dramatic reduction in dietary fat might help explain the lack of health benefits observed in the Women's Health Initiative diet study, despite the increase in dietary fruit and vegetables during the low-fat arm.
ACKNOWLEDGMENTS
The author had no personal or financial conflict of interest with respect to the study by King et al.
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