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LETTER TO THE EDITOR |
Division of Metabolic Diseases
Piazza L Miraglia 2
80138 Naples
Italy
E-mail: dario.giugliano{at}unina2.it
Dear Sir:
We read with interest 2 articles published in the November 2005 issue of the Journal (1, 2). Both studies showed that a low-fat diet (
30% total energy from fat) lowered LDL-cholesterol concentrations by 7–10% in the short term (6 wk and 3 mo, respectively). However, there were some remarkable differences between the studies: HDL cholesterol decreased by 7% and triacylglycerols increased by 14% in the 6-wk trial (1), whereas there was no change in HDL cholesterol and a 12% decrease in triacylglycerols in the 12-wk trial (2). One possible explanation for the contrasting effects on the concentrations of circulating HDL cholesterol and triacylglycerol of the 2 similar low-fat diets, apart from the obvious difference in diet duration (6 wk compared with 3 mo), may be the constant weight the participants maintained throughout the 6-wk trial. In contrast, there was a mean reduction in body mass index (in kg/m2) of 1.2 (corresponding to 2 kg) in the subjects who followed the 3-mo diet. As pointed out by Ordovas (3), when low-fat diets produce weight loss, their detrimental effects (ie, reducing HDL cholesterol and increasing triacylglycerols) may no longer be evident.
Vincent-Baudry et al (2) showed no significant benefit of a Mediterranean-style diet on blood lipids compared with a standard low-fat diet, which led to the conclusion that both diets (Mediterranean-type and low fat) significantly reduced blood lipids and the calculated cardiovascular disease risk factors to an overall comparable extent. We think this message may underestimate the real advantage of the whole dietary approach in managing chronic disease. First, the follow-up may have been too short to detect a significant difference: for instance, in our study that compared a Mediterranean-style diet with a low-fat diet in subjects with the metabolic syndrome (4), the 2-y net change in lipid concentrations favored the Mediterranean-style diet [median (95% CI) changes: total cholesterol: –0.23 mmol/L (–0.44, –0.02 mmol/L); HDL cholesterol: 0.07 mmol/L (0.02, 0.14); and triacylglycerols: –0.21 mmol/L (–0.36, –0.06)]. Second, the positive effect of a Mediterranean-style diet on cardiovascular disease risk was also shown in the absence of any effect on blood lipids (5). Lastly, the global cardiovascular disease risk burden is composed of many components, of which lipids represent a huge part. However, the diet-lipids-heart hypothesis seems too reductive because it excludes many effects of diet on old and new risk factors, including blood pressure, endothelial function, vascular inflammation, insulin sensitivity, and oxidative stress (6).
ACKNOWLEDGMENTS
The authors had no conflicts of interest.
REFERENCES
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