CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Juan Ruano, MD, PhD,
Jose Lopez-Miranda, MD, PhD and
Francisco Perez-Jimenez, MD, PhD*
* Reina Sofia University Hospital, Lipid and Atherosclerosis Unit, Internal Medicine Department, Avda. Menendez Pidal s/n, 14004 Córdoba, Spain (Email: md1pejif{at}uco.es).
We want to convey our gratitude to Drs. Gori, Giugliano, and Esposito for their interest in our work, which has caused us to reflect on the most relevant data in our study (1). Both letters emphasize a series of points with which we generally agree. With respect to the issues advanced by Drs. Giugliano and Esposito, a number of studies have investigated the effects of acute ingestion of olive oil using various amounts of this foodstuff that have usually ranged from 25 ml (2), 44 ml (3), 50 ml (4,5) to 65 ml (6), and 108 ml (7). After administering the lowest quantity mentioned here, Weinbrenner et al. (2) did not observe any significant alterations in either postprandial lipemia or oxidation markers. In our study, we decided to employ a volume of 40 ml, an intermediate value among those mentioned above, and one that does not exceed the mean daily consumption in Mediterranean countries. This design led us to register an increase in the concentration of plasma triglycerides, with a peak level occurring 2 h after the ingestion of both breakfasts. Moreover, unlike the situation in the study of Bonanome et al. (7), none of the participants displayed intolerance or rejection in the course of ingestion. Our choice of volume was based on our interest in studying the effects of an ingestion of olive oil approximately equal to the amount utilized in tests of postprandial lipemia, which tend to be about 0.5 to 1.0 g/kg body weight. We believe it could be interesting now to look for a potential threshold for the ingestion of phenolic compounds, employing different volumes or types of virgin olive oil, with the aim of arriving at a breakfast that would be easy to consume while guaranteeing the potential beneficial effect.
The comments of Dr. Gori also merit particular attention; his letter demonstrates a profound understanding of the methods involved in the study of endothelial function. The most interesting finding of our study was the rise in the values of ischemic-reactive hyperemia (IRH) following the ingestion of olive oil with an elevated content of phenols. We employ the term IRH rather than "microvascular endothelial function" as used by other investigators, because of the uncertainty arising from the lack of exact knowledge of the relationship between this parameter and endothelial function, although previous studies claim to have established such a relationship (8).
Conversely, the correlation between the plasma concentration of nitrates and nitrites and IRH was high (R2 = 0.588), which suggests that the availability of nitric oxide (NO), proceeding from the endothelium, plays an important role in the observed response of IRH. At any rate, Dr. Gori’s discussion is of great interest, and it will be necessary in the future to study the possible role of the mechanisms of neurogenic regulation of vascular tone and of hormonal and metabolic processes, which we did not evaluate in our study.
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1. Ruano J, Lopez-Miranda J, Fuentes F, et al. Phenolic content of virgin olive oil improves ischemic reactive hyperemia in hypercholesterolemic patients J Am Coll Cardiol 2005;46:1864-1868.[Abstract/Free Full Text]2. Weinbrenner T, Fito M, Farre Albadalejo M, et al. Bioavailability of phenolic compounds from olive oil and oxidative/antioxidant status at postprandial state in healthy humans Drugs Exp Clin Res 2004;30:207-212.[Medline] 3. Mekki N, Charbonnier M, Borel P, et al. Butter differs from olive oil and sunflower oil in its effects on postprandial lipemia and triacylglycerol-rich lipoproteins after single mixed meals in healthy young men J Nutr 2002;132:3642-3649.[Abstract/Free Full Text] 4. Fito M, Gimeno E, Covas MI, et al. Postprandial and short-term effects of dietary virgin olive oil on oxidant/antioxidant status Lipids 2002;37:245-251.[CrossRef][Web of Science][Medline] 5. Miro-Casas E, Covas MI, Fito M, et al. Tyrosol and hydroxytyrosol are absorbed from moderate and sustained doses of virgin olive oil in humans Eur J Clin Nutr 2003;57:186-190.[Medline] 6. Sutherland WH, de Jong SA, Walker RJ, et al. Effect of meals rich in heated olive and safflower oils on oxidation of postprandial serum in healthy men Atherosclerosis 2002;160:195-203.[CrossRef][Medline] 7. Bonanome A, Pagnan A, Caruso D, et al. Evidence of postprandial absortion of olive oil phenols in humans Nutr Metab Cardiovasc Dis 2000;10:111-120.[Web of Science][Medline] 8. Vuilleumier P, Decosterd D, Maillard M, Burnier M, Hayoz D. Postischemic forearm skin reactive hyperemia is related to cardiovascular risk factors in a healthy female population J Hypertens 2002;20:1753-1757.[CrossRef][Web of Science][Medline]
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