**Acknowledgement**

Authors thank the volunteers who participated in the experiments carried out for the present work. Thanks also to J. de la Cruz (Department of Applied Economy, University of Basque Country, Spain), F. Ainz (Department of Physiology, University of Basque Country, Spain), and to J. Bilbao (Department of Statistics, University of Basque Country, Spain) for their participation in the analysis of the data; and to S. Rainieri (Food Research Division, AZTI-Tecnalia, Spain) for helpful comments on the original manuscript.

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This study was supported by the Foundation *Jesús de Gangoiti Barrera*. G.A.G. was supported by a European Marie Curie Post-doctoral Fellowship (ADCOMP project; Contract MEIF-CT-2006-025056). The CONSOLIDER INGENIO 2010 must be acknowledged for supporting partially this work through grant CSD2009-00067.
