Predicting whether dietary restriction would increase longevity in species not tested so far.
- Eric Le Bourg
- Ageing research reviews
The book Calorie restriction, aging and longevity edited by Everitt, Rattan, Le Couteur, and de Cabo has been written in a time of transition between the epoch when nearly every biogerontologist was convinced that caloric restriction (CR, also called dietary restriction, DR, by other authors) increases longevity and the current time, when a growing number of experts think that the longevity variations have to be linked with the composition of the diet rather than with calories per se. The sentence of Brian Morris introducing his chapter: ‘‘It is well established that caloric restriction (CR) extends lifespan of all species tested’’ illustrates the opinion of many experts and the reader could be thus disappointed when reading the chapter by Simpson and Raubenheimer, who clearly show that calories have no effect on longevity of various species, but rather that it is dependent on the ratio between carbohydrates and proteins, i.e., CR does not increase longevity. The first part of the book, which describes the effects of CR in various species (humans, monkeys, flies, yeast, etc.) in seven chapters, is suffering from a major problem, according to me: some authors are so convinced by the validity of CR/DR to extend lifespan that they overlook contradictory results. For instance, the chapter on monkeys by Messaoudi et al. concludes that it has been reported ‘‘a lower incidence of agerelated deaths in monkeys after more than 20 years of study’’, but ignores other longevity results and criticisms of other authors (review in Le Bourg 2010). Similarly, that on Drosophila melanogaster written by Poirier et al. ignores authors who have reported absence of longevity increases and concludes that ‘‘extending Drosophila life span via DR has been firmly established’’, without also considering that studies on other fly species could not report longevity increases. The chapter on human beings by Everitt et al. curiously gives credence to the idea that the 102years longevity of Luigi Cornaro could be linked to DR, while his birthdate seems to be unknown (various sources report dates varying between 1457 AD and 1484 AD). This chapter is in fact more concerned with the effects of diet, lifestyle, body-mass index, and so on, on longevity than with that of CR itself, as no results showing that CR could increase longevity in human beings have been published (see the debate in Biogerontology, 2006, vol. 7, issue 3). The second part of the book is entitled ‘‘Biochemical and metabolic mechanisms of calorie restriction’’ and contains six chapters. In their chapter on oxidative stress, Merry and Ash conclude that there is a ‘‘limited support only that oxidative stress and damage is important in controlling the rate of aging and is the mechanism through which DR feeding acts to increase longevity’’, while this idea of a link between DR and free radicals was often considered in É. Le Bourg (&) Université Paul-Sabatier, Centre de Recherche sur la Cognition Animale, UMR CNRS 5169, 118 route de Narbonne, 31062 Toulouse cedex 9, France e-mail: firstname.lastname@example.org