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Earlier and more rapid ageing: Does nutrition contribute?

Table 1. Regressing the onset of ageing on the rate of ageing.
Gompertz Gamma-Gompertz
Without controls Controlling for cohort and country Without controls Controlling for cohort and country
Intercept 66*** 61*** 76*** 66***
Rate of ageing –193*** –166** –294*** –224***
2
R 0.28 0.83 0.38 0.83
** p < 0.01, *** p < 0.001,
Source: Authors’ computation on HMD Data.

3.1 Comparing Our Results with the Outcomes of the Calorie Restriction Experi-
ments
If an acceleration of physiological ageing did indeed occur over time, it seems natural to
wonder why. We do not know the answer, but we submit that the changed nutritional ha-
bits may have possibly played a major part in all this.
The relationship between nutrition and mortality has always interested demographers
since the times of Malthus (1798). In the last two to three decades, calorie restriction ex-
periments on animals have improved our knowledge because when the external (disturbing)
factors are kept under control or altogether eliminated, the role of nutrition can be better
understood. What holds for animals may hold for humans too or at least give some insights
into the process.
The first experiment of calorie restriction (CR) on rats dating back to the 1930s by
McCay et al. (Masoro, 2005), led to the counter-intuitive conclusion that a restriction in
food intake resulted in an extension of the rats’ lives. However, these results did not attract
much attention until the 1980s when they were confirmed by other similar experiments.
CR experiments have been carried out on yeast (Jiang, Jaruga and Repnevskaya, 2000),
fruit flies (Bross, Rogina and Helfand, 2005; Mair, Goymer, Pletcher et al., 2003), nema-
todes (Houthoofd, Braeckman, Lenaerts et al., 2002; Lenaerts, van Eygen and van Fleteren,
2007; Yen and Mobbs, 2008), crustaceans (Ingle, Wood and Banta, 1937), spiders (Austad,
1989), rodents (Masoro, 2005; 2009), dogs (Kealy, Lawler, Ballam et al., 2002), cattle
(Pinney, Stephens and Pope, 1972), primates (Bodkin, Alexander, Ortmeyer et al., 2003;
Colman, Anderson, Johnson et al., 2009; Colman, Beasley, Kemnitz et al., 2014; Mattison,
Roth, Beasley et al., 2012), and occasionally even on humans (Bartke, 2012; Holloszy and
Fontana, 2007; Longo and Fontana, 2009; Roth and Polotsky, 2012).
The outcomes of these experiments were summarized in Figure 5 (redrawn from Fon-
tana, Partridge and Longo, 2010) which showed three different conditions of food intake:
starvation, calorie restriction and normality. The normal condition was defined as a situa-
tion of ad libitum feeding, starvation meant that caloric intake was very low (below 50–

Figure 5. Relationship between food intake and median life span.
Source: Redrawn from Fontana (2010).

International Journal of Population Studies | 2015, Volume 1, Issue 1 50