The ageing process and our body's metabolism are closely linked. Ageing is a very complex process in which the interaction of different organs, environmental influences or, for example, the microbiome play a role. The health benefits of a balanced and healthy diet have been known for a long time [1, 2]. However, research results have also shown that a reduction in food intake leads to a healthier and often longer life in many organisms - potentially also in humans . Importantly, dietary restriction is defined as reduced food intake while avoiding malnutrition .
Animal research is essential in understanding the basics of the ageing process
Some people voluntarily reduce their food intake to age more healthily and live longer, such as the International Calorie Restriction Society. Initial studies show that this voluntary dietary restriction has positive effects on mood, sexual behaviour and sleep in participants . However, in humans, the effects of external influences on the ageing process can never be ruled out. For example, genetic predisposition and external factors such as nutrition, environment and stress affect the ageing process . Animals in a laboratory environment provide the opportunity to keep these external factors constant, and thus allow studying ageing process independent of these variables. In addition, they allow for causal and in-depth studies that are essential to elucidate underlying molecular processes.
Understanding complex mechanisms such as the ageing process requires research on living organisms. Only in this way can the interaction of the various organs, but also the influence of the body's immune system, metabolism and hormone systems be taken into account. Research into the ageing process in model organisms such as mice, fish, flies and worms is therefore essential.
Mice live healthier and longer under dietary restriction treatment
Mice live longer and are healthier in old age if they are given 40 percent less food starting at young age, than mice that are allowed to eat at will. The mice are fed food enriched with vitamins and minerals to prevent malnutrition. Dietary restriction animals receive food once a day - in other words, they perform interval fasting. Compared to animals that are provided with food around the clock and whose body weight steadily increases with age, these animals maintain their body weight throughout their lives . They generally show higher levels of physical fitness, improved learning and memory function, and are better protected against age-related diseases such as diabetes or cancer.
Our recent dietary restriction experiments with mice, showed, that if mice only reduced their food intake in their senior years, their life expectancy remains largely the same. The body therefore had a kind of memory of the earlier diet and dietary restriction at old age had no beneficial effect on survival .
Thus, dietary changes in mice are only healthier if they are started early and maintained into old age. Scientists conclude that healthy behaviours need to be established earlier in life to improve health in old age and extend lifespan, which might also be important in the human context.
- Moore, K., et al., Diet, nutrition and the ageing brain: current evidence and new directions. Proc Nutr Soc, 2018. 77(2): p. 152-163.
- Pallauf, K., et al., Nutrition and healthy ageing: calorie restriction or polyphenol-rich "MediterrAsian" diet? Oxid Med Cell Longev, 2013. 2013: p. 707421.
- Fontana, L., L. Partridge, and V. D. Longo, Extending healthy life span--from yeast to humans. Science, 2010. 328(5976): p. 321-326.
- Fontana, L., et al., Long-term calorie restriction is highly effective in reducing the risk for atherosclerosis in humans. Proc Natl Acad Sci U S A, 2004. 101(17): p. 6659-6663.
- Martin, C. K., et al., Effect of Calorie Restriction on Mood, Quality of Life, Sleep, and Sexual Function in Healthy Nonobese Adults: The CALERIE 2 Randomized Clinical Trial. JAMA Intern Med, 2016. 176(6): p. 743-752.
- Melzer, D., L. C. Pilling, and L. Ferrucci, The genetics of human ageing. Nat Rev Genet, 2020. 21(2): p. 88-101.
- Hahn, O., et al., A nutritional memory effect counteracts benefits of dietary restriction in old mice. Nat Metab, 2019. 1(11): p. 1059-1073.