Ageing
The biological processes that gradually damage cells and tissues with age, on which diet has a documented influence, notably through oxidative stress and muscle mass.
Ageing is not a single phenomenon but the sum of several mechanisms: accumulation of oxidative damage, shortening of telomeres, declining mitochondrial efficiency, glycation of proteins and a decline in autophagy, the cellular recycling that clears out damaged components.
Two nutritional levers stand out consistently. The first is countering oxidative stress: the polyphenols, carotenoids and antioxidant vitamins in plants limit the damage caused by free radicals. The second, more neglected, is preserving muscle mass: sarcopenia sets in from your forties and speeds up afterwards, yet muscle determines independence, balance and basal metabolic rate.
Protein needs rise with age, they do not fall. This is a common misconception. Ageing brings anabolic resistance: you need more protein to get the same muscle synthesis as at thirty. Recommendations for older adults have therefore been revised upwards, and intake works best when spread over all three meals rather than concentrated in the evening.
Calorie restriction and fasting are the subject of a great deal of longevity research, mainly in animals. In humans, caution is needed after 65: cutting intake without watching protein simply speeds up muscle loss, the opposite of what is intended.