As Daniel Patrick Moynihan, an American sociologist, politician, and diplomat once said: “Everyone is entitled to his own opinion, but not his own facts”. And we wholeheartedly agree. A shared set of facts is the first step to building a better world with longevity for all. In that spirit, we are creating a series that covers 101 indisputable facts about ageing, health and longevity.
Greying hair, though entirely cosmetic, is one of the most well recognised signs of ageing. Over time, individual hair strands lose their colouration. This process can begin earlier or later in life depending on environmental and genetic factors, but the hairs on one’s head usually go grey before anywhere else on the body.
Hair acquires its colour from a pigment called melanin, which is produced by cells called melanocytes located at the base of each hair follicle. There are only two types of melanin in hair: black-brown eumelanin and yellow-red pheomelanin. The ratio of these two pigment determines hair colour, while the overall amount of pigment determines the ‘lightness’ of the hair. As we age, melanocytes produce less melanin and eventually die, leading to the loss of colour. This is thought to be mainly due to damage caused by reactive oxygen species – molecules that steal electrons from other molecules and cause them to break.
The main determinant of when and how rapidly hairs turn grey is your genes. However, studies suggest that environmental factors are associated with accelerated greying including smoking, poor diet and obesity, exposure to ultraviolet light and some nutrient deficiencies, though these associations are generally weaker than genetic factors. There may also be some truth to the idea that stress can turn your hair grey, and a study in 2020 suggests that this process is not always permanent. They found that greying of individual hairs was correlated with stressful life events, but that hairs could return to their original colour after just a few days once stress levels fell.