It’s not just genes, diet or exercise – children also need love, hope and happiness to grow tall and develop physically, a human development expert has said.
Professor Barry Bogin, a biological anthropologist at Loughborough University, said a young person’s emotional wellbeing is critical for preventing stunted growth.
He said that not being loved by those nearest and lacking any hope for the future causes “toxic emotional stress” that can harm the body, “including blocking hormones needed for growth and height”.
Prof Bogin said: “The human species requires strong social and emotional attachments, that is love, between younger and older people (and) indeed between people of all ages.
“These attachments are required to promote nearly all biological functions, such as food digestion and absorption into the body, a good immune system, and an overall happiness and positive outlook on life.”
Prof Bogin, who has been studying how humans grow for nearly five decades, said that countries like Guatemala, where citizens live in uncertainty, political turmoil and are exposed to violence, has some of the shortest people in the world.
The average Guatemalan man is around 163cm tall while the average woman grows to around 149cm.
Prof Bogin said that, on the other hand, Netherlands – which has the tallest people in the world with men averaging around 183cm and women 169cm – have policies that support the social care and security of its citizens.
He said: “If you don’t have security, healthcare, education and you worry about the future, you can’t have hope and that is what leads to chronic toxic stress and blocking of hormones (that promote physical growth).”
As part of his review, published in the Journal of Physiological Anthropology, Professor Bogin analysed the historical records of height spanning nearly two centuries from the 1800s to the 1990s.
This period covered the Long Depression – a period global economic recession that lasted from 1873 to 1879.
As well as causing hardships such as famine and illnesses, the Long Depression harmed the wellbeing of people globally, Prof Bogin said.
Data from historical records of the heights of soldiers, conscripts and prisoners showed men born in the US in 1873 – at the start of Long Depression – were around 3cm taller than those born in 1890 – the aftermath of the economic crisis.
In the UK, the average height of men also stagnated during the same period – showing a slight rise of 1cm from 1873 to 1880 followed by a similar decrease from 1880 to 1890.
After that, the average male height increased rapidly for every year of birth, from around 169cm in 1890 to 177cm in 1960 in the US and from around 167cm in 1890 to just over 176cm in 1960 in the UK.
Prof Bogin said this data is important because height is a “sensitive indicator of economics in times when there were no economic data, especially for the working class”.
He said in cases like these, genetics, diet and physical activity cannot explain the changes in height.
However, Prof Bogin also added other periods of global crisis, such as the Great Depression of the 1930s as well as the First and the Second World War did not have a similar impact on height, possibly because the UK and US governments put “massive public works programmes that put people to work”.
He said: “They didn’t make a lot of money but having a job and a livelihood is essential to self-esteem, and hope for the future.
“So I think there was an enlightened attitude towards those governments.”