As we go through life, our health and wellbeing is impacted by a variety of factors that in turn affect our growth and development.
These include social, economic, political, and emotional factors, and they are working on us all the time - even now!
Though these factors can have a positive impact on our bodies, they can also have a negative effect; issues such as poverty, loss of a loved one, safety fears, and job insecurity can result in a prolonged and constant feeling of stress, known as ‘chronic stress’.
Chronic stress can lead to a variety of different biological changes in the body – ranging from cellular-level tweaks to altering hormone levels – and can contribute to many health problems in adults.
And if experienced regularly by children, chronic stress can stunt growth.
“If you live with intense levels of fear or stress, it gets internalised and turned into stress hormones”, explains Emeritus Professor Barry Bogin, an expert in Biological Anthropology in the School of Sport, Exercise and Health Sciences.
“If you have high levels of stress hormones every day, these stress hormones actually stop bones from growing.
“Chronic stress inhibits the production of the two most powerful hormones that promote bone growth.
“These are growth hormone and insulin-like growth factor-1. A lack of these hormones can stop growth in height.”
In the latest episode of the Cuppa with a Scientist podcast, Professor Bogin discusses the impacts of stress on the body and his research into the interactions between human biology and culture.
He tells host Meg Cox about his studies focused on the children of Maya communities, from Guatemala, and how he found migrant Maya children grow physically taller over relatively short periods of time after moving to more affluent areas.
When asked why Maya children are of scientific interest, Professor Bogin said: “Guatemala is the one country in the Americas that has the most stunted children – 47% of all under five-year-olds are of very short stature and that is a sign that living conditions are bad for them.
“Most people think that when they're that short it's because they're not eating or they're very ill, but that’s not the case.
“And the real kicker in Guatemala is that 17% of newborns to five-year-olds from the richest families are still stunted.”
He continued: “Guatemala is home to 18 million people, yet 260 people control 50% of all the wealth in the country, and the whole society pays the price.
“Everybody lives in fear. I think it’s the 12th highest murder rate in all the world for murders per 100,000 people and it’s the third highest murder rate for women across all categories.
“Only one out of every hundred murders ever go to court, which means murderers are getting away with it…rich people are sending their kids to school in bulletproof automobiles with armed guards.
“If you live with that kind of fear, it gets internalised into the stress hormones that slow growth.”
In the early 90s, Professor Bogin visited a Florida school that gave places to very poor children, 200 of which were from Maya communities.
“I measured the children, and they were already three inches taller than the same aged, same-sex children back in Guatemala”, Professor Bogin said.
“Then in 2000, anthropologist James Loucky and I found that Maya children in Florida and Los Angeles were five inches taller than the children in Maya communities, and some of those kids had been born in Guatemala.
“We almost did a minute-by-minute analyses, and we found the longer the children were in the United States, the taller they were.
“It was the biggest increase in height ever measured in that short period of time in one generation.”
In his papers ‘As tall as my peers – similarity in body height between migrants and hosts’ and ‘Fear, violence, inequality and stunting in Guatemala’, Professor Bogin concludes that more food, better health care, and better education are key factors in the change in height.
“But also shared by everyone is the reduction in violence and fear that exists in Guatemala and the psychological stimulus to grow taller and be like ‘real’ United States people”, Professor Bogin added.
“In the USA, the Maya remain economically poor, but they have greater safety and security, and this can make people grow taller.”