Understanding stunting

There’s no getting around the fact that stunting is a controversial and stigmatising term. A stunted plant, for instance, is not something you’d want in your garden.   

To determine if children in a population are experiencing stunting, their height, often measured at two years of age, is compared to a global average. Those falling two standard deviations below are deemed to be stunted and very likely saddled with a physical and mental handicap for the rest of their lives.  

At first glance, height might seem an unlikely predictor for matters so profound. And surely such predictions are confounded by the fact that height is strongly controlled by genes.  Take well-nourished Europeans: the Dutch are notoriously tall compared to their southern European neighbours. Or compare populations of less well-nourished Africans: the Sudanese are far taller than central Africans. 

Travel around Asia and people are uniformly smaller. Surely, they’re not all stunted? 

According to the World Health Organisation definition of stunting, about a third are. 

So, is it valid to compare diverse ethnic populations to a global average? 

After more than a decade of fielding such concerns, public health experts are unshakeable in their confidence that for adequately nourished humans, the rate of growth for all healthy infants is the same.

Their confidence stems from a set of WHO standard growth curves introduced in 2003. Based on the six-year Multicentre Growth Reference Study, they captured the growth of 8500 well-nourished children from Brazil, Ghana, India, Norway, Oman and the US.   

According to WHO, “The standards describe normal child growth from birth to five years under optimal environmental conditions and can be applied to all children everywhere, regardless of ethnicity, socioeconomic status and type of feeding”.

A 2014 study published by researchers from Oxford University in the UK and funded by the Bill & Melinda Gates Foundation supported the WHO finding, showing that in 60,000 women living in heathy environments, across the US, UK, Brazil, Italy, China, India, Kenya and Oman, the mean birth length for full term newborns was the same: 49.4 centimetres.  {%recommended 618%}  

Of course, that does not mean that every well-fed newborn on the planet will be the same length.  Every population shows a spread of heights for people at any age.  

In well-nourished populations, 2.5% of children are likely to be stunted. But throughout Asia and Africa, the entire growth curves are shifted to the left. 

“It means the population as a whole is not meeting its full growth potential,” says Jessica Blankenship, a UNICEF nutrition specialist based in Bangkok, Thailand.

The idea that people are small because of their genes is also challenged by the fact that in poor countries the growth of affluent children matches that of the WHO growth curves.   Every public health worker tells a similar story.

Working as a community doctor with Tibetan hill tribes in the late 1990s, Chris Morgan, a paediatrician at Melbourne’s Burnet Institute,  found “100% of the people were well below normal height”.  But the more affluent population in Lhasa were much taller. 

And it’s not just the affluent. Many developing countries are making nationwide gains.  Mongolia is a stand-out, reducing its child stunting levels from 33% to 11% in 20 years. 

Others, such as Laos, Thailand and Mynamar, are making slower gains; PNG and Timor Leste appear to have stalled.  Overall, a recent press release from the US Food and Agriculture Organisation warned, the Asia Pacific will not reach the target set in 2012 by the World Health Assembly   to reduce stunting levels by 40% by 2025. 

Nevertheless, stunting as a marker of population health and development still throws up conundrums. 

For instance, one place you would expect stunting rates to be low is Kerala, one of the most developed states of India with 92% female literacy and rates of infant mortality on par with that of the US.  Yet the rate of childhood stunting is 19%, similar to that of Senegal, a West African nation with 47% female literacy and over four times the infant and maternal mortality rate. 

As a recent online Indian article noted, “surely an impossibility”.

Not for Blankenship, who studied in Kerala.  She suspects poor rates of breastfeeding and cultural beliefs such as eating less in pregnancy to avoid a large baby could be involved.

Combating stunting, she acknowledges, is complex.  “It’s not just about access to resources; it’s about knowledge.” 

The first part of this investigation, looking at stunting in Papua New Guinea, can be found here.