Poor nutrition in first two years has permanent effect on growth and development, and could spell disaster for country

Afghanistan is raising a stunted generation whose hobbled development could spell disaster for the country's feeble economy and undermine the impact of billions of dollars in aid poured into health, education and other areas.

More than half of Afghan girls and boys suffer damage to their minds and bodies that cannot be undone because they are poorly nourished in the crucial first two years of life, doctors and other experts say. The finding raises serious questions about the legacy of more than 10 years of western involvement in Afghanistan.

"After the age of two years, stunting is largely irreversible, and has an impact on growth and development and cognitive function," says Carrie Morrison from the World Food Programme. "Over the longer term, it can have a very damaging effect on the national economy. Young people are not able to attain what they should be able to attain. Women who marry young and are stunted themselves give birth to a small infant and the cycle goes on."

Children who are not getting enough nutrients from their food suffer from what is known as chronic malnutrition. The problem afflicts poor countries worldwide, but in Afghanistan it is particularly widespread and persistent.

A decade after the fall of the Taliban government, 55% of the country's children are stunted because of inadequate food, Afghan government and UN data shows.

The statistic is a damning one for western powers that have poured billions into Afghanistan to fund development and reconstruction. The US alone has spent $90bn (£54bn). Such funding aimed to modernise Afghanistan, but return on the spending seems to have been low.

As foreign troops prepare to head home, violence is spreading and Afghanistan remains one of the world's poorest countries, with low life expectancy and poor healthcare for mothers and young children. The malnutrition problem is caused by the basic poverty of those who cannot afford healthy food, as well as poor hygiene and healthcare, the tradition of child marriage, and a web of other issues.

"We have whole families where food insecurity means they are all malnourished, but we [also] have rich families that have one child who is sick," says Alam Mohammad, 25, a doctor who swapped the chance of an easy city practice to work in Feroz Nakhchair, on the gruelling frontline of a fight for the country's future.

Half an hour's drive down a dirt track from the nearest country road, in a valley on the fringes of Taliban territory, every day he sees dozens of cases like Mojabeen, a thin 19-year-old mother of three whose leopard-print dress beneath her burqa seems incongruous with her life of constant hardship. She and her family live in a one-room house on a plain that is periodically flooded.

Her husband earns $2 or $3 a day, if he can find work, which is not enough to feed the small family. "My second child is living with my mother, as we can't provide for him," says Mojabeen, as she waits for her new baby to be weighed and examined.

Her children were at a disadvantage even before they were born because Mojabeen was so starved of nutrients that she could not pass on what they needed during pregnancy. In a district of around 13,000 people, the problem is so widespread that a programme set up for around 100 pregnant and breastfeeding mothers is serving more than four times that number.

Nevertheless, it can be hard for charities and the government to focus attention or funds on chronic malnutrition when the country is battling a more dramatic type of hunger, which is more straightforward to address: acute malnutrition.

In clinics nationwide, tens of thousands of babies and toddlers have experienced such severe shortages of calories that they have the protruding bones and distended stomachs familiar from photographs of famine victims. Acute malnutrition affects more than one in four children in some areas, but it can usually be resolved relatively quickly with a steady supply of high energy Plumpy'Nut feeding paste.

In some ways, children who suffer from chronic malnutrition are harder to treat as their need for help may not be so obvious.

"You might see a child who appears underweight, or short for their age, but it doesn't really tell you much unless you line them up against a well-nourished child. But it [chronic malnutrition] prevents them growing up to lead a more productive life," says Morrison.

She says a lack of iron, which affects three-quarters of Afghan children, reduces activity and productivity. In young children, it disrupts brain development, with effects including "stunting, sickliness, poor school attendance, and lower levels of concentration and memory". A lack of iodine is the world's leading cause of preventable mental impairment, and a lack of vitamin A hobbles the immune system, pushing up death rates among children under five. So severe is the damage that tackling it by lacing basic foods such as salt and flour with micronutrients has been rated one of the most economical ways to do good.

"In the worst-affected countries, the benefits of supplementation with vitamin A and zinc can be up to 100 times higher than the costs," according to a research paper on the impact of giving children "micronutrients".

The government has launched a five-year programme to fortify flour used to make flat bread – often the only daily food for poor families – oil and other foodstuffs.Progress has been slow on women's education, healthcare and hygiene

A recent World Bank study found a direct link between sanitation and height: a five-year-old child in a community where everyone uses a toilet is on average more than 2cm taller than a child from one where people defecate in the open.

But poverty is also a pressing problem, in a country where a third of all citizens do not always know where their next meal will come from. A recent UN study found that even a minimally healthy diet was beyond the reach of the majority of Afghans; in some provinces, only one in five could afford regular balanced meals.

While aid workers try to address problems that can take years to solve, health workers are held back by a focus on apparently more pressing problems. "We do worry about chronic malnutrition, but all we can give them is advice," says Nehmatullah Majidzafa, a nutrition nurse at an Oxfam-backed project near the city of Balkh, where most funds support feeding those children in most obvious need.

That includes demonstrations, with nurses chopping onions into a basic pressure cooker before adding lentils, rice and vegetables, and warnings to spend money on protein rather than the sugary foods many lavish on their children.

The information does help, because "parents don't know much about health here", says Mohammad. But many are already beyond his help.

"If a child comes in after too long with chronic malnutrition, he cannot fully recover. We can only teach the parents so they take more care it doesn't happen with their other kids."

Hunger in Afghanistan

Extreme poverty and a harsh climate mean many Afghans go hungry. One-third of the population do not get enough food to live healthy, active lives, and another third hover around the borderline of "food insecurity", or not knowing where their next meal will come from. But the food shortages are particularly damaging to young children, who need to develop fast.

International studies show that children who are properly fed can earn between a third and a half more as adults than those who did not get a proper diet, the World Food Programme's Morrison says.

And overall malnutrition shaves 2%-3% off Afghanistan's national income each year, the World Bank says. That's around half a billion dollars lost to an already very poor country.