You are what mum eats

By MARTIN JOHNSTON health reporter

Audiences shunned Professor David Barker when he first suggested that the answers to some of the West's worst diseases lay in the womb. "People used to walk out of the room," he says.

Now they queue to hear the head of the British Medical Research Council's epidemiology unit speaking about his theory that what happens before birth can set people up for heart disease, diabetes and stroke in later life.

Professor Barker says the key problem is a nutritional mismatch: shortages in the womb, followed by surpluses in childhood and adulthood.

Heart disease remains the leading killer of New Zealanders, accounting for nearly 30 per cent of deaths, despite a big reduction since 1970. And the incidence of diabetes is soaring as the country's waistline expands.

Professor Barker says adult lifestyle, the target of healthy-heart campaigners, provides some of the answers to heart disease. But it could not explain why one person who gulped cream and smoked lived to 95, while another who obeyed the health messages on diet, exercise and smoking died at 40.

"To say it's genetic is to dismiss it. The reality is that it's about how the body learned to handle it [nutritional deficits]."

In the 1980s, Professor Barker examined the birth and death records of thousands of people born in Hertfordshire in Britain early last century. "It became quite clear that people who are small at birth are at increased risk of coronary heart disease. So, too, are people who then grow well in the first year after birth."

Those weighing 2.5kg or less at birth had double the rate of death from coronary heart disease of those weighing 4kg or more. Smaller babies were also at greater risk of high blood pressure, stroke, type 2 (so-called adult-onset) diabetes and living a shorter life.

Professor Barker suggested that maternal malnutrition was largely responsible.

"The human baby is very plastic," said Professor Barker, brought to New Zealand by Auckland University for a series of public lectures. "It responds to the mother, it's shaped by the mother. If the mother is undernourished, the baby is undernourished."

He argues that babies' bodies become "hard-wired" for life - developing in different directions depending on nutrition in the womb, which in turn depends on the mother's reserves rather than on just her daily food intake.

One example would be a foetus that receives too little sugar. Its muscles will make do with less so that its brain and other organs get enough. But this can cause insulin resistance, which can lead to type 2 diabetes.

Another example of "hard-wiring" is that people who are smaller at birth have many fewer kidney cells. But the kidneys still have to do their job of purifying the blood, so each cell receives more blood.

"If you shove a lot of blood through tissue you can harm it," Professor Barker said. The damaged tissue, combined with the normal loss of kidney cells caused by ageing, can lead to high blood pressure.

Professor Barker's theory implies huge increases in heart attacks and other diseases for classes in poor countries that are affluent enough to improve their nutrition.

"India is in the middle of a huge epidemic of heart disease now," he said. "It's because the low-birthweight babies of India, of which there are a huge number, are for the first time in large numbers being raised to a stage of accelerated weight gain.

"There is better nutrition for adults and children, but it has left the foetuses untouched. The average birthweight in India is less than 6lb [2.7kg]."

Despite early controversy about Professor Barker's "foetal origins hypothesis", other studies have reinforced it. One involved Dutch people conceived or born during a famine in 1944 and 1945.

"The babies who were in-utero at the time undoubtedly have been altered permanently by the experience, the way we would expect.

"The interesting thing is that the babies grew quite well. They were able to grow because the mothers were well-nourished before the pregnancy.

"So there was a lot of reserve there. But they grew at a cost. They did various tricks which were fine at the time but predisposed them to diabetes later on, and coronary heart disease."

An American study of more than 120,000 women also backed the Barker theory. It found that those weighing 2.3kg to 2.5kg at birth had a 23 per cent higher risk of heart disease than those weighing 3.2kg to 3.9kg.

But the researchers also found that lighter babies have a much lower chance than heavier ones of developing breast cancer as adults.

Auckland University's Liggins Institute has an extensive research programme linked to the foetal origins theory.

Liggins director Professor Peter Gluckman, head of an international council on researching the theory, said his team was the first to demonstrate the diabetes link in a clinical trial of humans. It also proved the theory with experiments in animals.

Current studies include how twin and premature babies are affected, animal experiments on the mechanisms by which the uterine environment influences development, and whether the low-birthweight predisposition to disease was reversible.

Heart Foundation medical director Dr Diana North said there was now good evidence for the Barker theory. "We are trying to understand better the mechanisms of how it works."

Professor Barker said that based on his theory, more should be done to ensure that adolescent girls were eating a healthy, varied diet to reduce the next generation's disease risks.

Dr North said New Zealand had healthy-diet messages for pregnant women, but not specifically for adolescent girls.

"I think that's an area that will develop."

nzherald.co.nz/health