Why tall people have higher hopes of good health

Measuring a young boy's height

By the time we reach adulthood, how tall we are is something we are powerless to change.

Our parents' height is a major determining factor, but genes are not the whole story.

What we eat, how we live and our general health are all important too, especially early in life.

New research which found that taller men and women have an increased risk of getting cancer may be a depressing thought for those towering over 6ft.

But don't start planning any drastic action just yet.

The increased cancer risk is very small in comparison to the risk posed by smoking, for example, and cancer experts say tall people should not be alarmed.

In general, being tall is still associated with better health.

Prof Tim Cole, from the Institute of Child Health at University College London, says tall people tend to have a good start in life and continue doing well.

"Broadly, if you compare economic groups, the higher social classes are taller because they have a less constrained lifestyle and better nutrition."

Genes v environment

Up to 80% of our final height and stature is thought to be down to genes.

The most important period of growth occurs in infancy - during the first two years of life.

This is a crucial time when factors like diet, general health, standard of living and environment can have an influence on what is inherited from mum and dad.

Image caption American Robert Wadlow was 8ft 11in tall in 1940.

And it is also when any adult height trends can first be picked up.

A recent report written by Prof Cole said that: "The increase in height from one generation to the next occurs mainly in the first two years of life, due to increases in leg length."

Since the mid-19th Century, adult height has been increasing in many parts of the world, with grown-up children ending up taller on average than their parent of the same sex.

But average heights in England have changed very little over the past 15 years.

Figures collected by the Health Survey for England show that in 2009 the average height of women aged 16 and over was 5ft 3in (1.61m). The average height of men over 16 was 5ft 9in (1.75m).

These figures lag way behind average heights in Holland and Norway, the tallest countries in Europe, where male adults average 6ft in height.

In the UK, the upper limits of normal height are around 5ft 11in for women and 6ft 5in for men.

Footballer Peter Crouch, at 6ft 7in, and ex-model Sophie Dahl, at 6ft, are both unusually tall - but they are simply the product of tall parents.

Other very tall people may have genetic abnormalities that make them grow way beyond the normal height range.

Tallest of all

The record-breaking Robert Wadlow from Illinois, the tallest man in medical history at 2.72m (8ft 11in), was an anomaly.

His exceptional height was attributed to an overactive pituitary gland, which produced much higher levels of growth hormone than normal.

Medical science would be able to treat such problems today - but in the 1920s there was no therapy available.

His stature, like other extremely tall men, caused a variety of medical problems.

He had trouble walking as he grew taller throughout his life and eventually had to wear braces on his legs.

He died in 1940 after developing an infected blister following the fitting of a brace.

So is there an ideal height for humans?

Noel Cameron, professor of human biology at Loughborough University, says there is no such thing as an optimum height.

Instead, he says, there is a normal or average height which differs significantly between populations.

"In Somalia, for example, children who survive are smaller and have adapted to their poor environment. The conditions in which you live are important.

Image caption Boys and girls have different growth rates during puberty.

"Children still get infectious diseases, despite rapidly improving healthcare, so the first few years of life are fundamentally important. But to be tall you've got to live in environments conducive to good growth."

Boys to men

One thing for certain is that men are, on average, taller than women.

Prof Cameron says this is because puberty occurs later in boys than in girls.

"The adolescent growth spurt occurs in males around 12 years old then they start growing quickly between the age of 14 and 18. Girls start puberty two years earlier and stop growing at 16.

"The extra growing time for boys gives them 5cm more height per year and explains the 12-13cm difference in height between men and women."

When we reach maturity and stop growing vertically, the long bones in our legs and arms stop lengthening, which occurs when the growth plates close and ossify.

After that, the only movement is likely to be downward as we shrink in old age.

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