Child getting height checked by a doctor. Child getting height checked by a doctor. A new study says there's more to determining a person's height than genes. (Photo: Image Point Fr / Shutterstock)

Why are some folks short? New study says it’s more than genes

Your first year of life goes a long way toward determining how tall you will be.

What determines how tall we grow? Many believe it's largely a product of the genetic material handed down by our parents. But new research says it's not just genes that predict your eventual height. 

The findings, published in the Journal of Pediatrics by a team of doctors from three Israeli institutions, suggest the "nature" side of the equation plays only a small role in your growth – the "nurture" side, environment you were born into, comprises a larger percentage of height predictors than genetics.

Specifically, the study points to evidence that the period between gestation and age 1 is the most important period in determining a person's height.

To make their case, researchers followed 536 children over the course of two years. Most of the children were twins; 56 pairs were identical, 106 pairs were fraternal, and the rest (106) were pairs of siblings. Rather than waiting for the children to grow up in order to measure their final height, researchers instead focused on a stage of growth called the infancy-to-childhood transition (ICT). Defined mainly as the period that starts around 7 months of age and ends around 12 months, the ICT is the biggest predictor of adult height. Researchers found that a delay in ICT – that is, if a child does not undergo a significant growth spurt to signify the transition from infancy to childhood during those five crucial months – can increase the likelihood that the child will end up on the shorter end of the spectrum.

“Here we discovered the remarkable power of the environment in shaping a person.” – Professor Ze'ev Hochberg

So what causes this delay? Scientists say it's a combination of factors, including nutrition from mother to baby in the womb, and social and family interactions. For example, children who grow up in a malnourished environment will be shorter than they would have been had they grown up in a properly nourished environment, because they will require less food as they get older. 

“Following the genetics revolution, today it is customary to attribute our personal traits to the genes,” said Dr. Ze'ev Hochberg of the Rappaport Faculty of Medicine at the Technion-Israel Institute of Technology, who led the study along with Dr. Alina German of Bnai Zion Hospital in Haifa. “Indeed, there is no doubt that many of our features are genetic. However, as can be seen in our study, environmental conditions have a very significant role – around 50 percent – in determining growth and height.

“Studies on twins let us test the balance between genes and the environment,” Hochberg continued. “The difference between identical and fraternal twins shows the impact of genetics. Here we discovered the remarkable power of the environment in shaping a person."

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