Height- What Establishes One's Height, can it be Changed?

Animation of the structure of a section of DNA. The bases lie horizontally between the two spiraling strands. (Photo credit: Wikipedia)

Height:

What Establishes One's Height, can it be Changed?

People come in a wide range of sizes and shapes.

Height is a quality of the body that draws a lot of attention.

In infancy, all of us use height to help us know if our baby is growing well.

Later in childhood, we all wonder, how tall will my child be, and the child eventually picks up on this wonder, asking, how tall will I be?

Many parents ask us, how is one's height determined?  Will exercise or nutrition influence how tall you can be?  When to worry about height?  What can be done to get taller?

How is Height Determined?

The maximum height a person will attain is set very firmly by that person's DNA, or genetic code.  It turns out there is not that much range to human height.  Nearly all humans are somewhere between 4 and 8 feet tall.  If you take a brief look at all of life, the range is far more dramatic.  Some forms of life never get taller than a tiny fraction of an inch (e.g., bacteria), and some forms can grow to be several hundred feet tall (e.g., trees).

Notice that for every form of life, though, there is a very narrow range of heights.  Dogs can only grow so tall, elephants attain a similar size across families of elephants, etc.  Just so for us humans.  These patterns give clear evidence that our height is as strictly dictated as the number of arms we will develop, or how many eyes we will have and where they appear on the face.  In short, a person's height is a structural rather than functional property of the body.  It's how the body is built, is the product of the structural design, and is not defined by how we use our bodies.

Not so with weight.  Weight varies far more dramatically and is defined by how much we eat and exercise. Our weight does reflect what we do.

Although we do not have the technology to do so yet, we do know that how tall a person will be, and the day they will reach that height, is all set in the information inside a fertilized egg.   Once a person's DNA is set, so is that person's ultimate height.

Will Exercise or Nutrition Change my Height?

One can make your height shorter than expected by severe malnutrition, but a healthy, well-nourished child cannot get taller by eating differently, or via specific exercise programs. Further, it takes quite a severe degree of malnutrition to decrease one's final height.  Sadly, this is not rare.  Much of the world is exposed to malnutrition severe enough to shorten ultimate height, and many more American children suffer this fate.

But the fact remains that if a child is well-fed, there are no foods or exercises that can increase one's height.

This makes sense if you think about the structural nature of height.  At conception, how tall someone will be is defined, so if the right materials are on hand to make that happen, it becomes difficult to add more to get more height.

When to Worry about Height?

There are two main reasons that raise concern when it comes to height: 

An abnormally slow rate of height gain, abnormally low height itself.

Before we look at each, a word about normal rate and height.
As noted, there are two aspects to height- your actual height at any age, and the rate of growth.
Normal actual height at any age is defined by a range of normal.  The most important word here is range.
For example, at 5 months of age, a male infant could be anywhere from 24-28 inches long and have perfectly normal height, even though the average is 26 inches.  That range of 24-28 includes about 95% of all male 5 month olds.  But not all.  About 1 in 20 very healthy, very normal 5 month olds will be a bit less than 24 inches long or more than 28 inches long.  

When it comes to rate of growth, there is more uniformity.  By age 2 or 3 years old, up to puberty, most children, boys and girls, grow about 2-2 1/2 inches a year.  Interestingly, that rate is pretty much the same whether the child is tall or short.  So kids destined to be 6 feet tall and those destined to be 5 feet tall both grow about 2-2 1/2 inches a year.

Last point on normality:  the percentiles are fun to observe and watch, and to share with family and friends, but by themselves, there is no "normal" percentile.  It is just as normal to be at the 10th percentile for height as it is the 90th.   As noted below, it is the actual height and rate of growth that determine if there should be concern, not the percentiles in the normal range.

So, the two situations when we get concerned are:

1.  The rate of growth is abnormally low.

Children who grow much less than 2 inches a year during the ages of 3-puberty do raise concern and should have their height gain evaluated.   The rate of growth in infancy varies quite widely, with younger babies growing faster than older infants.   Often during the newborn and early infancy stage, an infant can attain yearly, annualized rates of growth of 12 inches a year!  This rate, of course is not sustained. One of the great powers of the growth curve is that it can tell us at any age, at any height, if your child's rate of height gain is normal or of concern.

2.  The height is too low
As noted above, actual height has a bigger range than rate of growing.   Again, thinking about the 5 month old, there is an average height at that age in boys of 26 inches, but the range is 24-28 to cover about 95% of all boys this age.   We would typically say any height in the range that covers 95% of people is normal, but if it is far less, it does raise concern and should be evaluated.

What Can Be Done to Get Taller
As already mentioned, it is very hard to change your height upwards.  Since height is set by complex mechanisms set forth by one's DNA, boosted nutrition, extra nutrients, special exercises, and/or customized herbal mixes cannot increase your height.
The only mechanism yet proven to be able to increase a well-fed person's height is growth hormone.
Growth hormone works by turning on the division of various cells in the body, mainly bone cells.
But even when daily injections of growth hormone are given to a child, sometimes there is no increase in the eventual outcome of that child's height, dramatically demonstrating how hard wired a person's growth is.

A mention should be made of the special case of growth hormone deficiency.  Some children have a deficiency in this hormone and they typically will have lower than normal rates of height gain that lead to evaluation, as outlined above.  Or they may present with very short stature.  Injections of growth hormone are the only known treatment for this condition, but even in this setting, some children do not grow faster, although most do.

BOTTOM LINES
1.  Height is set very firmly by each person's DNA.  
2.  One's final height can be shortened by severe malnutrition or serious diseases, but in healthy children it is very difficult to increase their ultimate height.
3.  That is, special diets and exercises and medications cannot increase height, with the sole exception of growth hormone.
4.  The use of growth hormone is a very serious intervention that subjects the child to daily injections and exposure to a powerful hormone.  It should not be used except after very careful evaluation.
5.  The concept of normal for height is defined by a range of actual height and of rate of height growth at any age.
6.  Most boys end up somewhere between their Mom's height plus 5 inches, and their  Dad's height.
7.   Most girls end up somewhere between their Mom's height and Dad's height minus 5 inches.


Dr. Arthur Lavin

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