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Things that Yoram knows: Is it healthy to be tall?

DP asks: Big dogs live less than small ones, so how is it that taller humans are healthier?

Height differences between humans. Image:
Height differences between humans. Image:

The world, we must admit, belongs to the tall: only in eight out of 30 election campaigns in the US since 1900 has the short candidate defeated his tall opponent, about 90% of the CEOs are taller than average and statistical data consistently show a distinct gap in income in favor of the tall. It seems that the economic and social success of the tall is also related to their health: studies show that short people get more heart disease. A study that compared no less than 35,000 pairs of twins found that even though they grew up in the same environment and some of them (the identical twins) shared the exact same genetic load, the shorter twin's chances of dying from heart disease were distinctly and consistently higher than their taller brother's. As a general rule, an increase of 5 cm in height reduces mortality from heart disease by about 6% and mortality from stroke by over 10%.

Since the middle of the 19th century, there has been a jump in life expectancy at the same time as an equally impressive leap in height: the average European is no less than 20 centimeters taller than his ancestors and outlives them by about half a jubilee. This increase in body size has devastating environmental consequences: in order to feed, clothe, house and transport a person 180 cm tall, greater resources must be invested in energy, water and land than is required for a person 160 cm tall. If we multiply this difference by the 9.7 billion people expected to populate the planet in 2050, we will see that the increase in height is a difficult problem for future generations. But does humanity benefit from this growth, at least in terms of health? 

In nature, large animals live longer than small ones: elephants and whales reach an almost human lifespan, while rodents spend no more than two years in the world. The reason for this, most biologists agree, is that small animals consume more energy in relation to their weight and therefore the cumulative damage to the tissues is also faster. Why shouldn't the same legality apply to big people as well? Apparently it is difficult to argue with such clear findings linking height to health, in almost every human culture women will prefer a tall partner and it seems that this is indeed a "natural" marker of health that medical research confirms its reliability. And yet there are those who challenge this assumption.  

 Thomas Samaras, who has written quite a bit about the connection between height and health, tries to prove that the statistics lie: the health problems that short people suffer from are not the result of the lack of centimeters, but the opposite: the short stature is the result of childhood diseases that continue to take a toll throughout life. The maximum height to which a person can grow is fixed in the genes and the height they actually reach at the end of puberty, that is, the degree to which this potential is realized is related to nutrition, childhood diseases (so, for example, infectious diseases of the digestive tract and respiratory tract infections take a toll) and the resources that were available to us even before Birth: twins are shorter on average than those who grew up alone in the womb.

Maximizing the potential

In Japanese, for example, the height potential is smaller than in the average American, but the person who has reached the maximum of his height potential is the one who had a healthy childhood and this health will accompany him further regardless of the final height. Thus, even though within each ethnic group the taller ones are healthier than the lower ones, under equal environmental conditions the lower groups are actually healthier. In California, where a comparison can be made between different immigrant communities that all receive adequate nutrition and advanced medical services, East Asians are actually healthier than their white neighbors, who are about 10 cm taller than them on average. But Samars is not satisfied with this statistical clarification. According to him, height in itself is not only not useful but actually harmful to health.  

To pump blood to a longer body, the left ventricle of the heart that feeds the aorta needs to be larger and heavier in a tall person and this large heart muscle is a risk factor for heart disease. The blood pressure of tall people is also higher which increases the risk of stroke. Other researchers point to another risk factor to the detriment of tall people: to grow a long body, you need more cells, meaning more cell divisions during growth. As we know, the number of divisions that each cell can go through is not unlimited, therefore tall people have more "old" cells than their short friends. To test this, the regenerative capacity of the fibroblasts was tested: the cells responsible for the production of collagen is the protein that keeps our skin taut in 90-year-olds. The relationship between height and the number of divisions these cells are still able to undergo was tested.

Since people in their 90s tend to lose height as a result of the thinning of the cartilage between the vertebrae of the spine, the span of the hands was also measured: the distance between the fingertips of the two hands when they are spread out to the sides, approximately equal to the height (as Leonardo da Vinci already knew when he painted the famous Vitruvian Man). As the researchers expected, the cells taken from the short sixties were able to divide more times than the cells of the tall elders.

To circumvent the bias in favor of the tall in studies of groups of people with similar genetics, Samars suggests comparing neighboring ethnic groups that share the same environment but differ in height due to genetic differences and shows that the short are consistently healthier than the tall. Thus, for example, only about 2% of Muslims in the Indian subcontinent suffer from heart disease compared to 7% of their Hindu neighbors who are taller than them. Among American Indian tribes, heart disease increases as the average height of the members of the tribe increases, and among European nations, Portuguese men (average height 165 cm) are healthier than Italians (170 cm) and much more so than Germans (175 cm). The patients with the most heart diseases are also the tallest - the Scandinavians. Another evidence of the advantage of short is the long life expectancy of older twins. The reduction of resources in the overcrowded womb makes twins, and in particular twins identical to smaller ones at birth and in adulthood, meaning that they are a sort of human equivalent of bonsai trees (some of which reach extreme longevity). A study that followed twins born between 1917 and 1927 and who served in the US Army (that is, a sample that does not include those whose low birth weight caused early death or disability) found that the life expectancy of the identical twins was 82 years, of the non-identical twins 80.5, while the life expectancy of The average of those who were born alone in those yearbooks was only 73 years. The tendency of armies, since the First World War, to record the height of young recruits is a statistical gold mine: in a study of the life expectancy of former soldiers on the island of Sardinia (a fairly homogeneous population in terms of genetics and nutrition) it was found that a height lower than 161 cm at age 20 predicts an increase of two years to life.

Since it is difficult to separate genetics from the environment in humans, some researchers turn to the help of our best friend. In dogs, a clear trend is observed: the small breeds live longer than the large ones: Chihuahuas live longer than wolfdogs and very large dogs such as Great Danes or Saint Bernards die at the age of 6-7. The phenomenon is seemingly paradoxical: when comparing life spans between different species, there is an obvious preference for the large ones, but when you examine different varieties of the same species or closely related species of the same type, the small ones actually lead, thus the small Asian elephant lives much longer than the large African elephant and the pony reaches extreme old age compared to the tall racehorses . 

An accepted theory holds that the length of the growth period does not change much so that large breeds reach their dimensions by growing faster in childhood and this burden of rapid growth takes a toll on health in adulthood. Thus, the Great Dane puppy had to grow 100 times in the first year of life, while the poodle is content with a 20-fold increase in weight in the same period of time (our Tifat sisters are content with a 3-fold increase in weight by the first birthday). Rapid growth creates a lot of free radicals, the damage they cause will be felt by the large creature in adulthood. Studies from recent years focus on the life-shortening effect of growth hormone. The hormone that until a few decades ago was marketed as a virtue for eternal youth turns out to increase the risk of a variety of diseases from cancer to diabetes and accelerates the deterioration of brain abilities in old age. When growth hormone was given to a strain of life-extending dwarf mice, the mice grew more and died younger than their siblings who did not receive the hormone supplement, life extension was recorded even when growth was inhibited through dietary restriction.

Since no one would think of raising "Bonsai children" by such means, height, whatever its health significance, is not under our control, so all that is left is to reassure parents that their child's height percentile bothers them and hope that Samars' gloomy predictions will not come true in the tall world to which they are growing.

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