Human height is complex, and many factors affect how tall a person will grow. But how much of your height is genetic and how much is due to environmental influences such as nutrition?
Many studies have estimated the heritability of human height. In this blog post, we'll have a look at a few of them and explore the relationship between your genetics and your body height.
How Genetics Affect Your Height
Human height is a confusing trait genetically. Your height is strongly determined by the inherited DNA sequence variants. Yet, it's only partially understood in which genes these DNA sequences are located in and what impact they have.
Your body consists of about 60 trillion cells. Inside the nucleus of each cell are 46 chromosomes. 23 are inherited each from the mother's egg and the father's sperm. These chromosomes are engraved with genes that represent our appearance, constitution, character, and responsiveness to disease.
Researchers have identified more than 700 variants of genes that affect human height. Many more are expected to be discovered in the next years. Some of these genes affect the cartilage in the growth plates, which are located in the long bones of your legs and arms where new bone is produced.
The function of many other height-associated genes remains unknown. Researchers have identified hundreds of other genes that are involved in rare growth disorders that have an extreme effect on height.
By studying the dramatic effects of altered genes, scientists hope to better understand the complex interactions among genes that contribute to normal height.
Heritability for Height Increases with Age
An international study published in 2012, examined the genetic and environmental influences on variance in weight, height, and BMI, from birth through 19 years of age. More than 12,000 twin pairs (boys and girls) from four different countries: Canada, Sweden, Denmark, and Australia were included in the analysis.
The results showed the heritability for body weight, height, and BMI was low at birth but increased over time. For body height, the effect of the common environment remained significant for a longer period during early childhood (up through 12 years of age). Sex-limitation of genetic and shared environmental effects was observed.
Genetics appear to play an increasingly important role in explaining the variation in height from early childhood to late adolescence, particularly in boys. Common environmental factors such as nutrition, exert their strongest and most independent influence especially in pre-adolescent years and more significantly in girls.
Girls' Height is Less Affected By Genetics than Boys' Height
In another study among Finnish twins, a difference in the genetic influence of gender was found. According to the study results, male height is more genetically affected (78%) than the height of women (75%). Subsequently, this means that women are more affected by environmental factors than men.
This study also showed that changing environmental factors affect the heritability of height. The heritability is slightly higher when the standard of living is better. A well-nourished, healthy, and active child is likely to be taller as an adult than will be a child with a poor diet, infectious diseases, or inadequate health care.
Studies on immigrant families have shown that moving to a country with better access to nutritious food, healthcare, and employment opportunities can have a substantial influence on the height of the next generation.
Genetic Impact on Height Depends on the Geographic-Cultural Region
In an international study with 45 twin cohorts from 20 different countries, the genetic impact between geographic-cultural regions (Europe, North-America, Australia, and East-Asia) was observed.
The genetic variance was greatest in North America and Australia, and lowest in East-Asia. However, the relative proportion of genetic variation was roughly similar across these regions.
This study supported the theory that the genetic influence on height is higher for men (up to 83%) than for women (up to 76%).
Body height is a characteristic that is influenced by both genetic and environmental influences. The genetic background of body height is not yet well known.
However, the latest studies suggest that the heritability of height is around 80% in well-developed countries. The genetic influence on height is higher for boys than for girls, which means that proper nutrition, is even more important for girls to maximize their height potential.
How does your height compare to your parents' and your siblings' heights? Let us know in the comment section below.
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