Does heart disease run in your family? Diabetes? Or cancer? Or maybe you come from a family that lives well into their 90s. People will often say it’s in your genes. And it’s not just in health or disease that genes matter. Who your parents are, and their genes, are involved in everything from the way you walk to your eye colour to even how you think. But your genes aren’t the same as fate. And a healthy lifestyle can do a lot to offset bad genes.
Genetics 101
Your body is made up of 20-30 trillion cells. And in almost all of those cells are somewhere between 20 000-30 000 genes. Each gene is made from deoxyribonucleic acid (commonly known as DNA) and encodes a unique protein. Proteins can be hormones, muscles, antibodies and enzymes, as well as for storage and transporting molecules throughout your body. Without DNA, we wouldn’t have proteins and wouldn’t exist.
While genes may differ from person to person, within the same person, the same genes are found in almost every cell in the body. But not all genes are used in each cell. Or all the time. For example, the proteins needed in your eyes differs from those needed for your heart. Therefore, genes are regulated within the cell depending on their purpose. Similar to lights in a house, genes are turned on and off as you need them.
Genes and DNA are referred to as hereditary material because you get your genes from your biological parents. Within each cell you have two copies of the same gene. One from each parent. It’s like an old family recipe that gets passed on for generations. That’s why people can often look like their parents and even distant ancestors. However, within these genes, there’s variation. This variation is extremely small <0.001% (and smaller between those who are related). But it’s these differences that account for why two people aren’t exactly the same.
How do your genes relate to your health?
The variation in genes can also affect your health. Sometimes these variations (or mutations) can lead directly to diseases such as cystic fibrosis, sickle cell anemia or familial hypercholesterolemia. These diseases are often rare (1 in 4000), show symptoms at a young age and compromise one’s health. However, this isn’t the case with most common diseases.
Diseases such as heart disease, type 2 diabetes and cancer do have a genetic component. And people who have one or more parents with these diseases may be more likely to get them themselves. But it’s far more complex than that. Each of these diseases have numerous factors involved and each of these factors have numerous genes involved. So, when most people get a disease, it’s hard to pinpoint as genetic. Even something seemingly as simple as height is complex. From twin studies it’s estimated that 80% of height is due to genetics. But this entails nearly 10 000 genetic variations.
A general rule of thumb is that the younger a person is when they get a chronic disease, the more likely it has a strong genetic foundation. However, since most diseases also involve a lifestyle component, this needs to be considered. For example, a person having a heart attack in their 40s may be the result of genetics. But if that person has been smoking for twenty years, doesn’t exercise and eats poorly, could it be due to poor lifestyle habits?
Genes can also be associated with better health and longer life. We often hear of stories of people who drink, smoke and never exercise living into their 90s. These people may be said to have “good” genes. Indeed, research has indicated a strong genetic link among families with long lifespans. And genes associated with longer life are those involved in DNA repair and the process of protein coding. This makes sense as poor DNA repair has been associated with shorter lifespan.
Can a healthy lifestyle make a difference?
If you’re at risk for a disease (or already have one), your doctor will likely ask if anyone else in your family has the disease too. Determining family history is an important part of a clinical assessment. And studies in twins indicate that the heritability of heart disease is between 40% to 60%, and for cancer it can range from 27% to 58% depending on the type of cancer. But that doesn’t mean if your parents or siblings have a certain disease, you will get it too.
Apart from rare genetic diseases, most diseases have a strong lifestyle component to them. In addition, life expectancy has increased in almost every country in recent decades. The percentage of people living past 100 continues to grow across the world. It’s unlikely this is due people’s genetics being changed in such a short time. Now some of this is due to improvements in prevention and health care, but people who live past 100 usually engage in regular exercise, have health diets and are socially connected.
Other research suggests the genetic contribution to lifespan is much less than we previously thought. One study found married couples have somewhat similar lifespans. And not much different from siblings. Another reported that less than 10% of the variation in lifespan is due to genetics. Together these studies concluded that lifestyle and environmental factors were more important to how long you will live.
Indeed, regular activity, healthy nutrition, adequate sleep, limiting alcohol and not smoking can extend your life regardless of your genetics. And the effect may be greater for those people who may be prone to have a shorter lifespan. These behaviours were associated with an extra 4.4 years of life in people who had a genetic risk for shorter life compared to 3.8 years in those with low risk. Studies in exercise and nutrition have shown these behaviours can be beneficial to how your genes work.
So, while you can’t change your genes, you can change how they affect you and your health.
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