How genetic information can support your family’s health: a guide

Medical conditions, disorders, and diseases can be caused by many things. Bacterial and viral attack, for example, can result in illness. Sometimes environmental factors come into play, like lifestyle and dietary choices, as well as complications arising when we have an accident. But what if the source of the problem comes from within the body — from problems with our genetic code? That's when advances in genetic information become so vital to understanding our health. Being armed with information can help us not only understand but improve our family's health.

This article includes information on the following topics:

• Adverse drug reactions
• Allergies and intolerances
• Genetics and metabolism
• Genetics and nutrition
• Hereditary conditions and family medicine
• Pneumonia
• Stroke
• COPD (chronic obstructive pulmonary disease)
• Cancer
• Heart disease

What is our genetic code?

Within the nucleus of human cells, there are 23 pairs of chromosomes — each of these made from two long DNA molecules. Sections of these molecules, known as genes, contain a code to tell the cell how to grow, perform, and renew itself. We get one set of chromosomes from each of our biological parents and they dictate things like eye and hair colour, whether you can roll your tongue, and whether you write with your right hand or your left.

This code is made up of the way that four basic biological compounds are put together. These are called adenine, cytosine, guanine, and thymine (referred to as A, C, G and T, respectively). Similar to the way in which different combinations of letters make up words, different combinations of these letters make up what’s known as a gene. There are thousands of genes on one strand of DNA.

There is also a small amount of DNA found outside the nucleus, in the mitochondria. These are tiny structures within each cell that convert food into energy and help to manage the life and death of the cell. A relatively new area of study, scientists have discovered a number of conditions linked to mitochondrial DNA, which is exclusively passed along the maternal bloodline¹.

What happens when things go wrong?

Mutations or changes can happen in our genetic code. This can be brought about by environmental conditions, such as exposure to certain chemicals like those contained in tobacco or pollutants in the air.

Some people are born with genetic disorders. For a few, the effects are so serious they don’t make it past childhood. Others don't discover that there's a problem until later in life, and some people have no symptoms at all. It’s also possible to have a genetic disorder, develop no illness from it but then pass it on to your children. This is known as being a 'carrier'. Then there are people born with extra chromosomes, such as individuals with Down’s syndrome.

How can science and medicine help?

The field of study that looks into genes and their interaction with our health is called genomic medicine. According to the U.S. National Human Genome Research Institute, this is:

"… an emerging medical discipline that involves using genomic information about an individual as part of their clinical care (e.g. for diagnostic or therapeutic decision-making) and the health outcomes and policy implications of that clinical use."²

In other words, it's about investigating the complex biological details of an individual and using these for effective diagnosis and tailor-made treatment.

This article looks into the findings, outcomes, limitations, and new advances in the field, but first explores some of ways in which a person’s genetic code can affect their health and, by extension, that of their family.

Read our introduction to genomic medicine here.

The difference between the terms genetic and genomic

There’s a subtle but profound difference between the two fields of study and you’ll come across both terms throughout this guide.

Genetics looks at specific genes or groups of 'letters' along the DNA strand. This is useful for finding specific abnormalities in the code that lead to conditions such as cystic fibrosis and haemophilia.

The term genomic refers to the study of someone's entire genetic makeup: including all the genes together with their chemical environment. It's about how they relate and react with each other and is associated with conditions that have a broader range of triggers such as diabetes, heart disease, cancer and asthma.

Managing risk and making changes

The World Health Organization (WHO), which gathers data and makes informed plans to help raise the level of human health around the world, monitors the number of cases of non-communicable disease every year. Non-communicable diseases include cancer, heart disease, and stroke — the types of illnesses that are not spread from human to human in the way that bacterial and viral ones are.

They are of interest to WHO and those working in the field of genetic medicine because, very often, they are caused by an interaction of environmental factors and genetic tendency. This means that someone who is at risk can work with their doctor and other health care professionals to minimise their chance of developing the condition.

Heart disease

There are many conditions that can affect the heart. According to WHO, cardiovascular disease was the leading cause of non-communicable disease deaths in 2012, claiming the lives of 17.5 million people.³ Some heart conditions are passed on genetically from parents to children: hypertrophic cardiomyopathy, for example, hardens the muscle wall of the heart. If a family member already suffers from a heart condition, or if there is a history of sudden cardiac arrest in the family, a person might take preventative tests to find out in advance if they’re likely to suffer from the same condition. But sadly, such conditions often lead to unexpected deaths with little or no previous symptoms.

Recent pioneering research has led to a new blood test that can screen for all known inherited heart conditions.⁴ Where previous tests involved more work and time, and were limited in what they could pick up, new technology can look for abnormality across a wider range of genes.⁵

Those with a family history of heart disease, but no symptoms, often need to be monitored to make sure that if the condition does develop, it can be managed. If they undergo this form of genetic testing and it proves they're not at risk in this way, the monitoring will be unnecessary. Not only can this save lives but it can also save money too.

Cancer

It is estimated that cancers caused 8.1 million deaths worldwide in 2012.⁶ Caused by genetic mutations, there are two types. Acquired mutations are the most common and come about through exposure to certain environmental triggers such as tobacco, UV radiation, and age. Some cancers, (about five to 10 percent)^(Ibid) are caused by what's known as germline mutations, which are inherited, passing from generation to generation through cells in the body. While the body is good at dealing with altered genes on a day-to-day basis, sometimes a certain changed gene or a build-up of many may cause cells to grow uncontrollably, and this is what causes harmful tumours to develop.

A progressive approach to pharmaceutical and surgical interventions means that in countries like the UK, for example, more people than ever are surviving cancer⁷ and, in recent years, attention has been increasingly drawn to prevention as well as cure. As part of this, it is now possible to have a genetic test to ascertain your risk of getting certain cancers for example: ovarian, breast, thyroid, and colon. Although it cannot tell you for certain whether or not you will go on to develop cancer, at least you'll know if you need regular screenings and to make lifestyle changes in order to lower your risk. It also gives you an indication on whether you're likely to pass the mutated genes on to your children.

COPD

COPD, or chronic obstructive pulmonary disease, claims more lives than any other non-communicable condition worldwide, with 17.5 million people dying from it in 2012.⁸ In reality, it's not one condition but an umbrella term that includes diseases such as bronchitis, which involves narrowing and inflammation of someone’s airways, and emphysema, which is responsible for damaging the lungs' capacity to work properly.

Environmental factors can lead to COPD. Prolonged job-related exposure to chemicals or dust, air pollution, and second-hand smoke can damage your lungs, but by far the most common cause is smoking — with as many as eight out of 10 cases⁹ of COPD being caused through direct tobacco use.

However, it is thought that as many as one in six people(Ibid) who develop COPD have never smoked, and in some people it is caused by a genetic condition called AAT deficiency.¹⁰ A disease that starts with the production of abnormal proteins in liver cells, it affects the balance of certain vital functions and leads to lung as well as liver damage. A blood test to ascertain AAT levels is used as part of the diagnosis process, but a genetic test is also available to assess whether it's possible to pass the condition on to the next generation. While there are a number of ways to effectively manage AAT deficiency, it's best diagnosed earlier rather than later. Genetic testing in someone who has the condition can help with assessing risk for the rest of the family.

Stroke

It's estimated that stroke causes 10 percent of all deaths worldwide and it's the third biggest killer in developed nations¹¹. There are different variants, but generally speaking it's caused by an interruption of blood flow to the brain — either by blockage or an accumulation of blood in and around the brain.

It's well accepted that lifestyle choices affect risk.¹² Smoking, lack of exercise, and poor diet can lead to fatty deposits building up on the blood vessel wall — either causing a blockage in-situ or breaking off and stopping blood flow elsewhere.

From a genetic standpoint, there are many conditions that can lead to stroke in which hereditary tendencies play a part — it's believed that these can contribute up to 50 percent of an individual's risk.¹³ For example, a high level of harmful cholesterol in someone's body will put them in danger. For some, this will be as a result of diet and poor lifestyle choices but, for others, this is genetic, as we don't just eat cholesterol, our bodies make it too. Because there is such an array of conditions that can contribute to stroke risk, there is, as yet, no one singular genetic test that can assess this for an individual. But collaborative research is underway to pool resources and publish research on the subject.¹⁴

Pneumonia

Caused by a bacterial or viral infection, pneumonia is not generally accepted as a genetically triggered condition.

It can be an indicator of an underlying genetic disorder, however, particularly in those who have regular and persistent bouts. There are no tests to reveal whether a healthy person is susceptible to the pneumonia, but for those with specific conditions, it throws up certain patterns. A study in 2010¹⁵ looked at people with the autoimmune condition lupus (or systemic lupus erythematosus — SLE) and drew a link between bouts of pneumonia and faults on a certain gene.

Accountable for 16 percent of childhood deaths under the age of five, pneumonia killed 920,000 children in 2015.¹⁶ It is a common but life-threatening condition that needs to be taken seriously. With advances in medicine and research, doctors may at some point be able to pinpoint genetic markers to help identify pre-symptom tendencies that can be picked up through screening.

Hereditary conditions and family medicine

Sometimes it's said that a condition 'runs in the family'. This can be caused by environmental factors, such as family and social habits relating to food, exercise, employment, and local climate. At other times, the reason is purely genetic, and for some it’s the effect of the interaction between nature and nurture. There are also conditions that are more common in certain ethnic groups: like sickle cell anaemia in those with an African, African-American or Mediterranean background, for example.

Family medicine means just that: care for you and your family at a local level. A doctor you know and trust and who knows you and those close to you. Someone who can refer you for specialist treatment if necessary, but retains general oversight of your care and who acts as a central point of reference for day-to-day concerns.

Providing a full family history at this level is important. The American Medical Association recommends doctors to compile a comprehensive history and has a number of tools to assist.¹⁷ The kind of information required includes: age of relatives (or how old they were when they died), certain details about close and more removed relatives, ethnicity, and conditions that seem to run in the family. Building this complete picture means that the physician can arrange necessary screening, look for early symptoms, help the individual manage risks and have a care plan in place should problems arise. From a holistic point of view, they can arrange counselling if necessary.

Genetics and nutrition

On a very basic level, nutrition is central to good health. Most people with a known family history of stroke or heart disease, for example, can improve their chances of a healthy life by restricting their intake of LDL or bad cholesterol¹⁸ and the American Heart Association's Healthy for Good movement advocates eating as many colours of fruit and veg as you can.¹⁹ Of all the external influences, food is thought to be the most likely to affect the level of risk.

Moving beyond minimising risk, a new area of science and medicine is looking at a more direct link between genes and nutrition and whether disease caused by a faulty gene can be stopped in its tracks.²⁰

While much of the language for how our cells replicate is already hardwired into them, there is evidence to show that what we eat can have an effect on how this language is expressed. In other words, there is a link between nutrition and the way our genetic make-up affects our lives. It adds weight to what some people have known for a long time: food and medicine can work together, even when considering serious conditions such as cancer.²¹

There are also studies suggesting that a good diet goes hand in hand with DNA stability.²² In other words, what we eat can either provoke or prevent harmful genetic mutations that can then go on to cause disease.

Genetics and metabolism

Just as diet can affect the way our genes work, our genes can affect the way our body processes what we eat. The word metabolism describes the complex chemical reactions that happen within our body, the way that it breaks down our food into a form it can use to function properly, and then how it gets rid of the waste.

Problems can arise when this chemical process is out of balance, causing low blood sugar levels, liver problems and muscle wastage, for example. There are hundreds of genetic metabolic disorders and, like most conditions, they are best treated or managed when they're diagnosed as early as possible.

There is also a cutting-edge area of research related to obesity. According to the WHO, worldwide obesity has more than doubled since 1980 and 11 percent of men and 15 percent of women over the age of 18 were obese in 2014.²³ One of WHO's global targets is to reduce this alarming rate of increase through education and research. Scientists have identified a few genes that can affect the way in which people put on weight.²⁴ While it’s emphasised that this doesn't need to be someone's destiny, it does explain why some people struggle with their weight, and having this knowledge to hand will help them to take steps to combat it.

Allergies and intolerances

Allergies cause daily misery for millions around the globe, from those causing minor symptoms to others that pose mortal danger. It happens when the body mistakes a normal substance as harmful and puts its barriers up, causing things like a runny nose, watery eyes, a rash, and swelling. It becomes dangerous when this leads to anaphylactic shock. With symptoms such as a blocked airways, fainting, and a racing heartbeat, it's a serious condition that needs urgent medical treatment. The most common allergens are grass and tree pollen, dust mites, and animal skin or hair. Materials such as latex can trigger a problem, as can foods like nuts, fruit, milk, and shellfish. The list is endless as it’s possible to develop a reaction to just about anything.

One of the most common conditions linked with allergies is asthma, with common symptoms including coughing, wheezing, and difficulty in breathing. It is thought that 300 million people suffer worldwide and the condition is responsible for 250,000 deaths annually²⁵ — so it's something that needs to be taken seriously.

Each of us is a unique organism that responds in a different way to our surroundings. There is a play between genetics and environment but, depending on the allergy and the person, the balance between the two can be subject to wide variance. Research has highlighted over a hundred contributory genes and, as asthma is not one disease but an umbrella term covering many illnesses with similar symptoms, it’s difficult to pinpoint exact family tendencies.²⁶

But the research continues and scientists remain positive. One study suggests that a genetic glitch, not directly triggering an allergic reaction but part of the signal pathway that leads to it, could be common to most allergies.²⁷ Although genomic medicine is some way off from preventing allergies, at least this approach may help to limit the risk they pose.

Adverse drug reactions

A new emerging area of medicine, pharmacogenetics²⁸ is an area of study that aims to avoid adverse drug reactions and optimise pharmaceutical use.

Studies indicate that there are certain ethnic groups who have a tendency to adverse reactions, as a result of genetic variation. Take, for example, the anticonvulsant carbamazepine, often used by people with epilepsy. It's been shown that patients with South East Asian ancestry are more likely to develop a life-threatening skin condition after taking this drug, and the underlying problem has been traced to a variation in the section of genetic code that controls our responsive immune system.²⁹ Considered such a serious problem, in 2008 the U.S. Food and Drug Administration recommended screening the ethnic group for the particular gene type before prescribing the drug.³⁰ Of course, there is always the voice of caution: screening should not take the place of medical vigilance.

Time to think

By understanding that which is already written down in our genetic code, it is possible to predict and manage what happens in the future. New advances in genomic medicine create an environment where we can make sound health care plans, seek advice, and get treatment in the vital early stages of disease.

Click here to read more about genomic medicine

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