For the last 15 years, since discovering the human genome, studies have found connections between our genetic profile and the likelihood of developing certain diseases. A genetic predisposition or susceptibility is the increased chance of developing a particular disease based on your genes. Our genetic predisposition comes from specific genetic changes that are inherited from our parents. These genetic changes contribute to the development of a disease, but they do not directly cause it. Some people with a predisposing genetic variation will never get the disease, while others will. Why is this? It is because risk of disease generally does not have a single cause, but depends on a variety of different factors, including lifestyle and environment. It is therefore possible, by having a healthy lifestyle, to reduce the chance of disease risk even if there is a genetic predisposition.
Certain genetic changes can have a large effect on the chance of developing a particular disease. The BRCA1 and BRCA2 genes are a good example. These genes greatly increase a person’s risk of developing breast and ovarian cancer, and little lifestyle factors can change this.
Other genetic changes have a much smaller effect on the chance of developing disease. Research is focussing on identifying those genetic changes that have a small effect on disease risk, but that are common in the general population. Often, when several different gene changes occur, that combination increases the disease risk greatly. Disease such as cancer, obesity, diabetes, heart disease and mental illness have been shown to be linked to many small changes in the genes.
Lifestyle risk factors still play the larger role in the development of diseases than genetic risk factors. Lifestyle factors such as diet, exercise, smoking and alcohol consumption can play a large role in determining whether or not you develop a disease. What research is showing us is that our lifestyle choices can actually change our health at the gene level. What this means is that positive lifestyle choices (healthy eating and exercising) have a strong effect on our genes. Studies have shown that if you eat healthily you can ‘turn off’ the genes that put you at a higher risk for heart problems. In one study, people who ate more fruit and vegetables had a lower risk of heart disease, regardless of whether they carried the genes that increase their risk for heart disease. In this study, people who genetically had the highest risk of having a heart attack, had double the risk if they did not include fruit and vegetables in their diet.
Nutrigenomics is the study of how food components effect our gene expression. This gives us a better understanding on how to optimise our nutrition on an individual basis, depending on our genes.
There are some fantastic studies being done on obesity and nutrigenomics. Because of our genetic variations, we all respond differently to diet. One of the most studied genes related to obesity is the FTO gene. People with the AA genotype of this gene had a higher BMI (body mass index) than those with a TT genotype, and this was found especially in those who had a very high fat or carbohydrate diet. This means that if you have the AA genotype for the FTO gene, you will struggle with your weight if you have a high carbohydrate OR a high fat diet (both of these nutrients need to be moderate in this case). You may have seen how a ketotic diet, which is a very low carbohydrate and very high fat diet, only works for some people.
It is important to understand that your genes affect your health, but that the level of risk to getting the disease depends on your lifestyle. Prudent eating (which consists of a diet of fruit, vegetables, legumes, nuts, fish, whole grains and low-fat dairy products) has been shown to help protect against genetically predisposed diseases. Making healthy lifestyle choices therefore means avoiding a health issue rather than experiencing it. Will you choose health?