Chronic disease — a broad category that includes such common conditions as diabetes, cardiovascular disease, and cancer — is the leading cause of death worldwide. According to the World Health Organization, noncommunicable conditions account for two-thirds of the 57 million deaths each year and almost half of the decreased life expectancy and disability caused by diseases around the world. In the United States and the developed world, where people tend to eat energy-dense foods and lead sedentary lives, many of the leading causes of death are chronic diseases, which in many cases can be prevented. Meanwhile, developing countries struggle to address both chronic and infectious diseases within their nascent, underfunded health care systems. Present and future public health efforts must focus on strategies to combat chronic disease, including the application of genomic research.
Indeed, the mapping of the human genome seemed to put the unreachable almost within our grasp, promising genetic interventions to halt diseases at their source. It turns out, however, that while genes play a large role in disease susceptibility, it is nearly impossible to single out a specific gene sequence that causes chronic disease.
Chronic disease arises and progresses from multiple causes. Many of the risk factors — such as poor diet, lack of exercise, and smoking — can be addressed by changes in behavior. Others are changeable in theory but not necessarily under the control of the individual, such as stress, poverty, toxin exposures, and other cultural or environmental conditions. Still other important contributing causes are known as “non-modifiable risk factors” — fundamental attributes such as genetics, gender, family history, and age. It is important to note here that many behavioral risk factors and social conditions affect how genes are expressed and thus influence the progression of chronic disease through the “non-modifiable” risk factor of our genetic code. When health care professionals prescribe implementing lifestyle modifications to stave off chronic disease, the patient should understand that these positive health behaviors, although sometimes hard to sustain, improve health by working at the genetic level.
Thus in the realm of chronic disease prevention, genomic medicine has developed in a new direction, one that is beginning to have practical applications. Nutrigenomics is the study of hereditary factors that influence a person’s response to diet — both how genes influence nutrient absorption and metabolism, and how nutrients influence gene expression. That is, we are beginning to understand in detail how the “modifiable” lifestyle risk factors for disease are linked to and expressed through the supposedly “non-modifiable” risk factor of our genes.
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