of ways that may cause adverse health effects, especially when their reaction is fierce and violent. According to the American Psychological Association (APA), stressful circumstances hold the potential to affect several systems in the human body in a harmful way.
Key Point
Neck and head muscle tension has been linked to tension-type experiences and migraine headaches.
Under stressful conditions muscles are strained in an attempt to repel stress. However, chronic stress renders muscles constantly tensed, which in turn can lead to other abnormalities – neck and head muscle tension has been linked to tension‐type experiences and migraine headaches. It has been suggested that stress relaxation techniques can ease tensed muscles, reduce the occurrence of impairments linked to stress, and enhance the feeling of wellness and well‐being.
Key Point
Stressful circumstances hold the potential to affect several systems in the human body in a harmful way.
Under stressful conditions, breathing becomes harder. This change can prove burdensome for people with chronic respiratory disorders, such as asthma. However, stress can also induce asthma attacks in people free of respiratory diseases and panic attacks among vulnerable people. Furthermore, psychological stress has been shown to increase heart rate, mainly due to increased secretion of stress hormones, such as adrenaline, noradrenaline, and cortisol. Thus, being under constant stress may result in aggravated heart function; in the long term, this condition may cause hypertension, CHD, or stroke.
Key Point
Being under constant stress may result in aggravated heart function.
Stressful experiences can trigger an inflammatory response, mainly in the coronary arteries, which is thought to be one of the mechanisms for the development of heart diseases. The way people cope with stress may affect blood cholesterol levels, which is also related to CVD events. Finally, stress hormones enhance hepatic glucose production and induce insulin resistance. Repeated stressful experiences can also cause disturbances in the gastrointestinal tract, the nervous system, and the male and female reproductive systems.
Lifestyle‐Induced Epigenetic Alterations and NCD Risk
As mentioned in Chapter 2, the genetic background plays an important role in the development of several degenerative diseases. Nevertheless, the expression of genes that gives a variety of phenotypes linked to chronic diseases can be influenced by factors other than heritability. These factors and processes may be of developmental nature, occurring both in utero and during childhood, they may be chemicals found in the environment, drugs and/or pharmaceuticals, or caused by the aging progress and poor dietary habits (Figure 3.7). Provided that these parameters do not alter the DNA sequence but only the way genes act and are expressed, they are thought to exert an additional effect on the conventional genetic inheritance, thus characterized as epigenetic mechanisms – with the prefix epi‐ deriving from the Greek prefix επÌ‐ meaning over, outside of, around.
The term epigenetic mechanisms refers to the parameters involved in the modifications of gene regulation, including DNA methylation, histone modifications, and RNA‐based mechanisms. Nutrigenomics is the epigenomics sector focusing on the effects of food and food constituents on gene expression. For example, adoption of a Mediterranean diet pattern rich in olive oil for 3 years can reduce the detrimental effects of the risk variant of the IL‐6 gene, associated with weight gain, among middle‐aged and older persons with high CVD risk. Compared to the noncarriers and those heterozygous for the risk allele of the IL‐6 gene, the homozygous ones had higher adiposity indexes pre‐intervention, but after three years on the Mediterranean diet rich in olive oil, they appeared to have the most weight loss.
FIGURE 3.7 Epigenetic mechanisms.
Source: National Institutes of Health (2018).
Key Point
Nutrigenomics is the epigenomics sector focusing on the effects of food and food constituents on gene expression.
Moreover, variations in the gene‐expressing adipokine (hormone) adiponectin have been implicated in weight gain in a cohort of middle‐aged and elderly individuals at increased risk for CVD. Nevertheless, following a Mediterranean diet for three years proved to be advantageous in reversing weight gain among the carriers of the adiponectin gene SNPs, compared to noncarriers. Similarly, when the carriers of the fat‐mass obesity (FTO) polymorphism, which is responsible for increased body weight, followed a Mediterranean diet pattern for three years, they appeared to have the lowest increase in weight after intervention, compared to the noncarriers.
The phytochemicals present in fruits and vegetables, herbs, and spices have been shown to be protective not only against oxidative stress but also chronic low‐grade inflammatory responses, which constitute established risk factors of age‐related brain impairments. Moreover, phytochemicals hold the potential to attenuate the oxidative damage of macromolecules, such as DNA. They can also protect against the deranged expression of genes, which can progressively lead to debilitating effects on brain function and the advent of brain disorders associated with aging.
The Effect of Maternal Health and Lifestyle Habits During Gestation
It is now widely accepted that maternal health and lifestyle habits, as well as infants' early nutrition and exposure to environmental factors, are involved in the development of metabolic diseases later in life. For instance, the presence of gestational diabetes mellitus (GDM) is related to reductions in methylation of the mesoderm‐specific transcript (MEST) gene, a feature detected also among morbidly obese adults. When the fetus is exposed to GDM, the abnormal programming of the MEST gene increases the susceptibility of developing obesity later in life.
Another prenatal condition with future ramifications on the epigenome is that of famine exposure. Being exposed to famine prenatally can lead to alterations in the DNA methylation. Findings from a cohort study revealed that more young adults exposed to famine in gestation were underweight compared to young adults that were either exposed to famine postnatally or were never exposed. In contrast, more young adults exposed to famine postnatally were overweight compared to those gestationally exposed or unexposed. Underweight adults exposed to famine in gestation were hyperglycemic following a glucose tolerance test, and those exposed postnatally had elevated fasting glucose, compared to those unexposed.
Take‐Home Messages
An unhealthy diet has been associated with the development of a number of diseases, including CVD, cancer, diabetes, hypertension, liver and gallbladder diseases, and obesity.
Excess caloric intake can adversely affect insulin sensitivity as well as plasma glucose, insulin, and triglyceride levels, which are all linked to obesity. Overeating has also been associated with increased aging rate and the development of age‐related diseases.
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