Diet and Heart Disease: Three Research Studies Reviewed

Introduction: Diet, Heart Disease, and the Health Belief Model

In exploring the impact of diet on heart disease, it is important to consider the theoretical perspective of the Health Belief Model (HBM), which is the most commonly used model in health promotion and education. The HBM claims that health behavior is determined by personal beliefs about disease and the specifics surrounding prevention and treatment (Glanz, Lewis, & Rimer, 1997). The four facets of this model involve personal perception and include perceived seriousness, perceived susceptibility, perceived benefits, and perceived barriers (Glanz, Lewis, & Rimer, 1997). This theory is integral to exploring the relationship between diet and heart disease, as it allows researchers to examine not only the medical aspects of cardiac health but also the role of individual behavior in dietary and heart-related care.

This article is based on the premise that the first course of action in the prevention of heart disease is dietary modification. The study seeks to identify whether there is a correlation between consuming a diet enriched in fiber and oxidative stress in cardiac tissue. Previous studies have shown that dietary fiber has been integrated into dietary programs as a means of lowering serum glucose and cholesterol (Diniz et al., 2003). However, the impact of dietary fiber on cardiac functioning, as well as the effect of fiber-enriched eating on oxidative stress in cardiac tissue, had not been fully explored through research and therefore became the focus of this study.

Article 1: Dietary Fiber, Oxidative Stress, and Cardiac Health

Researchers utilized 40 male Wistar rats, which were randomly divided into groups by computer sampling. Each group was fed a different diet depending on their grouping: control, fiber-enriched, or dietary-restricted. While all diets provided sufficient nutritional values, they differed in the amount and concentration of fiber. Results were measured by recording body mass each week, and at week six the rats were fasted and sacrificed (Diniz et al., 2003). The bodies of the rats were then studied to determine what impact, if any, the introduction of dietary fiber had on heart disease — particularly oxidative stress.

The results showed that rats with fiber added to their diet had increased body mass. Researchers identified a direct link between dietary fiber and metabolic responses (Diniz et al., 2003), and these results were more significant than those of food consumption alone. In terms of cardiac functioning, dietary fiber was found to increase glycogen concentrations, which increases cardiac viability. Furthermore, dietary fiber was found to inhibit the development of oxidative disease in cardiac tissues (Diniz et al., 2003).

This study sought to determine whether the amount of dietary iron can result in myocardial injury. Many recent studies have indicated that higher stored iron in the body can increase the incidence of heart disease. This risk was elevated when combined with high levels of cholesterol intake and was further confounded by diabetes, hypertension, and smoking (Malaviarachchi et al., 2002). Malaviarachchi et al. (2002) sought to confirm the findings of these previous studies, with particular focus on the impact of dietary iron and heme iron on the risk of myocardial infarction, while controlling for lifestyle and other health risk factors.

Article 2: Dietary Iron as a Risk Factor for Myocardial Infarction

Malaviarachchi et al. (2002) identified 3,684 non-institutionalized individuals between the ages of 18 and 74, whose demographics were spread evenly across age, sex, and county. The Nova Scotia Nutrition Survey was administered to participants via face-to-face interview, along with a 24-hour dietary intake recall questionnaire. Participants were also asked to complete a modified food frequency questionnaire and to provide information about their demographics, socioeconomic status, and health risk factors (Malaviarachchi et al., 2002).

Macro- and micronutrients in participants' diets were calculated using the Canadian Dietary Information software program (Malaviarachchi et al., 2002). Body mass index was also recorded. Participants were then followed for eight years to track the incidence of myocardial infarction and death.

Results demonstrated a myocardial infarction incidence rate of 4.3% among all participants, seven of which resulted in death (Malaviarachchi et al., 2002). There was no relationship between high intake of iron and heme iron and increased risk of myocardial infarction. In fact, those participants with higher iron and heme iron intake were at lower risk for myocardial infarction, though the results did not achieve statistical significance (Malaviarachchi et al., 2002). As a result, concerns about the public health promotion of lean meat as an appropriate source of iron were not validated by this study.

The study did find that age and certain health factors correlated with the development of myocardial infarction. As individuals age, their risk of myocardial infarction approximately doubles with each decade of life. Individuals with diabetes, smokers, and those with a high BMI were also found to be at increased risk. Finally, the authors noted that diet is influenced by culture and therefore varies by country and region, suggesting that continued research at local levels is necessary to support these findings.