Dietary Patterns and Risk of Coronary Heart Disease
Cardiovascular diseases (CVD) are a group of disorders of the heart and blood vessels which include coronary heart disease (CHD), cerebrovascular disease, peripheral arterial disease, rheumatic heart disease, and etc. (World Health Organization, 2011). Key facts of CHD are (1) CHDs are the number one cause of death globally; (2) approximately 7.2 million people died from CHD s in 2004, (3) by 2030, almost 23.6 million people will die mainly from heart disease and stroke (World Health Organization, 2011).
American Heart Association (AHA, 2011) has identified several major risk factors that cannot be changed: increasing age (over 83% of people who die of CHD are 65 or older), male (men have greater risk of heart attack than women), and heredity (children of parents with heart disease are more likely to develop it themselves). Major risk factors found are tobacco smoke, high blood cholesterol, high blood pressure, physical inactivity, obesity and overweight, and diabetes.
In the UK, one in five men and one in six women will die of coronary heart disease (CHD) and it remains the most common cause of death (Allender, Peto, Scarborough, Boxer, and Rayner, 2007; as cited in Farrimond, Saukko, Qureshi, and Evans, 2010). Therefore, identifying and treating patients at high risk of CHD in primary care is a key component of the UK National Services Framework (Department of Health, 2000; as cited in Paula et al, 2010) and international guidelines for CHD prevention (Pearson et al, 2001; as cited in Farrimond et al, 2010).
Distinct eating patterns reflect various dietary traditions worldwide, which may be related to rates of coronary heart disease (CHD) in different countries. Mediterranean and Asians populations have very low rates of CHD compared with Western populations (Hu, Rimm, Stampfer, Ascherio, Spiegelman, and Willet, 2000). Nonetheless, the rates of CHD among countries may also vary due to several of CHD risk such as physical activity and obesity. Hu et al. (2000) emphasized that because of strong correlations, studies of individual foods or nutrients can be hard to interpret. Additionally, dietary interventions may be easier to implement and may be more inclusive when initiated as a change in the overall dietary patterns. Furthermore, Hu et al (2000) added that in clinical studies, changes in dietary patterns appeared to be more effective in lowering blood pressure. And last but not least, dietary patterns analysis is potentially useful in making dietary recommendation as it is easier for the public to interpret into diets (Hu et al, 2000).
Hu, Stamper, Manson, Rimm, Colditz, Rosner, Hennekens, and Willet (1997) did a study on dietary fat intake and the risk of coronary heart disease (CHD) in women. A total of 8,082 women who were aged between 34 and 59 and had no known coronary disease, cancer, diabetes, stroke, or hypercholesterolemia in 1980 were recruited. Hu and colleagues (1997) documented 939 cases of non-fatal myocardial infarction or death from CHD for 14 years of follow-up. They found that the increasing of energy intake from saturated fat, as compared with equivalent energy intake from carbohydrates, was associated with an increasing in the risk of CHD whereas total fat was not significantly related to the risk of CHD. Hu and colleagues (1997) estimated that the replacement of 5 percent of energy from saturated fats would reduce risk by 42 percent and that the replacement of 2 percent of energy from Trans fat with energy from unhydrogenated, unsaturated fats would reduce risk by 53 percent. Hu and colleagues (1997)'s findings suggest that replacing saturated and Trans unsturated fats with unhydrogenated monounsaturated and polyunsaturated fats is more effective in preventing CHD in women than reducing overall fat intake. In other words, a higher dietary intake of saturated fat and Trans unsaturated fat was associated with an increased risk of CHD, whereas a higher intake of monounsaturated and polyunsaturated fats was associated with a decreased risk but total fat intake was not significantly related to the risk of CHD (Hu and colleagues, 1997).
Mente, Koning, Shannon, Anand (2009) conducted a systematic review of the evidence supporting a causal link between dietary factors and coronary heart disease (CHD). Bradford Hill guidelines were used to derive a causation score based on 4 criteria (strength, consistency, temporality, and coherence) for each dietary exposure in cohort studies and examined for consistency with findings (Mente et al., 2009). Results indicated strong evidence supports valid associations of protective factors, including intake of nuts, vegetables, and "Mediterranean" and high-quality dietary patterns with CHD, and also associations of harmful factors which including intake of trans- fatty acids and foods with high glycemic index (Mente et al., 2009). Nonetheless, only a Mediterranean dietary pattern is significantly associated with CHD. In addition, evidence found to support a causal relationship for intake of whole grains, dietary vitamins E and C, fish, and fiber but weak evidence of causation for intake of saturated and polyunsaturated fatty acids, meat, and etc.
Boniface and Tefft (2002) investigated the relationships of dietary fats to subsequent coronary heart disease (CHD) mortality in men and women while taking account of other CHD-related behaviors. A cohort randomly selected men and women aged 18 or older were interviewed face-to-face in 1984-1985 in their own homes which is the Health and Lifestyle Survey, and monitored subsequently for 16 years for deaths. The interview covered health, health-related behaviors, socio-demographic details, physical measurements, and a dietary questionnaire. Saturated, polyunsaturated and total fat intakes were estimated. To demonstrate a possible effect of diet on subsequent CHD death, Boniface and Tefft (2002) added, the excluding for individuals whose diet was likely to have been influenced by awareness of a specific illness or condition itself carrying a raised CHD risk was necessary. Otherwise, the relationship of fat intakes to CHD could be masked. Furthermore, information was obtained about general dietary habits via questions about the quantities and frequency of consumption of butter, bread, milk, coffee, tea, sugar, and the frequency of consumption of 30 different food groups according to six categories ranging from never to more than once a day (Boniface and Tefft, 2002).
According to Boniface and Tefft (2002), results indicated that not consuming alcohol nor smoking, not exercising and being socially disadvantaged were related to high saturated fat intake and CHD death. Results also reported for total fat and the relative effects of polyunsaturated and saturated fats. Nevertheless, strong evidence was found for cohort relationship of dietary fat and CHD death in women while no evidence was found for a relationship in men (Boniface and Tefft, 2002). One possibility highlighted by Boniface and Tefft (2002) is that the single measure of dietary fat at interview is a less valid estimate of the diet in men because women were more likely to be purchasing and preparing food while men are more likely to be eating out while at work. Hence, this could lead to women reporting their diets more accurately than men. Another possibility mentioned by Boniface and Tefft (2002) is that the non-dietary behaviors (smoking, alcohol, exercise) relate to dietary fat and CHD death in various ways in men. In addition, a third possibility is the role played by social factors which is known to be linked to lifestyle factors, for instance, smoking, alcohol intake, diet, and exercise (Marmot et al, 1991; Bolton-Smith et al, 1991; as cited in Boniface and Tefft, 2002).
With increasing appreciation of the complexity of diets consumed by free-living individuals, Kant (2010) was interested in assessing the overall dietary patterns in which multiple related dietary characteristics are considered as a single exposure. The two most frequently used methods to derive dietary patterns use are (i) scores or indexes based on prevailing hypotheses about the role of dietary factors in disease prevention, and (ii) factors and clusters from exploration of available dietary data (Kant, 2004; as cited in Kant, 2010). The third method, Kant (2010) added, "A hybrid of the hypothesis-driven and data-driven methods, attempts to predict food combinations related to nutrients or biomarkers with hypothesized associations with particular health outcomes". Examination of nutritional biomarkers meaning validating the dietary pattern and most of the available evidence is limited to cross-sectional associations (Newby et al, 2004; Kant and Graubard, 2005; as cited in Kant, 2010). Furthermore, in the Women's Healthy Eating and Living (WHEL) randomized trials, intervention with a low fat, high-vegetable pattern, and high-fruit was linked with changes in plasma carotenoid profiles reflective of increased fruit and vegetable intake (Howard et al, 2006; Pierce et al, 2007; as cited in Kant, 2010). Kant (2010) reported, "Results showed that there is a relatively modest degree of reduction in risk of mortality and CHD in association with dietary patterns consistent with healthy diet whereas results from observational studies suggest that the healthy dietary patterns were linked with significant but modest risk reduction for all-cause mortality and coronary heart disease (CHD)". However, by using knowledge about dietary nutrients or biomarker linked with disease as dependent variables is limited by incomplete information regarding whether the dietary nutrient or biomarker associations with disease are causal or merely markers (Kant, 2010).
Frank, Eric, Meir, Alberto, Donna, and Walter (2000) were interested in examining whether overall dietary patterns derived from a food-frequency questionnaire (FFQ) predict risk of coronary heart disease (CHD) in men. A total of 44875 men aged 40-75 without diagnosed cardiovascular disease or cancer recruited for this study. By using factor analysis, Frank et al. (2000) identified two major dietary patterns by using dietary data collected via a 131-item FFQ. The first factor, which is the "prudent pattern", was characterized by higher intake of fruit, whole grains, vegetable, fish, whereas the second factor which is the "Western pattern", was characterized by higher intake of red meat, sweets and desserts, chips, and high-fat dairy products (Frank, 2000). It was found that men with higher Western pattern score were more likely to smoke and drink alcohol; they also had higher intakes of saturated fat, cholesterol, and monounsaturated fat and lower intakes of protein, fiber, and carbohydrate. Besides, consumption of red meat, eggs, refined grain, sweets, and butter was positively correlated with the Western pattern score (Frank et al, 2000). Findings suggest that with the increasing of prudent pattern score, the risk of CHD decreased. Conversely, there is a positive correlation between the Western pattern score and the risk of CHD where as Western pattern score increased, the risk of CHD increased.
Reduced consumption of trans-fatty acids (TFA) could lower the risk of coronary heart disease (CHD). Partially hydrogenated vegetable oils (PHVO) that contain both TFAs and other fatty acids could be replaced with alternative fats and oils. Clarke and Mozaffarian (2009) conducted a study by using quantitative estimates of CHD effects if a person's PHVO consumption were to replace with alternative fats and oils based on randomized dietary trials (RDT) and observational studies. Clarke and Mozaffarian (2009) suggested that the effects on CHD risk of removing PHVO from a person's diet vary depending on the TFA content of the PHVO, and also the fatty acid composition of the replacement fat or oil. However, Clarke and Mozaffarian (2009) added, TFAs in foods cannot simply be replaced on a 1:1 basis but the unit of replacement is the PHVO, which is composed of various fatty acids, which including TFAs, saturated fatty acids (SFA), cis-polyunsaturated fatty acids (PUFA) and cis-monounsaturated fatty acids (MUFA). For instance, PHVO in a person's diet might be replaced by tropical oils, vegetable oils or butter. Moreover, different PHVO formulations can contain varying amounts of TFAs. Thus, the potential effects on an individual's CHD risk would depend on both on the average TFA content of the PHVO being replaced, and the type of fat and oil being used for replacement (Clarke and Mozaffarian, 2009). The effects on CHD risk were calculated based on two evidences: (1) risk factors in trials, and (2) disease outcomes in cohorts. Findings indicated that the replacement of PHVO with alternative fats and oils would substantially decrease CHD risk. Meanwhile, on the basis of the amounts and formulations of PHVO being replaced and the alternative fats and oils used, the total predicted benefit for a given individual, population or food product could be determined (Clarke and Mozaffarian, 2009).
Kerver, Yang, Bianci, and Song (2003) conducted a study testing the dietary patterns associated with risk factors for cardiovascular disease (CHD) in healthy US adults. With the use of food-frequency questionnaire (FFQ) data from the third National Health and Nutrition Examination Survey (Kerver et al, 2003), dietary patterns of healthy US adults were identified by factor analysis. Subjects in this study were participants in the third National health and Nutrition Examination Survey (NHANES III), conducted in 1988-1994. All interviewed persons were invited to the mobile examination center and blood and urine specimens were obtained. Besides, a number of tests and measurements, including body measurements and blood pressure testing were performed, too (Kerver et al, 2003). By using FFQ, subjects were asked how often in the past month they had eaten specific food items. The foods were listed in groups that targeted those high in vitamins A and C and calcium but also represented all major food groups consumed by the US population (Kerver et al, 2003). Furthermore, the consumption of other food and beverage items was also asked by the interviewers, which were included in the current analyses. Findings suggest that the relation of the dietary patterns to sociodemographic and lifestyle characteristics supports the theory that healthy food choices are a part of a larger pattern of health-related characteristics and behaviors which indicated that relations between a Western dietary pattern and subject characteristics of being male, nonwhite, and less-educated; smoking; having lower income; and having low vitamin or mineral supplementation, and having low physical activity (Kerver et al, 2003).
Farrimond, Saukko, Qureshi, and Evans (2010) were interested in exploring how "high risk" of CHD patients make sense of their new risk status. Therefore, identifying and treating patients at high risk of CHD in primary care is a key component. However, past intervention studies indicated that, patients often find it difficult to change their lifestyles (Imperial Cancer Research Fund OXCHECK study, 1995; as cited in Farrimond et al, 2010) or only respond to intensive and costly intervention (Steptoe et al, 1999; as cited in Farrimond et al, 2010). A total of 49 participants identified as "high risk" was invited for interview approximately two weeks after their follow-up consultation. Sampling followed a maximum variation approach, with respect to gender, age, occupational class, ethnicity, geographical location, and family history status (Patton, 2002; as cited in Farrimond et al., 2010). Most of their interviews were conducted face-to-face at homes of participants, or at their place at work.
Results indicated many participants found being identified as "higher risk" were shocked for those who understood themselves to be "healthy" or having a healthy lifestyle (Farrimond et al, 2010). On the other hand, age manifested itself in several ways in the interviews. Firstly, many participants mentioned "ageing" and "getting older" as risk factors for CHD (Farrimond et al, 2010). Nonetheless, reflecting on age does not make them feel less vulnerable. According to previous research, suggested that people with a family history of CHD tend to compare their own age to their relatives when they died (Hunt, Emslie, and watt, 2001; as cited in Farrimond et al, 2010). Farrimond et al (2010) added, although ageing was normal, many argued that as risk increases with age, it leads to the increasing of the need for monitoring and treatment. Also, participants found to perceive behavior change by their age and stage of life. First of all, many reported that they had made many lifestyle changes particularly regarding the dietary modification. Moreover, SES differences were regarded as in relation to quitting smoking, a behavior which is strongly associated with poverty (Jarvis and Wardle, 1999; as cited in Farrimond et al, 2010). Farrimond et al (2010) suggested one of the coping strategies was to minimize their feelings of personal vulnerability. However, the real-life referents for social comparisons made by participants it is crucial to be identified.
Hu, Rimm, Smith-Warner, Feskanich, Stampfer, Ascherio, Sampson, and Willet (1999) examined the reproducibility and validity of dietary patterns (Western patterns and the prudent patterns) defined by factor analysis using dietary data collected with a food-frequency questionnaire (FFQ). A sample of 127 men from the Health Professionals Follow-up Study in a diet validation study in 1986 was recruited. A 131-item FFQ was administered twice, 1 year apart, and two 1-week diet records and also blood samples were collected during this 1 year interval (Hu et al, 1999). First of all, the participants completed the same FFQ twice, 1 year apart (FFQ1 and FFQ2). Then, participants indicated their average frequency of consumption over the past year for each food item in the FFQ. Besides, participants also completed also completed two 1-week diet records. An attempt was made to math each of the 1565 unique food codes to one or more items on the questionnaire to obtain daily food measurements from the diet records that were comparable with those from the FFQs. After that, participants were required to provide blood samples before completing the FFQ2. According to Hu et al (1999) reported, the correlations between each of the FFQs and the records for the 2 patterns suggesting reasonable comparability between the FFQs and the diet records in characterizing dietary patterns. Additionally, the correlations between the factor scores and plasma concentrations of biomarkers were in the expected direction. Hence, these data indicate reasonable reproducibility and validity of the major dietary patterns (Hu et al, 1999).
Hu (2002) did a review on dietary patterns, and discussed quantitative methods for analyzing dietary patterns and their reproducibility and validity, and the available evidence regarding the relationship between major dietary patterns and the risk of cardiovascular disease (CHD). Hu (2002) listed a few limitations of traditional analysis in nutritional epidemiology typically examine diseases in relation to a single or a few nutrients or foods. First of all, people eat meals consisting of a variety of foods with combinations of nutrients instead of isolated nutrients. Secondly, the high level of intercorrelation among some nutrients makes it difficult to examine their separate effects. Third, in clinical trials, it appeared to be more effective at lowering blood pressure by interventions altering patterns than single nutrient supplementation. Furthermore, "single nutrient" analysis may be confounded by the effect of dietary patterns because nutrient intakes are found to be commonly associated with certain dietary patterns (Hu, 2002).
Three approaches have been used in the literature for defining dietary patterns: factor analysis, cluster analysis, and dietary indices. Factor analysis uses information reported on food frequency questionnaire (FFQs) or in dietary records to identify common underlying dimensions of food consumption. On the other hand, cluster analysis assembles individuals into homogeneous subgroups with similar diets. Lastly, dietary indices are constructed on the basis of dietary recommendations (Hu, 2002).
In a previous study done which done by Hu et al (1999; as cited in Hu et al, 2002) examined the reproducibility and validity of dietary patterns was defined by factor analysis. By using factor analysis, Hu et al (1999; as cited in Hu et al, 2002) identified two major eating patterns (Western pattern and prudent pattern). Data indicated reasonable reproducibility and validity of the major dietary patterns. From the review of past journals, there is no data are available on the reproducibility or stability of the clusters over time. Also, studies are needed to evaluate the reproducibility and validity of the proposed diet quality indices (Hu, 2002). In contrast to the traditional analytical approach used in nutritional epidemiology, Hu (2002) emphasized that, dietary pattern analysis considers overall diet rather than individual nutrients or foods.
The aim of the current intervention is to prevent and reduce the potential risk of coronary heart disease (CHD) and the minor aim of this intervention is to promote healthy eating to everyone regardless of one's health condition, gender, SES, and so on. This intervention will make an effect on reducing the risk by method of healthy eating. The name of the intervention is called "Market Sweep" and it shall be outlined in the methods section. There are two hypotheses outlining in this intervention. The first hypothesis is that the risk of CHD of participants in treatment group will be reduced. The second hypothesis is that there is no major difference of health condition of the participants in the control group.
Methods, Participants, and Procedures
An experimental design of study will be conducted. A total of 2000 voluntary participants with no prior history of CHD will be recruited from health magazine advertisements. They will be randomly assigned to the treatment group (1000 participants) or control group (1000 participants). Participants in the treatment group will be on a low-fat diet whilst participants in control group will be on a normal diet. This is a longitudinal study as it will keep track on participants for one year. This intervention can be proposed to supermarkets (e.g. Tesco) to have 365 days a year of promotion, where any individuals who purchases the highest amount of healthy food or low-fat food (vegetable, whole grain, fish, and etc.) will be rewarded with a voucher at the end of the week to purchase any healthy snack of their choice (amount of voucher to be confirmed by supermarket). Psychology plays a role here because this intervention uses the method of "conditioning" where individuals are conditioned to change their dietary patterns because this intervention rewards with free healthy snack, individuals who take part will have no choice but to consume a healthy diet. The introduction of healthy food into the body on a daily basis would lead the body of the individual eventually accepting the healthy food in terms of taste, flavor, and etc) thus rejecting unhealthy food. Furthermore, the cost for intervention is the advertising cost used to recruit participants while the supermarket has to bear the cost of giving out voucher. However, the supermarket will not lose any profits as the team of researchers of the intervention would in favor to promote their company, too.
Ethical issues of proposed intervention are clearly identified and proposals to deal with them are provided in detailed. Besides, proposed intervention will be interviewed by the Ethical committee. Consent form will be given to participants in order to participate in the intervention. In addition, participants in treatment group must be taken into consideration that high-fat diet may impact their health on a long term basis.
Proposed Evaluation and Future Recommendation
Desirable outcomes are expected in a way that intervention group would report that the participants in treatment group are consuming more servings per day of grains, vegetables, and etc. compared with control group. Also, findings would be suggesting that low-fat diet would reduce the risk of CHD. One of the limitations underlying this intervention is that no control on over whether participants read their leaflets and use the guidelines provided. Second limitation could be that the sample is small which could not be generalized to the whole population. Another limitation might be the duration of the treatment is not long enough; therefore there might be only slight changes on differences before and after treatment of the participants from treatment group. As for future recommendations, low-fat interventions could be introduced for both the population and individual levels, to reduce CHD risk. Also, these interventions should be translated into policies which promote healthy diets and discourage unhealthy diets, for instance, governments, international organizations (e.g. World Health Organization), and responsible sections of the food industry.
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