Diet & Heart Disease

Heart disease is the leading cause of death in the United States. In 2006, an estimated 81,100,000 people in the United States were suffering from one or more forms of cardiovascular disease (Lloyd-Jones, 2010). Heart disease, often referred to as cardiovascular disease, is a broad term that refers to many diseases that affect the heart or blood vessels. As cardiovascular disease claims hundreds of thousands of lives each year researchers seek answers with the hope of reversing the trend. One area of research that generates warranted attention is that which examines dietary factors associated with an increased risk for heart disease. Media outlets are constantly reporting results from research studies, however preliminary the study may be, as definitive explanations for the large number of heart related problems. The continuous reports from news programs, newspapers, and magazines make one question which reports truly are "news" as opposed to simply "noise."

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Major causes of death in 2006 (Lloyd-Jones, 2010).

Important Definitions:

  • Atherosclerosis is a common disorder of the arteries. It occurs when fat, cholesterol, and other substances build up in the walls of arteries and form hard structures called plaques. Eventually, the plaques can make the artery narrow and less flexible, making it harder for blood to flow. If the coronary arteries become narrow, blood flow to the heart can slow down or stop. This can cause chest pain (stable angina), shortness of breath, heart attack, and other symptoms.
  • Cardiovascular disease is the class of diseases that involve the heart or blood(arteries and veins).
  • Cholesterol is a waxy steroid metabolite found in the cell membranes and transported in the blood plasma of all animals.
  • Triglycerides are esters derived from glycerol and three fatty acids.It is the mainof animal fats.
  • Coronary heart disease refers to the failure of coronary circulation to supply adequate circulation to cardiac muscle and surrounding tissue.
  • Hypertriglyceridemic waist phenotype consists of a waist wider than 90 cm in men and 85 cm in women, along with a plasma triglyceride concentration of 2.0 mol/l (177 mg/dl) or over.
  • Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs.
  • Longitudinal quantitative studies are the study of a group of individuals at regular intervals over a relatively long period of time.
  • Glycemic index, or GI, is a measure of the effects of carbohydrates on blood sugar levels.
  • Monounsaturated fats are fatty acids that have a single double bond in the fatty acid chain and all of the remainder of the carbon atoms in the chain are single-bonded. By contrast, polyunsaturated fatty acids have more than one double bond.
  • Saturated fatty acids have no double bonds between the carbon atoms of the fatty acid chain and are thus fully saturated with hydrogen atoms.
  • Diabetes mellitus, often simply referred to as diabetes—is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced.
  • Phytochemicals are chemical compounds that occur naturally in plants and is generally used to refer to those chemicals that may affect health, but are not yet established as essential nutrients.
  • Antiapoptotic refers to something that prevents apoptosis. Apoptosis is a type of cell death in which a series of molecular steps in a cell leads to its death.
  • Myocardium is the middle and thickest layer of the heart wall and is composed of cardiac muscle.
  • A hypothesis is a proposed explanation for an observable phenomenon.

Links to Individual Group Members' Nutrition Headlines


Lewis: Low-carbohydrate and high-protein diet increases the risk for atherosclerosis and impaired blood vessels; The Medical News

The news article "Low-carbohydrate and high-protein diet increases the risk for atherosclerosis and impaired blood vessels" summarizes findings from an experiment following several different diets consumed by mice and their respective effect on the mouse's cardiovascular health (Foo, 2009) The article mentions that researchers were puzzled by the fact that high-protein low-carbohydrate (HPLC) diets were leading to an increased risk of cardiovascular disease (CVD) without increasing blood cholesterol levels in mice. Researchers first came up with the idea to test the effects of different diets on cardiovascular health in mice after seeing patients with CVD come into the clinic while on a HPLC diet. Mice were fed one of three diets: a standard chow (65 percent carbohydrate, 15 percent fat, 20 percent protein), a "Western diet" in keeping with the average human diet (43 percent carbohydrate, 42 percent fat, 15 percent protein, and 0.15 percent cholesterol), or a low-carb/high-protein diet (12 percent carbohydrate, 43 percent fat, 45 percent protein, and 0.15 percent cholesterol). Researchers studied the mice after 6 and 12 weeks and examined various biomarkers of CVD like weight gain, atherosclerosis, animals' cholesterol and triglyceride levels, oxidative stress, insulin and glucose, as well as levels of some inflammatory cytokines without finding any relation. Finally, researchers discovered that the mice on HPLC diets had a statistically significant lower number of endothelial progenitor cells, a cell that helps repair damaged vascular tissue. What was truly eye-opening about these finding was that fat is not the only macronutrient to consider when thinking about CVD, but protein and carbohydrates are important also.

When considering a person’s risk for CVD, healthcare professionals typically look at several biomarkers that act as reliable risk factors for the disease. Weight, blood pressure, certain cholesterol levels (LDL, HDL, and VLDL), or even blood glucose levels can all be associated with an increased risk for CVD. Recently, researchers have been identifying other biomarkers that may be associated with an increased risk for CVD (Vasan, 2006). One study conducted identified 10 specific biomarkers that, when elevated, were associated with an increased risk of CVD (Wang, 2006). Foo’s study certainly shows that more research is warranted on other biomarkers.

At this point, I think this issue is a little bit more "noise" than "news," but has potential to become substantial. The Medical News website did a great job reporting on this research and provided pretty well-balanced information about the research without making too wild of claims. The only other thing I would have liked to see differently from the article would have been a paragraph explaining that although these results were seen in mice, it is hard to say the same outcomes would be observed in humans. The article provided a good explanation of the story behind the experiment and the experiment itself very well. The article convinced me that more research is needed on other biomarkers that can be linked to CVD.

Olsen: Increased waistline and high triglyceride levels indicate risk of coronary heart disease, study finds; ScienceDaily

The news article "Increased Waistline and High Triglyceride Levels Indicate Risk of Coronary Heart Disease, Study Finds" is based off a cohort study conducted by the European Prospective Investigation into Cancer and Nutrition (EPIC) – Norfolk study. This study showed that the combined presence of increased waist circumference and increased triglyceride levels was associated with the highest risk of coronary heart disease. The hypertriglyceredemic-waist phenotype is indicated as having a waist circumference of more than 90 cm and plasma triglyceride level more than 2.0 mmol/L in men and more than 85 cm and 1.5 mmol/L in women (Arsenault, 2010). People with these measurements have had an unadjusted hazard ratio for future coronary heart disease, with those who didn’t have the phenotype.

The EPIC – Norfolk study looked at a group of 21,787 men and women aged 45 to 79 years old living in Norfolk, United Kingdom. During the follow-up period of 8 to 10 years, 1,295 men and 814 women developed coronary heart disease. These men and women had an increased waist circumference (even without increased triglyceride levels) and increased triglyceride levels (even without higher waist circumference). From these results, doctors Benoit Arsenault and Jean-Pierre Despres, from Laval University in Quebec City,said “the presence of the hypertriglyceridemic waist is predictive of a substantially increased risk of coronary heart disease.” However, this is one of many factors that can indicate risk of coronary heart disease. Arsenault and Despres also mentioned that even though hypertriglceridemic waist is a marker of excess intra-abdominal adiposity, it cannot be used on its own to properly assess coronary heart disease risk.

In my opinion, the headline article is more “noise” than “news” because we aren’t completely sure that having an increased waistline and having high triglyceride levels can alone indicate risk of coronary heart disease. Even the doctors in the study believe more needs to be taken into consideration. Many other factors come into play, such as lifestyle and eating habits. All of these factors can contribute to the risk of coronary heart disease including increased waistline and high triglyceride levels. The headline article did show that there was correlation, but since the article didn't rule out all other factors of decreasing the risk of coronary heart disease, the conclusion isn't entirely reliable.

Aullman; Blood Pressure-Lowering Diet May Also Reduce Risk Of Heart Disease, Especially In African Americans; Medical News Today
The news article, “Blood Pressure-Lowering Diet May Also Reduce Risk of Heart Disease, Especially in African Americans”, summarizes the findings from the population-based randomized control trial. It seems to imply that adherence to the dietary approaches to stop hypertension (DASH) diet will greatly decrease occurrence of coronary heart disease. This article is based off of a John Hopkins study published in Circulation,Cardiovascular Quality and Outcomes.In this study 459 people, with slightly elevated blood pressure, adhereto three different diets, namely: the DASH diet, a control diet, and a fruit and vegetable diet. The DASH diet focuses on consumption of fruits, vegetables, low-fat dairy products, and it includes whole grains, poultry, fish, and nuts. A possible reason that this diet reduces coronary heart disease is that it reduces blood pressure and cholesterol levels, which are two things associated with coronary heart disease. The 10-year risk of coronary heart disease was estimated from the data collected using an equation that estimates future risk of heart failure. Since it is hard and expensive to conduct a study that shows the actual risk of heart disease over 10 years, that was a limiting factor in this study. Patients on the DASH diet hada consistent reduction in the risk of coronary heart failure, “ with the exception of an interaction between dietary pattern and race suggesting a greater risk reduction in blacks than whites” (Chen, 2010). The reduction in risk of coronary heart disease was 22 percent for African Americans compared to 8 percent in white subjects that participated in this study.

In another study the effects of “a healthy dietary pattern constructed using factor analysis and characterized by high intake of fruit, vegetables, whole grains, and legumes, similar to the DASH diet, was associated with a reduced rate of MI (myocardial infarction)” (Levitan, 2009). The adherence to a DASH diet has shown a 37 percent lower incidence of heart failure in those whose diets closely resembled the DASH diet. Life styles may have an effect on these results and were taken into consideration but cannot be controlled. The basis of the DASH diet, which is eating less red meats and increasing vegetable and fruit intake, can greatly decrease blood pressure, which in effect will decrease the chance of heart disease. The results of decreased risk of heart disease were even more apparent in African Americans who are at a greater risk of developing heart disease.

Thus, the headline article's claim that a blood pressure-lowering diet may also reduce risk of heart disease, especially in African Americansis in my opinion more “news” than “noise”, and lends evidence to the fact that adhering to the DASH diet may be strongly associated with decreased heart disease, especially in African Americans. The 22 percent decrease in heart disease for African Americans and the 8 percent decrease for whites show a significant association between the DASH diet and reduced heart disease. “The DASH diet is now recommended in national guidelines”(Sacks, 2001) which further supports the fact that this diet is more news then noise. There is one drawback of the study and that is that it relies on estimates for determining heart disease risks in the long term instead of having actual evidence. This study, although it has some limitations, does show a significant association with the DASH diet and decreased heart disease.

Benson; White bread, rice, and other carbs boost heart disease risk in women; CNN Health
The CNN news article "White bread, rice, and other carbs boost heart disease in women" is based off of results from a longitudinal quantitative study done in Italy (Sieri, 2010). The researchers assessed a large sample of volunteers' diets using quantitative food frequency questionnaires. In order to follow the volunteers, the researchers were given access to future medical records, which allowed them to track mortality and new diagnoses. The researchers found no significant association between glycemic index or glycemic load in men. However, in women, the study showed that the women in the highest quartile of carbohydrate intake, glycemic load, and glycemic index had a significantly higher risk of developing heart disease than those in the lowest quartile. The relative risk was determined by comparing the highest quartiles with the lowest quartiles. Based on the results, researchers suggested that women may process carbohydrates differently than men. Although the study had a large sample size, it also has a significant weakness in that researchers were unable to track dietary changes.

Similar observational studies have examined the association between glycemic index and heart disease. In 2009 an analysis was done comparing the results from 8 subcohorts that included a total of 338,410 volunteers (Mente, 2009). The analysis found published data to be strong and consistent in support of the claim that glycemic index or load may increase risk for heart disease in women, but not in men. Interestingly, the analysis found that studies done in the United States report a higher risk of heart disease associated with glycemic index/load than the studies done in Europe. This finding may suggest that there are other factors contributing to heart disease that are not being accounted for. The analysis only found and reported results from observational studies. Hence, an association between glycemic index and heart disease is becoming evident, but causation is yet to be established. Recently it has been discovered that foods with a high glycemic index induce transcription in genes coding for proinflammatory cytokines, adhesion molecules, and other inflammation mediators (all of which may contribute to heart disease in high concentrations) (Dickinson, 2008). This mechanism is a reasonable explanation for how high glycemic foods contribute to heart disease. Also the researchers did not report any difference between males and females.

In my opinion "White bread, rice, and other carbs boost heart disease risk in women" is currently “noise,” but has the potential to become “news” in the near future. There is mounting evidence that high glycemic foods may contribute more to risk of heart disease in women than men, but clinical studies are required in order to determine causation rather than association. All potential factors must be accounted for. For example, in the Italian cohort study, women in the lowest quartile of glycemic load ate the most protein, monounsaturated fat, polyunsaturated fat, and saturated fat during a typical day. Furthermore, it is important to note the differences in physical activity as 46.2% of women in the highest quartile of glycemic load considered themselves inactive compared to 29.3% in the lowest quartile (Sieri, 2010). The study found an interesting association between glycemic index and heart disease, but the CNN article is premature.

Although the conclusions drawn in the CNN article may be premature, the article draws needed attention to the severity of heart disease in women. For more information about heart disease in women watch the following clip from Mayo Clinic.


Johnson: Blueberries May Lower Risks of Diabetes and Heart Diseases: Testcountry.com
The news article "Blueberries May Lower Risks of Diabetes and Heart Disease" summarizes findings from an animal study conducted by the University of Michigan that showed the association between a blueberry-supplemented diet and heart disease. This study seems to imply that including blueberries in your diet may be a good way to reduce the occurrence of risk factors for cardiovascular diseases and diabetes. A factor that is being closely observed in the research is that blueberries have a naturally occurring phytochemical called anthocyanins. Seymour, a research scientist with the University of Michigan, used overweight rats in this animal study. Some rats were fed freeze-dried blueberry powder as part of a low-fat diet while another group was also fed blueberry powder, but as a part of a high-fat diet. Some rats were not given blueberry powder at all. Ninety days after, rats that were given blueberry powder had less abdominal fat, as well as low triglyceride levels compared to the rats who were not given blueberry powder. Rats fed with blueberries also showed improvement in blood sugar level as well. The study also observed how blueberries had more significance in the low-fat diet, and the same was shown with the high-fat diet. Except later on, the benefits of a low-fat diet with blueberries were a lot more evident than those with the high-fat diet.

Dark pigmented fruits like blueberries are rich in anthocyanins, which have anitiapoptotic and anti-inflammatory properties. These properties produce a tissue protective effect reducing age-related behavioral and neuronal deficits which inhibit inflammatory cytokines in rat glial cells and reduce hippocampal cell loss following induced stroke. In humans, a major factor leading to progression of coronary heart failure is the cumulative cell loss in myocardium (Ahmet, 2009). Therefore, a blueberry enriched-diet may provide a tissue protective effect in humans like it has been found in rats.

In my opinion, the article "Blueberries May Lower Risks of Diabetes and Heart Disease" is more “noise” than “news.” While one study showed that a blueberry enriched diet had beneficial effects on rats, a human trail study was performed resulting in no added benefits (Duthie, 2006).This hypothesis of a blueberry enriched diet influencing heart disease is fairly new and somewhat preliminary. I think it brings about awareness of the effect anthocyanins may have on heart disease, however further research is needed to help support and prove this hypothesis.


Conclusion

It is apparent that the media is constantly looking to research studies in hopes of finding a story capable of captivating an audience and generating a buzz. With the intent of selling a story, study findings are often exaggerated. Although most studies provide strong evidence for associations between certain foods or an increased waistline with heart disease, few provide definitive evidence explaining causation. However when the media reported on professionally accepted principles, such as those outlined in the DASH diet, they were reliable. It should be noted that the DASH diet incorporates a balanced diet with a variety of foods, whereas many of the articles only reported on a few factors. Many of studies that the media bases their reports on should be followed up with another study in an attempt to show causation, not a report leading audiences to astray. Because the majority of news articles were based off of animal or observational studies we feel that most of the news articles related to diet and heart disease were more "noise" than "news."

References



Lloyd-Jones D, Adams RJ, Brown TM, et al. Heart Disease and Stroke Statistics-2010 Update. Circulation. 2010;121(7):e46-e215.

Foo SY, Heller ER, Wykrzykowska J, et al. Vascular effects of a low-carbohydrate high-protein diet. Proc Natl Acad Sci U S A 20009;106 15418-15423.

Vasan RS. Biomarkers of cardiovascular disease: molecular basis and practical considerations. Circulation 2006;113:2335– 62.

Wang TJ, et al. Multiple biomarkers for the prediction of first major cardiovascular events and death. N. Engl. J. Med. 2006; 355 25: 2631

Arsenault BJ, Lemieux I, Despres JP, et al. The hypertriglyceridemic-waist phenotype and the risk of coronary artery disease: results from the EPIC-Norfolk Prospective Population Study. Available at: http://www.cmaj.ca/cgi/content/abstract/cmaj.091276v1. Accessed September 12, 2010.

Chen ST, Maruthur NM, Appel LJ. The Effect of Dietary Patterns on Estimated Coronary Heart Disease Risk: Results From the Dietary Approaches to Stop Hypertension (DASH) Trial. Circulation,Cardiovascular Quality and Outcomes. 2010; 3(5):484-489.

Levitan EB, Wolk A, Mittleman MA. Consistency with DASH Diet and Incidence of Heart Failure. Archives of Internal Medicine. 2009; 169(9):851-857.

Sacks FM., Svetkey LP., Vollmer WM., et al. Effects on Blood Pressure of Reduced Dietary Sodium and the Dietary Approaches to Stop Hypertension (DASH) Diet. The New England Journal of Medicine. 2001; 344:3-10.

Sieri S, Krogh V, Berrino F, et al. Dietary Glycemic Load and Index and Risk of Coronary Heart Disease in a Large Italian Cohort. Arch Intern Med. 2010;170(7):640-647.


Mente A, Koning L, Shannon HS, Anand SS. A Systematic Review of the Evidence Supporting a Causal Link Between Dietary Factors and Coronary Heart Disease. Arch Intern Med. 2009;169(7):659-669.

Dickinson S, Hancock DP, Petocz P, Ceriello A, Brand-Miller J. High–glycemic index carbohydrate increases nuclear factor K-B activation in mononuclear cells of young, lean healthy subjects. Am J Clin Nutr. 2008;87(5):1188-1193.



Ahmet I, Spangler E, Shukitt-Hale B, el at. Survival and Cardioprotective Benefits of Long-Term Blueberry Enriched Diet in Dilated Cardiomyopathy Following Myocardial Infarction in Rats. PLoS One. 2009; 4(11): e7975.


Duthie S, Jenkinson A, Crozier A, et al. The effects of cranberry juice consumption on antioxidant status and biomarkers relating to heart disease and cancer in healthy human volunteers. European Journal of Nutrition 2006;45(2):113-122.



Messina MJ, Wood CE. Soy isoflavones, estrogen therapy, and breast cancer risk: Analysis and commentary. Nutr J. 2008;7:17-21.