Within the last century, there have been several major changes in dietary patterns and lifestyles in developing countries. This is particularly due to the development of high processed, mass-produced canned, frozen and convenience foods that provide many calories with few nutrients. Many cultures have moved from plant-based diets to high-fat, energy-dense animal-based diets while at the same time becoming more physically inactive. This has led to a rise in chronic diseases such as cardiovascular disease, cancer, obesity, and diabetes.
Cardiovascular disease (CVD) is currently the leading cause of death worldwide and includes myocardial infarction, angina, stroke, transient ischemic heart attacks, claudication, limb ischemia and other disorders of the cardiovascular system (Abunnaja, Sanchez, & Maulik, 2013). By the year 2030, the World Health Organization (WHO) predicts that CVD will be the cause of around 24.2 million deaths worldwide (Abunnaja et al., 2013). In the year 2011, about 787,000 people in the United States died from CVD. The total direct and indirect cost for CVD in the U.S. totals more than 320.1 billion dollars annually (Mozaffarian et al., 2014).
ROLE OF CHOLESTEROL
Hypercholesterolemia or elevated cholesterol is considered to be one of the most important modifiable risk factors associated with CVD. Cholesterol has many vital biological roles in the human body. Some of them include hormone manufacturing, precursors for bile salt, and structural components of cell membranes (Talwalkar, Sreenivas, Gulati, & Baxi, 2013). Cholesterol travels throughout the body with the aid of proteins called lipoproteins. These lipoproteins travel through the cardiovascular system to carry lipids to various cells. They come in three different classes; high density lipoprotein cholesterol (HDL-cholesterol), low density lipoprotein cholesterol (LDL-cholesterol), and very low density lipoprotein cholesterol (VLDL-cholesterol). LDL -cholesterol is known colloquially as “bad cholesterol” and contributes to plaque formation that clogs and narrows arteries. HDL –cholesterol is known as “good cholesterol” because it removes cholesterol from the arteries to be transported to the liver for excretion. The risk of cardiovascular disease is increased when blood lipid levels are high in total cholesterol (or serum cholesterol) and LDL- cholesterol while being low in HDL- cholesterol.
A traditionally plant based diet minimizes the consumption of meat and animal products and processed foods while maximizing the intake of nutrient dense fruits, vegetables, legumes, whole grains, nuts, and seeds. The goal of adopting a plant based diet should be to improve health (Tuso, Ismail, Ha, & Bartolotto, 2013). Plant based diets may have a positive impact on cardiovascular risk due to the lower intake of saturated and trans-fats, and high intake of fiber and a variety of antioxidants and phytosterols and stanols, which have been shown to have lipid lowering properties when consumed as part of a generally healthful diet (Kutcha et al., 2016).
Plant based diets comprise heavily of fruits, vegetables, legumes, seeds, nuts, and whole grains. There are a variety of plant based variations including vegan, vegetarian, lacto-vegetarian, ovo-vegetarian, lacto-ovo vegetarian and Mediterranean diets (Tuso et al., 2013). A whole foods, plant based vegan diet excludes animal products while encouraging plant foods to be consumed mostly in their whole form. Lacto-vegetarian incorporates dairy products while excluding meat, poultry, eggs, and seafood. Ovo-vegetarians include eggs while excluding meat, seafood, poultry, and dairy products. Lacto-ovo vegetarians exclude all meat products except eggs and dairy. The Mediterranean diet limits meats and poultry to small amounts and encourages the increased intake of fish, olive oil, whole fruits and vegetables, nuts and seeds (Tuso et al., 2013). The most common trait between all variations of plant-based diets is that they all include whole foods items that are minimally processed or preserved, with some exceptions.
COMPARING VARYING DEGREES OF ANIMAL AND PLANT INTAKE
In a 2014 study that included healthy individuals, both male and female, of varying ages, body mass indexes (BMI’s) and activity levels, omnivores, pescatarians, vegetarians (lactoovo-vegetarians) and vegans were compared based on their lipid profiles to determine the diet that would lend itself most appropriately to the prevention of cardiovascular disease. The omnivores, pescatarians, vegetarians, and vegan’s serum cholesterol averages were 5.28, 5.07, 4.87 and 4.41 mmol/L, respectively (Bradbury et al., 2014). This data indicates that not only does a plant-based diet contribute to lower serum cholesterol levels, but a strictly plant-based diet–such as the diet observed by vegans–could be even more beneficial to a patient seeking to decrease their serum cholesterol through diet alone. Clinicians can take this to mean that recommending a pescatarian diet or even a heavily plant-based omnivorous diet could result in reduced serum cholesterol and, as also determined by Bradbury et al., lead to reduced LDL-Cholesterol, reduced blood pressure, reduced triglycerides and increased HDL-cholesterol (2014).
However, another study completed in Northern England with only forty-three subjects found that a vegetarian diet among individuals whose physical activity levels did not change with study participation did not cause a significant decrease in total cholesterol when diet alone was considered (Robinson, Hackett, Billington, & Stratton, 2002). It should be remarked that this study allowed patients to develop their own description for vegetarianism without concern for consistency between subjects. Theoretically, the vegetarians could have been eating dairy, eggs, cheese, yogurt and/or fish without the researchers differentiating between the subject’s cholesterol levels in relation to diet, which could create inconsistencies between results.
Sterols and Stanols
Phytosterols are bioactive compounds found in all foods of plant origins. They compromise of both plant stanols and plant sterols. The regular consumption of phytosterols is associated with lower total cholesterol, especially LDL-cholesterol, when compared to similar counterparts consuming fewer phytosterols. A healthy diet, high in phytosterols, is valuable in the management of hypercholesterolemia (Ras, Geleijnse, & Trautwein, 2014). Stanols and sterols work, at least in part, by inhibiting absorption of both dietary cholesterol and endogenously-created cholesterol. Supplementation has been shown to inhibit cholesterol supplementation from the diet by as much as 60% (Lichtenstein & Deckelbaum, 2001).
Soluble and insoluble fibers are found commonly in fruits, vegetables, legumes, nuts, seeds and whole grains due to the structure of the cell wall found in plants (Dragstead & Maulik, 2013). Insoluble fiber intake is linked to decreased serum cholesterol as well as decreased blood pressure and triglycerides, while soluble fiber has also been linked to decreased triglycerides (Moreno-Franco et al., 2014). A 2002 study found that subjects ingesting a high-fiber diet, including both Beta-glucan and psyllium, significantly decreased total cholesterol, LDL-cholesterol, and triglycerides, when compared to a low-fat diet in participants with similar demographic and medical records (Jenkins et al., 2002).
Antioxidants, like anthocyanins, which are found in red, dark red, blue, and purple colored fruits and vegetables and red wines, have been found to decrease total cholesterol and LDL-cholesterol, as well as reducing blood pressure and triglycerides when consumed as part of a standard diet. Flavanones, which are most often found in white beans and peas and teas, have been shown to decrease serum and hepatic cholesterol, LDL-cholesterol and triglycerides when consumed as part of a healthy diet. The supplementation of cocoa and chocolate products has also been shown to improve high blood pressure and to exhibit anti-inflammatory properties in those patients suffering from chronic illness; although sufficient data on the effects cocoa and its derivatives may have on blood lipids have not been extensively researched (Nalini, Santiago, & Maulik, 2013). Resveratrol, which is found in large quantities in red wine, has been shown to increase HDL-cholesterol and decrease blood pressure and inhibit platelet aggregation. Many antioxidants have also been found to increase endothelial function, reduce oxidative stress, and protect against a variety of cancers, making them multi-taskers in the prevention of CVD.
As the rates of cardiovascular disease are continue to climb throughout first world countries across the globe, researchers continue to look for ways to prevent or treat an illness that was has only grown as first world countries develop access to more advanced healthcare. This is leading to increased healthcare costs, hospitalizations, death rates, loss of productivity and a decreasing lifespan among first world countries with advanced healthcare and treatment options (Abunnaja, Sanchez, & Maulik, 2013). An elevated serum cholesterol level is not only a risk factor associated with CVD, but it is a modifiable one.
Even though chronic diseases such as CVD can’t be cured, they may be able to be prevented or controlled with a suitable diet. By encouraging the public to implement a plant based diet that includes a variety of fruits, vegetables, legumes, nuts, and whole grain products instead of foods that are fried and processed or meals that are fatty or heavily salted could be a step toward treating existing CVD or preventing the diagnosis of CVD in some individuals altogether. With proper education and promotion, plant based diets can help improve health outcomes of future generations.
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By: Germaine Guy and Brandy Legg