The Adoption of a Vegetarian diet in Women and its Effects on the Reduction of Cardiovascular
Disease Risk Factors
Ashley Holmes
March 11, 2008
HNFE 4004
Abstract
Currently, cardiovascular disease it the number one cause of death in the United States, especially in
women. There are several risk factors associated with cardiovascular disease both modifiable and non
modifiable. Modifiable risk factors include state of overweight, diabetes, undesirable lipid profiles,
and elevated blood pressure. These factors can be significantly controlled through diet. Non
modifiable risk factors include age, gender, and race. Vegan or vegetarian dietary intervention studies
have been hypothesized to reduce the modifiable risk factors. Many studies have been performed in
diabetics, overweight pre and postmenopausal women. The subjects are assigned an intervention diet
after a baseline period is observed. The subjects were then evaluated in terms of cholesterol
concentrations, body mass, blood pressure, and glucose control. Each study resulted in improvements
in these risk factors thus being indicative of significant improvements in cardiovascular health. The
researchers disclose that a vegan or vegetarian diet is both preventative method as well as a treatment
method to those at high risk or already have cardiovascular disease. While long term studies are
needed to evaluate the long term effects of a vegan diet and ease of obedience, it can be determined
that a vegan diet is a positive risk reducer for cardiovascular disease.
Introduction
Increasingly, cardiovascular disease is the primary cause of death in women (Barnard, 2000).
Contributing factors to cardiovascular disease are obesity and diabetes (Barnard, 2005). Other risk factors
include hypertension and high blood cholesterol levels. High blood pressure typically results from diets high in
saturated fats and sodium, in addition to being low in soluble fiber. Elevated cholesterol levels can stem from
diets high in saturated fats, trans fats, and cholesterol. In addition, low-density lipoprotein (LDL) can undergo
oxidation from free radicals which can increase plague formation. Numerous studies have been designed and
conducted to evaluate dietary interventions that result in a decrease cardiovascular disease risk in humans. A
frequently evaluated dietary intervention has been vegetarian and vegan diets. A vegan diet does not permit the
consumption of meat in addition to milk, eggs, cheese, and any other animal byproducts. A vegetarian diet only
omits meat and fish (Davis and Melina, 2000). Previous research studies have found vegetarian diets as a risk
reducer of cardiovascular disease as well as effective for weight loss (Turner-McGriery, 2007). In addition to
obesity and diabetes, other non-modifiable factors such as age and gender influence cardiovascular risk. Women
experience an elevated risk for cardiovascular disease after menopause (Barnard, 1999). An abundance of
studies have been conducted testing a low-fat vegetarian or vegan diet and its effects on lipid profiles, weight,
blood pressure, and insulin sensitivity in both pre and postmenopausal women. It is hypothesized that dietary
interventions consisting of vegetarian and/or vegan guidelines will result in an overall decrease in the major
cardiovascular disease risk factors.
Vegetarian Intervention effects on cholesterol
Plasma cholesterol concentration is correlated with positive or negative risk for cardiovascular disease.
A standard lipid profile includes total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein,
and very low-density lipoprotein (VLDL). TC concentrations are expected to be less than 200 mg/dl. LDL
concentrations are desired to be less than 130 mg/dl. HDL is expected to be greater than 40 mg/dl. TC, LDL,
and HDL concentrations that exceed the desired ranges are increasing the risk for cardiovascular disease.
Increases of cholesterol are associated with being overweight or obese defined as a body mass index (BMI) of
over 26 kg/m2. Diabetes, defined as having fasting plasmas glucose (FPG) of more than 126 mg/dl, is also
linked to increases in cholesterol concentrations. Other factors such as genetics, age, gender, and ethnicity, also
have effects on plasma cholesterol concentrations. Dietary intake influences cholesterol and diet modifications
are frequently used as a tool to decrease lipid plasma concentrations (Methods Lab Manual, 2008).
Numerous studies have tested the cholesterol lowering effects of a low-fat vegetarian diet, especially in
women, since they are at higher risk for cardiovascular disease. A study performed by Barnard et al., tested their
hypothesis that in healthy premenopausal women subjects, a low-fat vegetarian intervention diet would decrease
serum lipid concentrations. The subjects, after a baseline period of one menstrual cycle, were randomly assigned
either the intervention diet or the control diet. The intervention diet eliminated animal products and allowed
grains, fruits, and vegetables. A macronutrient breakdown of the intervention diet determined about 10 percent
of calories was from fat. The intervention period had a 2 menstrual cycle duration. Upon completion of the
intervention diet plasma concentrations were measured as well as weight and compared to baseline values. The
vegetarian diet results yielded a decrease of 13.2 percent in mean TC from 163 mg/dl to 141 mg/dl (p< 0.001).
Also, mean LDL concentrations in the intervention group decreased by 16.9 percent from 97 mg/dl to 80 mg/dl
(p<0.001). These results were significantly higher compared to changes in the control group’s lipid
concentrations. Mean HDL concentration also yielded a decrease of 16.5 percent. A decrease in HDL is not
necessarily desired but the LDL and HDL decreased equally, thus maintaining the LDL/HDL ratio. The authors
conclude that a low-fat vegetarian diet had significant impact on decreasing serum lipid concentrations, thus
reducing the risk of cardiovascular disease. The authors suggest that a low-fat vegetarian diet should be a
preventative method of reducing lipid concentrations as well as a treatment with those who have already been
diagnosed with cardiovascular disease. Also noted, is the ease of compliance to a low-fat vegetarian diet is
more readily adhered to than a calorie restricted diet (Barnard et al, 2000).
Increasing age appears to increase total cholesterol especially in women. Causal factors of this age
related increase in cholesterol can be attributed to collective damage from smoking, being overweight, minimal
physical activity, and a diet consisting of large percentages of saturated fats. Vegetarians, by nature of their diet
consume significantly less saturated fat than non-vegetarians. This difference in saturated fat consumption
alone has been attributed to decreased lipid concentrations. A statistical study performed by Richter et al.
evaluated the lipid concentrations of 417 vegetarians and 10,550 non-vegetarians. The subjects represented
several age groups, to evaluate the age related increase in lipid concentrations. Plasma TC, HDL, and non HDL
were determined from dry-chemistry Reflotron Systems. Also analyzed in this study were BMI, waist-to-hip
ration, and blood pressure. The results yielded, as the authors expected, the vegetarians with lower total
cholesterol than non-vegetarians. In addition to vegetarians having lower TC, they also had lower age
dependent increases in cholesterol than the non-vegetarian population. Furthermore, vegetarians had lower LDL
concentrations compared to the non-vegetarians. Each of these results indicates that a low-fat vegetarian diet
reduces lipid concentrations, and thus is a negative risk factor for cardiovascular disease (Richter, et al., 2004).
It has become evident that a low-fat vegetarian diet is a dietary intervention that has reduced cholesterol
in those who adhere to it. Vegetarians consume significantly less dietary cholesterol and saturated fats which
are factors that increase blood cholesterol, in addition to consuming larger amounts of cholesterol reducing
foods such as unsaturated fats and dietary fiber. These two combined aspects of a vegetarian diet are indicative
to reducing cardiovascular disease.
Vegetarian Intervention Effects on Obesity
Obesity is a significant issue in for the current population. Obesity negatively affects insulin sensitivity,
blood pressure, and cholesterol. All these factors are positive risk factors for cardiovascular disease.
Reductions in weight can significantly reduce the risks associated with obesity. Several research studies have
tested a variety of weight loss diets and its effects on cardiovascular disease risk, including a low-fat vegetarian
diet. Barnard et al., developed a dietary intervention study to evaluate the effects of a plant-based diet on body
weight in postmenopausal overweight women. Half of the women were randomly assigned an intervention diet
that consisted of 10 percent of calories from fat, 15 percent of calories from protein, and 75 percent of calories
from carbohydrates. The other women were placed on a control diet that was based on recommendations from
the National Cholesterol Education Program Step II Guidelines. This control diet allotted less than 30 percent of
calories from fat, which less than 7 percent could come from saturated fat. Protein and carbohydrate
percentages were 15 and 55 percent respectively. The assigned diets were followed for 14 weeks, upon which
body weight, body composition, and hip and waist measurements were conducted and compared to baseline
values. Body weight was ascertained on a digital scale while body composition was determined by air
displacement plethsmography. A tape measure was used to identify hip and waist measurements. The data was
analyzed and the results yielded a higher decrease in body weight in the vegetarian diet group than the control
diet group. Data reveals the decrease in weight experienced in the vegetarian intervention group was an average
of 5.8 kg as compared to only 3.8 kg in the control group. The weight loss in both groups is combined with
reductions in BMI and body fat percentage. While both groups experienced decreases in BMI and body fat
percentage, the vegetarian intervention group experienced more significant decreases than the control diet
group. The authors discuss the reasons for this more significant reduction in the subjects. They attribute
elevated consumption of fiber and a more severe decrease in fat consumption for the changes in body
composition. These positive results indicate that, as with cholesterol, consuming a low-fat vegetarian diet
decreases cardiovascular risk significantly. The authors also note that the long term effects of a low-fat
vegetarian diet lack research studies to prove or disprove its effectiveness. However, a study developed by the
same researchers (Turner-McGrievy, et al.) evaluated the long term compliance of a vegan diet and its effects on
cardiovascular disease risk factors. As with the previous study, postmenopausal women were divided into two
groups, one group that consumed a low-fat vegan diet and a group that consumed a diet based on the National
Cholesterol Education Program for 14 weeks. This study’s methodology is essentially identical to the previous
study, because it is the same group of researchers performing this study. Upon completion of the 14 weeks
diets, only weight changes were documented. After the study half of the subjects in each group (vegan and
control) were made accessible to support groups for one year. The remaining subjects in both diet groups were
not offered this support system. At one and two years post intervention weights were taken from remaining
subjects and diets were analyzed with Nutritionist V software. The results after one year indicated that those
who followed the vegan diet lost more weight at both one and two years post intervention than the control group
regardless if they were offered support or not. As the authors had anticipated that subjects in the supported
groups also lost more weight at one and two years post intervention. The authors again attribute the more
significant weight loss in the vegan diet to an increase in fiber intake and decreased fat consumption.
Furthermore, the subjects who received continuing support and nutritional education lost more weight than those
who did not have access to support, regardless of diet consumed. This study’s results indicated that a vegan diet
continues to have positive effects on weight loss even in the long term. Additionally, the weight loss is
maintainable and even more so with outside support years after the intervention period (Turner-McGrievy, et al.,
2007). There are limited research studies that have tracked long term effects of a low-fat vegan diet…..
Vegetarian Intervention effects on Diabetes
A corresponding factor to obesity is diabetes. These two conditions are significant positive risk factors
for cardiovascular disease. There are two types of diabetes, Type 1, in which the beta cells of the pancreas does
not produce insulin. With Type 2 diabetes, the pancreas produces insulin but it is not used by the body because
of decreased insulin sensitivity. A major cause of Type 2 diabetes is being overweight or obese. Another risk
factor related to obesity is where on the body the fat is concentrated. Persons who carry more weight around the
abdominal area are more likely to develop diabetes (Davis and Melina, 2000). A study by Barnard et al.,
researched the effects of a vegan diet versus a diet prescribed by the American Diabetics Association (ADA)
and their effects on the glycemic control of type 2 diabetics. The researchers developed the study based on the
hypothesis that the vegan diet would improve glycemic control significantly more than the ADA diet. The diets
were similar in macronutrient percentages differing mostly in the exemption of animals products in the vegan
diet group. The subjects were not provided with food and were asked to maintain their current exercise regimen.
Nutrition counseling with a registered dietitian occurred in both intervention groups at the initiation of the diet.
Subjects were asked to provide 24 hour food consumption recalls and well as several 3-day records of food
intake. Upon the completion of the 22 week intervention period several tests were performed and compared to
values obtained at baseline. These tests included body weight, plasma glucose, plasma cholesterol, and blood
pressure. In terms on body weight changes, the results yielded a decrease of 5.8 kg (p<0.0001) and 4.3 kg
(p<0.0001) in the vegan and ADA group respectively. Total cholesterol, measured by enzymatic methods,
experienced a decrease of 33.5 mg/dl for the vegan group and the ADA group had a decrease of 19.0 mg/dl.
Plasma glucose levels were measured by glycosylated hemoglobin (HbA1c) concentrations by an Abbott
Spectrum analyzer and glucose oxidase method. The results yielded a decrease of .96 and .56 percentage points
in the vegan and ADA groups respectively. Results were not documented for blood pressure changes from
baseline and 22 week intervention period. The authors conclude the study with the declaration that both dietsvegan and ADA are beneficial in terms of weight loss, reducing cholesterol, and increase plasma glucose
control. The researchers attribute the vegan to more significant changes in weight, cholesterol, and glucose
control. The fundamental aspects of the vegan diet are linked to these changes. Vegan diets consistently higher
in fiber which is an essential aspect of regulating insulin sensitivity. In addition, the elimination of animal byproducts results in a diet significantly lower in calories, fat, and cholesterol. Improving insulin sensitivity, body
weight, and lipid profiles will not only reduce cardiovascular risk but will also decrease complications from
diabetes. The authors make the conclusion that both diets are in fact beneficial, but disclose that further studies
studying the long term effects of the diets as well as their ease of compliance should be developed (Barnard, et
al., 2006).
Conclusion
The results of each of the outlined studies have indicated a significant correlation between a vegetarian
and vegan diet and the reduction of cardiovascular risk factors. These risk factors include body weight, blood
pressure, lipid protein concentrations, and insulin sensitivity. In addition to these factors reducing
cardiovascular disease they are also beneficial to general health and well-being. Each study incorporated an
intervention diet and control diet to evaluate the effects of a low-fat vegan diet. The authors of each study
contributed the substantial changes that resulted from the adherence to a vegan diet to the characteristics of the
diet. The elimination of animal products, as well as the increased intake of vitamins, minerals, and fiber results
in a better health profile. Vegan diets are commonly used as a prevention method for cardiovascular disease,
but it is also can be a treatment method for diabetes and cardiovascular disease (Davis and Melina, 2000).
Being healthy is a lifelong commitment to having a balanced intake of essential nutrients and keeping unhealthy
food intake at a minimum. The authors of each study previously referenced, acknowledged that a vegan diet is
one of difficult compliance because of its elimination of more than one food group. Long term studies that
evaluate the effects of a vegan diet and its rate of compliance are necessary to fully determine the benefits of the
diet. For those who are vegan, it is evident that it is not a diet, but a lifestyle that requires commitment and
knowledge of nutrition principles. Even so, the benefits that arise from the adherence to a vegan or vegetarian
diet can significantly decrease cardiovascular disease in diabetics, overweight, pre and postmenopausal women.
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