by Jack Norris, RD • Last updated September 2018
- Blood Lipids
- Blood Pressure
- Body Mass Index
- Body Fat
Numerous studies have measured cholesterol levels, blood pressure, obesity, and other markers of disease in vegans. Most of these studies included information on lacto-ovo vegetarians (lacto-ovo), fish-eaters (pesco), and non-vegetarians (non-veg). This article surveys those published since 1980. Not much was published on vegans before that time.
Lipids are fat-soluble substances, including cholesterol and fatty acids. Blood lipid measurements generally include total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides.
Total cholesterol is a measure of all the various types of cholesterol in the blood. Cholesterol can be separated according to the lipoprotein that carries it in the blood. Cholesterol carried by low-density lipoproteins (LDL) is considered “bad” because it tends to be deposited on the artery walls, causing heart disease. Cholesterol carried by high-density lipoproteins (HDL) is considered “good” because it tends to be taken to the liver where it is then broken down or excreted into the digestive tract in the form of bile. Dietary fiber (especially soluble) can then bind to some and it will be excreted in the stool.
There are also other lipoproteins, such as very low density lipoproteins (VLDL). They will not be examined here as they have not been measured in many vegans.
Cholesterol in EPIC-Oxford (2013)
The most recent report of cholesterol in vegans is from the EPIC-Oxford study in which vegetarians were compared to meat-eaters with healthy lifestyles (41). The results are in Table 1 and show vegans to have a 34 mg/dl and 23 mg/dl lower cholesterol level than meat-eaters for men and women respectively. Most of this difference was in the non-HDL cholesterol. Adjusting the results for body mass index reduced the difference by 13% for men and 17% for women.
Vegans also had a significantly lower amount of apolipoprotein B which is thought to promote fat deposits in the arteries.
The authors of the study suggest that vegans have lower cholesterol levels due to a lower body mass index, replacement of saturated fats with polyunsaturated fats, and higher fiber intakes.
|Table 1. Cholesterol Levels in EPIC-Oxford (2013) in mg/dl41|
|Total Cholesterol||170||188||196||204||< .001|
|Apolipoprotein B||82||89||93||100||< .001|
|Total Cholesterol||172||184||188||195||< .001|
|Apolipoprotein B||76||81||82||87||< .001|
|Results adjusted for age, alcohol, and physical activity.|
Cholesterol in Western Vegans (1980 – 2002)
Between 1980 and 2002, cholesterol levels of vegans living in Western countries was measured in 17 studies. The average cholesterol level of vegans was 160 compared to 202 mg/dl for non-vegetarians. Table 2 shows the results.
|Table 2. Cholesterol in Western Vegans (1980-2002)1–17|
|Cholesterol : HDL||3.1||3.3||3.2||3.7|
|aNumber of people measured|
Cholesterol in USA Vegans
Of the 17 studies in Table 2, five were of vegans living in the USA. Of those studies, the lowest average finding for total cholesterol for vegans was 135 mg/dl. The data from all 5 studies is compiled in Table 3. The total cholesterol of the 135 vegans averaged out to 146 mg/dl.
|Cholesterol : HDL||3.2||3.5||3.7|
|aNumber of people measured|
Elevated triglycerides are generally thought to increase the risk for heart disease. However, there is a debate as to whether moderately high triglycerides are merely associated with other risk factors for heart disease, while not being a cause in themselves. Normal triglycerides for adults is 40-160 mg/dl for men and 35-135 mg/dl for women (20). Triglyceride levels above 250 mg/dl are more of a concern (20).
Some people are concerned that, although a vegan diet can lower cholesterol levels, it may increase triglyceride levels. As can be seen from Table 4, in the 11 studies that measured triglycerides, vegans were shown to have lower levels than lacto-ovo and non-veg.
|aNumber of people measured|
The total cholesterol of Western vegans averages out to 160 mg/dl. This is 40 points lower than the non-vegetarians in these studies and well below the “desirable” level of less than 200 mg/dl according to the National Heart Lung and Blood Institute. It is possible to eat a vegan diet that is high in fat and hydrogentaed oils and is highly processed with little fiber. This sort of diet might not provide the benefits seen in the studies compiled above. Additionally, some people have a strong genetic predisposition to high cholesterol. The American Heart Association recommends that people over the age of 20 have their cholesterol levels checked every 4 to 6 years (18).
|Table 11. Relative Rates of High Blood Pressure in AHS-2 (2009)39|
|Adjusted for age, gender, and race.|
In 2009, preliminary cross-sectional date from Adventist Health Study-2 was reported. Relative rates for having high blood pressure are show in Table 11. Vegans had a considerably lower rate of high blood pressure. Results were not adjusted for smoking.
In 2012, a more thorough, cross-sectional report was published from Adventist Health Study-2. It included only white people, and results didn’t appear to be adjusted for anything. Rates for having high blood pressure are shown in Table 12; vegans had considerably lower rates of blood pressure.
|Table 12. Relative Rates of High Blood Pressure in AHS-2 (2012)40|
|Semi-Veg & Pesco||.92 (.50-.79)|
In 2002, a study was published in which 11,004 participants of the EPIC-Oxford study were asked if they had high blood pressure (22). Results are shown in Table 5.
|Table 5. High Blood Pressure in EPIC-Oxford (2002)22|
|aNumber of people measured|
The lower percentage of vegans with high blood pressure was statistically significant. This is the only study that has compared the percentage of vegans with high blood pressure to other diet groups.
Blood pressure was then measured in 8,663 participants who did not have high blood pressure. Those results are in Table 6. Results from the 4 other studies measuring blood pressure in vegans since 1980 are also in Table 6. Finally, the combined results of all 5 studies are listed in Table 6.
Table 6. Blood Pressure in Vegans (mm Hg)
|Systole / Diastole||119 / 73.4
|121 / 74.5
|120 / 73.5
|121 / 74.8
|All Studies Except EPIC-Oxford7, 11, 12, 21|
|Systole / Diastole||121 / 76.9
|127 / 78.0
|123 / 78.7
|All Studies7, 11, 12, 21, 22|
|Systole / Diastole||120 / 73.9
|121 / 74.7
|120 / 73.5
|121 / 74.9
|aNumber of people measured|
The results show that vegans have slightly lower blood pressures than those in other diet groups. If the data from Epic-Oxford had included all the participants, rather than only those without high blood pressure, the differences between the vegans and non-veg in Table 6 would have been larger. The difference also might have been larger if the participants in one study (7) had randomly chosen non-vegetarians to participate, rather than choosing non-vegetarians with a similar BMI to the vegans in the study.
Vegetarians and Blood Pressure Meta-Analysis
In 2014, researchers from Japan published a meta-analysis of clinical trials and cross-sectional observational studies of a vegetarian diet and blood pressure (42). Many of these vegetarians were actually semi-vegetarians.
Among seven clinical trials, a vegetarian diet was found to reduce systolic and diastolic blood pressure by an average of 4.8 and 2.2 mm Hg, respectively. Among the 32 cross-sectional studies, vegetarians were found to have a lower systolic and diastolic blood pressure of 6.9 and 4.7 mm Hg respectively.
These findings were statistically significant. The authors said, “According to Whelton et al, a reduction in systolic BP of 5 mm Hg would be expected to result in a 7%, 9%, and 14% overall reduction in mortality due to all causes, coronary heart disease, and stroke, respectively.”
Why Do Vegans Have Lower Blood Pressure?
EPIC-Oxford (22) and Adventist Health Study-2 (40) found lower body mass index explained most of the differences in blood pressure among the diet groups. Other contributory factors could be higher consumption of potassium, lower consumption of sodium, modulation of baroreceptor sensitivity, direct vasodilatory effects, changes in catecholamine and renin–angiotensin–aldosterone metabolism, improvement of glucose tolerance with lower insulin levels, and lower blood viscosity in vegetarians (40).
Body Mass Index
Body mass index (BMI) is measured by taking one’s weight in kilograms and dividing it by their height in meters squared (i.e., kg/m2). It is a way of measuring weight while taking into consideration differences in height. A healthy BMI is considered to be between 20 and 25. Generally, a BMI of 30 or higher is considered obese (32).
Recent research has shown that a BMI of 22.5 to 25.0 is associated with the lowest mortality rate. It has been known for some time that a lower BMI has been associated with an increased risk of death, but that was thought to be due mostly to smoking-related diseases. A 2009 meta-analysis of 900,000 people found that even in those who never smoked, there is a slight increase in mortality below a BMI of 22.5 (37). The excess mortality below 22.5 has not been explained. One theory is that the excess mortality might be due to lower fat-free mass, which would most likely be lower muscle mass (though could also technically be bones, or even some organs) (37, 38). Studies on BMI and mortality to date have not differentiated between fat and fat-free body mass.
2013 Report from Adventist Health Study-2
In 2013, cross-sectional data on BMI were released from the Adventist health Study-2 (43).
|Table 7. Body Mass Index in Adventist Health Study-2 (2013)43|
|BMI—Body Mass Index • Semi-Veg—eat red meat and poultry ≥ 1 time per month and < 1 time per week • aNumber of people measured • Adjusted for age, sex, race|
In AHS-2, vegans had a lower BMI than all other diet groups. The study wasn’t focused on BMI, and the report didn’t mention testing for statistical significance.
2003 Report From EPIC-Oxford
A report on BMI from EPIC-Oxford was published in 2003. Results are in Table 8.
|Table 8. Body Mass Index in EPIC-Oxford (2003)34|
|Body Mass Index = kg/m2 • Adjusted for age, smoking, education level, physical activity, marital status, ethnicity, parity. • Differences between the vegans and other groups were statistically significant. • aNumber of people measured|
The differences between the vegans and meat-eaters was accounted for mostly by differences in protein, polyunsaturated fat, and fiber intake. The authors note that protein intake’s influence on weight has not been reported often in the literature, but there is some mention of it altering hormones in a way that increases abdominal fat. They also note that low fiber intakes have been previously associated with higher body weight and this is thought to be via making people feel full on less calories, insulin control, and reducing fat absorption.
Body Mass Index Over Time as a Vegan
A 1996 letter to the editor of the British Medical Journal from the authors of the EPIC-Oxford study (31) reported BMI according to the time on current diet (less than or greater than 5 years). The number in each group were:
- 1,652 Vegan
- 8,827 Lacto-ovo
- 3,776 Pesco
- 6,850 Non-veg
The actual BMIs were not given, but a graph was provided (which can be viewed at bmj.com/cgi/content/full/313 /7060/816/F1). The graph shows that those on a vegan diet for more than 5 years had the lowest BMI, followed by those on a vegan diet for less than 5 years, for both men and women. This is impressive, as most weight loss is not sustained for more than one year. Of course, weight loss can sometimes be difficult even for vegans, and some people actually gain weight after becoming vegan. But, on average, the evidence supports the notion that becoming vegan is conducive to permanent weight loss.
In 2006, a report from EPIC-Oxford (35) showed that over a 5 year period, vegans had the lowest weight-gain compared to meat-eaters, fish-eaters, and lacto-ovo vegetarians. The group who had switched to a diet of eating less animal products had the lowest weight gain of all. The group of people who reverted to a diet of more animal products had the most weight-gain, but this was not statistically significant. All groups had some weight gain over the 5 year period.
What does it matter if vegans weigh less if they simply have less muscle mass? Above (Table 9) we saw that vegans have an average BMI of about 22.2 to 22.5, which is right in the middle of the healthy range of 20 to 25. So, vegans are not too thin. But what if a lower percentage of their body weight is muscle (which would mean that a higher percentage of their body weight is fat)?
Table 10 lists the studies that measured percentage of body fat or skinfold thickness (an indicator of body fat) in vegans. Determining the percentage of body fat can vary greatly from method to method, so averaging the results would not be appropriate. Instead, we should look at the general trend. In the 5 comparisons made, the vegans had lower body fat in all five. In three of those comparisons, the differences were statistically significant.
|Table 10. Percentage of Body Fat in Vegans|
21 M & 17 F
6 M & 5 F
20 M & 19 F
|None. Vegans had more men.||Not SSa|
|Vegans slightly older.||P < .05a|
|Vegans were older.||P < .05a|
|Tricep Skinfold Thickness|
11 M13.5 mm
11 M17.3 mm
|Matched for age, body build. Energy intake did not differ.||NR|
|Sum of skinfold measurements|
12 M & 10 F
12M & 10 F
|Matched for age, height, ethnic, socio economic status.||P < .01a|
|F—female • M—male • NR—not reported • SS—statistical significance • P—the % chance that the finding was due to random chance • aStatistically significant between vegans and non-veg|
So, we now know that vegans have lower BMIs and they also tend to have lower body fat percentage (though the numbers measured are small).
There is one marker of disease that has recently garnered much interest: blood homocysteine levels. Elevated homocysteine levels are associated with heart disease, stroke, and early death. Numerous studies have looked at homocysteine in vegans and indicated that if vegans are not taking vitamin B12, they probably have high homocysteine levels. For more information, please read the chapter B12 and Chronic Disease: Homocysteine in Vitamin B12: Are You Getting It?
In summary, the evidence shows:
- Vegans have lower total cholesterol, LDL cholesterol, and triglycerides, while having about the same HDL cholesterol as
lacto-ovo and non-veg.
- Vegans have lower rates of high blood pressure than lacto-ovo and non-veg.
- Vegans have a lower BMI and body fat percentage than lacto-ovo and non-veg. People who have been vegan for more than
5 years have the lowest BMI of all diet groups studied here.
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