Disease Markers: Cholesterol Levels, Blood Pressure, Body Weight, Homocysteine

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 (LOV), fish-eaters, and non-vegetarians (NV). This article surveys those published in the 25 years before 2003. Not much was published on vegans before that time.

Blood Lipids

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.

Total Cholesterol in Vegans in the United States

As of February 4, 2003, numerous sites on the Internet report the cholesterol levels of U.S. vegans to be 128 mg/dl. In the 5 studies since 1980 of U.S. vegans, the lowest was 135 mg/dl.

The data from all 5 studies is compiled in Table 1. The total cholesterol of vegans in the U.S. averaged out to 146 mg/dl. However, there were only 135 vegans represented, which is not a high enough number to provide much confidence for claiming it is representative of U.S. vegans.

Table 1. Cholesterol Levels in Studies Including Vegan Adults in the USA in mg/dl.2,4,5,11,13   Vegan (number) LOV (number) NV (number) Total Cholesterol 146.4 (135) 177.3 (174) 194.2 (117) LDL 67.1 (110) 103.0 (149) 117.0 (10) HDL 46.0 (135) 50.2 (174) 52.7 (81) TC:HDL 3.2 3.5 3.7

Total Cholesterol in Western Vegans

The cholesterol levels of vegans living in Western countries have been measured in 17 studies since 1980. The results (including the 5 studies of U.S. vegans in Table 1) are listed in Table 2. The average cholesterol level of vegans was 160 compared to 202 mg/dl for non-vegetarians (NV).

In 13 studies, a statistically significant (SS) difference was found between the vegans and NV.^{1,2,4,5,6,7,8,10,11,12,14,16,17} Two studies did not find a SS difference.^3,13 One study found a SS difference for the men only,⁹ and the remaining study did not include any non-vegans.¹⁵

Table 2. Cholesterol Levels in Studies Including Vegan Adults in Western Countries in mg/dl.1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17   Vegan (number) LOV (number) Fish (number) NV (number) Total Cholesterol 160.0 (749) 185.3 (2,135) 196.2 (467) 201.5 (1,857) LDL 90.3 (398) 106.0 (1,859) 113.7 (467) 120.9 (1,516) HDL 51.9 (472) 56.7 (1,898) 61.0 (467) 55.0 (1,587) TC:HDL 3.1 3.3 3.2 3.7 Fish - eat no meat other than fish

Confounding Variables

Cholesterol levels can increase with age. Of the 17 studies:

• Seven chose participants of a similar age at the beginning of the study.^{1,3,5,7,8,9,10}
• Two adjusted their numbers for age.^6,16
• Five had no differences in age between vegans and non-vegans.^{2,11,13,14,17}
• The vegans were older in 1.⁴
• One study of 9 vegans (avg. age of 41) did not have any non-vegans.¹⁵
• One study had 18 vegans (avg. age of 33.0) and 78 NV (avg. age of 37.5).¹²

Thus, it seems fair to say that there was no tangible age difference working in favor of the vegans in these studies.

One study from 2000,¹⁶ using subjects from the EPIC-Oxford, adjusted for body mass index, age, smoking, and exercise. It found similar numbers to those in Table 2:

• 233 vegans, cholesterol: 159 mg/dl
• 226 NV, cholesterol: 188 mg/dl

There was a large statistical significance (p < .0001; i.e., less than a .01% chance of being due to random chance). It is safe to assume that the differences in total cholesterol levels found between vegans and NV (and probably other diet groups as well) is a real effect of the diet.

Total Cholesterol: Do Vegan Men and Women Differ?

Of the studies measuring total cholesterol levels of vegans, nine reported totals for men separately,^{2,3,4,7,8,9,11,12,16} and eight reported totals for women separately.^{2,3,4,7,8,9,11,12} The details are in Table 3. There is practically no difference between male and female adult vegans.

Table 3. Total Cholesterol Levels of Men and Women (in mg/dl).   Vegan (number) LOV (number) Fish (number) NV (number) Men 157.3 (340) 172.3 (368) 215.8 (26) 189.2 (398) Women 156.6 (128) 188.1 (138) 220.5 (26) 196.0 (98) Fish - eat no meat other than fish

Why are Vegans Cholesterol Levels Lower?

The largest study looking at vegans' cholesterol levels (of 233 men)¹⁶ did not attempt to determine why vegans had lower levels. The second largest study, the Oxford Vegetarian study, was summarized in a 1999 paper.¹⁸ They found that total cholesterol decreased as fiber intake increased, and that total cholesterol increased as the Keys Dietary Score increased. The Keys Dietary Score predicts that saturated fat and cholesterol intake will increase, while polyunsaturated fat will decrease, total cholesterol levels (it does not account for monounsaturated fat). Thus it appears that higher fiber and polyunsaturated fat intake, and lower cholesterol and saturated fat intake, is at least partially responsible for lower cholesterol levels in vegans.

LDL & HDL Cholesterol of Western Vegans

Table 2 shows the numbers for 11 studies reporting LDL (bad) cholesterol in vegans.^{2,3,5,6,8,9,10,11,12,14,15} The differences in cholesterol levels between vegans and other groups can largely be explained by differences in LDL cholesterol.

There is some concern that vegan diets may lower HDL (good) cholesterol levels. Table 2 includes 14 studies reporting HDL cholesterol levels in vegans,^{2,3,4,5,6,8,9,10,11,12,13,14,15,17} and shows this concern to be largely unfounded. Fish-eaters appear to have higher HDL levels than other diet groups (a statistically significant finding in one large study of 415 fish-eaters).⁶ However, when the ratio of total cholesterol to HDL is calculated, vegans have the lowest ratio, as noted in Table 2. This indicates that vegans' somewhat lower HDL is more of a function of their low overall cholesterol rather than an unhealthy lack of HDL cholesterol.

Triglycerides

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 LOV and NV.

Table 4. Triglyceride Levels in Studies Including Vegan Adults in Western Countries.2,3,4,5,9,10,11,13,14,15,17 Vegan (number) LOV (number) NV (number) Triglycerides (mg/dl) 86.5 (310) 107.6 (253) 107.5 (281)

Summary

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 College of American Pathologists recommends that people over the age of 20 have their cholesterol levels checked every 5 years.¹⁸

Blood Lipid References

1. Sanders TA, Ellis FR, Dickerson JW. Am J Clin Nutr 1978 May;31(5):805-13.
2. Lock DR, et al. 1982 Sep;31(9):917-21.
3. Roshanai F, Sanders TA. Hum Nutr Appl Nutr. 1984 Oct;38(5):345-54.
4. Kritchevsky D, Tepper SA, Goodman G. Am J Clin Nutr. 1984 Oct;40(4 Suppl):921-6.
5. Fisher M, et al. Arch Intern Med. 1986 Jun;146(6):1193-7.
6. Thorogood M, et al. Britain.Br Med J (Clin Res Ed). 1987 Aug 8;295(6594):351-3.
7. Sanders TA, Key TJ. Hum Nutr Appl Nutr. 1987 Jun;41(3):204-11.
8. Thorogood M, et al. BMJ. 1990 May 19;300(6735):1297-301.
9. Sanders TA, Roshanai F. Eur J Clin Nutr. 1992 Nov;46(11):823-31.
10. Thomas EL, Frost G, Barnard ML, et al. Lipids. 1996 Feb;31(2):145-51.
11. Toohey ML, et al. J Am Coll Nutr. 1998 Oct;17(5):425-34.
12. Li D, et al. Eur J Clin Nutr. 1999 Aug;53(8):612-9.
13. Haddad EH, et al. Am J Clin Nutr. 1999;70(suppl):586S-93S.
14. Krajcovicova-Kudlackova M, et al. Scand J Clin Lab Invest. 2000 Dec;60(8):657-64.
15. Fokkema MR, et al. Prostaglandins Leukot Essent Fatty Acids. 2000 Nov;63(5):287-92.
16. Allen NE, et al. Br J Cancer 2000 Jul;83(1):95-7.
17. Bissoli L, et al. Ann Nutr Metab. 2002;46(2):73-9.
18. CAP. College of American Pathologists. Cholesterol Testing Information. http://www.cap.org/health_and_wellness/Cholesterol_CAP.html. Accessed February 7, 2003.
19. Appleby PN, et al. Am J Clin Nutr. 1999 Sep;70(3 Suppl):525S-531S.
20. LAB. Fischbach F. A Manual of Laboratory & Diagnostic Tests, 6th Ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2000.

Blood Pressure

In 2002, a study was published in which 11,004 participants of the EPIC-Oxford study were asked if they had high blood pressure.⁵ Results are shown in Table 5.

Table 5. Percentage with High Blood Pressure in 11,004 participants of the EPIC-Oxford Study.5 Percentage with high BP Vegan (number) LOV (number) Fish (number) NV (number) Men 6% (272) 10% (786) 10% (297) 15% (996) Women 8% (467) 9% (3,014) 10% (1,431) 12% (3,741)

The lower percentage of vegans with high blood pressure was statistically significant. This was the only study that 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. Average Blood Pressure in Vegans (mm Hg) Compared to Other Diet Groups. Vegan LOV Fish NV EPIC-Oxford5 Number 612 3,233 1,404 3,524 Systole / Diastole 119 / 73.4 121 / 74.5 120 / 73.5 121 / 74.8 All Studies Except EPIC-Oxford1,2,3,4 Number 104 192 0 100 Systole / Diastole 121 / 76.9 127 / 78.0 123 / 78.7 All Studies1,2,3,4,5 Number 716 3,315 1,404 3,624 Systole / Diastole 120 / 73.9 121 / 74.7 120 / 73.5 121 / 74.9 Fish - eat no meat other than fish

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 NV in Table 6 would have been larger. The difference also might have been larger if the participants in one study² had randomly chosen non-vegetarians to participate, rather than choosing non-vegetarians with a similar BMI to the vegans in the study.

Why Do Vegans have Lower Blood Pressure?

EPIC-Oxford⁵ was the only study that examined possible reasons for vegans having lower blood pressure. The study found that body mass index accounted for most of the differences among the diet groups.

Blood Pressure References

1. Sacks FM, Wood PG, Kass EH. Hypertension. 1984 Mar-Apr;6(2 Pt 1):199-201.
2. Sanders TA, Key TJ. Hum Nutr Appl Nutr. 1987 Jun;41(3):204-11.
3. Toohey ML, et al. J Am Coll Nutr. 1998 Oct;17(5):425-34.
4. Li D, et al. Eur J Clin Nutr. 1999 Aug;53(8):612-9.
5. Appleby PN, Davey GK, Key TJ. Public Health Nutrition 2002;5:645-654.

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 27 or higher indicates obesity.²⁰

Table 7 shows the combined results of the 17 studies measuring the BMI of Western vegans. The results for NV in two of these studies (a total of 40 NV) were not included because the researchers specifically chose NV who weighed the same as the vegans.^3,4 Additionally, a study¹⁸ with 25 vegans was not included because the participants had to be within 120% of their ideal body weight, possibly biasing the BMI results.

Because the BMIs of many of the people measured were calculated using weights and heights reported by participants by way of questionnaires, rather than being directly measured by the researchers, the results in Table 7 are divided into two groups accordingly.

Table 7. Body Mass Index (kg/m2) in Studies of Vegan Adults in Western Countries.   Vegan (number) LOV (number) Fish (number) NV (number) Height and Weight Measured by Researchers1,2,3,4,6,8,9,10,11,12,13,14,15,16 Male 22.2 (84) 24.3 (112) 22.0 (4) 23.4 (33) Female 22.1 (78) 25.9 (109) 22.0 (5) 22.1 (37) M & F 22.1 (279) 24.2 (334) 22.0 (9) 24.2 (212) Height and Weight Reported by Participants Using a Questionnaire5,7,17 Male 22.5 (974) 23.5 (3,994) 23.6 (1,682) 24.9 (7,544) Female 21.9 (1,617) 22.7 (14,017) 22.9 (8,060) 24.3 (25,159) M & F 22.1 (2,591) 22.9 (18,011) 23.0 (9,742) 24.4 (32,703) Totals of All 17 Studies Above Male 22.5 (1,058) 23.5 (4,106) 23.6 (1,686) 24.9 (7,577) Female 21.9 (1,695) 22.7 (14,126) 22.9 (8,065) 24.3 (25,196) M & F 22.1 (2,870) 22.9 (18,345) 23.0 (9,751) 24.4 (32,915) Fish - eat no meat other than fish Note: You cannot obtain the "M & F" totals by combining the Male total with the Female total as some studies did not break down BMI according to gender.

The results in Table 7 show vegans to have the lowest BMI in all scenarios. BMI for vegans were practically the same regardless of whether reported by questionnaire or measured by researchers. The BMIs for participants using a questionnaire are the same as the totals of all 17 studies.

The largest study of 2,488 vegans and 32,594 NV found a statistically significant difference between the vegans and NV.^17,21

2003 Update

A report on BMI from EPIC-Oxford was published in 2003 after this article was originally written. Findings were similar:

Body Mass Index (kg/m2) in 2003 Report of EPIC-Oxford.22   Vegan (number) LOV (number) Fish (number) NV (number) Male 22.5 (570) 23.4 (2,888) 23.4 (1,095) 24.4 (4,318) Female 22.0 (983) 22.7 (9,419) 22.7 (5,096) 23.5 (13,506) Fish - eat no meat other than fish Adjusted for age, smoking, education level, physical activity, marital status, ethnicity, and in women only, parity. Differences between the vegans and other diet groups were statistically significant.

The differences between the vegans and meat-eaters was accounted for mostly by diffences 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. Because this was only a cross-sectional study, it is possible that the differences could be explained by leaner individuals being more likely to adopt a vegan diet.

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 (Key et al.¹⁹) reported BMI according to the time on current diet (less than or greater than 5 years). There were:

• 1,652 vegans
• 8,827 LOV
• 3,776 fish eaters
• 6,850 meat-eaters

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-Oxford²³ 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.

BMI References

1. Abdulla M, et al. Am J Clin Nutr 1981 Nov;34(11):2464-77.
2. Carlson E, et al. J Plant Foods. 1985;6:89-100.
3. Rana SK, Sanders TA. Br J Nutr. 1986 Jul;56(1):17-27.
4. Sanders TA, Key TJ. Hum Nutr Appl Nutr. 1987 Jun;41(3):204-11.
5. Thorogood M, et al. BMJ. 1990 May 19;300(6735):1297-301.
6. Ross JK, Pusateri DJ, Shultz TD. Am J Clin Nutr. 1990 Mar;51(3):365-70.23.
7. Key TJ, et al. Br J Nutr. 1990 Jul;64(1):111-9.
8. Sanders TA, Roshanai F. Eur J Clin Nutr. 1992 Nov;46(11):823-31.
9. Janelle KC, Barr SI. J Am Diet Assoc. 1995 Feb;95(2):180-6.
10. Thomas EL, et al. Lipids. 1996 Feb;31(2):145-51.
11. Toohey ML, et al. J Am Coll Nutr. 1998 Oct;17(5):425-34.
12. Li D, et al. Eur J Clin Nutr. 1999 Aug;53(8):612-9.
13. Krajcovicova-Kudlackova M, et al. Scand J Clin Lab Invest. 2000 Dec;60(8):657-64.
14. Fokkema MR, et al. Prostaglandins Leukot Essent Fatty Acids. 2000 Nov;63(5):287-92.
15. Herrmann W, et al. Clin Chem. 2001 Jun;47(6):1094-101.
16. Bissoli L, et al. Ann Nutr Metab. 2002;46(2):73-9.
17. Davey GK, et al. Public Health Nutrition. 2003. (In Press)
18. Haddad EH, et al. Am J Clin Nutr. 1999;70(suppl):586S-93S.
19. Key T, Davey G. BMJ. 1996 Sep 28;313(7060):816-7.
20. MA. Mahan LK, Escott-Stump S. Krause's Food, Nutrition, & Diet Therapy, 10th Ed. Philadelphia, PA: W.B. Saunders, Co. 2000.
21. Personal communication with Paul Appleby. February 17, 2003.
22. Spencer EA, Appleby PN, Davey GK, Key TJ. Diet and body mass index in 38000 EPIC-Oxford meat-eaters, fish-eaters, vegetarians and vegans. Int J Obes Relat Metab Disord. 2003 Jun;27(6):728-34.
23. Rosell M, Appleby P, Spencer E, Key T. Weight gain over 5 years in 21,966 meat-eating, fish-eating, vegetarian, and vegan men and women in EPIC-Oxford. Int J Obes (Lond). 2006 Sep;30(9):1389-96. Epub 2006 Mar 14.

Body Fat

What does it matter if vegans weigh less if they simply have less muscle mass? Above (Table 7) 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 8 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 5. In 3 of those comparisons, the difference was statistically significant.

Table 8. Percentage of Body Fat in Vegans Compared to Others. Year Country Vegan LOV NV Adjustments SS between vegans and NV Body Fat (number) 19965 UK 21.9% (21M, 17F) 22.5% (6M, 5F) 24.0% (20M, 19F) None. Vegans had more men. Not SS 19954 Canada 23.7% (8F) 24.1% (15F) 27.4% (22F) Vegans slightly older. p < .05 19903 USA 8.0% (15M) 8.6% (20) 14.0% (18M) Vegans were older. p < .05 Tricep Skinfold Thickness (number) 19872 UK 8.8 mm (11M) 13.5 mm (11F)   10.7 mm (11M) 17.3 mm (11F) Matched for age, body build. Energy intake did not differ. NR Sum of skinfold measurements (number) 19781 UK 43 mm (12M, 10 F)   76 mm (12M, 10F) Matched for age, height, ethnic, socioeconomic status. p < .01 F - female,     M - male,     mm - millimeter,     NR - not reported,     SS - statistical significance p - the % chance that the finding was due to random chance (i.e., p < .05 means there was less than a 5% chance the results were due to random chance)

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).

Body Fat References

1. Sanders TA, Ellis FR, Dickerson JW. Am J Clin Nutr. 1978 May;31(5):805-13.
2. Sanders TA, Key TJ. Hum Nutr Appl Nutr. 1987 Jun;41(3):204-11.
3. Ross JK, Pusateri DJ, Shultz TD. Am J Clin Nutr. 1990 Mar;51(3):365-70.
4. Janelle KC, Barr SI. J Am Diet Assoc. 1995 Feb;95(2):180-6.
5. Thomas EL, et al. Lipids. 1996 Feb;31(2):145-51.

Homocysteine

There is one marker of disease that has recently garnered much inerest: 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 my article Vitamin B12: Are You Getting It?

Conclusion

In summary, the evidence shows:

• Vegans have lower total cholesterol, LDL cholesterol, and triglycerides, while having about the same HDL cholesterol of LOV and NV.
• Vegans have lower rates of high blood pressure than LOV and NV.
• Vegans have a lower BMI and body fat percentage than LOV and NV. People who have been vegan for more than 5 years have the lowest BMI of all diet groups studied here.