The American Journal of Clinical Nutrition 31: MAY 1978, pp. 805-813. Printed in U.S.A. 805

Studies of vegans: the fatty acid compositionof plasma choline phosphoglycerides,erythrocytes, adipose tissue, and breast milk,and some indicators of susceptibility toischemic heart disease in vegans andomnivore controls12T. A. B. Sanders,3 Ph.D., Frey R. Ellis,4 M.D., F.R.C.Path.,

and J. W. T. Dickerson,5 Ph.D., F.I.Biol., F.I.F.S. T., F.R.S.H.

ABSTRACT The fatty acid composition of erythrocytes, of plasma choline phosphoglycer-

ides, and of adipose tissue, serum cholesterol, triglyceride and vitamin B12 concentrations,

weights, heights and skinfold thickness were determined on 22 vegans and 22 age and sex

matched omnivore controls. The fatty acid composition of breast milk from four vegan and four

omnivore control mothers, and of erythrocytes from three infants breast fed by vegan mothers

and six infants breast fed by omnivore control mothers was determined. The proportions of

linoleic acid and its long-chain derivatives were higher, the proportion of the long-chain

derivatives of a-linolenic acid was lower, and the ratio of 22:5o3/22:6co3 was greater in the

tissues of the vegans and infants breast-fed by vegans than in controls; the most marked

differences were in the proportions of linoleic (18:2v6) and docosahexenoic (22:6w3) acids.

Weights, skinfold thickness, serum vitamin B12, cholesterol and triglyceride concentrations were

less in vegans than in controls. The difference in serum cholesterol concentration was most

marked. It is concluded that a vegan-type diet may be the one of choice in the treatment of

ischemic heart disease, angina pectoris, and certain hyperlipidemias. Am. J. Clin. Nuir. 31:

805-813, 1978.

Vegans in the United Kingdom are agroup of British people who for ethicalreasons eat no foods of animal origin. Ve-gans, who have pursued their dietary prac-

tices out of choice and not economic neces-sity for years and even lifetimes in times andareas of relative affluence, provide a unique

opportunity to study the long-term effectson health of diets that do not contain anyfoods of animal origin.

The few clinical studies (1-3) made so farin Britain and the United States have not

been able to identify any real differences in

the health of vegans compared with omni-vores . Epidemiological evidence , however,shows that the incidence of certain diseases,notably IHD6, is lower in countries wherethe typical diet contains a low proportion ofanimal products; in particular, the incidenceof IHD has been correlated with the propor-tion of animal fat in the diet (4). Therefore,we decided to study the fatty acid composi-tion of some accessible tissues and also some

indicators of susceptibility to IHD (serumcholesterol and triglyceride concentrations

I From the Department of Pathology, Kingston

Hospital , Kingston-upon-Thames, Surrey and Depart-

ment of Biochemistry, University of Surrey, Guildford,

Surrey, England.

2 Supported by a grant from the South West Thames

Regional Health Authority. This incorporates data

from a thesis for which TABS. was awarded the

degree of Doctor of Philosophy in the University of

London.

3 Research Nutritionist, Department of Pathology,Kingston Hospital. ‘ Consultant I-lacmatologist, Dc-

partment of Pathology, Kingston Hospital. � Profes-

sor of Human Nutrition, Department of Biochemistry,

University of Surrey.

Ii Abbreviations: IHD, ischemic heart disease;

GLC, gas-liquid chromatography; TLC, thin-layerchromatography; BHT, 2-6-di-tert-butyl-p-cresol;

EDTA, ethylene-diamine-tetraacetic acid; DMA, di-

methyl acetal. In the abbreviation of the fatty acids,

the first two digits state the number of carbon atoms,

the third digit states the number of double bonds, and

the digit after the oi states the number of carbon atoms

from the methyl end of the acyl chain to the nearest

double bond.

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806 SANDERS ET AL.

and degree of obesity) in vegans and omni-yore controls.

Materials and methods

Vegans were approached through . the Vegan Soci-

ety, 47 Highlands Road, Leatherhead, Surrey. The

criteria used for their selection were that their diets

should not contain any foods of animal origin , including

margarines made from animal and fish oils, and that

they had taken such a diet for at least 1 year; whether

they took vitamin B12 supplements was noted. Twenty-

two vegans (1 2 males, 1 0 females) were selected for

examination; the subjects were Caucasians and be-

longed predominantly to the professional and middle

classes; they were not members of any particular

religious sect . The mean age of these subjects was 38

years (range 21 to 66 years) and they had taken a

vegan diet for a mean duration of 8 years (range 1 to

30 years). Most of these subjects were using Tomor

kosher margarine (Van den Berghs).

Controls were chosen from the general omnivorous

population . The criteria for choosing these controlswere that they should be healthy, and not taking any

special diet , and they they should match the vegan

subjects with regard to age, sex, height, ethnic origin,

and socioeconomic background . The first volunteers

fulfilling these criteria were taken.

In addition to the 22 vegans and 22 omnivore

controls already described, 10 mothers, four vegans

and six omnivores, and their infants were studied. The

vegan mothers had been on the diet for an average of

7 years (range 3 to 12 years). All the infants were

exclusively breast fed for a minimum of 3 months.

Medical histories were taken and attention paid toany symptoms that could be associated with nutritional

deficiency. Subjects were weighed, their heights taken,

and the percentage standard weight for height was

calculated using the tables in Documenta Geigy (5).Measurements of skinfold thickness were made at

four sites (biceps, triceps, subscapular, and suprailiac)

with a Harpenden caliper (6). Blood samples were

obtained by venipuncture with stasis in the morning

from subjects who had been fasting overnight; samples

for fatty acid analyses were anticoagulated with EDTA.Adipose tissue samples were obtained from consenting

subjects by needle biopsy (7) from the triceps skinfold.

Breast-milk samples, about 20 ml, were obtained from

four vegan and four omnivore mothers at the start of a

morning feed between the 2nd and 6th months post-

partum; smaller samples, about 2 ml, were also ob-

tamed in the middle and end of the feed from the samebreast . Sufficient blood samples, anticoagulated with

lithium heparin, for erythrocyte fatty acid analyses,

were obtained by heel prick from nine infants, three ofvegan and six of omnivore mothers, 3 months postpar-

tum.

Fatty acid analyses

Chemicals. BHT was added at a level of 50 mg/liter

to all solvents, except hexane, and TLC sprays and at

a level of 500 mg/liter to all TLC solvents to minimize

losses of polyunsaturated fatty acids due to auto-oxi-

dation (8). 2’7’-Dichlorofluorescein spray reagent

(0.1% w/v in 95% methanol) was washed with hexane

prior to use to remove contaminants (9). Toluene was

Aristar grade (BDH Chemicals, Poole, Dorset), hex-

ane and diethyl ether were Puriss grade (Koch-Light

Laboratories, Berks) . Chloroform and methanol were

Analar grade (BDH Chemicals), and were redistilled

prior to use . Fatty acid methyl ester standards were

obtained from Nu-Chek Prep. Inc. (Elysian, Minne-

sota) and from the Sigma Chemical Company (Norbi-

ton , Surrey). All glassware was cleaned with chromic

acid. All other chemicals were at least Analar grade,

and were generally obtained from BDH Chemicals.Preparation of methyl esters and dimethyl acetals

erythrocytes. Suspensions of washed erythrocytes were

prepared immediately from freshly drawn blood and

lipids were extracted with isopropanol: chloroform

(1 1 :7 v/v) from aliquots containing 0.5 to 1 .0 ml.

packed erythrocytes (10). The lipid extract was taken

to dryness under nitrogen in a centrifuge tube provided

with a Teflon-lined screw cap. The dry lipid was

dissolved in benzene (1 ml) and 5% (w/v) hydrogen

chloride in anhydrous methanol (2 ml) was added. Thetube was flushed with nitrogen, sealed and heated for

2 hours at 100 C. The derivatives were extracted by

adding water containing 5% NaCI (5 ml), then hexane

(5 ml), at room temperature, shaking briefly, and

centrifuging until both layers were clear, followed by

collection of the upper phase . A second extraction was

carried out with hexane (5 ml) to ensure recovery of

the dimethyl acetals (8) and the extract pooled with the

first. The combined extracts were washed with water

oontaimng 2% w/v NaHCO3 (4 ml), dried over anhy-

drous NaSO4, filtered, and taken to dryness under

nitrogen . The methyl esters and dimethyl acetals were

taken up in a small volume of hexane (50 to 100 s.d)for analysis by GLC.

Plasma choline phosphoglycerides. Lipids were cx-

tracted from plasma with chloroform:methanol (2: 1 v/

v) and non-lipid contaminants removed (1 1). An ali-

quot of lipid extract, equivalent to 1 ml of plasma, was

taken to dryness under nitrogen , redissolved in chloro-

form (50 s.d) and applied as a narrow band 1 .5 to 2 cm

from the origin of a 20 x 20 cm TLC plate coated with

0.5 mm layer of Silica Gel HR (Merck); TLC plates

were prepared with distilled water and activated for 1

hr at 1 1 0 C before use . The plate was developed withacetone:hexane (1 :3 v/v) under conditions of tank

saturation at 4 C to isolate the phospholipids (8). The

solvent front was allowed to reach the top of the plate.

The plate was removed from the tank, dried under a

stream of nitrogen , and redeveloped in the same di-

rection with chloroform:methanol:acetic acid:water(25:15:4:2 v/v) under conditions of tank saturation at

4 C to separate individual phospholipids (1 2). Theplate was removed from the tank, when the solvent

front was about 2 cm from the top of the plate, and

dried under a stream of nitrogen . Bands were made

visible under ultraviolet light by spraying with a 0.1%

solution of 2’7’-dichlorofluorescein in 95% methanol.

The choline phosphoglycerides were identified by com-

parison of their migration on the TLC plate with an

authentic standard (egg yolk lecithin, type V-E, Sigma

Chemical Company). The area of silica gel containing

the choline phosphoglycerides was transferred into acentrifuge tube fitted with a Teflon-lined screw cap.

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STUDIES OF VEGANS 807

Methanol (1 ml), then 14% w/v BF3 in methanol (1

ml) was added, the tube flushed with nitrogen, sealed

and heated for 10 mm at 100 C (13). The methyl esters

were extracted by adding hexane (4 ml), then water (2

ml), shaking briefly, centrifuging until both layers were

clear, and the upper phase collected; the dichlorofiu-

orescein dye remained in the lower aqueous phase.The upper phase was dried over anhydrous NaSO4,

filtered, and taken to dryness under nitrogen. The

methyl esters were taken up in 50 p�l for analysis by

GLC.

Adipose tissue. Lipids were extracted with chloro-

form:methanol (2: 1 v/v) and non-lipid contaminants

removed (1 1). Methyl esters were prepared by reaction

with BF3 in methanol as described by Morrison and

Smith (13) and samples dissolved in hexane were taken

for analysis by GLC.

Breast milk. Lipids were extracted from breast-milk

with chloroform:methanol (2:1 v/v) and non-lipid con-

taminants removed (11). Methyl esters were prepared

as above (13). Methyl esters were purified on TLC

plates, 20 x 20 cm coated with an 0.5 mm layer of

Silica Gel G (Merck), and developed with toluene (14)at 4 C. Plates were dried under nitrogen and methyl

esters were made visible under ultraviolet light after

spraying with a 0.1% solution of 2’7’-dichlorofluores-

cein in 95% methanol. The area of silica gel containingthe methyl esters was transferred into a centrifuge tube

fitted with a Teflon-lined screw cap. One percent acetic

acid in methanol (2 ml) was added, and the tube was

flushed with nitrogen, sealed and heated for 10 mm at

100 C. On cooling, hexane (4 ml), then distilled water

(2 ml) was added, shaking briefly and centrifuging until

both layers were clear, followed by collection of the

upper phase; the dichlorofluorescein dye remained in

the lower aqueous phase with the adsorbent . The upper

phase was dried over anhydrous NaSO4, filtered, and

taken to dryness under nitrogen. An aliquot of the

purified methyl esters was taken up in a little hexane

for analysis by GLC. Recovery of mixtures of polyun-

saturated fatty acids of known composition taken

through this procedure was 100 ± 4.7% (mean ± SD).

An aliquot (2 to 5 mg) of the purified methyl esters

was separated according to degree of unsaturation on

TLC plates, 20 x 20 cm coated with a 0.5 mm layer of

Silica Gel 0 containing 10% w/w AgNO3, developed

with hexane:diethyl ether (90: 10, v/v) at 4 C (8).

Plates were dried under nitrogen and bands were made

visible under ultraviolet light by spraying with a 0.1%

solution of 2’7’-dichlorofluorescein in 95% methanol.

The areas containing the methyl esters of polyunsatu-rated fatty acids were identified by comparison of their

migration with authentic standards . The methyl esterswere eluted from the adsorbent as previously described

in the text and samples dissolved in hexane were taken

for analysis by GLC. Recovery of mixtures of polyun-

saturated fatty acids taken through this procedure was

100 ± 2.9 (mean ± SD).

GLC analysis ofmethyl esters and d.imethyl acetals.

A Perkin Elmer Fl 1 Chromatograph fitted with dual

flame ionisation detectors and linear temperature pro-

gramming facilities was used for all analyses. Chromat-

ograms were recorded on a Perkin Elmer 159 Re-corder. All glass columns (6’ x V4” outside diameter,

obtained from Perkin Elmer, Bucks) were used, and

nitrogen was used as the carrier gas; all gases were

obtained from British Oxygen Corporation. Methyl

esters and dimethyl acetals were identified by compar-

ison of their retention times on isothermal analyses

with authentic standards and secondary reference stan-

dards and by the use of a plot of log retention time

versus the carbon number and by the calculation of

separation factors (15).

Total erythrocyte methyl esters and dimethyl acetals.

Analyses were made on paired columns packed with

15% w/w EGSS-X on Chromosorb W (100 tol 20

mesh) AW/DMCS with a carrier gas flow rate of 40

ml/min. The column temperature was maintained at

165 C for 10 mm after injection of the sample, and

then increased at a rate of 2 C/mm to 200 C. Analyses

were additionally made on a column packed with 10%

w/w EGSS-Y on Chromosorb W (100-120 mesh) AWl

DMCS, carrier gas flow rate 25 ml/min at 200 C.

Chromatograms were quantified by measuring the areaunder the peaks using a computer-linked integrator.

The total methyl ester and dimethyl acetal composition

was estimated using the data from both analyses; 14:0

and 16:1 were not quantified.

Plasma choline phosphoglycerides methyl esters.Analyses were made on a column packed with 1 0% w/

w EGSS-Y on Chromosorb W (100 to 120 mesh) AWl

DMCS at 200 C with a carrier gas flow rate of 25 ml!

mm. Identity of methyl esters was confirmed by analy-

ses on a column packed with 15% w/w EGSS-X on

Chromosorb W (100 to 120 mesh) AW/DMCS at 200C with a carrier gas flow rate of 40 ml/minute. Chro-

matograms were quantified by taking the retention

time X peak height as proportional to the weight of

component. The methyl esters of 14:0 and 16:1 were

not quantified.

Adipose tissue methyl esters. Analyses were made on

a column packed with 10% w/w PEGA on Diatomite

C (100-120 mesh) AW/DMCS at 185 C with a carrier

gas flow rate of 40 ml/minute . Chromatographs were

quantified by measuring the areas under the peaks

corresponding to the methylestersofl6:0, 18:0, 18:1,

18:2o6 and 18:3o3, using a computer-linked integra-

tor.

Breast-milk methyl esters. Analyses of total breast-

milk methyl esters were made on a column packed with

10% w/w PEGA on Diatomite C (100 to 120 mesh)

AW/DMCS at 180 C with a carrier gas flow rate of 40

ml/min. Analyses were confirmed on a column packed

with 15% EGSS-X on Chromosorb W (100 to 120

mesh) AW/DMCS at 170 C with a carrier gas flow rate

of 40 mI/mm. Chromatograms were quantified by

measuring the areas under the peaks using a computer-

linked integrator. The polyunsaturated methyl esterfraction was analyzed on a column packed with 10%

w/w EGSS-Y on Chromosorb W (100 to 120 mesh)

AW/DMCS at 200 C with a carrier gas flow rate of 25

mI/mm; chromatograms were quantified by taking the

peak height x retention time as proportional to the

weight of the component.

Other biochemical investigations

Serum vitamin B12 was assayed microbiologically

(16), and serum cholesterol (17) and triglyceride (18)

concentrations were determined by standard laboratory

methods in routine hospital use.

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808 SANDERS ET AL.

a Values are means for the no. of subjects shown. 5Statistical significance of difference between meanvalues shown when P < 0.05 and Cwhen P < 0.01.

Statistical treatment of data

Wilcoxon’s test for pair difference was used to test

for between group differences. A two sample t test

(two-tailed) was used to test between group differences

for the fatty acid composition of breast-milk and for

the fatty acid composition of erythrocyte lipids from

the breast fed infants.

Results

All the subjects appeared to be healthy.The vegans were lighter than their controlsin weight for the same height, and the sum

of the skinfold thickness measurements waslower (Table 1) . Six vegans were takingvitamin B12 tablets (Cytacon, Glaxo) regu-

larly, 1 1 were taking vegetable foods sup-plemented with the vitamin (Barmene,Granogen , Plamil) . Five vegans were takingneither vitamin B12 tablets nor foods supple-mented with the vitamin, and they hadtaken a vegan diet for 2,4,6,6, and 13 years,

respectively; their serum vitamin B12 con-centrations were 200, 225, 230, 180, and

120 ng/liter. The mean serum vitamin B12concentration in the vegans was 289 ng/liter(range 1 20 to 675 ng/liter) compared with371 ng/liter (range 250 to 775 ng/liter), in

their controls.Serum cholesterol and triglyceride con-

centrations were lower in the vegans, andthis difference was particularly marked in

the case of serum cholesterol (Table 2).The adipose tissue samples from vegans

contained lower proportions of 16:0 and18:1 fatty acids and a high proportion of18:2w6 (Table 2). The plasma choline phos-phoglycerides of vegans contained lowerproportions of 16:0, 18:1, 20:&o3, 22:5w3,

and 22:6cu3 and higher proportions of18:2o6, 20:2o6, 20:4o6 and 22:4.o6 (Table3); the ratio of 22:5o3/22:6w3 was higherin the vegans (0.68 ± 0.08 compared with0.27 ± 0.03, P < 0.01). The erythrocytesfrom vegans contained lower proportions of18:ODMA, 20:5w3, 22:5o3, and 22:fxo3

and higher proportions of 18:2w6, 20:2co6,and 22:4.o6 (Table 4); the ratio of 22:5w3/22:&v3 was higher in the vegans (1 .31 ±

0.14 compared with 0.48 ± 0.03, P <

0.01).

The breast-milk of vegans contained

TABLE 2

Adipose tissue fatty acids in vegans

and omnivo re controls”

Methyl es-ters

Vegans Controls

16:0

Mean

SERange

191b

19

118-331

269

19

133-338

18:0

Mean

SE

Range

45b

3

22-65

78

9

45-126

18:1

Mean

SE

Range

485

13

390-542

513

24

353-657

18:2w6

Mean

SE

Range

254b

17

170-336

11

62-173

18:3w3

Mean

SE

Range

24

6

8-77

15

3

5-33

a Values are means expressed as mg/g of the total

fatty acid methyl esters and are for 1 2 subjects of each

kind. b5tatistical significance of difference betweenmean values shown when P < 0.01.

TABLE 1

Anthropometric measurements and serum lipid concentrations in vegans and omnivore controls”

Investigation Mean SE Range

0/0 Standard weight for height Vegans

Controls

22

22

91b

102

3

3

71-125

86-117

Sum of skinfold measurements (mm) Vegans

Controls

16

16

43C

76

4

7

20-72

25-124

Serum cholesterol (mmole/liter) Vegans

Controls

22

22

4.1c

6.1

0.17

0.19

3.0-5.4

3.9-7.7

Serum triglycerides (mmole!liter) Vegans

Controls

21

21

0.95c

1.35

0.07

0.14

0.60-1.90

0.45-2.95

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STUDIES OF VEGANS 809

TABLE 3

Plasma choline phosphoglyceride fatty acids in vegans and omnivore controls”

Methylesters

Vegans Controls

Mean SE Range Mean SE Range

16:0 232b 7�3 185-282 267 9.9 219-330

18:0 131 8.4 85-194 129 7.2 85-175

18:1 124b 6.6 94-181 145 6.9 109-17118:2w6 333( 11.5 251-386 260 7.1 212-302

20:2w6 55 0.4 3-7 3 0.3 2-6

20:3w6 32 3.3 14-51 34 2.2 24-52

20:4o6 106” 5.5 71-138 91 4.1 76-11422:4w6 6� 1.0 3-12 3 0.2 3-422:5co6 4 1.0 Tr”-12 2 0.4 1-5

20:5w3 2� 0.2 1-3 13 0.9 8-19

22:5w3 W’ 0.7 5-13 11 1.2 2-18

22:6c�i3 14C 1.7 7-29 40 2.5 27-53

a Values as means expressed in mg/g total fatty acid methyl esters detected for 12 subjects of each

kind. b5tatistical significance of difference between mean values shown when P < 0.05 and �when P <

0.01 . dTr denotes less than 0.5 mg/g.

TABLE 4

Erythrocyte lipid fatty acids and aldehydes in vegans and controls”

.Methyl esters and di.

methyl acetals

Vegans Controls

Mean SE Range Mean SE Range

16:ODMA 14 1.5 6-35 16 1.0 3-2216:0 207 5.5 175-245 206 4.6 181-264

18:0 DMA 20� 1 .8 6-32 29 1 .6 4-3518:0 151 4.2 119-195 150 2.8 127-17522:0 17 1.5 9-36 14 1.2 7-2524:0 39 3.0 16-57 36 2.0 16-4518:1 139 5.4 102-185 135 3.0 116-160

24:1 49 5.6 15-106 54 3.2 37-87

18:2w6 l13� 4.2 79-136 87 3.5 52-112

20:2w6 7c 0.9 2-18 4 0.8 1-13

20:3w6 13 2.6 1-45 12 1.1 4-2320:4w6 126 4.2 99-155 125 2.4 102-149

22:4o6 43b 2.2 29-67 23 1.6 9-38

22:5w6 6 1.4 1-25 6 0.5 3-1120:5o3 1b 0.2 Tr”-3 8 0.7 3-16

22:5w3 21c 2.2 9-43 26 1.0 18-3222:6w3 19” 2.3 6-36 58 3.8 37-106

a Mean values expressed in mglg total methyl esters and dimethyl acetals detected for 18 subjects of each

kind. 5Statistical significance of difference between mean values shown when P < 0.01 and cwhen P <

0.05. dTr denotes less than 0.5 mgJg.

lower proportions of 16:0, 16: 1 , 18:0 and20:4co3 and higher proportions of 18:2w6,18:3w3 and 20:2w6 (Table 5); the propor-tions of 20:5o3 and 22:6oi3 also tended to

be lower. No major differences were notedin the fatty acid composition of the breast-milk lipids between the start, middle, andend of feed. In one vegan mother milk

samples were obtained on months 2, 4, and6, and the values obtained for linoleic acidwere 283, 369, and 291 mg/g, respectively.The erythrocytes of infants breast-fed by

vegan mothers contained lower proportionsof 18:1 , 20:5o3 and 22:6w3 and higherporportions of 18:2co6, 20:2o6, and 22:4o#{244}(Table 6); the ratio of 22:5w3/22:&o3 was

also higher in vegan breast-fed infants (0.9± 0.17 compared with 0.3 ± 0.03; P <

0.01).

Discussion

The proportion of linoleic acid (18:2w6)in all the tissues studied was higher in the

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810 SANDERS ET AL.

TABLE 5

Breast-milk fatty acids in vegans and omnivore controls”

Vegans ControlsMethyl

esters Mean SE Range Mean SE Range

12:0 39 12.5 21-76 33 7.1 19-51

14:0 68 17.0 50-118 80 5.3 68-90

16:0 16& 14.4 139-204 276 10.5 246-293

18:0 526 5.9 37-66 108 8.5 84-123

16:1 12b 0.9 11-15 36 5.3 25-46

18:1 313 25.0 277-383 353 11.1 331-383

18:2w6 317b 44�5 202-397 69 8.1 56-91

18:3w3 15” 2.4 9-20 8 0.5 7-9

20:2w6 51b 0.7 4.3-7.2 1.8 0.3 1.4-2.6

20:3w6 3.1 0.8 1.2-4.6 2.3 0.2 2.0-2.6

20:4oi6 7.2 2.1 2.1-12.1 5.4 1.3 3.4-9.2

22:4o6 1.4 0.5 0.4-2.7 0.8 0.3 0.4-1.2

22:5w6 0.9 0.4 0.1-2.0 1.5 1.2 0.1-5.1

20:4o3 0.Y’ 0.1 0.2-0.4 0.9 0.2 0.4-1.5

20:5w3 0.4 0.1 0.2-0.8 2.0 0.8 0.4-3.6

22:5o.3 2.7 1.4 0.5-6.6 5.2 2.7 2.0-13.3

22:6w3 2.3 1.1 0.2-5.5 5.9 2.3 2.4-12.2

a Mean values expressed as mg/g total methyl esters detected for four vegans and four omnivore

controls. b5tatistical significance of difference between means shown when P < 0.05.

TABLE 6

Erythrocyte fatty acids in vegan breast-fed infants and omnivore breast-fed infants0

. Breast-fed by vegans N = 3 Breast-fed by omnivores N - 6Methyl esters and di-

methyl acetalsMean SE Range Mean SE Range

16:ODMA 23 5.8 17-35 23 1.9 16-30

16:0 216 19.2 184-250 204 4.9 187-224

18:ODMA 26 0.7 25-27 25 1.7 19-3118:0 158 11.9 142-181 177 1.5 172-182

22:0 19 4.7 10-25 24 2.5 18-32

24:0 43 5.4 32-49 46 3.9 39-63

18:1 107” 3.8 101-114 128 2.3 120-137

24:1 51 8.1 36-64 52 5.1 32-68

18:2o6 109b 2.7 104-113 60 3.1 51-72

20:3u9 Trr 2 0.3 1-320:2w6 6� 0.3 5-6 Tre

20:3u6 13 1.2 11-15 9 1.0 6-11

20:4oi6 133 6.1 121-141 137 6.2 114-156

22:4w6 35b 3.2 29-40 23 3.0 15-3322:5cu6 7 2.0 4-11 5 3.2 1-21

20:5cu3 26 0.3 1-2 7 1.7 2-12

22:5co3 17 4.4 9-24 18 1.6 12-24

22:6w3 19b 3.2 15-25 62 4.1 45-72

a Mean values expressed in mg/g total methyl esters and dimethyl acetals detected for the no . of subjects

shown. b5tatistical significance of difference between mean values shown when P < 0.05. cTr denotes less

than 0.5 mg/g.

vegans than in their controls implying they

had higher intakes of linoleic acid. A studyin the United States (19) estimated theaverage daily intake of linoleic acid to be 28g in male and 22 g in female vegans com-pared with 16 g in male and 1 1 g in femaleomnivores. Linoleic acid is an essential con-stituent in the diet of animals and man; the

minimum requirement is estimated to be inthe region of 1 % of the total dietary energyintake (20), but an upper limit to its concen-tration in the diet has yet to be defined.

Neither linoleic (18:2w6) nor a-linolenic(18:3w3) acid can be synthesised by mam-malian cells (20-22). Both can, however,undergo chain-elongation and desaturation

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STUDIES OF VEGANS 811

in animal tissues to give rise to two separate

series of polyunsaturated fatty acids, the w6and w3 series, derived from linoleic and a-linolenic acids respectively . No interconver-sion occurs between the two series of fatty

acids, but a common enzyme system is usedfor chain-elongation and desaturation , and

so competition occurs. At the same relativeconcentration, long-chain polyunsaturatedderivatives are formed more readily from

ct-linolenic acid but this preference can bereversed by increasing the relative concen-tration of linoleic acid so that, when thedietary fat contains a high ratio of linoleic/a-linolenic acids, chain-elongation and de-

saturation of a-linolenic acid is stronglysuppressed (23, 24). This seems to be alikely explanation for the higher proportionof w6 derivatives and the lower proportion

of w3 derivatives found in the tissues of thevegans and the infants breast fed by vegan

mothers.Whether the long-chain derivatives of a-

linolenic acid perform any essential functiondeserves consideration . The highest concen-

tration of these o3 derivatives is found inthe brain (24), for example the phospho-

glycerides of grey matter contain more than20% docosahexaenoic acid (22 :6w3), a fact

that argues strongly in favor of the parentacid, a-linolenic, being regarded as a die-tary essential. However, docosahexaenoicacid can be replaced by a w6 derivative,docosapentaenoic acid (22:5.o6), in thebrains of rats when the dietary fat containsa high ratio of linoleic/a-linolenic acids(24). Behavioral abnormalities have beenreported in the offspring of rats fed suchdiets (23, 25) but are prevented by increas-ing the vitamin E content of the diets (23)As yet, there is no conclusive evidence toshow that a-linolenic acid and its derivatives

are essential nutrients for mammals. It ispossible that the apparently benign differ-ences in the electroencephalogram record-ings between vegans and omnivores (2, 26)might reflect differences in brain fatty acidprofiles. The precursor of prostaglandin E3,

eicosapentaenoic acid (20:5*�.o3) (21), wasmuch lower in the vegans; high intakes oflinoleic acid reduce platelet aggregation(27), perhaps a change in prostaglandin E3production may be involved. It is clear that

further research is needed to establishwhether differences in the proportions of o3derivatives in tissues are of physiologicalimportance.

The long-chain derivatives of linoleic and

a-linolenic acids are absent from higherplants (28), so it follows that they would not

be found in a vegan diet. Crawford and hiscolleagues (28) have contended that thesederivatives are necessary in the diet and this

appears to be the case for the cat whichcannot desaturate linoleic or a-linolenicacids. Our evidence shows that man canform long-chain derivatives from linoleicand a-linolenic acids and this suggests thatthese derivatives are not needed in the diet.The elevated ratio of 22:5w3/22:6w3 foundin the tissues of the vegans and the infantsbreast fed by vegan mothers are similar to

Crawford’s observations of herbivores (28)and could be taken to indicate a low �4desaturase activity; the significance of this is

not clear, and needs further research.In agreement with other studies (1-3),

the adult vegans were lighter in weight forthe same height than their age and sexmatched omnivore controls because they

had a smaller amount of body fat. Obesityis well known to be associated with a higher

incidence of certain diseases such as gout,gall-stones, and cardiovascular disease (30),and it would seem in these respects a vegandiet could have a beneficial effect.

There is also abundant evidence that highplasma lipid concentrations, especially cho-lesterol, are associated with an increased

risk of IHD (31 , 32). Serum cholesterol andtriglyceride concentrations were lower inthe vegans than in their age and sex matched

controls, and this difference was particularlymarked in the case of serum cholesterol.This confirms earlier reports from the sameand other laboratories (2, 3, 19). Thesefindings suggest that vegans are less prone

to IHD than omnivores.The level of plasma lipids can be reduced

in many subjects by increasing the ratio ofpolyunsaturated to saturated fatty acids anddecreasing the amount of cholesterol in the

diet (31, 33). Generally this involves substi-tuting vegetable for animal fats in the diet.The lower proportion of palmitic acid (16:0)and the higher proportion of linoleic acid in

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812 SANDERS ET AL.

the breast milk of the vegans is of interest,as palmitic acid has a marked hypercholes-terolaemic effect and linoleic has a weakerbut opposite hypocholesterolaemic effect(33); this would suggest that vegan com-pared with omnivore breast milk would

have a marked hypocholesterolemic effecton the plasma of the infant which could be

regarded as an advantage if the develop-ment of IHD is regarded as a paediatricproblem (34).

The difference between the serum choles-

terol concentrations of the vegans and theirage and sex matched controls was greaterthan can generally be brought about bymanipulation of dietary fat intake and thissuggests that other factors may be involved.Indeed, there is some evidence to suggest

that vegetable protein compared with ani-mal protein has a strong hypocholestero-

laemic effect independent of the fatty acidsand cholesterol in the diet (35). Recentlyfour patients suffering from severe anginapectoris were treated with a vegan diet andthe results were sufficiently encouraging tojustify a controlled trial (36). A vegan dietcomposed of a mixture of unrefined cereals,nuts, pulses, fruits and vegetables supple-mented with vitamins B12 and D appears tobe adequate to permit normal blood forma-tion (37). It is tempting, therefore, to sug-gest that a vegan-type diet may be the oneof choice in preventing and even treating

IHD, angina pectoris, and certain hyperli-pidemias. a

The authors are grateful to all the subjects who

volunteered to participate in this study. We thank Dr.

B . W . Meade for the serum cholesterol and triglyceride

estimations and Mr. J. P. Sheldon for the serum

vitamin B,2 estimations.

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