Available via license: CC BY-NC-ND 3.0
Content may be subject to copyright.
Type of Vegetarian Diet, Body Weight, and
Prevalence of Type 2 Diabetes
SERENA TONSTAD,
MD, PHD
1
TERRY BUTLER,
DRPH
2
RU YAN,
MSC
3
GARY E. FRASER,
MD, PHD
4
OBJECTIVE — We assessed the prevalence of type 2 diabetes in people following different
types of vegetarian diets compared with that in nonvegetarians.
RESEARCH DESIGN AND METHODS — The study population comprised 22,434
men and 38,469 women who participated in the Adventist Health Study-2 conducted in 2002–
2006. We collected self-reported demographic, anthropometric, medical history, and lifestyle
data from Seventh-Day Adventist church members across North America. The type of vegetarian
diet was categorized based on a food-frequency questionnaire. We calculated odds ratios (ORs)
and 95% CIs using multivariate-adjusted logistic regression.
RESULTS — Mean BMI was lowest in vegans (23.6 kg/m
2
) and incrementally higher in lacto-
ovo vegetarians (25.7 kg/m
2
), pesco-vegetarians (26.3 kg/m
2
), semi-vegetarians (27.3 kg/m
2
),
and nonvegetarians (28.8 kg/m
2
). Prevalence of type 2 diabetes increased from 2.9% in vegans
to 7.6% in nonvegetarians; the prevalence was intermediate in participants consuming lacto-ovo
(3.2%), pesco (4.8%), or semi-vegetarian (6.1%) diets. After adjustment for age, sex, ethnicity,
education, income, physical activity, television watching, sleep habits, alcohol use, and BMI,
vegans (OR 0.51 [95% CI 0.40 –0.66]), lacto-ovo vegetarians (0.54 [0.49 –0.60]), pesco-
vegetarians (0.70 [0.61– 0.80]), and semi-vegetarians (0.76 [0.65–0.90]) had a lower risk of type
2 diabetes than nonvegetarians.
CONCLUSIONS — The 5-unit BMI difference between vegans and nonvegetarians indicates
a substantial potential of vegetarianism to protect against obesity. Increased conformity to veg-
etarian diets protected against risk of type 2 diabetes after lifestyle characteristics and BMI were
taken into account. Pesco- and semi-vegetarian diets afforded intermediate protection.
Diabetes Care 32:791–796, 2009
V
egetarian diets may play a beneficial
role in promoting health and pre-
venting obesity (1–3). Vegetarian-
ism encompasses a spectrum of eating
patterns: from diets that leave out all ani-
mal meats and products (vegan) to diets
that include eggs, milk, and milk prod-
ucts (lacto-ovo vegetarian) or even fish in
addition to eggs, milk, and milk products
(pesco-vegetarian). A previous study has
indicated that BMI increases when a wider
spectrum of animal products are eaten.
Specifically, the European Prospective In-
vestigation found that BMI was highest in
meat eaters, lowest in vegans, and inter-
mediate in fish eaters (4). The protective
effects of vegetarianism against over-
weight may be due to avoidance of major
food groups, displacement of calories to-
ward food groups that are more satiating
(5), or other factors.
Based on a review of experimental
data, investigators have suggested that the
portfolio of foods found in vegetarian di-
ets may carry metabolic advantages for
the prevention of type 2 diabetes (6). This
notion has been confirmed in observa-
tional studies. In the Nurses Health
Study, intakes of red meat and processed
meats were associated with increased risk
of diabetes (7). In a study of Seventh-Day
Adventists, diabetes was less prevalent in
vegetarian than in nonvegetarian church-
goers (8). Likewise, Fraser reported a
lower prevalence of diabetes in vegetari-
ans than in semi- or nonvegetarians (1)
and Vang et al. (9) found that processed
meat consumption was a risk factor for
diabetes. However, these church-based
cohorts were initiated in the 1960s–
1970s and included primarily non-
Hispanic whites. Furthermore, the type of
vegetarianism or diabetes was not
specified.
A pertinent question is whether veg-
etarian diets remain protective in current
obesity-promoting environments and in
diverse populations. We studied a Sev-
enth-Day Adventist cohort that included
a population of whom ⬃25% of subjects
were black and that was characterized by
vegetarian and nonvegetarian eating pat-
terns. We hypothesized that more exclu-
sively vegetarian diets, e.g., vegan, lacto-
ovo, or pesco-vegetarian, are associated
with lower prevalence of obesity and type
2 diabetes compared with semi- or non-
vegetarian diets.
RESEARCH DESIGN AND
METHODS — The Adventist Health
Study-2 cohort, initiated in 2002–2006,
longitudinally follows 97,000 Adventist
church members in the U.S. and Canada
(10). Participants were recruited through
their churches and were eligible if aged
ⱖ30 years and proficient in English. The
study was reviewed and approved by the
institutional review board of Loma Linda
University, Loma Linda, California, and
informed consent was obtained.
These analyses are based on cross-
sectional data obtained at baseline.
Data were collected from a 50-page self-
administered questionnaire (11).The
questionnaire included sections on ill-
ness, diet, physical activity, demograph-
ics, height, and weight. Cases of diabetes
were ascertained by asking whether a
physician had ever diagnosed type 1 or
type 2 diabetes and whether the respon-
dent was treated for this in the last 12
months. Race and ethnicity were divided
into the following categories: black
●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
From the
1
Department of Health Promotion and Education, School of Public Health, and the Department of
Preventive Medicine, School of Medicine, Loma Linda University, Loma Linda, California; the
2
Depart
-
ment of Biostatistics, School of Public Health, Loma Linda University, Loma Linda, California;
3
Loma
Linda University, Loma Linda, California; and the
4
Department of Cardiology, School of Medicine, Loma
Linda University, Loma Linda, California.
Corresponding author: Serena Tonstad, stonstad@llu.edu.
Received 17 October 2008 and accepted 2 February 2009.
DOI: 10.2337/dc08-1886
© 2009 by the American Diabetes Association. Readers may use this article as long as the work is properly
cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.
org/licenses/by-nc-nd/3.0/ for details.
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby
marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Clinical Care/Education/Nutrition/Psychosocial Research
ORIGINAL ARTICLE
DIABETES CARE, VOLUME 32, NUMBER 5, MAY 2009 791
(black/African American, West Indian/
Caribbean, African, or other black) and
non-black (white non-Hispanic, His-
panic, Middle Eastern, Asian, Native
Hawaiian/other Pacific Islander, or
American Indian). Education was catego-
rized to high school or less, some college,
and college or higher based on eight op-
tions. Income was categorized into earn-
ings of ⱕ 10,000, 11,000 –30,000,
31,000–50,000, and ⱖ51,000 USD.
Assessment of lifestyle exposures
The food-frequency portion of the ques-
tionnaire covered 130 hard-coded foods
or food groups that are commonly con-
sumed and space for ⬃50 write-ins and
are assessed for diet during the past year.
For different food items, there were 7–9
frequency categories. A standard portion
size was given for each item, and subjects
could select that or a smaller or larger por-
tion. Previous validation of the question-
naire pertained to nutrients including
vitamin, antioxidant, and fatty acid in-
takes (12,13). Vegetarian status was cate-
gorized by defining vegans as subjects
who reported consuming no animal
products (red meat, poultry, fish, eggs,
milk, and dairy products ⬍1 time/
month), lacto-ovo vegetarians as consum-
ing dairy products and/or eggs ⱖ1 time/
month but no fish or meat (red meat,
poultry, and fish ⬍1 time/month), pesco-
vegetarians as consuming fish ⱖ1 time/
month and dairy products and/or eggs
but no red meat or poultry (red meat
and poultry ⬍1 time/month), semi-
vegetarians as consuming dairy products
and/or eggs and meat (red meat and poul-
try ⱖ1 time/month and ⬍1 time/week),
and nonvegetarians as consuming animal
products (red meat, poultry, fish, eggs,
milk, and dairy products ⬎1 time/week).
Alcohol was defined as consumption of
any amount or none during the past 12
months.
Physical-activity questions were pre-
viously validated in non-black and black
subjects (14,15). These were separated
into six intensity levels, including nap-
ping, lying down, and light, moderate,
vigorous, and extremely vigorous activity.
Participants reported the amount of time
spent in each type of activity on a normal
weekday and on Saturday and Sunday.
Moderate, vigorous, and extremely vigor-
ous activities were assigned scores of 4, 8,
and 10, respectively, to represent the ap-
proximate MET values expended and
were weighted according to the amount of
time spent in each activity to estimate av-
erage daily energy expenditure (informa-
tion available in the online appendix
[http://care.diabetesjournals.org/cgi/content/
full/dc08-1886]). Participants reported aver-
age number of hours of sleep and hours per
day of television watching. Responses were di-
vided into three categories (ⱕ6, 7, and ⱖ8h
of sleep and ⬍1, 1–2, and ⱖ3 h of television
watching).
Ascertainment of disease
A representative subgroup of 1,007 study
subjects participated in a calibration
study and provided blood samples for
measurement of fasting serum glucose
levels (16). The calibration sample was
generated by a two-stage random-selection
method involving church size and sub-
jects within the church. Subjects who re-
fused participation were replaced with
individuals randomly chosen from the
same church and matched by race, age,
and sex.
We used a fasting glucose level ⱖ126
mg/dl to categorize subjects as probably
diabetic. We attempted telephone inter-
views with subjects who, despite glucose
measurements ⬍126 mg/dl, reported a
physician-based diagnosis of type 2 dia-
betes and subjects whose glucose mea-
surement was ⱖ126 mg/dl but who did
not report type 2 diabetes. Of subjects
who had reported type 2 diabetes but had
a low glucose level (n ⫽ 55), all 44 who
were contacted confirmed that they had
type 2 diabetes, whereas 9 could not be
reached and 2 were too deaf to under-
stand the question. Of subjects who did
not report type 2 diabetes but had a
high glucose level (n ⫽ 53), 38 had no
knowledge of diabetes, were informed of
diabetes by their physician after the
questionnaire was administered, were in-
formed only of a high or borderline glu-
cose level, or had not been treated in the
past 12 months; 1 had diabetes but had
skipped that page of the questionnaire; 6
Table 1—Distribution of participants by history of type 2 diabetes treated within 12 months in
conjunction with nondietary variables
Type 2 diabetes
reported Not reported P
N 3,430 57,473
Age (years) 62.5 ⫾ 11.8 56.1 ⫾ 13.7 ⬍0.0001
Female 61.7 63.3 0.0604
Black 32.5 23.4 ⬍0.0001
BMI (kg/m
2
)
32.1 ⫾ 7.1 26.9 ⫾ 5.7 ⬍0.0001
Physical activity: METs ⬍0.0001
0–3.2 38.6 24.8
3.2–8.6 23.2 24.5
8.6–21.0 20.6 24.6
⬎21.0 17.6 26.1
Education ⬍0.0001
High school or less 26.0 17.9
Some college 31.9 27.6
College or higher 42.1 54.6
Income ⬍0.0001
ⱕ10,000 USD 25.0 19.5
11,000–30,000 USD 42.9 36.3
31,000–50,000 USD 19.0 23.6
ⱖ51,000 USD 13.1 20.6
Television watching ⬍0.0001
None to ⬍1 h/day 11.8 27.0
1–2 h/day 42.9 47.4
ⱖ3 h/day 45.3 25.6
Sleep ⬍0.0001
ⱕ6 h/night 39.4 31.7
7 h/night 28.8 36.8
ⱖ8 h/night 31.9 31.5
Alcohol use in last 12 months 7.1 10.4 ⬍0.0001
Data are means ⫾ SD or percent unless otherwise indicated. Percentages might not total 100 because of
rounding.
Vegetarian diet type, body weight, and type 2 diabetes
792 DIABETES CARE, VOLUME 32, NUMBER 5, MAY 2009
were deceased; and 8 could not be
reached.
Statistical analyses
The allocation of subjects into dietary cat-
egories required responses to questions
regarding 27 variables including meat,
fish and poultry, dairy, and egg consump-
tion. Because on average ⬃7% data were
missing for any particular variable, multi-
ple imputation was used to fill missing
information. For about half of these vari-
ables, we had a random subset of initially
missing data filled in later by telephone
and used this to guide the imputation
(17). For other variables, we assumed that
the data were missing at random, which,
even if not quite correct, will have little
influence when the missing data rate is
small (17). The imputation algorithm in-
cluded age, sex, race, and food groups
(meat, fish, dairy, and eggs). These food
groups were subdivided into blocks of
variables for which we had the random
subset of filled-in data and those for
which we did not (e.g., fish variables that
were included in those later filled in ver-
sus fish variables not so included) for pur-
poses of imputation. The imputation
software used was the Hmisc package for
R, version 2.6.0 (18).
2
tests and one-way ANOVA were
used to analyze categorical and continu-
ous variables, respectively. Multiple logis-
tic regression analysis was used to obtain
ORs and 95% CIs of the relation between
characteristics, diet, and diabetes. All sta-
tistical testing was two-tailed. Analyses
were performed using SPSS, version 13.0.
RESULTS — There were 83,031 sub-
jects whose questionnaire responses al-
lowed categorization by vegetarian or
nonvegetarian diet. Of these, 1,427 did
not respond to the diabetes ascertainment
question. A further 634 who reported
treatment for type 1 diabetes were ex-
cluded, and another 14,124, 4,638, 317,
852, and 136 were missing data regarding
physical activity, income, education, tele-
vision watching, and sleep, respectively.
This left 22,434 men and 38,469 women.
Of these 60,903 subjects, 3,430 (5.6%)
reported type 2 diabetes.
Table 1 shows that participants
treated for type 2 diabetes differed with
regard to a variety of characteristics from
those who did not report diabetes diagno-
sis. Only 1,070 (1.8%) participants had
smoked one or more cigarettes daily in
the past 12 months.
The consumption of major food
groups differed among the dietary groups
(data not shown). The prevalence of type
2 diabetes increased incrementally among
vegans, lacto-ovo vegetarians, pesco-
vegetarians, semi-vegetarians, and non-
vegetarians (Table 2). This increase was
concomitant to an incremental increase in
mean BMI in the respective dietary
groups; additionally, demographic and
lifestyle characteristics differed among
the dietary groups (Table 2). For BMIs
ⱖ30 kg/m
2
, the prevalence of diabetes
was 8.0% in vegans, 9.4% in lacto-ovo
Table 2—Unadjusted prevalence of type 2 diabetes and distribution of nondietary variables according to diet
Vegan
Lacto-ovo
vegetarian
Pesco-
vegetarian
Semi-
vegetarian Nonvegetarian P
N 2,731 20,408 5,617 3,386 28,761
Type 2 diabetes 2.9 3.2 4.8 6.1 7.6 ⬍0.0001
Age in years 58.1 ⫾ 13.3 58.1 ⫾ 14.1 57.2 ⫾ 13.8 57.7 ⫾ 13.6 54.9 ⫾ 13.2 ⬍0.0001
Female 60.1 62.3 65.9 65.7 63.2 ⬍0.0001
Black 19.9 12.5 34.9 15.0 31.2 ⬍0.0001
BMI (kg/m
2
)
23.6 ⫾ 4.4 25.7 ⫾ 5.1 26.3 ⫾ 5.2 27.3 ⫾ 5.7 28.8 ⫾ 6.3 ⬍0.0001
Physical activity: METS ⬍0.0001
0–3.2 24.8 26.3 24.3 26.8 25.2
3.2–8.6 24.7 25.8 24.5 24.0 23.5
8.6–21.0 24.8 24.6 24.6 23.7 24.3
⬎21.0 25.7 23.3 26.6 25.6 27.1
Education ⬍0.0001
High school or less 16.7 14.0 17.2 19.1 21.7
Some college 26.7 24.2 26.1 28.5 30.7
College or higher 56.6 61.8 56.7 52.4 47.6
Income ⬍0.0001
ⱕ10,000 USD 27.8 21.1 18.0 20.2 18.6
11,000–30,000 USD 38.6 35.8 34.4 38.0 37.4
31,000–50,000 USD 18.3 24.2 24.0 23.4 23.1
ⱖ51,000 USD 15.3 18.9 23.6 18.4 21.0
Television watching ⬍0.0001
None to ⬍1 h/day 49.5 36.0 26.8 25.2 16.9
1–2 h/day 37.4 45.4 50.2 48.7 48.6
ⱖ3 h/day 13.2 18.6 23.0 26.1 34.5
Sleep ⬍0.0001
ⱕ6 h/night 25.8 25.3 34.9 29.8 37.3
7 h/night 38.3 39.8 36.3 36.9 33.7
ⱖ8 h/night 35.9 34.9 28.9 33.4 29.0
Alcohol use in last 12 months 1.1 2.9 7.1 8.6 17.1 ⬍0.0001
Data are means ⫾ SD or percent unless otherwise indicated.
Tonstad and Associates
DIABETES CARE, VOLUME 32, NUMBER 5, MAY 2009 793
vegetarians, 10.4% in pesco-vegetarians,
11.4% in semi-vegetarians, and 13.8% in
nonvegetarians, indicating the same trend
as that in the entire population. For BMIs
⬍30 kg/m
2
, the prevalence was 2.0, 2.1,
3.3, 3.7, and 4.6% in the groups,
respectively.
In multiple logistic regression analysis,
vegan, lacto-ovo, and pesco- and semi-
vegetarian diets were associated with a
lower prevalence of type 2 diabetes (Table
3). The vegetarian diets were more strongly
associated with less diabetes when BMI was
removed from the analyses (Table 3).
CONCLUSIONS — The main finding
was that vegan and lacto-ovo vegetarian di-
ets were associated with a nearly one-half
reduction in risk of type 2 diabetes com-
pared with the risk associated with nonveg-
etarian diets after adjustment for a number
of socioeconomic and lifestyle factors, as
well as low BMI, that are typically associated
with vegetarianism. Pesco- and semi-
vegetarian diets were associated with inter-
mediate risk reductions: between one-third
and one-quarter. These data indicate that
vegetarian diets may in part counteract the
environmental forces leading to obesity and
increased rates of type 2 diabetes, though
only vegan diets were associated with a BMI
in the optimal range. Inclusion of meat,
meat products, and fish in the diet, even on
a less than weekly basis, seems to limit some
of the protection associated with a vegan or
lacto-ovo vegetarian diet. These findings
may be explained by adverse effects of meat
and fish, protective effects of typical constit-
uents of vegan and lacto-ovo vegetarian di-
ets, other characteristics of people who
choose vegetarian diets, or a combination of
these factors.
The notion that animal protein stim-
ulates insulin secretion and possibly insu-
lin resistance was proposed decades ago
(19). However, a number of other dietary
constituents are associated with protec-
tion against diabetes in observational
studies or influence insulin sensitivity in
food trials (6). Vegetarian diets are rich in
vegetables and fruits, foods that reduce
oxidative stress and chronic inflamma-
tion. The vegan group consumed ⬃650
g/day of fruits and vegetables, which is
about one-third more than the amount
consumed by nonvegetarians (data not
shown). Observational evidence has
shown that these dietary constituents are
associated with a reduction in type 2 dia-
betes of ⬃40% (6). Vegetarian diets con-
tain substantially less saturated fat than
nonvegetarian diets, and saturated fatty
acids have been shown to reduce insulin
sensitivity, though a recent review con-
cluded that some of the data supporting
this idea was flawed (20). The vegetarian
diet typically includes foods that have a
low glycemic index such as beans, le-
gumes, and nuts. We did not calculate the
glycemic load of the diets. Though low-
glycemic-response diets are associated
with less prevalence of type 2 diabetes,
cohort studies have not consistently
found a relation between dietary glycemic
index or load and risk of diabetes (21,22);
furthermore, whether the glycemic re-
sponse causes diabetes is not established.
Protection against type 2 diabetes as-
sociated with vegetarian diets is partly
due to the lower BMI of vegetarians (Table
3), where the effects of diet when not ad-
justed for BMI were greater yet. Disentan-
gling the effects of diet on insulin
sensitivity independent of lower adiposity
among vegetarians may be difficult. Only
sparse data have investigated whether
vegetarians matched to nonvegetarians
with regard to adiposity differ in insulin
resistance or sensitivity. In a study that
matched vegetarians and nonvegetarians,
nonvegetarians had higher insulin, glu-
cose, and homeostasis model assessment
values than vegetarians (23). Whether
vegetarians and nonvegetarians were
matched with regard to abdominal girth
was not reported. The protective effect of
vegetarianism in the current study was ev-
ident in individuals with BMI below or
above 30 kg/m
2
, further strengthening
the notion that independent effects of the
diet are present.
Church attendees tend to have higher
body weight than nonattendees (24), and
increasing trends in BMI in the general
population have also been observed
among Adventists (data not shown). Veg-
ans were the only church members whose
mean BMI was ⬍25 kg/m
2
. Previous stud
-
ies have reported a difference of ⬃2 BMI
units between vegans and meat eaters (4).
In the current study, the difference of 5
BMI units may indicate greater protection
in current environments where a variety
of high-energy dense foods are available.
Some evidence indicates a temporal rela-
tionship between initiating plant-based
diets and leanness (2,3), though a ran-
domized study found that a vegetarian
Table 3—Multiple logistic regression analysis of the relation between diet and type 2 diabetes
OR (95% CI)* OR (95% CI)†
Age 1.04 (1.04–1.05) 1.03 (1.03–1.04)
Female vs. male 0.67 (0.62–0.72) 0.78 (0.72–0.84)
Non-black vs. black 0.66 (0.61–0.72) 0.64 (0.59–0.69)
BMI 1.11 (1.11–1.12)
Physical activity: METs
3.2–8.6 vs. 0–3.2 0.85 (0.77–0.93) 0.76 (0.69–0.83)
8.6–21.0 vs. 0–3.2 0.77 (0.69–0.85) 0.65 (0.59–0.72)
⬎21.0 vs. 0–3.2 0.65 (0.58–0.72) 0.52 (0.47–0.58)
Education
Some college vs. high school or less 1.00 (0.91–1.11) 1.04 (0.95–1.15)
College or higher vs. high school or less 1.00 (0.90–1.10) 0.95 (0.86–1.05)
Income (USD)
11,000–30,000 vs. ⬍10,000 0.87 (0.80–0.96) 0.82 (0.75–0.90)
31,000–50,000 vs. ⬍10,000 0.77 (0.68–0.86) 0.72 (0.65–0.81)
ⱖ51,000 vs. ⬍10,000 0.66 (0.58–0.76) 0.61 (0.53–0.70)
Television watching (h/day)
1–2 1.31 (1.16–1.47) 1.54 (1.37–1.73)
ⱖ3 1.62 (1.44–1.83) 2.26 (2.01–2.54)
Sleep (h/night)
7 vs. ⱕ6 0.83 (0.76–0.91) 0.77 (0.71–0.85)
ⱖ8 vs. ⱕ6 0.94 (0.86–1.03) 0.86 (0.79–0.94)
Alcohol use during last 12 months vs. none 0.69 (0.60–0.80) 0.64 (0.55–0.73)
Diet
Vegan vs. nonvegetarian 0.51 (0.40–0.66) 0.32 (0.25–0.41)
Lacto-ovo vegetarian vs. nonvegetarian 0.54 (0.49–0.60) 0.43 (0.39–0.47)
Pesco-vegetarian vs. nonvegetarian 0.70 (0.61–0.80) 0.56 (0.49–0.64)
Semi-vegetarian vs. nonvegetarian 0.76 (0.65–0.90) 0.69 (0.59–0.81)
*Adjusted for all factors. †Adjusted for all factors except BMI. OR, odds ratio.
Vegetarian diet type, body weight, and type 2 diabetes
794 DIABETES CARE, VOLUME 32, NUMBER 5, MAY 2009
diet did not improve long-term weight
loss (25). As with most dietary trials, the
participants’ compliance to the diet de-
clined substantially over time.
The present cohort is likely to be
more homogenous than general popula-
tions regarding nondietary factors allow-
ing comparisons between dietary groups
to be less affected by other differences.
This may be true regarding smoking and
alcohol use, which are practices strongly
discouraged by the church. One of the
major confounders of diet and disease as-
sociations in observational studies is cig-
arette smoking. As the participants were
almost exclusively nonsmokers, the con-
founding effects of smoking on body
weight and risk of type 2 diabetes were
avoided. The cohort exhibited an unusu-
ally wide range of dietary exposures and
included one of the largest numbers of
vegans studied in any sample. The results
are likely to be generalizable given that
we found expected relationships be-
tween diabetes and age, ethnicity, sex,
BMI, physical activity, sleep, and televi-
sion watching.
Study limitations
Our data are cross-sectional and do not
allow causal inferences to be made. How-
ever, reverse causation is unlikely in that
subjects diagnosed with diabetes would
be less expected to differentially change
their diet from vegetarian to omnivorous
than subjects without diabetes. We were
unable to assess physical activity for about
one-sixth of the cohort because responses
to one or more of the questions required
for the calculation of MET units were
missing. Food-frequency questionnaires
involve a certain degree of measurement
error; however, the ability to allocate sub-
jects into a broad dietary pattern is prob-
ably very strong. All variables were self-
reported; however, our calibration study
found evidence for good validity for the
diagnosis of diabetes. Diabetes may have
been underreported in the vegan and
other vegetarians because of their lower
BMIs; however, this is unlikely to affect
the study conclusions substantially given
the association we observed between diet
and diabetes in individuals with BMI both
below and above 30 kg/m
2
.
The cohort was not representative of
the general population; i.e., participants
were church attendees. Members who
choose vegetarianism are likely to be
more compliant with other church tenets
and to differ from nonvegetarians with re-
gard to major determinants of type 2 dia-
betes. This was indeed the case with
regard to some factors; e.g., nonvegetar-
ian diets were more associated with black
ethnicity, less education, more television
watching, and fewer hours of sleep than
were vegetarian diets. On the other hand,
nonvegetarians were younger and re-
ported more physical activity and alcohol
consumption, which are all established
protective factors against type 2 diabetes.
Nevertheless, the association between
diet and type 2 diabetes remained strong
after adjustment for these factors.
In conclusion, this study showed that
all variants of vegetarian diets (vegan, lacto-
ovo, and pesco- and semi-vegetarian) were
associated with substantially lower risk of
type 2 diabetes and lower BMI than nonveg-
etarian diets. The protection afforded by
vegan and lacto-ovo vegetarian diets was
strongest.
Acknowledgments— This work was sup-
ported by National Institutes of Health Grant
1R01CA94594 and by the School of Public
Health, Loma Linda University, Loma Linda,
California.
No potential conflicts of interest relevant to
this article were reported.
References
1. Fraser GE. Associations between diet and
cancer, ischemic heart disease, and all-
cause mortality in non-Hispanic white
California Seventh-day Adventists. Am J
Clin Nutr 1999; 20(Suppl.):532S–538S
2. 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 2006;30:1389–1396
3. Phillips F, Hackett A, Billington D, Strat-
ton G. Effects of changing from a mixed to
self-selected vegetarian diet on anthropo-
metric measurements in UK adults. J
Hum Nutr Diet 2004;17:249–255
4. Spencer EA, Appleby PN, Davey GK, Key
TJ. Diet and body mass index in 38,000
EPIC Oxford meat-eaters, fish-eaters, veg-
etarians and vegans. Int J Obes 2003;27:
728–734
5. Appleby PN, Thorogood M, Mann JI, Key
TJ. Low body mass index in non-meat eat-
ers: the possible roles of animal fat, di-
etary fibre and alcohol. Int J Obes 1998;
22:454–460
6. Jenkins DJA, Kendall CWC, Marchie A,
Jenkins AL, Augustin LSA, Ludwig DS,
Barnard ND, Anderson JW. Type 2 diabe-
tes and the vegetarian diet. Am J Clin Nutr
2003; 78(Suppl.):610S–616S
7. Fung TT, Schulze M, Manson JE, Willett
WC, Hu FB. Dietary patterns, meat intake,
and the risk of type 2 diabetes in women.
Arch Intern Med 2004;164:2235–2240
8. Snowdon DA, Phillips RL. Does a vegetar-
ian diet reduce the occurrence of diabe-
tes? Am J Public Health 1985;75:507–512
9. Vang A, Singh PN, Lee JW, Haddad EH,
Brinegar CH. Meats, processed meats,
obesity, weight gain and occurrence of di-
abetes among adults: findings from Ad-
ventist Health Studies. Ann Nutr Metab
2008;52:96–104
10. Butler TL, Fraser GE, Beeson WL, Knutsen
SF, Herring RP, Chan J, Sabate J, Montgom-
ery S, Haddad E, Preston-Martin S, Bennett
H, Jaceldo-Siegl K. Cohort profile: the Ad-
ventist Health Study-2 (AHS-2). Int J Epi-
demiol 2007;37:260–265
11. Montgomery S, Herring P, Yancey A, Bee-
son L, Butler T, Knutsen S, Sabate J, Chan
J, Preston-Martin S, Fraser G. Comparing
self-reported disease outcomes, diet and
lifestyles in a national cohort of black
and white Seventh-day Adventists. Prev
Chronic Dis 2007;4:A62
12. Knutsen S, Fraser G, Beeson W, Lind-
sted K, Shavlik D. Comparison of adi-
pose tissue fatty acids with dietary fatty
acids as measured by 24-hour recall and
food frequency questionnaire in black
and white Adventists: the Adventist
Health Study. Ann Epidemiol 2003;13:
119–127
13. Knutsen S, Fraser G, Lindsted K, Beeson
W, Shavlik D. Validation of assessment of
nutrient intake: comparing biological
measurements of vitamin C, folate, alpha-
tocopherol and carotene with 24-hour di-
etary recall information in non-Hispanic
blacks and whites. Ann Epidemiol 2001;
11:406–416
14. Singh PN, Tonstad S, Abbey DE, Fraser
GE. Validity of selected physical activity
questions in white Seventh-day Ad-
ventists and non-Adventists. Med Sci
Sports Exer 1996;28:1026–1037
15. Singh PN, Fraser GE, Knutsen SF, Lind-
sted DS Bennett H. Validity of a physical
activity questionnaire among African-
American Seventh-day Adventists. Med
Sci Sports Exer 2000;33:468–475
16. Jaceldo-Siegl K, Fraser GE, Chan J,
Franke A, Sabate´ J. Validation of soy pro-
tein estimates from a food-frequency
questionnaire with repeated 24-h recalls
and isoflavonoid excretion in overnight
urine in a Western population with a wide
range of soy intakes. Am J Clin Nutr 2008;
87:1422–1427
17. Fraser GE, Yan R. Guided multiple im-
putation of missing data: using a sub-
sample to strengthen the missing-at-
random assumption. Epidemiology 2007;
18:246–252
18. R Development Core Team. R: a lan-
guage and environment for statistical
computing [article online], 2007. Vi-
enna, Austria, R Foundation for Statis-
tical Computing. Available from http://
Tonstad and Associates
DIABETES CARE, VOLUME 32, NUMBER 5, MAY 2009 795
biostat.mc.vanderbilt.edu/s/Hmisc/html/
areglmpute.html. Accessed 10 January
2008
19. Chaussain JL, Georges P, Gendrel D, Don-
nadieu M, Job JC. Serum branched-chain
amino acids in the diagnosis of hyperin-
sulinism in infancy. J Pediatr 1980;97:
923–926
20. Galgani JE, Uauy RD, Aguirre CA, Diaz
EO. Effect of the dietary fat quality on in-
sulin sensitivity. Br J Nutr 2008;100:471–
479
21. Salmeron J, Manson JE, Stampfer MJ,
Colditz GA, Wing AL, Willett WC. Di-
etary fiber, glycemic load, and risk of non-
insulin dependent diabetes mellitus in
women. JAMA 1997;277:472–477
22. Sahyoun NR, Anderson AL, Tylavsky FA,
Lee JS, Sellmeyer DE, Harris TB, the
Health, Aging, and Body Composition
Study. Dietary glycemic index and glyce-
mic load and the risk of type 2 diabetes in
older adults. Am J Clin Nutr 2008;
87:126–131
23. Valachovicˇova´ M, Kracˇovicˇova´-Kud-
la´cˇkova´ M, Blaz´ícˇek P, Babinska´K.No
evidence of insulin resistance in normal
weight vegetarians: a case control study.
Eur J Nutr 2006;45:52–54
24. Gillum RF. Frequency of attendance at re-
ligious services, overweight, and obesity
in American women and men: the Third
National Health and Nutrition Examina-
tion Survey. Ann Epidemiol 2006;16:
655–660
25. Burke LE, Hudson AG, Warziski MT, Styn
MA, Music E, Elci OU, Sereika SM. Effects
of a vegetarian diet and treatment prefer-
ence on biochemical and dietary variables
in overweight and obese adults: a ran-
domized clinical trial. Am J Clin Nutr
2007;86:588–596
Vegetarian diet type, body weight, and type 2 diabetes
796 DIABETES CARE, VOLUME 32, NUMBER 5, MAY 2009
