Serum 25-hydroxyvitamin D status of vegetarians, partial vegetarians,
and nonvegetarians: the Adventist Health Study-21–4
Jacqueline Chan, Karen Jaceldo-Siegl, and Gary E Fraser
Background: Vegans and other vegetarians who limit their intake
of animal products may be at greater risk of vitamin D deficiency
than nonvegetarians, because foods providing the highest amount of
vitamin D per gram naturally are all from animal sources, and
fortification with vitamin D currently occurs in few foods.
Objective: We assessed serum 25-hydroxyvitamin D [s25(OH)D]
concentrations and factors affecting them in vegetarians, partial
vegetarians, and nonvegetarians in a sample of calibration study
subjects from the Adventist Health Study-2.
Design: Food-frequency questionnaires and sun-exposure data were
obtained from 199 black and 229 non-Hispanic white adults. We
compared s25(OH)D concentration, dietary and supplemental vita-
min D intake, and sun exposure in the different dietary groups.
Results: We found no significant difference in s25(OH)D by vege-
tarian status for either white or black subjects. Among whites, di-
etary vitamin D intake and sun behavior were different between
vegetarian groups, but there was no difference in skin type distri-
bution. Among blacks, no significant differences were observed for
any of these variables between vegetarian groups. The mean (6SD)
s25(OH)D was higher in whites (77.1 6 10.33 nmol/L) than in
blacks (50.7 6 27.4 nmol/L) (P , 0.0001).
Conclusions: s25(OH)D concentrations were not associated with
vegetarian status. Other factors, such as vitamin D supplementation,
degree of skin pigmentation, and amount and intensity of sun ex-
posure have greater influence on s25(OH)D than does diet.
Clin Nutr 2009;89(suppl):1686S–92S.
The diseases associated with low concentrations of serum 25-
hydroxyvitamin D [s25(OH)D; the measure of vitamin D ade-
the big killers—heart disease, cancers, and diabetes—as well as
autoimmune diseases, depression, and chronic pain (1). Foods
providing the highest amount of vitamin D per gram naturally
are all from animal sources: cod liver oil, finfish, and shellfish
(2). The only naturally occurring plant sources of vitamin D are
certain types of mushrooms in which it is present in small
amounts (2). Fortification of foods is limited both in amount and
distribution. Does this mean that vegetarians, who choose to
limit their intake of animal products because it has been asso-
ciated with better overall health (3), are at greater risk than
nonvegetarians of vitamin D deficiency and its accompanying
diseases? The Adventist Health Study-2 (AHS-2) is an ideal
cohort to examine these questions because its subjects range
from vegans to omnivores, with 4.2% vegan, 31.6% lactoovo-
vegetarian, 11.4% pescovegetarian (include fish with their oth-
erwisevegetarian diet), 6.1% semivegetarian (eat meat ,1 time/wk),
and 46.8% nonvegetarians (4).
STUDY POPULATION AND METHODS
The AHS-2has beendescribed indetail elsewhere(4). Inbrief,
it is a prospective epidemiologic study of 96,000 Seventh-day
Adventists designed to examine the relation of lifestyle (par-
ticularly soy, calcium, vitamin D, and fat intakes) to risks of
prostate, breast, and colon cancers. Enrollment to AHS-2 oc-
curred between 2001 and 2007. More than 26,000 of the en-
rollees are black, and study members live in every state and
province of the United States and Canada. Every 2 y, a ques-
tionnaire designed to gather information about all hospital-
izations is mailed. The second of these questionnaires included
additional detailed questions about sun exposure.
Subjects included in this report are members of the AHS-2
calibration study. Details of the calibration study methods have
been described elsewhere (5). Briefly, calibration subjects (n ¼
1007) were randomly selected from among the 97,000 enrollees
to the AHS-2. They were required to attend a clinic during
which weight and height were measured, and fasting blood
samples were collected. These clinics were held from November
2003 to May 2007 (none were held during February, June, or
July because of weather or vacation time). The detailed method
of the clinic portion of the calibration study is similar to that of
the pilot clinics that have been described elsewhere (6). Cali-
1From the Adventist Health Study-2, School of Public Health, Loma
Linda University Loma Linda, CA.
2Presented at the symposium, ‘‘Fifth International Congress on Vegetar-
ian Nutrition,’’ held in Loma Linda, CA, March 4–6, 2008.
(5F32HL082435, RO1 CA094594).
4Reprints not available. Address correspondence to GE Fraser, Adventist
Health Study-2, Loma Linda University, 24785 Stewart Street, Loma Linda,
CA 92350. E-mail: email@example.com.
First published online April 1, 2009; doi: 10.3945/ajcn.2009.26736X.
NationalInstitutes of Health
Am J Clin Nutr 2009;89(suppl):1686S–92S. Printed in USA. ? 2009 American Society for Nutrition
bration subjects also provided three to six 24-h telephone diet
recalls, completed a food-frequency questionnaire (FFQ) within
1–3 mo of blood sample collection, and provided detailed sun
exposure information for the 2 mo before their clinic attendance.
The subjects of this report are limited to 199 blacks and 229
non-Hispanic whites (whites) who were enrolled in the cali-
bration study as of June 2006, and who completed ?3 diet re-
calls and a FFQ within 1–3 mo of their clinic visit. Clinic sites
for subjects of this report were scattered across the United
Blood collected at clinics from calibration study subjects was
sent on frozen gel packs overnight to reach the processing lab-
oratory at Loma Linda University, CA, within 30 h of sample
collection. Plasma and red blood cells were separated by cen-
trifuge at the clinic sites. S25(OH)D was measured with the use
of a 2-step radioimmunoassay procedure (DiaSorin, Stillwater,
MN). The selected samples were couriered from the Loma Linda
laboratory to the Reproductive Endocrine Research Laboratory,
Department of Obstetrics and Gynecology, University of
Southern California Keck School of Medicine on dry ice and
stored again in liquid nitrogen until time of assay. Assay was
performed in 3 batches. Typical intra- and interassay CVs at this
laboratory are 10% and 16%, respectively.
Dietary and supplemental vitamin D intakes
Vitamin D intake was assessed by the AHS-2 FFQ that was
moderately correlated against 24-h telephone recalls. Validity
coefficients were 0.61, 0.59, and 0.63 in all, black, and white
subjects, respectively. Dietary vitamin D included D2 (plant
source, ergocalciferol) and D3(animal source, cholecalciferol)
obtained from foods, both naturally occurring and fortified. The
vitamin D content of foods included the amount reported in the
NUTRITIONAL DATA SYSTEMS (NDS) database (version
5.03; Nutrition Coordinating Center, University of Minnesota,
Minneapolis, MN), plus amounts from fortification not included
in the NDS. The latter values for foods such as cereals, yogurt,
margarines, liquid diet foods, health bars, and soy milk were
determined by contacting the manufacturers or consulting rele-
vant websites. Supplemental vitamin D included vitamin D
taken in the form of pills or liquid. Subjects were asked to name
all pills and supplements they were consuming, including brand
names, and amounts. Values for vitamin D from supplements
were also verified from manufacturers’ websites. No differen-
tiation was made for D2or D3for either food or supplemental
sources because it could not always be determined.
Dietary vitamin D was adjusted for energy intake with the use
of the residual method (7). Supplemental intake was not energy
adjusted. Total vitamin D intake was the sum of the population
mean dietary intake, the energy-adjusted residual, and supple-
Definition of vegetarian groups
Approximately 43% of whites and 26% of blacks in this study
group werevegetarian. We based thevegetarian categories on the
frequency of self-reported intake of fish, meat, dairy, and eggs.
Vegans consumed any animal product ,1 time/mo. Lactoovo-
vegetarians were those who ate meat and fish ,1 time/mo, and
dairy or eggs ?1 time/mo. Semivegetarians ate meat and fish ?1
time/wk. Pescovegetarians ate meat ,1 time/mo, and fish ?1
time/mo. Nonvegetarians ate meat and fish totaling ?1 time/wk
(4). Because there were relatively few vegans and semivegetarians
in this substudy, vegans were combined with lactoovovegetarians
to form the ‘‘vegetarian’’ group, and semi- and pescovegetarians
were combined to form the ‘‘partial vegetarian’’ group.
Categories according to Fitzpatrick sun-reactive skin types I
through VI (8) were defined according to response to prolonged
sun exposure: types I: no tan; II: tan very lightly; III: tan
moderately; IV: tan darkly; V: already brown; and VI: already
black. Types I and II were collapsed for both blacks and whites
because so few reported skin type I, and types V and VI were
collapsed because of similar response to vitamin D production
by sun exposure.
Differences between the white and black ethnic groups for
selected continuous and categorical baseline characteristics were
calculated with Student’s t test and Pearson’s chi-square test,
respectively. Analysis of variance and estimated means adjusted
for age and sex were used to determine the levels and signifi-
cance of relations between various vegetarian categories and
s25(OH)D for selected variables known to affect s25(OH)D. A
chi-square test for independence was used to determine the
percentage categorized as sufficient, insufficient, or deficient for
s25(OH)D concentrations, by vegetarian group and ethnicity.
Dietary vitamin D was adjusted for energy intake with the re-
sidual method (7). Supplemental intake was not energy adjusted.
Total vitamin D intake was the sum of the population mean
dietary intake, the energy-adjusted residual, and supplemental
intake. Analyses were conducted using S-PLUS software, ver-
sion 7.0 (Insightful, Seattle, WA).
The wide geographic distribution of subjects of this report is
(1) that might affect the s25(OH)D concentration by ethnic group
Number of subjects and clinics, by ethnicity and geographic region
No. of subjects
Geographic regionBlack Non-Hispanic whitesNo. of clinics
VITAMIN D STATUS OF VEGETARIANS
are shown in Table 2. Mean s25(OH)D was 52% higher among
whites than among blacks. The white subjects were older, had
lower body mass index (in kg/m2), and had a higher proportion of
males. Distributions of vegetarian status and skin type were sig-
nificantly different between ethnic groups. The proportion of
vegetarians and nonvegetarians was almost equal among whites,
whereas therewere twice as manynonvegetarians compared with
vegetarians among blacks. The proportion of partial vegetarians
was the same for both ethnic groups. None among the whites re-
skin types. Variables that did not differ significantly between
ethnic groups included vitamin D intake (dietary, supplemental,
and total), time spent in the sun, amount of body exposed, and
exposure factor, the product of the last 2 variables.
The estimated means for selected variables affecting
s25(OH)D according tovegetarian status adjusted for age and sex
are shown in Table 3. The means are those estimated for
a population with mean age and equal numbers of males and
females. The mean age was 63 y for white and 58.3 y for blacks.
In white subjects, no significant difference in s25(OH)D was
observed between vegetarian groups, although dietary vitamin
intake increased significantly from vegetarians to partial vege-
tarians to nonvegetarians. No significant difference was ob-
served in supplemental vitamin D intake, total vitamin D intake,
or time spent in the sun among the dietary groups. However, the
product of duration and percentage of body exposed to the sun
(9), exposure factor, was significantly higher in partial vegeta-
rians than in nonvegetarians and total vegetarians.
For blacks, the estimated means for s25(OH)D did not vary
significantly between vegetarian groups (range: 48.65–51.51
nmol/L). Unlike the white subjects, no significant differences
were observed between the vegetarian groups for any of
the personal characteristics or nutritional or sun exposure
The proportion of subjects who are sufficient, insufficient,
and deficient in s25(OH)D by vegetarian status within each
ethnic group is shown in Table 4. The distribution of s25(OH)D
status was not significantly associated with vegetarian status
for either ethnic group. In general, ethnicity had a far greater
effect on s25(OH)D than did diet. Blacks have ?3 times higher
percentage in the deficient category than whites for all dietary
Selected baseline characteristics of the study group according to ethnicity
Characteristic Non-Hispanic whites (n ¼ 229)
77.1 6 10.333
Blacks (n ¼ 199)
50.7 6 27.4
Serum 25-hydroxyvitamin D (nmol/L)2
Categories of serum 25-hydroxyvitamin D concentrations [n (%)]
Deficient (,50 nmol/L)
Insufficient (50 to 74.9 nmol/L)
Sufficient (?75 nmol/L)
Males [n (%)]
Dietary vitamin D intake (IU)4
Supplemental vitamin D intake (IU)5
Total vitamin D intake (IU)6
Vegetarian status [n (%)]
Skin type [n (%)]10
Type I, no tan or freckles
Type II, tans lightly
Type III, tans moderately
Type IV, tans darkly
Type V or VI, skin brown or black
Time spent in the sun daily (min)
Percentage of body exposed to sunshine11
62.9 6 14.0
26.9 6 5.1
140 6 96
244 6 316
388 6 249.2
58.0 6 12.5
30.3 6 6.7
132 6 96
224 6 296
352 6 312
89.6 6 83.0
9.3 6 6.5
913.9 6 1251.3
88.3 6 86.1
8.7 6 6.9
952.0 6 1467.9
1Student’s t test or chi-square test difference of means or percentages.
2Assayed by 2-step radioimmunoassay procedure (DiaSorin, Stillwater, MN).
3Mean 6 SD (all such values).
4Adventist Health Study-2 food-frequency questionnaire collected within 1–3 mo of blood sample. Calorie adjusted by residual method (7).
5Adventist Health Study-2 food-frequency questionnaire collected within 1–3 mo of blood sample.
6Sum of the population mean dietary, energy-adjusted residual, and supplemental intakes.
7Ate meat and/or fish ,1 time/mo.
8Ate meat and fish ,1 time/wk or ate meat ,1 time/mo and fish ?1 time/mo.
9Ate meat and fish totaling ?1 time/wk.
10Fitzpatrick sun-reactive skin types I through VI (8).
11According to Wachtel’s burn chart, modified (9).
12Product of time in the sun and percentage of body exposed to sunshine because only one side of body faces sun at any one time.
CHAN ET AL
As in other studies (10–15), we found statistically significant
lower dietary vitamin D intake among vegetarians than among
nonvegetarians but only in our white subjects. But unlike those
same studies, we found no association between s25(OH)D
concentrations and vegetarian status in either our black or white
cohorts. This would indicate that factors other than diet have
a greater effect on s25(OH)D than vegetarian status. For all our
dietary groups, the mean dietary vitamin D intake was low,
119.45–165.32 IU in whites and 114.66–150.56 IU in blacks.
These values are ?41% than the Adequate Intake (AI) of 400 IU
recommended for the age group represented in this study (age
51–70 y) (16). Among whites, dietary vitamin D intake in-
creased from vegetarian to partial vegetarian to nonvegetarian,
but the absolute difference of ’46 IU was not large. Supple-
mental intake of 400 IU vitamin D/d raises s25(OH)D by only
7–12 nmol/L, depending on the starting point (17).
It is difficult to meet daily AIs for vitamin D from food,
number of foods are fortified (2). Foods with high concentrations
of naturally occurring vitamin D are not eaten frequently by
many, because they are expensive. For example, wild cooked
salmon contains one of the highest concentrations of vitamin D,
providing 360 IU vitamin D/ serving (100 g or 3.5 ounces), but it
is expensive. Cooked tuna, a less expensive and more commonly
eaten fish, provides only 200 IU/100-g serving.
Naturally occurring vitamin D in foods appropriate for some
vegetarians occur in trivial amounts, such as 20 IU from an egg
yolk. Fortified foods contribute higher, although still inadequate,
amounts. For example, 1 cup (237 mL) fortified milk, milk
Estimated means for selected variables affecting serum 25-hydroxyvitamin D concentrations by vegetarian status, adjusted
for differences in age and sex
Serum 25-hydroxyvitamin D (nmol/L)2
Dietary vitamin D intake (IU)6
Supplemental vitamin D intake (IU)7
Total vitamin D intake (IU)8
Time spent in the sun (min/d)
Percentage of body exposed to sunshine9
1Determined by using ANOVA. The means are estimated for a population with mean age and equal numbers of males
2Assayed by 2-step radioimmunoassay procedure (DiaSorin, Stillwater, MN).
3Ate meat or fish ,1 time/mo.
4Ate meat and fish ,1 time/wk, or ate meat ,1 time/mo and fish ?1 time/mo.
5Ate meat and fish totaling ?1 time/wk.
6Adventist Health Study-2 food-frequency questionnaire collected within 1–3 mo of blood sample. Calorie adjusted by
residual method (7).
7Adventist Health Study-2 food-frequency questionnaire collected within 1–3 mo of blood sample.
8Sum of the population mean dietary, energy-adjusted residual, and supplemental intakes.
9According to Wachtel’s burn chart (9). Modified because only one side of body faces sun at any one time.
10Product of time in the sun and percentage of body exposed to sunshine.
VITAMIN D STATUS OF VEGETARIANS
substitute, or fortified juice yields ,100 IU, or less than one-
fourth the daily AI for the age group represented in this study.
Furthermore, fortification of foods is spotty. Although the United
States permits fortification of cereal flours and related products,
calcium-fortified fruit juices and drinks, including some milk
replacements such as soy and nut ‘‘milk’’ and margarine (2), not
all foods in these categories are fortified. According to 2006–
2007 Food Label and Package Survey by the US Food and Drug
Administration, ’91% of cheeses, juices, and spreads, ’75% of
yogurts, slightly less than half of all milk substitutes, and ’25%
of ready-to-eat breakfast cereals are not fortified with vitamin D,
although most fluid milks are (18). With so little vitamin D
available from food, it is not unexpected that dietary intake of
vitamin D is low.
from plants only, mushrooms may become a valuable source.
Mushrooms with vitamin D2content boosted to 400 IU by ex-
posure to sunlight shortly after harvest were introduced to the
market this year (19, 20). They are identified as vitamin D–
enriched on their labels.
The variable causing the greatest difference in s25(OH)D
white and black subjects in our study did not meet sufficient
s25(OH)D status, regardless of their dietary preferences, but the
percentage with deficiencies was much higher among blacks
similar in both ethnic groups. These factors included dietary and
in the skin declines 2–4-fold from age 20 to 80 y (21). Any effect
because of age would decrease the difference between the ethnic
groups. Mean body mass index for blacks was higher than for
whites, 30.3 compared with 26.9, and this may have contributed
somewhat to blacks having lower s25(OH)D concentrations than
whites, because s25(OH)D is removed from circulation by se-
questration in adipose tissue (22).
The largest difference between the 2 ethnic groups is the
melanin content in skin which is much higher in blacks than in
whites. Although blacks were exposed to the same amount of
sunlight, they were not capable of producing the same amount of
cutaneous vitamin D as were whites. The same quantity of ul-
traviolet B (UVB) irradiation (290–315 nm) has been found to
produce as little as 10% the increase in s25(OH)D in those with
dark brown skin as those with light skin type (23). As much as
90–100% of vitamin D requirement for light-skinned people is
said to come from exposure to sunshine (23). Although it is
difficult to obtain vitamin D from dietary sources, cutaneous
production of relatively high amounts of vitamin D can occur in
a relatively short time in lighter skinned persons when their skin
is exposed to sufficiently strong sunshine. Exposure of a person
in a bathing suit to 1 minimal erythemal dose (enough sun to
turn the skin slightly red), is equivalent to an oral dose of vi-
tamin D of 10,000–20,000 IU (23). For a person with light skin,
this can take ?15 min (24).
Limitations of the study
The limitationsofthestudyconcern theaccuracyofmeasuring
the variables that contribute to s25(OH)D concentrations and the
strength of their effect in changing those concentrations. The
values used for vitamin D content of foods in the US Department
of Agriculture Standard Reference and related products (2) are
not entirely accurate and are currently undergoing review by the
Nutrient Data Laboratory (25).
We made no adjustments for possible difference in effects on
s25(OH)D concentrations of D2 (from plants) and D3 (from
animals). The data collected did not differentiate between them,
and their relative efficiency is still under debate. Early research
reported that D2was ’40% less efficient than D3(26, 27). A
more recent study reports that they have similar effects (28).
Estimates of 25(OH)D and other vitamin D metabolites present
in meat have not yet been assessed or included as dietary sources
of vitamin D by the NDS. Many animal products contain
25(OH)D, and this metabolite is absorbed better and faster than
vitamin D and has metabolic activities of its own in regulating
cell growth and calcium metabolism. Depending on the bio-
chemical reaction, it can have biological activity ?5 times that
of native vitamin D (29). 25(OH)D occurs in meat naturally but
also as a result of cattle in the United States being fed foods
highly fortified with vitamin D during the 8 d before slaughter to
tenderize the meat (30).
7 dehydroxycholesterol in the skin (23), the effect of UVB ex-
posure should be included as an adjustment when relating
s25(OH)D concentrations to nutritional sources. A complex
mixture of skin color, season of the year, geographical location,
amount of time spent in the sunshine, as well as how much skin
is exposed, must all be considered. This report included personal
sun behavior activity but not sun exposure because of season of
Percentages of each vegetarian group, by ethnicity, in the sufficient, insufficient, or deficient category1
Serum 25-hydroxyvitamin D categories
(n ¼ 98)
(n ¼ 35)
(n ¼ 96)
(n ¼ 52)
(n ¼ 35)
(n ¼ 96)
Sufficient (?75 nmol/L)
Insufficient (50–74.9 nmol/L)
Deficient (,50 nmol/L)
1P = 0.4 and P = 0.9 for whites and blacks, respectively (chi-square test for independence).
2Ate meat or fish ,1 time/mo.
3Ate meat and fish ,1 time/wk, or ate meat ,1 time/mo and fish ?1 time/mo.
4Ate meat and fish totaling ?1 time/wk.
CHAN ET AL