Vegetarian Nutrition

VN: Types and Diversity of Vegetarian Diets (2009)

Citation:

Draper A, Lewis J, Malhotra N, Wheeler E. The energy and nutrient intakes of different types of vegetarian: a case for supplements? Br J Nutr. 1993; 69: 3-19.

PubMed ID: 8457537
 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

The purpose of this study was to examine the diets and food choices of vegetarians in London (especially with reference to "new vegetarians") and to evaluate their knowledge and opinions about food, diet and health.

Inclusion Criteria:

Vegetarians in the London area who elected to modify their diets as adults.

Exclusion Criteria:

Those who had been brought up in a vegetarian lifestyle were excluded from this study.

Description of Study Protocol:

Recruitment

Subjects were vegetarian adults recruited through local radio, community events and centers such as a "green fair", health food shops (which displayed posters), societies of vegetarians and vegans, and personal contacts.

Design

This was a cross-sectional study that used three-day dietary intake data, food frequency questionnaires, and subject interviews on attitudes about diet, health and lifestyle to gather information about vegetarian food habits and health beliefs.

Data Definition

  • Instruction on how to complete a three-day dietary intake record
  • Food frequency questionnaire
  • Administration of subject interviews regarding attitudes about diet, health and lifestyle
  • Subjects were defined as demi-vegetarian, ovolactovegetarians or vegan via their self reported data.
    • Demi-vegetarian: Those who usually avoid meat
    • Ovolactovegetarians: Those who usually avoid all meat and fish
    • Vegan: Those who avoid all animal products.

Statistical Analysis

  • Statistical analysis was done using the SPSSPC+ package
  • Distributions of intakes were checked for skewness by the Kolmogorov-Smirnov test (lognormal transformation applied where appropriate)
  • Between-group comparisons were made using ANOVA
  • Comparisons between the main survey and the six-month follow-up survey were made by paired T-test.

 

Data Collection Summary:

Timing of Measurements

  • A three-day weighed dietary intake or three-day diary with household measures
  • Six months after the first dietary intake records, a 25% follow-up sub-sample was completed to test for seasonal variations in intake.

Dependent, Independent and Control Variables

This was a descriptive study.

 

Description of Actual Data Sample:
  • Initial N: 137 vegetarians
  • Attrition (final N): 127 vegetarians
  • Age: 20 to 60 years with the modal age range of 21 years to 30 years
  • Ethnicity: Not identified
  • Other relevant demographics:
    • Sample was from predominantly higher social classes and well-educated, e.g., 78% had at least one GCE/General Certificate of Secondary Education (GCSE) pass at "A" level, and 51% had a degree or equivalent (no significant between-group differences)
    • 58% were from first and second social classes (no significant between-group differences).
  • Anthropometrics: Mean reported body weights of subjects.
  Male (kg) Female (kg)
Demi-Vegetarians
74.7
57.9
Ovolactovegetarians
69.0
59.0
Vegans
64.4
55.4

*No significant between-group differences.

Location

London area, UK.

Summary of Results:

Energy, Protein, Carbohydrate and Alcohol Intakes of Vegetarians by Sex and Vegetarian Group
Mean Value Intake (±Standard Deviation) per Day

Group Demi-Vegetarian Ovolactovegetarian  Vegan Nationwide§
Sex/Number in Group
M/13
F/24
M/16
F/36
M/18
F/20
M/387
F/377
Energy (MJ)***
9.86±3.91
7.98±2.59
9.40±2.47
7.67±2.45
9.20±3.09
7.35±2.66
10.3
7.98
Protein (g) ++
82±39
59±20
66±21
56±17
65±27
47±18
87
66
Total Carbohydrate(g) ***
268±122
221±71
280±86
221±66
289±99
243±85
272
107
Sugars (g) *
109±74
104±50
126±55
97±35
122±64
104±52
121
91
Starch (g) ***
157±68
117±43
154±51
123±49
165±81
138±64
150
105
Alcohol (g)
17.5±24.4
8.8±14.4
12.2±25.2
12.3±25.2
11.6±18.6
3.3±8.9
24
8
Dietary Fiber (g)*+
35±20
30±10
34±13
33±12
44±16
36±17
26
20

Demi-vegetarian usually avoids meat; ovolactovegetarian avoids all meat and fish; vegan avoids all animal products.
The effect of sex was significant (ANOVA): *P<0.05; ***P<0.001.
The effect of group was significant (ANOVA): +P<0.05; ++P<0.01.
§Nationwide survey of British adults (Gregory et al 1990) social classes one and two.

  • All mean intakes were close to the UK Deptartment of Health recommended intakes
    • There was a highly significant effect of sex on energy intake but no effect of vegetarian group
    • All mean intakes of protein were more than the UK recommendations, although less than those in the nationwide sample
    • No significant difference in the sugars to starches ratio between the vegetarians and UK sample
    • Non-starch polysaccharide intakes in all groups were more than the nationwide sample mean, and approximately 80% higher in vegans.

Fat Intakes of Vegetarians by Sex and Vegetarian Group
Mean Value Intake and Standard Deviation per Day

Group Demi-Vegetarian Ovolactovegetarian Vegan Nationwide§
Sex/Number in Group M/13 F/24 M/16 F/36 M/18 F/20 M/387 F/377
Total Fat (g)**
100±51
85±34
93±35
77±36
85±43
67±42
104
76
Fat Energy %
37±11
40±8
37±8
37±11
34±10
34±8
38
38
Saturated Fatty Acids (g)**+++
37.3±23.5
28.5±15.9
32.6±16.2
25.1±13.9
18.0±11.5
15.7±7.9
42.5
31.9
Monounsaturated Fatty Acids (g)**
29.6±14.4
24.1±7.8
26.3±9.0
22.7±9.0
26.9±12.9
19.6±7.0
31.3
22.5
N-3 Polyunsaturated Fatty Acids +
2.48±1.00
2.30±1.68
2.14±0.70
1.72±0.80
1.95±0.91
1.51±0.79
2.03
1.38
N-6 Polyunsaturated Fatty Acids ++
17.8±8.7
20.2±8.6
19.2±6.7
18.5±8.2
28.6±12.2
22.4±13.4
14.5
10.4
Trans Fatty Acids** ++
5.3±2.6
3.48±1.96
5.41±3.03
3.38±2.26
2.70±2.80
2.80±1.70
5.53
3.9
P:S Ratio +++
0.64±0.43
0.95±0.73
0.71±0.51
0.94±0.77
1.79±0.96
1.47±0.86
0.36
2.96
Cholesterol (mg)‡
330±235
218±191
275±178
155±116
14±18
23±31
396
296

Demi-vegetarian usually avoids meat; ovolactovegetarian avoids all meat and fish; vegan avoids all animal products.
The effect of sex was significant (ANOVA): **P<0.01
The effect of group was significant (ANOVA): +P<0.05; ++P<0.01; +++P<0.001
‡Cholesterol in vegan diets is attributed to food table error
§Nationwide survey of British adults (Gregory et al 1990) social classes one and two.

  • Mean total fat intakes and percentage energy from fat of demi-vegetarians and ovolactovegetarians were similar to those of UK omnivores
  • Only vegans had lower total fat intakes than those of omnivores, and all vegetarians had more favorable polyunsaturated to saturated fatty acid ratio.

Mineral Intakes, Including the Contribution of Supplements, by Sex and Vegetarian Group
Mean Value Intakes and Standard Deviations per Day

Group Demi-Vegetarian Ovolactovegetarian Vegan Nationwide§
Sex/Number in group M/13 F/24 M/16 F/36 M/18 F/20 M/386 F/377
Calcium (mg)* +++
1,122±505
840±313
995±370
891±269
582±225
497±236
1,006
790
Magnesium (mg)***+++
434±166
385±126
412±131
423±129
939±403
538±269
342
261
Iron (mg) *
16.6±8.90
13.2±3.45
15.4±4.74
15.0±6.01
18.9±6.81
14.8±5.37
15
12.9
Copper (mg) +++
1.81±9.78
2.08±0.92
1.78±0.54
2.08±0.89
3.41±1.54
2.44±1.46
1.67
1.35
Zinc (mg) **
10.3±5.32
8.4±2.54
9.4±2.36
8.8±2.45
10.1±4.43
7.0±2.90
11.8
9
Iodine (ug) ***+++
253±164
172±91
216±73
167±-59
98±42
66±22
244
190

Demi-vegetarian usually avoids meat; ovolactovegetarian avoids all fish and meat; vegan avoids all animal products
Effect of sex was significant (ANOVA): *P<0.05; **P<0.01; ***P<0.001
The effect of group was significant (ANOVA): +++P<0.001
§Nationwide survey of British adults (Gregory et al. 1990) social classes one and two.

  • The iron, zinc, magnesium and copper intakes of all three vegetarian groups were above or similar to those of the UK nationwide.
  • Vegans were distinguished by lower calcium and iodine intakes.

Vitamin Intakes, Including the Contribution of Supplements, by Sex and Vegetarian Groups
Mean Value Intake and Standard Deviation per Day

Group Demi-Vegetarian Ovolactovegetarian Vegan Nationwide§
Sex/Number in group M/13 F/24 M/16 F/36 M/18 F/20 M/387 F/377
Retinol (ug)*++
610±300
495±311
538±156
374±199
181±149
172±124
1,735
1,722
Carotene (mg)
4.67±3.56
5.15±3.24
6.01±4.83
5.42±4.55
6.71±5.50
4.28±3.23
2.73
2.53
Vitamin D (ug)++
3.24±1.64
3.02±2.32
3.00±1.45
2.21±1.51
1.87±1.54
1.58±1.32
4.2
3.3
Vitamin E (mg)
14.7±5.81
17.2±9.98
15.8±4.99
16.1±10.0
23.1±9.60
16.5±7.45
12.4
8.7
Thiamine (mg)
1.79±0.73
2.03±2.27
1.88±1.57
1.59±0.45
2.14±0.69
1.58±0.57
2.5
1.6
Riboflavin (mg)+
1.90±1.04
1.93±2.04
2.09±0.89
1.71±0.61
1.37±0.52
0.98±0.30
2.7
2
Niacin (mg)***
37.8±12.2
27.8±7.3
33.0±9.7
27.7±7.7
33.2±12.1
24.5±7.7
43
33
Vitamin B6 (mcg)
2.4±0.53
2.4±0.72
2.2±0.50
2.3±0.58
3.2±1.0
3.3±0.91
3.0
3.3
Vitamin B12 (mcg)**+++
4.34±3.25
3.06±3.06
2.72±1.22
1.81±0.92
0.68±0.92
0.60±1.20
7.14
6
Total folic acid‡ (mg)
370±110
328±91
366±98
354±97
448±129
298±78
321
235
Ascorbic acid (mg)
123±78
126±52
119±84
131±55
172±97
124±70
97
96

Demi-vegetarian usually avoids meat; ovolactovegetarian avoids all fish and meat; vegan avoids all animal products.
The effect of sex was significant (ANOVA): *P<0.05; **P<0.01; ***P<0.001.
The effect of group was significant (ANOVA): ++P<0.01; +++P<0.001.
‡The interaction between sex and group for folate was significant (P<0.05).
§Nationwide survey of British adults (Gregory et al, 1990), social classes one and two.

 

Author Conclusion:

Findings from the present and other studies suggest a need for dietary supplementation at two stages in an adult vegetarian life cycle. 

  • The "new" vegetarian, who has recently given up some or all animal products, may go into negative mineral balance. If mineral absorption mechanisms need time to adjust to reduced intake of minerals (especially heme-Fe) and increased non-starch polysaccharides, then a modest supplement might ease this transition. Fe, Zn and Ca would be affected.
  • The vegetarian who progresses to veganism certainly requires additional vitamin B12, and iodine and riboflavin should be recommended as well. 

Two thirds of vegans in this study believed that their food could supply all necessary vitamins. Only 54% of these vegan subjects were members of a vegetarian society that educates about the need for vitamin supplements. Nutrient supplements recommended for adults are also needed by children receiving similar diets, and in addition a dietary vitamin D intake is considered essential for children (Dept. of Health 1991).

Funding Source:
Government: Ministry of Agriculture, Fisheries and Food
Reviewer Comments:

This study highlighted food, nutrient and lifestyle data from a small (N=127) non-random British volunteer sample group studied before March 1991. Results and conclusions of this study may not be relevant to vegetarians in the United States in 2008.

Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? N/A
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? N/A
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? No
  2.4. Were the subjects/patients a representative sample of the relevant population? No
  3. Were study groups comparable? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? Yes
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) Yes
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
  4. Was method of handling withdrawals described? Yes
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
  5. Was blinding used to prevent introduction of bias? N/A
5. Was blinding used to prevent introduction of bias? N/A
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) N/A
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
  6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
  7. Were outcomes clearly defined and the measurements valid and reliable? Yes
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? N/A
  7.1. Were primary and secondary endpoints described and relevant to the question? N/A
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
  8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? N/A
  8.6. Was clinical significance as well as statistical significance reported? N/A
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
  9. Are conclusions supported by results with biases and limitations taken into consideration? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? N/A
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
  10. Is bias due to study's funding or sponsorship unlikely? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes