health-related
parameters in
vegetarian and
omnivorous students
P. Clarys
P. Deriemaeker and
M. Hebbelinck
The number of people choosing a vegetarian lifestyle is growing (Hebbelincket al., 1999). Earlier motives for a vegetarian lifestyle were mainly of philosophical or religious origin. Nowadays more and more people choose a vegetarian lifestyle because the vegetarian diet is often related to a healthy lifestyle. Another factor often cited is the respect for animals or environmental concern. Indeed, the use of meat as a nutrient source is more polluting and energy consuming compared to plants as a nutritional source (O'Brien, 1998; Rifkin, 1992).
However, vegetarianism is not always accepted since doubt remains concerning the completeness of a vegetarian diet, especially when people with specific demands are involved such as children, pregnant women and athletes.
The results of several vegetarian world-class athletes however, demonstrate that a
vegetarian lifestyle can go together with top performances, for example:
. Edwin Moses (world and Olympic champion 400m hurdler);
. Martina Navratilova (world-class tennis player);
. Dave Scott (six times triathlon iron man); and
. Surya Bonaly (five times European champion figure skater).
A balanced vegetarian diet is often referred to as healthier since the prevalence of prosperity diseases such as obesity, ischaemic heart disease and osteoporosis is significantly lower in vegetarians compared to omnivores (Dwyer, 1991; Keyet al., 1996). However, other factors are equally in play since most vegetarians adhere to a healthier life style with no smoking, low or no alcohol consumption and with regular physical exercise (Fraser and Becson, 1997; Frentzelet al., 1988; Keyet al., 1996; Thorogoodet al., 1994)
The aim of the present study was to evaluate the average nutrition intake of a group of vegetarian students and to compare with matched pairs of non-vegetarian students. It was equally the aim to compare several critical blood parameters as an indicator for the subjects' health or as an indicator of the completeness of the diet. Furthermore, the physical performance of the vegetarians was compared with that of the non-vegetarians. Anthropometry was carried The authors
P. Clarys,P. DeriemaekerandM. Hebbelinckare all at the Faculty of Physical Education and Physiotherapy, Vrije Universiteit Brussel, Brussels, Belgium.
Keywords
Vegetarians, Diet, Health, Food, Fitness
Abstract
The completeness of a vegetarian diet is often questioned. Nevertheless, the literature indicates that a well balanced vegetarian diet is often healthier since the prevalence of prosperity diseases is significantly lower in vegetarians compared to omnivores. A total of 24 vegetarian students were examined regarding food intake, several critical blood parameters, physical performance and
anthropometrical measures. The vegetarian population was compared with 24 omnivorous students for the same parameters. A lower energy intake for the vegetarians compared to the non-vegetarians was found. The distribution of the three macronutrients differed significantly between the two populations. Vitamin intake was comparable and within the recommended daily intake. A similar profile was found for the mineral intake. The blood profile showed significantly lower vitamin B12 values for the vegetarians compared to the non-vegetarians but values were within the recommended limits. Physical performance and anthropometric were completely comparable between the two populations.
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Volume 30 . Number 5 . 2000 . pp. 243±249
out as a control for a proper matching of the vegetarian with the non-vegetarian subjects.
Methods
Subjects
A total of 24 vegetarian students (14 males and 10 females, aged 20.6 2.1 and 19.8 1.4 years, respectively) were recruited in the student restaurant at the vegetarian counter. Criteria for inclusion were that the students were healthy and had followed a vegetarian diet for a least one year. A vegetarian diet was defined as one that may include dairy products and eggs but not meat, fowl or fish. No vegan subjects, avoiding dairy products and eggs as well, were included.
Each vegetarian student was asked to introduce to the study an omnivorous student of the same age, sex and life style (smoking, drinking, physical activity). In this way it was hoped to obtain a closely matched control group. As a consequence, the omnivorous control group consisted equally of 14 males and 10 females (mean age 20.92.7 and 20.5 1.4, respectively).
Dietary assessment
Nutrient intake was assessed using a seven-day dietary diary filled out by all the
volunteers. Subjects visited the laboratory and they were told how to complete the food diary. The information was coded using the Nubel food tables (Nubel, 1995). The dietary diaries were analysed using a computer program (BECEL- program). The mean macro nutrient intake of each individual was calculated as well as several vitamins (A, B1,B2, B3, B6, C) and several minerals (Na, K, Ca, P, Fe, Mg, Zn).
Blood profile
Subjects were asked to report sober at the university medical service. A brachial venous blood sample was taken and analyzed by the clinical laboratory of the university hospital. Samples were analyzed for some health related variables (lipid profiles, amount of red blood cells) as well as for some parameters which are often considered as ``critical'' for vegetarians (Dwyer, 1991). It concerns the content of iron, zinc, calcium, vitamin B12, folic acid, ferritine, transferrine and the total iron binding capacity.
Physical performance
Fitness assessment included hand dynamometry, standing long jump, 30 seconds of sit-ups, and the Queens' College step test as an expression of hand-grip strength, leg explosive strength, abdominal dynamic muscle endurance and cardio-respiratory endurance, respectively.
Hand-grip strength, standing broad jump and 30 seconds of sit-ups tests were executed according to the protocol of theEurofit Testbatterij(Lefevreet al., 1993). The Queens' College step test is a short test which can be used to predict the maximal oxygen
consumption capacity (Katch, 1983). The test consists of stepping up and down a 41-cm high step at a rate of 22 steps per minute for three minutes. Subjects remain standing after exercise, and a 15-second pulse count is multiplied by four to record the score in beats per minute.
Anthropometric measurements
Anthropometric measurements were taken as a control for the paired matching of the vegetarians with the non-vegetarians and in order to determine the body mass index (BMI) and somatotype of the subjects (Carter and Heath, 1990).
Hence, the measurements included weight, height, triceps, suprailiac, subscapular and calf skinfold tickness and perimeters of the upperarm, calf and bicondylar femur and humerus width. Measurements were carried out according to standardized techniques (Lohman et al., 1988).
Data treatment and statistics
Normality of the data was tested using the Kolmogorov goodness-of-fit test. Working with a matched pairs set up enabled us to use a pairedt-test for the comparison of the two populations. In the cases where parameters were sex dependent the populations were divided in a male and female subgroup. The significance level was set at 5 per cent.
Results
Dietary assessment Macronutrients
vegetarian subjects did not differ from that of their female counterparts. Vegetarian men and women had a total energy intake which was just beneath the recommended daily intake, while the male and female omnivores had an energy intake just above the
recommended intake (see Table I)
The distribution of the energy among the different macronutrients approximated better the recommended distribution for the vegetarians compared to the omnivores with significant differences for respectively the three macronutrients and the energy delivered by alcohol (Table II). The vegetarians had a carbohydrate intake of 56.1E per cent while the non-vegetarians had an intake of only 46.4E per cent which is clearly below the recommended 55 per cent. This difference was significant when comparing male vegetarians with non-vegetarians. Protein intake was significantly lower for male and female vegetarians compared to non-vegetarians. Mean values were respectively 12.4E per cent for the vegetarians versus 15.1 E per cent for the non-vegetarians. These figures are within the recommended (10-15E per cent) interval for the vegetarians while the non-vegetarians have a protein
intake just above the upper limit. The alcohol intake was significantly lower in vegetarians (1.7E per cent) compared to non-vegetarians (4.5E per cent).
Significant discrepancies were found for the lipid intake when comparing vegetarian with non-vegetarian volunteers. Besides the lower total lipid intake we found an equally significant lower cholesterol intake when comparing vegetarian with non-vegetarian subjects (p= 0.004). Moreover, the intake of saturated lipids is higher for the
non-vegetarians compared to the non-vegetarians. The amount of saturated lipids was above the recommended intake for the vegetarians and the non-vegetarians.
Finally, we noticed a significant difference (p= 0.007) for the fibre intake with an intake of 15g/4,180kJ for the vegetarians compared to 9g/4,180kJ for the non-vegetarians. Both populations reached the recommended quantity of fiber intake (9g/4180kJ).
Micronutrients
Vitamins. No remarkable differences were found when comparing vitamin intake between vegetarians and non-vegetarians (Table III). In both populations, vitamin intake (vitamins A, B1, B2, B6 and C) was above the recommended quantity. We found a slightly higher, but not significant, vitamin C intake for the vegetarians (146102mg/ day) compared to the non-vegetarians (10582mg/day). We found a significant Table ITotal energy intake for vegetarians and non-vegetarians
Total energy
11,2322,424 8,8202,199
13,7193,716* 9,0462,546
12,100 9,000
Note:* Significantly different for vegetarians compared to non-vegetarians, p < 0.05
Table IIEnergy balance for vegetarians and non-vegetarians
Energy balance
Note:* Significantly different for vegetarians compared to non-vegetarians, p < 0.05
Table IIIVitamin intake for vegetarians and non-vegetarians
Vitamin intake
(p = 0.017) lower vitamin B6 intake for the male vegetarians compared to their non-vegetarian counterparts with respective values of 1.320.42mg/day and 1.780.47mg/day.
Minerals. Calcium, phosphorus,
magnesium, potassium and sodium intake were all within the recommended quantities for the vegetarians and the non-vegetarians (Table IV). Iron intake was higher for the non-vegetarians compared to the vegetarians. The difference was only significant for the male sub-populations. However, all subgroups reached the recommend iron intake. The origin of iron differs significantly (p< 0.001) when comparing vegetarians with non-vegetarians: 98 per cent of the iron was non-haem iron for the vegetarians compared to 63 per cent for the non-vegetarians.
Zinc intake was significantly lower for the vegetarians compared to the non-vegetarians (p< 0.001). None of the sub groups reached the recommended zinc intake of 15 mg/day for men and 12 mg/day for women.
Blood profile
Blood was analyzed for several critical parameters (iron, vitamin B12, folic acid, calcium, zinc and cholesterol). Both
populations had blood concentrations within the recommended limits for the analyzed components (Table V). The non-vegetarians showed a significantly higher (p< 0.020) vitamin B12 level compared to the vegetarians (respective values of 0.310.08g/l and 0.24 0.14g/l).
The other blood parameters did not indicate differences between the two populations. Remarkable are the low blood cholesterol levels in vegetarians (161
30mg/dl) and non-vegetarians (162 21mg/dl).
Physical performance. Physical performance, as evaluated with different specific tests did not demonstrate differences when comparing vegetarians with non-vegetarians (Table VI).
Anthropometry. The anthropometric characteristics such as body mass index and somatotype did not demonstrate significant differences between the vegetarian and the non-vegetarian sub populations (Table VII). These results indicate the proper matching of our experimental population.
Comparison between food intake and blood profile. When comparing results obtained by the food questionnaire with the results from the blood analysis several discrepancies were detected. From the food analysis it was found that zinc intake was too low in vegetarians as well as in non-vegetarians with lower values for the vegetarians compared to the non-vegetarians. The blood profile, however, indicates inverse results with zinc values well between the recommended concentrations for both populations and with higher values for the vegetarians compared to the non-vegetarians.
Another discrepancy was found for cholesterol. Cholesterol intake was
significantly higher for the non-vegetarians compared to the vegetarians, with an intake above the allowed maximum for the non-vegetarians. Blood profiles indicate more or less similar values for vegetarians and non-vegetarians and do not indicate major differences for HDL and LDL cholesterol.
Discussion
In our study we examined 24 vegetarian students with 24 non-vegetarian subjects matched for age, sex, weight, height and lifestyle. Hence, we may assume that differences in health-related parameters between the two populations were mainly due to the differences in nutritional habits.
The biometrical profile measured for the two sub-populations indicated a proper matching, since we did not find differences between the vegetarians and the Table IVMineral intake for vegetarians and non-vegetarians
Mineral intake
Vegetarians (meanSD)
(mg/day)
Non-vegetarians (meanSD)
(mg/day)
Reference value (mg/day)
Calcium Phosphorus Magnesium
Males (n = 14) Females (n = 10) Sodium
Potassium Iron
Males (n = 14) Females (n = 10) Haem Iron Zinc
Males (n = 14) Females (n = 10)
1,065349 1,654491 397182 305122 2,7021,019 3,8651,062
13.64.8 10.94.1 0.272.9 6.52.9 4.21.1
894434 1,727715 319101 22692 3,3111,647 3,6551,200 16.93.8* 11.53.9 5.211.84* 11.73.2*
7.62.0* 900 900-1,286 420 330 575-3,500 1,600-3,100
9 8 (20**) ± 15 12
non-vegetarians for the body mass index and the somatotype.
The physical performance tests as a measure for explosive power and endurance performance demonstrated no differences when comparing vegetarians with non-vegetarians. Hence, we can assume
comparable physical performance regardless of the dietary habits. However, our
measurements represent only a very small population and they did not measure extreme performance. The results of vegetarian top athletes (see ``Introduction'' section) as well as research on repeated maximal exercise in vegetarians compared to non-vegetarians (Claryset al., 1998) indicate no differences in physical performance. Therefore we may postulate that a vegetarian diet delivers sufficient nutrients for physical performances at different levels.
The food questionnaire showed that both populations reached the recommended intake for the different nutrients. However, nutrient intake and energy balance were closer to the quantities advised for a healthy nutrition. Energy balance of the vegetarians was in accordance with the recommended
distribution while the non-vegetarians had a lipid intake above the allowed quantity with too much cholesterol and a carbohydrate intake which is too low. The vegetarians had a lower protein intake compared to the non-vegetarians although both groups had values within the recommended intake.
Nutrient intake demonstrated higher values for calcium and magnesium intake and lower sodium and phosphorus intake for vegetarians compared with non-vegetarians (without reaching statistical significance). Again, these trends may be an indication that the
vegetarian sub-population had an intake closer to what is recommended in a healthy diet.
Concerning the vitamins we found higher vitamin A and vitamin C intake for the vegetarians compared to the non-vegetarians, while intake of vitamins from the B group is comparable (with an exception of vitamin B6 for the male vegetarians). Only the zinc intake was too low for all the subjects and the vegetarians had a significantly lower intake Table VBlood profile for vegetarians and non-vegetarians
Blood profile
Vegetarians (meanSD)
Non-vegetarians
(meanSD) Reference value
Iron (mmg/dl) Calcium (mg/dl) Zinc (mmg/dl) Vitamin B12 (mmg/dl) Folic acid (mmg/dl) Cholesterol (mg/dl) HDL-cholesterol (mg/dl) LDL-cholesterol (mg/dl)
10445 9.40.4
9817 0.240.08
8.23.8 16130
5211 8926
12132 9.30.3
9212 0.310.14
7.53.8 16223
559 8523
50-170 8.6-9.8 70-150
0.22-0.94 2.0-14.0 <200
>39 <150
Note:* Significantly different for vegetarians compared to non-vegetarians, p < 0.05
Table VIPhysical performance for vegetarians and non-vegetarians Vegetarians Non-vegetarians
Hand grip (kg) Males (n = 14) Females (n = 10) Sit ups in 30 seconds
Males (n = 14) Females (n = 10) Standing long jump (cm)
Males (n = 14) Females (n = 10) Step test (beats/min)
Males (n = 14) Females (n = 10)
415 318
254 204
21318 16222
14425 15919
437 286
264 214
21024 15712
14020 15824
Table VIIAnthropomorphy for vegetarians and non-vegetarians
Vegetarians Non-vegetarians
BMI
Males (n = 14) Females (n = 10) Endomorph
Males (n = 14) Females (n = 10) Mesomorph
Males (n = 14) Females (n = 10) Ectomorph
Males (n = 14) Females (n = 10)
20.982.41 19.801.40
2.181.37 3.750.79
3.781.23 3.241.24
3.681.56 2.601.58
21.483.30 20.501.35
2.110.84 3.700.92
3.911.14 3.360.73
compared to the non-vegetarians, which were equally below the recommended intake.
Analysis of the food questionnaires indicated that the vegetarian nutrition approached more the intake recommended for a healthy nutrition, especially when considering energy distribution and lipid profile. Equally, for the minerals we found a better profile for the vegetarians since generally a Western diet contains too much sodium and phosphorus. The latter minerals were lower in vegetarians and closer to the allowed quantities.
In contradiction with the often quoted possible lack of calcium in the vegetarian diet, we found a higher calcium intake for the vegetarians compared to the non-vegetarians. Calcium intake is often related to the
prevalence of post-menopausal osteoporosis (Hegsted, 1986; Riggs, 1987). More recent literature points to the negative relation between calcium absorption and the amount of proteins in the diet (Breslau et al., 1988). Hence, the combination of a higher calcium intake and a lower protein intake in the vegetarian subjects may result in a better calcium absorption for the latter subjects. However, the significant higher intake of fibres may counteract this process, since fibres make some of the ions unavailable for absorption as these ions are bound to the phytates abundantly present in dietary fibre. The preventive action of vitamin A and vitamin C, substances known as anti-oxidants, is well known. These vitamins are normally found in higher quantities in a plant based food pattern. This has been
corroborated by the results of the present study where the vegetarians had higher intakes of these anti-oxidants compared to the non-vegetarians.
The discrepancies between the results of the food questionnaire and the blood analysis calls for a last comment. The low zinc intake, as noticed for all the subjects, is not reflected by the blood profile where we found normal zinc values. Furthermore, we found a significant lower zinc intake for the
vegetarians compared to the non-vegetarians while the blood profile indicates similar values for the vegetarians and the non-vegetarians. This may point to a better resorption process since the lower intake in the vegetarians does not result in low blood concentrations. Indeed, for some minerals a better resorption process is hypothesised when availability is
reduced. This may also be related to the interplay of proteins and fibres on the encretion of minerals. The higher cholesterol intake for the non-vegetarians does not result in higher blood cholesterol levels. The negative aspects of a high cholesterol intake are well known. The consequences of a high cholesterol intake only become apparent at higher age and are not present in our young subjects. The comparison between the results of the food questionnaire and the blood profiles need to be done with a certain caution since blood samples were not always taken during the week of the food questionnaire. Moreover, the food questionnaire and blood analysis are only temporary indications.
We can conclude that, within the limits of our experimental population, a vegetarian food pattern can be considered as complete with intake of all required nutrients in sufficient amounts. Moreover, the vegetarian food pattern is closer to a healthy diet compared to the non-vegetarian diet. We found equally that the vegetarian subjects had similar physical performances compared to the non-vegetarian subjects. Finally, it was found that for some nutrients great
discrepancies exist between food intake and blood concentrations, indicating that nutrient intake is not always directly linked with nutrient absorption.
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