Nutritional Adequacy of Vegetarian and Omnivore Dietary Intakes

Volume 1 | Issue 2 Nutritional Adequacy of Vegetarian and Omnivore Dietary Intakes Turner DR*1, Sinclair WH2 and Knez WL3 1Skin Cancer Research Group, School of Public Health Tropical Medicine & Rehabilitation Sciences, James Cook University, Queensland, Australia 2Institute of Sport & Exercise Sciences, School of Public Health, Tropical Medicine & Rehabilitation Sciences, James Cook University, Queensland, Australia 3Athlete Health and Performance Research Centre, ASPETAR–Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar


Introduction
Vegetarian diets take numerous forms with the exclusion of animal products being a shared factor.The most common variation is a lacto-ovo vegetarian diet, which excludes meat, fish and poultry but includes dairy and eggs [1].A vegan diet excludes all animal products so that meat, poultry, fish, dairy, eggs, gelatin, honey, animal derived additives and colours obtained from animal skeletons are not consumed [1,2].A fruitarian diet is a modified, more controlled version of the vegan diet that is primarily associated with the consumption of raw or dried fruits thus making this the least common of all vegetarian diets consumed and the one most likely to be lacking in essential nutrients [1].Interestingly, some individuals consider themselves to be vegetarian despite consuming meat products and a recent survey even reports a daily meat intake of approximately 80 grams by some selfidentified vegetarians [3,4].Consequently, research concerning vegetarianism can be limited by the definition of a vegetarian diet and the motivating factors for being vegetarian [4].
Literature investigating vegetarian athletes is mostly well dated [14][15][16] however athletes, particularly those involved in endurance events, may benefit from a vegetarian diet as it is naturally rich in complex carbohydrates [8].Research exploring the relationship between athletic performance and the consumption of vegetarian diets is limited which may be attributed to the small population of true vegetarian athletes from which to sample and their motivation for following the diet [8].This research aimed to compare the nutritional adequacy of usual dietary intakes of young adults who identify as vegan, vegetarian or omnivorous with an interest in fitness.
Participants were recruited to take part in a study investigating the effect of diet on aerobic performance.Information leaflets were placed on University campus which encouraged vegetarians and omnivores who exercised regularly to participate.The researchers ascertained dietary status (i.e.individuals were asked to identify as vegetarian or omnivore) whilst written consent to participate in the study was obtained.Individuals were classified as vegetarian if they did not consume any animal meat/flesh on a regular or occasional basis or vegan if they did not consume any animal derived products at all.The vegetarian cohort consisted of one male who was 20.0 years of age; 188.5cm in height; and had a body mass of 72.4kg and 4 females who were 21.7±2.0 years of age; 165.3±4.6cm in height; and had a body mass of 58.7±5.6kg.The vegan group consisted of one male who was 31.0 years of age; 181.5cm in height; and had a body mass of 89.1kg and two females who were 31.5±10.6 years of age; 176.9±8.3cm in height; and had a body mass of 69.7±8.9kg.Eight omnivore participants were matched for gender, age (21.1±1.9 years), height (168.1±6.0cm) and body mass (71.9±16.9kg).Participants did not use nutrition supplements nor did they smoke.The mean period of vegetarianism/veganism prior to testing was 6±4 yr.The investigation was conducted with the approval of the University Human Ethics Committee.
Participants completed a 7 day food diary and were instructed to provide as much information as possible regarding the quantity, type and manufacturer of food consumed.Participants were asked to use kitchen scales, measuring spoons and cups supplied to record food eaten as soon as practically possible (ideally immediately post consumption) to increase accuracy of the diet diary.Participants also provided food recipes, product labels and nutrition panels where possible.Diaries were analysed with FoodWorks (Xyris software, v.5, service pack 1, Highgate Hill, Australia) using nutrient reference values set for Australia by the National Health and Medical Research Council (NHMRC) [17].Participants were encouraged to consume foods that they would normally consume so that food diaries would be representative of typical diet.

Dietary analysis
SPSS statistical analysis software package (SPSS Inc., v.19 for Windows, Chicago, IL) was used for the statistical analysis of data.Normality tests indicated dietary data were not normally distributed.Subsequently the Kruskal-Wallis H test was used to compare dietary intake and data are presented as median [25 th quartile, 75 th quartile].Significance was set to 95% level of confidence (p<0.05).

Results
All participants met or exceeded the RDI of protein, thiamine, riboflavin, niacin, vitamin B 6 phosphorus, and vitamin C. Vegans consumed significantly less vitamin B 12 than omnivores and vegetarians (1.7µg compared to 4.5µg and 2.4µg respectively).Folate and vitamin C consumption was highest among the vegan group (p=0.007 and p=0.004 respectively) and vegans were more likely to meet the dietary requirements for magnesium and vitamin E (p=0.031 and p=0.017 respectively).Vegetarians consumed insufficient quantities of zinc while omnivores consumed inadequate amounts of iron and copper.All participants failed to meet the RDI of calcium.

Discussion
We found protein, thiamine, riboflavin, niacin, vitamin B 6 phosphorus, and vitamin C intakes were sufficient among our group of health-conscious vegetarians, vegans and omnivores.Vegans consumed inadequate amounts of vitamin B 12 and vegetarians failed to meet the recommended intake of zinc.The typical omnivorous diet consumed by our cohort was not rich in iron, magnesium or copper.Calcium intake by all participants was poor.
Folate consumption was highest among our vegan participants and lowest among the omnivorous cohort which is contrary to previous research [12,[18][19][20].Iron consumption was also higher among our vegans and vegetarians and unlike the omnivorous group they exceeded the RDI.Vegetarians are often assumed to consume insufficient quantities of iron however research reports similar [7,21] and increased intakes compared to omnivores [2,22,23].
Vitamin B 12 intake was lowest among our vegans and vegetarians which is a common finding [2,19,20].Vegetarians, especially vegans, are at a high risk for vitamin B 12 deficiency since plant based foods are a poor source of this vitamin [11,24].Consumption of vitamins C and E was markedly higher among our vegans and vegetarians although all dietary groups exceeded the RDI for vitamin C. Vegetarian diets usually contain increased amounts of vitamins C and E compared to omnivore diets [7,15,[25][26][27][28].
Low fat diets, especially those low in saturated fats such as vegetarian diets, are beneficial to health status as they may be able to reduce the risk of developing potentially fatal diseases such as CVD [12,13,23,27].Fat intake was lowest among our vegetarians whilst intake by vegans and omnivores was similar.Calcium is critical for bone health yet our participants reported inadequate intakes.The literature comparing calcium intake between vegetarians and omnivores is conflicting with research suggesting similar and insufficient intakes regardless of dietary preference [16,23,29,30].Vegetarians, particularly those who exclude dairy products and do not consume calcium-fortified alternatives may become calcium deficient therefore should take care to appropriately balance their diet [1].

Table 1:
Comparison of nutritional intake of omnivore,vegetarian and vegan cohort ^No reference value set by the NHMRC -Unable to be computed RDI -Recommended daily intake [17] AI -Adequate intake [17] Dietary preferences may account for differences in dietary intake of vitamins and minerals of our participants.Perhaps vegetarians had higher intakes of vitamins such as folate, vitamin C and vitamin E because they favoured and consequently consumed more foods naturally rich in these vitamins such as wholegrains, fruits, vegetables and nuts.Perhaps iron intake was higher (although not significantly so) among vegetarians because they were aware that iron obtained from animal sources, haem iron, is better absorbed than that from plant sources, non-heam, therefore made a conscious decision to eat more plant sources of iron [9].Lower intakes of minerals, for example zinc, by the vegetarian and vegan groups could be attributed to the exclusion of animal products since meat products can provide more minerals in a readily bio-available manner.Unlike prior research [2,[19][20][21]25] 368.2, -] 510.5 [381.7,638.0] 205.9 [188.4,255.0]Folate (µg) 0.007 174.0 [92.0, -] 128.0 [95.5, 159.5] 51.0 [47.0, 64.0] RDI Folate 0.067 457.5 [426.7,-] 337.9 [214.9, 482.4] 256.0 [190.6,310.5]Magnesium (mg) 0.031 148.0 [138.0,-] 109.0 [69.0, 138.0] 75.0 [61.0, 99.0] RDI Magnesium 0.267 974.5 [584.2, -] 870.9 [651.6,1131.9]776.4 [453.0,842.8]Calcium (mg) 159.0, -] 128.0 [78.5, 158.5] 88.0 [78.0, 121.0]AI Copper our Journal of Nutrition and Health Sciences Journal of Nutrition and Health Sciences Submit your next manuscript to Annex Publishers and benefit from: Submit your manuscript at http://www.annexpublishers.com/paper-submission.php→ Easy online submission process → Rapid peer review process → Open access: articles available free online → Online article availability soon after acceptance for Publication → Better discount on subsequent article submission → More accessibility of the articles to the readers/researchers within the field