Introduction

Worldwide there are 75 million vegetarians by choice and 1.45 billion by necessity.¹ This is consistent with the approximation of 25% of the world’s population consuming a largely vegetarian diet.²

There are ten recognised classifications of vegetarianism. The most common types being vegan, lactovegetarian (LV) and lactoovovegetarian (LOV).

The defining differences in these most common diets are as follows ^3-5:

Vegan

Diet excludes all animal flesh and animal products, and any product tested on animals.

LV

Diet excludes all animal flesh and animal products. They do consume dairy products.

LOV

As per LV, but with eggs included.

Please note that in this paper references to vegetarian or vegetarianism is to be taken as LV, LOV and vegan diets.

This investigation focuses on vegan, LV and LOV diets, with the aim of comparing daily intake of nutrients and energy content of these diets with published RDA and AIs. However,

It was highly unlikely that an accurate calculation of the sample size of a meaningful study could be established unless it was based on existing strong evidence.^6,7 In view of the rarity of existing published articles that cover this topic, the present pilot study undertaken was designed to provide an insight into the contents of these types of diets. Also, the statistical findings obtained relating to population variances and standard deviations will allow an accurate sample size to be calculated for each important item for future large definitive studies.⁸

Materials and Methods

This study comprises an in-depth analysis of the diet diaries of LV, LOV and vegans who previously took part in a double blind placebo controlled clinical pilot study conducted by the same authors of this paper and published in this journal.⁹ The study was conducted according to the guidelines laid down in the WMA Declaration of Helsinki¹⁰ and all procedures involving human subjects were approved by the University of West London Research Scrutiny & Ethics Sub-committee. Written informed consent was obtained from all subjects.

The research findings presented in this paper are therefore a follow-on from a previously conducted pilot study that did not address the analysis of the entire contents of the diets of the participating groups of vegetarians of the trial.

Recap of recruitment of participants

Over the period July 2012 to December 2013 a total of 39 volunteers living in the UK completed their diet diaries. These subjects were recruited via the Vegetarian and the Vegan Societies and who had been practicing vegetarianism for >3years. These subjects comprised of LV, LOV and vegans. In our study LV and LOVs were treated as one group, since there is no nutritional detrimental difference as far as the diet analysis is concerned.

Recap of inclusion criteria

Inclusion criteria were as follows, age between 18 and 65 years old; not participating in a weight reducing diet; not pregnant, lactating or trying to conceive; non-smoker; not consuming alcohol regularly (>2 units/day for females, >3 units/day for males); moderate  caffeine consumption (≤ 4 cups/day of strong tea or coffee); not suffering from genetic metabolic disease; not suffering from renal failure, diabetes, thyroid disease, cardiovascular disease, dementia or cancer not using medications known to influence nutritional status.      

Recap of data collection

Each participant completed a fourteen day diet diary under the strict supervision of a

Nutritional Therapist. This involved the daily recording of the quantity of all food and

beverages, consumed by the participants.

Statistical analysis

Following analysis of the diet diaries of the participants who completed the study (n=39) the

mean, SD, and CI 95% of daily consumed nutrients were calculated employing Microsoft Excel software.

Also, calculations were made of the daily mean, SD and CI 95% energy intake of the participants employing the same software.

Results and Discussion

The socio demographic characteristics of age, gender, and vegetarian classification of the participants who participated in this investigation are presented in Table 1, which shows that there were thirteen male participants with a mean age of 50.8±14.8 years old and twenty six female participants with a mean age of 44.1±14.4 years old.

Table 1: Socio demographic characteristics of volunteers who participated in the clinical trial

Adapted from:  Obersby et al.,⁹

It can be observed from Table 2 and Table 3 that both the LV-LOV and the vegan diets exhibited a wide range of daily mean nutrient deficiencies, when compared with appropriate RDA and AIs. It is important to note that in compiling Table 2 and Table 3, nutrient trace values have been taken as zero, since quantities are approaching the limits of detection.¹¹ Also, some nutrient values have been taken from manufacturers published data.

Specifically both male and female LV-LOVs as well as the vegan diets were deficient in the following components: water, protein, fibre, retinal, vitamin D, potassium, calcium, selenium, iodine, choline and TMG compared to their RDA and AIs. Furthermore, the diets of LVs and LOVs of both genders together with the female vegan diets do not meet the RDA for mean daily intake of vitamin E. Moreover, the diets of the LV-LOV for both genders did not meet the AI level for daily intake of vitamin B5. Also, the diets of the female LV- LOV diets did not meet the RDA for mean daily intake of carbohydrates; vegan diets of both genders did not meet the RDA for mean daily intake of vitamin B12. Both LV-LOV and vegan female diets did not meet the RDA for mean daily intake of vitamin B1, vitamin B3, chloride and iron. Both genders of LV-LOV and the male vegan diets did not meet the AI for mean daily intake of vitamin K. Female LV-LOV diets did not meet the AI for mean daily intake of sodium and finally male LV-LOV and female vegan diets fall slightly short of the RDA for the mean daily intake of magnesium.

Table 2: Analysis of daily diets of male LV-LOV and vegan pilot study participants

Legend:

(a) Non-starch polysaccharides, (b) Moderate activity
(c) Not determined, (d) Non-starch polysaccharides.
(e) Maximum, (f) Less than.
(x) Mean acceptable macronutrient distribution range (MAMDR)

Adapted from: Foods Standards Agency 12; Dunne 13; Zeisel et al. 14; Institute of Medicine of the National Academy of Science 15; National Institute of Health 16; The American Heart Association 17; Food and Nutritional Board, Institute of Medicine, 18; U.S. National Library of Medicine 19; Linus Pauling Institute, 20; Bitelog 21; USDA Agricultural Research Service 22.

Table 3: Analysis of daily diets of female LV-LOV and vegan pilot study participants

Legend:
(a) Non-starch polysaccharides, (b) Moderate activity
(c) Not determined, (d) Non-starch polysaccharides
(e) Maximum, (f) Less than
(x) MAMDR

Adapted from: Foods Standards Agency 12; Dunne 13; Zeisel et al.14; Institute of Medicine of the National Academy of Science 15; National Institute of Health 16; The American Heart Association 17; Food and Nutritional Board, Institute of Medicine 18; U.S. National Library of Medicine 19; Linus Pauling Institute 20; Bitelog 21; USDA Agricultural Research Service 22.

It is recognised that whilst both male and female LV-LOV and vegan diets contained only a mean daily intake of ≤ 1µg of vitamin D, which is much lower than the daily AI of 5µg. This shortfall has the potential to be supplemented by induced vitamin D, generated from sunlight to obtain a sufficient supply of this important essential nutrient.

Dietary energy intake calculations

Calculations of the daily energy intake are based on the formula shown in Figure 1 with the appropriate nutrient values taken from Table 2 and Table 3. Conversion factors for metabolizable energy as shown in Table 4 are also utilised. The calculated energy values are presented in Table 5 and Table 6 which, assumes polyols and organic acids are omitted in the calculation of metabolizable energy, as they only represent a small percentage of energy from which there is no published validated information available. Also, it should be noted that available carbohydrate is the sum of the free sugars (glucose, fructose, galactose, sucrose, maltose, lactose and oligosaccharides) and complex carbohydrates (dextrin, starch and glycogen). These are the carbohydrates which are digested and absorbed and are glucogenic in human beings.⁸ Furthermore, that digestibility does not vary significantly among the participants and conversion factors for metabolizable energy of the diets are taken from

Table 4: Conversion factors for metabolizable energy of the diet

Adapted from: Foods Standards Agency ¹².Food and Agriculture Organization of the United Nations ²³.

Table 5: Energy intakes of pilot study male participants who completed the study

Legend:
(a) Moderate activity.
(b) Average adult.
(c) Not determined.
(d) Based on an average energy contribution of 55 %.
(e) Based on an average energy contribution of 25%.
(f) Based on an average energy contribution of 20%.

Table 5: Energy intakes of pilot study male participants who completed the study

Legend

(a) Moderate activity.

(b) Average adult.

(c) Not determined.

(d) Based on an average energy contribution of 55 %.

(e) Based on an average energy contribution of 25%.

(f)  Based on an average energy contribution of 20%.

Mean energy intakes were found to be 1488 ± 203 kcal/d and 1648 ± 113 kcal/d for male LV-LOV and vegan diets respectively (Table 5). For female LV-LOV and vegan diets they were

found to be 1043 ± 146 kcal/d and 1129 ± 172 kcal/d respectively (Table 6).

The pictorial representation of the calculated mean energy intakes of the participants are presented in Figure 1 and Figure 2.

Figure 1: Pictorial representation of mean daily energy intake of male participants and total energy formula   Click here to View figure

Figure 2: Pictorial representation of mean daily energy intake of female participants   Click here to View figure

Analysis of the participant food diaries indicates that there is a considerable deficiency of dietary vitamin D for both LV-LOVs and vegans indicating a likely dietary vitamin D deficiency. This can be clearly observed in Table 2 and Table 3, and these individuals are probably unaware that they need to rely on their supply of vitamin D from synthesis by the body from the sun’s ultra violet radiation. Therefore, in this instance it is reasonable to recommend that both vegetarian groups should consider supplementing their diets with this very important essential nutrient, particularly during winter months. In terms of meeting the RDA and AIs both vegetarian groups need to increase their intake of appropriate nutrients in order to satisfy their RDA and AIs. Moreover, it would not be appropriate in this investigation to recommend an increase of nutrients that are based on mean values of groups of people. This can only be effectively achieved on an individual basis (n=39), which is outside the scope of this investigation. However, it is worth noting that the deficiency of the above nutrients can potentially raise health issues, these are summarised in Table 7. The evidence obtained from Table 5 and Table 6 indicates that the mean daily intake of energy 1488 ± 203 kcal/d for male LV-LOVs, 1648 ± 113 kcal/d for male vegans, 1043 ± 146 kcal/d for female LV-LOVs and 1129 ± 172 kcal/d for female vegans appears to be low when compared with the recommended AIs of 2500 kcal/d for males and 2000 kcal/d for females for average adults who undertake moderate physical activity.

Table 6: Energy intakes of pilot study female participants who completed the study

Legend

(a) Moderate activity.

(b) Average adult.

(c) Not determined.

(d) Based on an average energy contribution of 55 %.

(e) Based on an average energy contribution of 25%.

(f)  Based on an average energy contribution of 20%.

Table 7: Summary of some potential health issues due to inadequate intake and deficiency of nutrients. 

Adapted from: Institute of Medicine of the National Academy of Sciences ¹⁶; Kuwabara et al ²³; Obersby et al.,²⁴

In conclusion, the findings of this paper demonstrate that all vegetarian participants exhibit a deficiency of several important dietary nutrients that potentially could lead to chronic medical conditions. Whilst it was outside the scope of this research to recommend dietary changes on an individual basis, the results clearly show that on a group basis that there is a dire lack of vitamin B12, due to an absence of dietary animal products in vegan diets. Also, LV-LOV male diets only marginally meet the RDA for this very important nutrient. Furthermore, all groups exhibit a deficiency of dietary vitamin D, although dietary deficiency of vitamin D can be compensated by one’s exposure to sunlight.

The mean daily metabolizable energy intake for all groups of participants indicate that this is well below recommendations which, can in certain instances such as with high activity lead to certain individuals becoming significantly under weight.

The analysis of the diets provides suitable statistical data to allow the calculation of an accurate sample size for each important item of future large scale definitive studies.

Further research is called for into establishing the nutritional contents of practical vegetarian diets. Meanwhile, It is recommended for LV, LOV and vegans to carefully monitoring their diets and possibly supports these with supplements.

Acknowledgements

Our thanks go out to all respondents for their participation, Moreover, we would like to thank the Vegetarian and Vegan Societies for their help in recruiting the participants of the study, without which the research project could not have taken place.

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