Nutritional and Metabolic Status of Vegetarian and Omnivorous Portuguese Adults

Recruiting

• Conditions: Metabolic Profile; Diet, Vegan; Nutritional Status; Diet, Vegetarian
• Interventions: Other: Blood and urine collection, anthropometric analysis and answering to questionnaires

• Registration Number: NCT05408962
• Lead Sponsor: Universidade do Porto

Brief Summary

Vegetarian diets have low environmental footprints and are potential solutions to address climate change and the 2030 Agenda on the Sustainable Development Goals. Currently, there is no information regarding the nutritional quality of vegetarian diets in Portugal. As the trend for vegetarianism increases in the country, the aim of this study is to examine and compare nutritional and metabolic outcomes among vegetarian and non-vegetarian populations. We aim to implement a cross-sectional study that includes a total of 400 (distributed among the three diferent groups of omnivorous, lacto-ovovegatarians and vegans) healthy Portuguese adults aged 18-64 years. Blood and urine samples will be collected. Participants will be assessed for blood pressure, anthropometric parameters, micronutrient status, blood lipids, glicaemia and insuline resistance and will complete a validated food frequency questionnaire as well as a sociodemographic and lifestyle questionnaire. Dietary and nutrient analysis will be conducted to assess diet quality and nutritional inadequacies. The current proposal provides an unique opportunity to characterize and compare different population groups clustered by dietary behaviour and provide evidence that help achieve healthy and sustainable diets in Portugal.

Detailed Description

Plant-based diets have been proven to be sustainable and to have low environmental impact, highlighting the importance of promoting a dietary shift towards plant-based diets, with reduction in the consumption of animal food sources. In particular, vegetarian diets can refer to vegan (VEG) diets that completely exclude all animal derived foods or to lacto-ovo vegetarians (LOV) which include eggs and milk products and have low environmental footprint compared with omnivorous dietary patterns. Vegetarian diets are gaining popularity around the world. The reasons to follow a vegetarian diet are diverse and reported to be related to religion, animal welfare, sustainability and environmental reasons, as well as health related concerns. Literature has shown several health benefits of these diets. Regarding the efficiency of vegetarianism in promoting weight loss, studies in which a lacto-ovo vegetarian or vegan diet are administered to participants show that participants with previous plant based-diets that do not fully adhere to the prescribed weight loss diet loose more weight when compared to non-vegetarians. Moreover, vegan diets have been shown to be more effective in improving body composition and insulin resistance, when compared to an omnivorous diet. Despite the above referred evidence regarding beneficial effects on weight loss, some studies find no statistical differences on weight loss promoted by vegetarians, omnivorous or Mediterranean diets. Plant-based diets were also found to improve glycaemic control and insulin sensitivity. In fact, there is evidence on vegetarians having lower fasting insulin level and higher insulin sensitivity compared with matched omnivores. Moreover, these diets are considered to have a low inflammatory load to the point of being considered as an approach to lower inflammatory markers in patients with coronary artery disease. Nevertheless, since vegetarian diets are restrictive, they may give rise to nutritionally unbalanced regimens, particularly when adopted without nutritional counselling. In fact, several studies link vegetarian diets to poor nutritional status, including micronutrient deficiency. In this context, the great rise of vegetarian habits among Portuguese population, which are reported to have quadruplicated in the last 10 years, poses important health concerns. Nevertheless, data on the nutritional status characteristics and metabolic profile of such consumers and of the nutritional adequacy of their diet are scarce, particularly comparing with people with omnivorous dietary regimens.

So, it is crucial to assess the quality of vegetarian diets in the country, identifying clear health benefits and risks from a nutritional perspective. Considering the importance of promoting environmentally sustainable diets at national level and the lack of data regarding the diet quality of vegetarian diets in the country, we propose the implementation of the first cross-sectional study in the country to investigate and compare nutritional and health parameters among vegetarian and omnivorous populations. The current proposal provides an unique opportunity to characterize and compare different population groups clustered by dietary behaviour and identify potential risks and gaps to attain health and environmental goals, such as contributing to the Portugal commitments to achieve the 2030 Agenda on the Sustainable Development Goals.

Study Timeline

• Study First Submitted: 2022-06-03
• Study First Submitted QC: 2022-06-03
• Study First Posted: 2022-06-07
• Study Start: 2022-07-01
• Status Verified: 2023-10
• Last Update Submitted: 2023-10-18
• Last Update Posted: 2023-10-19
• Primary Completion: 2023-12
• Study Completion: 2024-06

Recruitment & Eligibility

• Status: RECRUITING
• Sex: All
• Target Recruitment: 400

Inclusion Criteria

• being a healthy adult
• being aged between 18 and 65 years
• having the reported dietary regimen for at least 1 year

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Exclusion Criteria

• being free from metabolic disorders
• being free from digestive disorders
• being free from renal disorders
• being free from haematological disorders
• being free from endocrine disorders
• being free from oncological diseases
• being free from food intolerances
• being free from eating disorders

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Study & Design

• Study Type: OBSERVATIONAL
• Study Design: Not specified

Arm && Interventions

Group	Intervention	Description
OMNI - omnivorous	Blood and urine collection, anthropometric analysis and answering to questionnaires	Healthy omnivorous adults with ages between 18 and 65 years and having the reported dietary regimen for at least 1 year, free from any chronic condition such as metabolic, digestive, renal, haematological, endocrine or oncological diseases and presenting no food intolerances or eating disorders.
LOV - lacto-ovovegetarians	Blood and urine collection, anthropometric analysis and answering to questionnaires	Healthy lacto-ovovegetarians adults with ages between 18 and 65 years and having the reported dietary regimen for at least 1 year, free from any chronic condition such as metabolic, digestive, renal, haematological, endocrine or oncological diseases and presenting no food intolerances or eating disorders.
VEG - vegan	Blood and urine collection, anthropometric analysis and answering to questionnaires	Healthy vegan adults with ages between 18 and 65 years and having the reported dietary regimen for at least 1 year, free from any chronic condition such as metabolic, digestive, renal, haematological, endocrine or oncological diseases and presenting no food intolerances or eating disorders.

Primary Outcome Measures

Name	Time	Method
Diet Quality Index for each regimen	7 months	Diet quality will be assessed through a Diet Quality Index (DQI) created by VeggieNutri's workteam. DQI is a tool that quantifies the quality of an individual's intake, scoring their food intake, assessed buy a Food Frequency Questionnaire (FFQ). Each question regarding their food intake will be scored from 0 to 10 points, depending on how close they are to complying with guidelines and recommendations (the closer to complying, the highest the scoring and the farthest, the lower the scoring).
Nutritional inadequacy prevalences	11 months	Nutritional inadequacy prevalences will be calculated based on DQI scores and also on reference values for micronutrients in blood or urine.

Secondary Outcome Measures

Name	Time	Method
Levels of vitamins B12, B6, B9 and D, homocysteine, iron, selenium, calcium, zinc and magnesium	6 months	Measured in blood samples.
Urinary iodine concentration	6 months	Assessed through the analysis of urine samples.
Waist circunference and percentage of body fat	6 months	Assessed through anthropometric analysis including bioelectrical impedance, on the recruitment day.
Fasting glycaemia and HOMA-IR	6 months	Quantification of fasting blood glucose and insulin.
Blood LDL, HDL and total cholesterol and triglycerides	6 months	Assessed through the analysis of blood samples.

Trial Locations

Locations (1)

Faculty of Medicine (FMUP); 🇵🇹 Porto, Portugal