14 Feb Exploring the nutritional landscape of vegan diets: challenges and considerations
This Thought for Food discusses the growing interest in the adoption of plant-based dietary patterns and outlines the considerations of trade-offs such as nutritional adequacy and cost in this diet transition.
Nutritional outcomes
Undeniably, vegetables, fruits and other whole plant products contribute vital nutrients. For example, in a previous Thought for Food which reviewed Dr Ty Beal’s research, dark green leafy vegetables were one of the densest sources of priority micronutrients. Some studies have discussed the potential health benefits that are achievable from a balanced diet rich in whole plant foods. These include reduced risks of mortality from cardiovascular diseases and some types of cancer. The current intake of dietary fibre in New Zealand is lower than recommended, so including more plant-sourced foods in our diet could be beneficial.
A vegan diet is the most restrictive form of the plant-based diet due to the absence of all animal-sourced foods. Achieving nutritional adequacy from a vegan diet is not impossible due to the wide variety of plant-based options available in foods and supplements. However, this comes with challenges, particularly for individuals who have higher nutritional requirements (e.g., young children and the elderly) but are unable to consume large portions of high-fibre and satiating plant foods to obtain the nutrient adequacy.
Plant foods are not always easily digested and nutrient release is often reduced by anti-nutritional factors such as phytates. This applies for nutrients like the indispensable amino acids, zinc, iron and calcium. Furthermore, omega-3 fatty acids and vitamin B12 are limited in unfortified plant foods or are present in forms that cannot be efficiently converted by the human body. The move towards elimination of all animal-sourced foods spurred by ethical, environmental and animal welfare concerns should be balanced with considerations of nutritional outcomes. If unbalanced, and unsupported by fortification or supplementation, these diets cannot be sustainable due to increased risks of deficiencies and subsequent negative impacts on health.
Cost of vegan diets
The transition towards a vegan diet in modern times inevitably involves including novel plant-based alternatives. However, as shown by this study, processed products may be less economically viable options as compared to traditional sources such as beans, peas and legumes.
On one hand, transitioning towards increasingly plant-based diets may require the support of these foods, especially for individuals lacking knowledge on how to prepare and cook palatable dishes from traditional sources. On the other hand, the high costs of these foods can be barriers to sustaining a long-term vegan diet.
Within the context of New Zealand, this study showed that the more constrained a diet was in food groups, the higher its cost. The simulated vegan diet scenario (NZ$789 per fortnight) deviated most significantly and was 35% more expensive as compared to the current diet (NZ$584). This was followed by the flexitarian diet (NZ$728) and the healthy diet (NZ$637). Plant-based dairy alternatives was one of the food groups contributing to the higher costs of the plant-based diets (flexitarian and vegan). Yet these products, with the exception of soy formulations may provide poorer sources of protein and indispensable amino acids. While plant-based meat analogues could contribute high protein content, they were also comparatively more expensive than traditional plant-based options, with some products containing high quantities of sodium and saturated fat.
Additionally, an increased variety and quantity of alternatives may be required to match the nutritional density that can be provided by a smaller amount of animal-sourced foods. This means a larger expenditure could be required to make regular purchases of these foods.
One study found higher purchasing power to be one factor associated with the increased consumption of ultra-processed and novel plant-based foods such as burgers, meat substitutes, coconut-oil based vegan and nut-based cheeses. This observation can also be influenced by the number of years since vegan diet adoption – experience and personal interest could positively influence knowledge in selecting plant-based options and home-cooking methods that require minimal processing.
Adoption of vegan diets must be supported by accurate information
Documentaries and different forms of social media have the power to influence because they can engage mass audiences with the use of creative and convincing storytelling. Information must therefore be responsibly conveyed and guided by evidence-based research. Incorrect or insufficient knowledge on how to achieve a balanced vegan diet that includes both fortified foods and supplements may lead to serious nutritional and health problems. Apart from portraying the benefits associated with vegan diets, it is important that documentaries take care to display both sides of the story, so that viewers obtain a complete view and understand the implications of restricting all animal-sourced foods from the diet, especially during pregnancy, weaning, periods of growth and ageing.
Vegan dishes should be nutrient dense, and prepared in ways that enhance nutrient bioavailability so that these may be utilised fully within the body. While social media is a source of creative plant-based recipes, methods to improve the digestibility of nutrients (e.g. soaking, draining, fermenting) are rarely described. Accurate information is not always easy to find online and does require the viewer’s discretion. Reaching out to health professionals may be an accessible option, especially for older adults and families with young children. To support healthcare professionals, sufficient evidence-based information with appropriate guidelines should be readily available. Furthermore, continual professional development such as seminars and courses, led by dietitians or researchers specialising in plant-based nutrition, are valuable training opportunities. These are areas that require urgent progress.
Future research: Challenges with data availability
Assessing food composition and digestibility data allows us to understand nutrient utilisation in the body. For example, an updated and consolidated database for protein quality in human foods is necessary to support discussions on varied protein requirements across different age groups. As discussed in this Thought For Food, evaluations of protein quality have been conducted on approximately 500 foods.
Many studies have focused on isolated foods, but humans consume foods as part of a mixed diet. More data is still required to provide estimations of overall digestibility in mixed vegan meals where food components may interact with each other to either increase or decrease the extent of nutrient release.
Achieving this is a challenge due to the continuous global emergence of plant-based alternatives with varied formulations and fortification strategies. This is also compounded by difficulties in obtaining perfect matches for nutrient compositions between universal databases and country-specific diets. However, achieving shared and consistent databases is within grasp, and may be expedited with research collaborations.
Take-home message
A vegan diet is the most restrictive form of a plant-based diet and its appropriacy in certain populations needs to be carefully examined. Nutritional profiles of the vegan diet are dependent on the selection of foods, which is in turn affected by other factors, such as affordability and acceptability. Importantly, evidence-based knowledge must accompany the personal drive for switching to or maintaining an entirely plant-based diet, to achieve optimal nutritional outcomes.
This Thought for Food was written by Patricia Soh, PhD Student, with the support of Jacob Knight, summer internship student, and the SNi team.
