Introduction to Plant-Based Diets

What is a plant-based diet?

• Plant-based diets are dietary patterns that emphasize foods from plant sources, with lower inclusion, or the exclusion of animal products.
• There is no single definition of a plant-based diet, which is often used to describe a vegan diet.
• Plant-based diets don't require complete avoidance of animal products
• The term ‘plant-based diet’ covers a spectrum of eating plans that emphasize plant produce, such as fruits, vegetables, whole grains, legumes, nuts, seeds and plant-based alternatives.
• These diets limit or exclude animal derived produce.
• Plant based (PB) diets are being described as ‘plant-centered’, ‘plant-predominant’, ‘plant-rich’, ‘plant-focused’, ‘plant-forward’
• Vegetarian diets are within the spectrum of plant-based diets, which can exclude the consumption of some or all forms of animal products.
• Considered 'flexitarian' approaches that emphasize consuming healthy plant foods.
• Meat and dairy are not necessarily avoided, but the amount consumed is reduced, and most of the nutrients come from healthy plant foods.

Common vegetarian diets

• Vegan diets omit all animal products, including meat, dairy, fish, eggs and usually honey.
• Lacto-vegetarian diets exclude meat, fish, poultry and eggs, but include dairy products such as milk, cheese, yoghurt and butter.
• Lacto-ovo vegetarian diets include eggs and dairy, but not meat or fish.
• Ovo-vegetarian diets exclude meat, poultry, seafood and dairy products, but allow eggs.
• Pesco-vegetarian (or pescatarian) diets include fish, dairy and eggs, but not meat.
• Semi-vegetarian (or flexitarian) diets are primarily vegetarian but include meat, dairy, eggs, poultry and fish on occasion, or in small quantities.

Health Benefits of a Plant-Based Diet

• Plant-based diets are widely associated with a lower risk of premature mortality and protection against noncommunicable diseases (NCDs)
• NCDs cause 71% of premature deaths (41 million per year)
• 80% of NCD deaths are attributed to cardiovascular diseases (17.9 million), cancers (9 million), chronic respiratory diseases (3.9 million) and diabetes mellitus (1.6 million)
• Limiting red meat (beef, pork and lamb) and processed meat (sausages and cured, smoked and salted meats) may protect against various NCDs.
• Vegan diets can raise concerns about micronutrient deficiencies (iron and vitamin B12).
• The protective benefit of plant-based diets is most likely due to many factors, including a lower energy density, high intakes of vitamins, minerals, unsaturated fats and fibre, as well as a reduction in saturated fat, sugars, salt and red and processed meats.
• People who follow plant-based diets are often health conscious and live healthier lifestyles.
• Observed benefits of plant-based diets may be attributable to other health behaviors.

Can a plant-based diet be unhealthy?

• Like all diets (animal or plant-based), the quantity and quality of the diet, are the deciding factors in determining health benefit.
• Plant-based diets high in fat, sugar and salt, increase peoples risk of disease
• Eliminating entire food groups will increase peoples risk of nutrient deficiencies.
• Plant-based diets that avoid all animal products (vegan diets) need to be adequately balanced.
• Vegan diets can be perfectly healthy if particular care is taken to meet requirements for certain nutrients.
• Nutrients like vitamin B12 may require particular care to meet requirements, through fortified foods and supplements

Macro- and micronutrient intake in plant-based diets

• There are some concerns about the nutritional adequacy of plant-based diets, especially vegan diets which exclude all forms of animal foods in their entirety.
• The absorption and availability of specific micronutrients (iron, vitamin A and zinc) may be lower in plant than animal foods.
• Recommended levels of nutrients can still be achieved with an appropriately planned vegan diet that includes a variety of different plant foods.
• For other micronutrients such as vitamin D and vitamin B12, vegans may consider the consumption of fortified foods and - in the specific case of vitamin D - adequate sun exposure.
• Vegan diets are typically associated with relatively low intakes of vitamins B2, B12, D, iodine, zinc, calcium and selenium.
• Intake of vitamin B12 is important for several bodily functions including a healthy nervous system.
• Vegan diets are characterized by lower consumption of saturated fat and higher consumption of beneficial unsaturated fat.
• Vegan diets are not associated with a risk of insufficient intake of vitamins A, B1, B6, B9 (folate), C, E and minerals iron, phosphorus, magnesium or copper in adult populations.
• Systematic review: a research technique that attempts to collect all empirical evidence in a particular field, to assess it critically and to obtain conclusions that summarize the research.

What about ultra-processed plant-based foods?

• Plant-based diets may include ultra-processed foods, such as imitation processed "meats", beverages (almond and oat "milk"), and plant-based "cheese" and "yoghurt".
• Ultra-processed foods as defined by the NOVA classification system, are formulations of substances derived from whole foods, such as starches, sugars, fats and protein isolates, with little, if any whole food.
• They often have added flavours, colours, emulsifiers and other cosmetic additives to improve shelf-life, palatability and visual appeal.
• There are descriptive criteria to assign foods to one of four groups based on processing-related criteria.
• Next-generation plant-based foods (such as meat, seafood, egg, and dairy analogs) are often criticized for being ultra-processed because of their high ingredient count and extensive manufacturing processes.
• Critics claim they may harm health because of high calorie, saturated fat, salt, and sugar content, along with low levels of protein, vitamins, and minerals.
• Research suggests some criticisms are overstated, and redesigning these foods can improve their nutritional profiles.
• Ultra-processing techniques can improve nutritional value, safety, and shelf life, but their reliance on added ingredients and complex processes challenges the criteria of the NOVA classification system.
• Careful in vitro and in vivo studies are essential to evaluate the health impacts of plant-based foods compared to the animal-based products they replace.

Other classifications for nutrient profiling

• other systems are used to assess food nutritional quality.
• The Nutri-Score system considers a food's levels (per 100 g) of more beneficial nutrients (protein, fiber, and percentages of fruits, nuts, vegetables, olive oil, canola oil, and walnut oil) and less beneficial nutrients (energy, total sugar, sodium, and saturated fat).
• Foods are assigned to one of five classes, which range from A (highest nutritional quality) to E (lowest nutritional quality).
• SAIN,LIM system: SAIN stands for "score of nutritional adequacy of individual foods" and expresses the density of five beneficial nutrients (protein, fiber, vitamin C, calcium, and iron) per 100 kcal of a food
• LIM stands for "limit" and expresses the levels of three less beneficial nutrients (sodium, free sugars, and saturated fatty acids) per 100 g of a food.
• Using thresholds for each score, four classes can be defined:
• 1 = high SAIN, low LIM (the best class)
• 2 = low SAIN, low LIM
• 3 = high SAIN, high LIM
• 4 = low SAIN, high LIM (the worst class)
• the Nutrient Rich Foods (NRF) Index is a formal scoring system that ranks foods on the basis of their nutrient content.
• It can help identify foods that are both nutritious and affordable when used with a food prices database.
• The current NRF algorithm, based on 9 nutrients to encourage and 3 nutrients to limit, is known as NRF9.3.

Environmental impacts of plant based foods

• Plant-based foods (fruits, vegetables, whole grains, beans, peas, nuts, and lentils) use less energy, land, and water, and have lower greenhouse gas intensities than animal-based foods.
• Animal products such as beef, lamb and dairy have a higher environmental impact and produce more greenhouse gases) than plant-based sources such as soy, nuts and pulses.
• Sustainable eating is more than just reducing animal products, it is also about reducing food waste, eating more local and seasonal food and choosing more sustainable packaging.
• Meat produces have larger carbon footprints per calorie than grains or vegetable products, due to the inefficient conversion of plant to animal energy and due to CH4 released from manure management and enteric fermentation in ruminants.

How are greenhouse gas emissions calculated?

• Carbon footprint: the total greenhouse gas (GHG) emissions caused directly and indirectly by an individual, organization, event, or product.
• Carbon footprint is calculated by summing the emissions resulting from every stage of a product or service's lifetime (material production, manufacturing, use, and end-of-life).
• GHGs (carbon dioxide (CO2), methane (CH4), and nitrous oxide (N₂O)) may be emitted throughout a product's lifetime, or lifecycle
• Differences in heat trapping are accounted for by the global warming potential (GWP) of each gas, resulting in a carbon footprint in units of mass of carbon dioxide equivalents (CO₂e).
• Life-Cycle Assessment: creates a detailed biography for a product or service, tracking emissions from "cradle to grave," covering everything from raw material extraction to disposal. It can be time-consuming and resource-intensive.
• Greenhouse Gas Protocol: a widely used framework that categorizes emissions into three scopes:
• Scope 1: Direct emissions from owned or controlled sources, such as company vehicles or fuel combustion in boilers.
• Scope 2: Indirect emissions from purchased energy, primarily electricity.
• Scope 3: All other indirect emissions within the value chain, including employee commutes and product disposal.
• Life cycle assessment (LCA) is a technique for assessing the environmental aspects and impacts of products, activities and services along the life cycle from extraction of raw materials, through to processing, manufacturing, distribution, use, and final waste management.
• The unit processes under study are collectively termed the product system
• LCA comprises four iterative phases:
• Goal and Scope definition: The goal and scope of the LCA study are defined in relation to the intended application.
• Inventory Analysis: the actual collection of data for individual unit processes and the calculation procedures, resulting in a table which quantifies the relevant inputs and outputs of the product system.
• Impact Assessment: translates the results of the Inventory Analysis into environmental impacts (climate change, ozone depletion). The aim is to understand the significance of the environmental impacts of the product system.
• Interpretation: conclusions and recommendations for decision-makers are drawn from the Inventory Analysis and Impact Assessment.
• Direct applications of LCA include product development, strategic planning, public policymaking, marketing, and other factors.
• The diagram shows that, in practice, LCA involves a series of iterations as its scope is redefined on the basis of insights gained throughout the study.
• Critical features of LCA that distinguish it from other environmental management approaches, include:
• Consideration of environmental aspects and impacts occurring along the life cycle of products and services, i.e. from raw material extraction through to final disposal.
• Assessment of more than one type of environmental impact.
• This distinguishes LCA from approaches such as carbon and water footprinting.
• Inclusion of environmental impacts in the assessment, irrespective of their geographical location and whether they occur in the past, present or future.
• Use of a functional unit that is defined in terms of the service delivered by the product system.
• The relative nature of LCA, which is expressed by defining environmental impacts relative to a reference unit (the functional unit) in a study.
• LCA studies suggest that animal-based foods have typically higher environmental impacts than plant-based alternatives.
• Meta-analysis of LCA studies suggest that 100 g of protein of beef from a beef herd has an average impact score for climate change of 50 kg CO2-equivalents and a land use of 164 m2 per year.
• Meta-analysis: a systematic method that uses statistical techniques for combining results from different studies to obtain a quantitative estimate of the overall effect of a particular intervention or variable on a defined outcome.
• Climate-change and land-use impacts of the protein-equivalent for peas, are over 100-fold and almost 50-fold lower than those of beef.
• Cultivation of irrigated wheat, rice, maize, and sugar cane are global drivers of water scarcity and land stress.
• GHG emissions in wheat are one-fifth of the carbon footprint per gram of protein in rice.

LCA of Emerging Food Technologies

• LCA studies are being conducted at the earlier stages of research and development, also for food systems and technologies.
• LCA could be used to assess the environmental impacts of cellular agriculture, i.e., the ensemble of technologies based on tissue engineering and cell culturing with the aim of growing cellular and acellular animal products in vitro, in the case of cultured meat.
• LCA could guide the developers of cultured meat) toward preferred sustainability pathways by quantifying the impacts of the current state-of-the-art lab or pilot food technologies.
• These studies could also project their potential evolution over time as the technology progresses, and compare their sustainability profile with existing alternatives.
• Other novel food technologies, such as plant-based protein alternatives for human and animal consumption, or novel practices, such as plant-based meal replacements, can be assessed similarly.

How to reduce the impact of food production on the environment

• Reducing emissions from the food sector requires changes at all stages, from producers to consumers.
• Shifting food systems towards plant-rich diets (beans, chickpeas, lentils, nuts, and grains), a reduced amount of animal-based foods (meat and dairy) and less saturated fats (butter, milk, cheese, meat, coconut oil and palm oil) leads to a significant reduction in greenhouse gas emissions compared to current dietary patterns in most industrialized countries.
• Alternative proteins provide promising prospects and are attracting growing demand, financial investment and technological innovation.

What are alternative proteins?

• Alternative proteins themselves are debated for their definition.
• A "category of proteins that do not originate from typical animal protein sources like red meat and chicken."
• Alternative protein sources are sourced from alternative, and of ten more sustainable sources (insects and plants)
• Proteins produced from sources that have low environmental impact to replace established protein sources. They can also be obtained from animal husbandry with good animal welfare."
• This definition encompasses both animal and non-animal protein sources, spanning from insects and cultured meat to plant-based alternatives, which can include some invasive plants.
• Alternative protein sources: Plants, microbes, algae, yeast, fungi, and insects.
• Plant-based proteins, cultured meats, dairy alternatives, and meat alternatives are all alternative proteins.