Sustainable Diets & Agrifood Systems

Slides prepared by Dr. Orlaith Casey

Presented by Orlagh Gaynor

Irish Doctors for the Environment

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July 2026

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Agenda

• Why Sustainable Diets Matter
• Environmental Impact of Food Systems
• Characteristics of a Sustainable Diet
• Dietary Patterns Considered More Sustainable
• Animal-Sourced Foods: A Balanced Discussion
• Food Waste and Sustainability
• Local, Seasonal and Sustainable Food Choices
• Health Benefits of Sustainable Diets
• Challenges and Criticisms
• What Can Individuals Do?

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What is a Sustainable Diet?

• Why are sustainable diets receiving attention?

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• Connection between food, health and the environment

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Diets with low environmental impacts that contribute to food and nutrition security and healthy lives

- Food and Agriculture Organisation

Why do Sustainable Diets Matter?

• Improve health: lower risk of chronic conditions

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• Reduce environmental impact

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• Conserve natural resources

How can we feed everyone while protecting the planet?

Why do Sustainable Diets Matter cont.

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• Protect biodiversity

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• Reduce food waste

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• Support local economies and communities

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Health Matters

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Food Systems

Solutions

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Problem

Benefits

• Food systems cause > 30% of global GHGs, drive deforestation, biodiversity loss, water stress….

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• Double burden of malnutrition: undernutrition & obesity co-exist.�
• Unsustainable farming & diets harm both people and planet.

• Sustainable diets: More plant-based foods, less red/processed meat.�
• Agroecology & regenerative farming to protect soil, water, and ecosystems.�
• Cut food waste: 30% of food lost or wasted globally.�
• Economic & Policy reform: Align subsidies, trade & food guidelines with health & sustainability.

• Protects biodiversity & climate�
• Preserves water & soil quality. �
• Reduces disease burden & healthcare costs.

Environmental Impact of Food Systems

• 1/3 of greenhouse gas emissions globally
• Livestock production, fertiliser use, food processing

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• Land use & deforestation: forests cleared to create farmland

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Environmental Impact of Food Systems

• Water use: 70% of global freshwater withdrawals

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• Biodiversity loss & soil degradation e.g., via pesticide use

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• Water and air pollution: via fertilisers & pesticides

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• Food waste: 1/3 of all food produced globally is lost or wasted!

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Sustainable Food Systems

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Making food systems more sustainable is one of the most important ways to address climate change, conserve natural resources, protect biodiversity & ensure long-term food security

How sustainable food systems can help:

• Increased consumption of plant-based foods
• Improving farming practices to protect soil and water
• Reducing food loss and waste
• Conserving forests and natural ecosystems
• Using water, fertilisers and energy more efficiently
• Supporting local and seasonal food production where possible

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Characteristics of a sustainable diet

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A sustainable diet should be:

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Planetary Health� Diet¹

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(1)

What is the Planetary Health Diet?

• Developed by the EAT-Lancet Commission in 2019

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• Designed to improve both health &environmental sustainability

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• Focuses on a mostly plant-based eating

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• Goal: Feed a growing global population while protecting Earth's natural resources

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Characteristics of the Planetary Health Diet:

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• Flexible, not prescriptive and can be adapted to local contexts.

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• Plant-based emphasis:
• Fruits & vegetables: High intake
• Whole grains: Main energy source
• Legumes, nuts & seeds: Major protein and fat sources
• Moderate to low animal products:
• Red meat: Very limited (~14g/day, or 1 beef burger per week)
• Poultry & fish: Small portions weekly
• Dairy: ~250g/day (a glass of milk)
• Low processed foods:
• Sugar: <5% of energy intake
• Refined grains and starchy vegetables: Minimized

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How can we follow it?

• Fill half your plate with fruits and vegetables

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• Replace some meat meals with beans or lentils

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• Choose whole grains over refined grains

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• Reduce food waste by planning meals & using leftovers

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• Buy seasonal & locally grown

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Small changes in what we eat can improve out health while helping protect the planet for future generations

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Dietary Patterns Considered More Sustainable

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Plant-forward Diets

• More vegetables
• Fruits
• Whole grains
• Legumes
• Nuts and seeds

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Examples:

• Mediterranean diet
• Vegetarian diet
• Flexitarian diet

Benefits:

• Lower emissions
• Reduced land and water use
• Improved health outcomes

What is the Mediterranean Diet?

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Vegetarian Diet

• Excludes meat, poultry and fish while emphasising a variety of plant-based foods.
• Main foods:
• Fruits and veg
• Whole grains
• Beans, lentils & peas
• Nuts & seeds
• Dairy products & eggs
• Lower environmental impact compared with meat-based diets

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Flexitarian Diet

• Mostly plant-based eating pattern that allows occasional consumption of meat, poultry and fish

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• Focus on increasing plant foods rather than eliminating animal products completely

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• Practical way of improving both personal health and sustainability by making plant-based foods the foundation of most meals

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Ultra-processed foods (UPFs)

• Ultra-processed foods (UPFs) are industrially manufactured foods that are made mostly/entirely from ingredients extracted from foods, chemically modified substances & additives, with little or no intact whole food remaining.
• ~30-50% of Irish diets consist of UPFs

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UPF examples

• Sugary breakfast cereals
• Soft drinks & energy drinks
• Packaged pastries & cakes
• Crisps and flavoured crackers
• Instant noodles
• Frozen ready meals
• Chicken nuggets & processed meat products
• Sweetened yogurts with additives
• Commercial packaged bread made with emulsifiers & preservatives

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UPFs and the environment

• Environmental Impacts of UPFs

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• Higher greenhouse gas emissions due to energy-intensive manufacturing, processing & transportation

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• Excessive packaging

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• Greater energy & water use during industrial food production

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• Reliance on commodity crops

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• Long global supply chains

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Reducing reliance on ultra-processed foods while choosing more whole, minimally processed plant foods can benefit both human health and environmental sustainability.

• Higher UPF intake associated with increased risk of early-onset colorectal adenomas (precancerous polyps)

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Animal-Sourced Foods

Environmental considerations

• Challenges:
• Livestock production contributes to greenhouse gas emissions, particularly from ruminants (e.g., cattle and sheep)
• Animal agriculture requires substantial land and water resources
• Expansion of grazing land and feed crop production can contribute to deforestation and biodiversity loss

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Animal-Sourced Foods: Potential benefits

• High-quality protein & important nutrients (e.g., vitamin B12, iron, zinc, calcium)

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• Well-managed grazing systems can support soil health, carbon storage and biodiversity

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• Livestock can utilize land unsuitable for crop production and convert grass into nutrient-dense food

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Animal-Sourced Foods: A Balanced-Discussion

• Environmental impact depends on the type of animal, production methods and the amount consumed

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• Shifting toward moderate consumption & choosing sustainably produced animal foods

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• Increase plant-based foods

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• Balance human health & environmental sustainability

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Food Waste and Sustainability

Scale of the problem

• Approximately one-third of food produced is wasted

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Environmental impacts

• Wasted water
• Wasted energy
• Methane from landfills
• Many, many more….

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Solutions

Individual-Level Solutions:

• Meal planning
• Buy only what you need
• Better storage – extend freshness (freeze food, etc)
• Creative ideas for food leftovers
• Compost food scraps

Community Solutions

• Redistribution programs – food donation programs
• Local composting programs

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What are local, seasonal & sustainable food choices?

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• Local food: Food grown or produced in Ireland (or nearby regions)

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• Seasonal food: Foods naturally harvested at specific times of the year in Ireland

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• Sustainable food: Food produced in ways that protect the environment, support farmers and reduce emissions

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Why it matters:

• Lower carbon footprint
• Fresher, more nutritious food

Life in Spain!

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Eating Seasonally in Ireland

Ireland’s climate supports strong seasonal eating patterns!

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Benefits:

• Less reliance on imports
• Better taste & nutrition!

Supporting Local & Sustainable Food in Ireland

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• Total carbon foodprint depends on full life cycle, not just distance
• Consider:
• What is being produced e.g., beef vs legumes
• How it is produced (energy inputs, farming methods)
• When it is produced (seasonal vs forced production)
• How it is transported and stored

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Health Benefits

Evidence suggests that many sustainable dietary patterns are associated with:

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• Lower cardiovascular disease risk

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• Lower obesity rates

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• Better metabolic health

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• Higher intake of fibre and micronutrients

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Good for people = Good for the planet

Eating Sustainably with Dental Limitations

• Plant-based soft foods: Lentil soups, hummus, bean purées
• Stewed vegetables
• Oats, soft grains
• Protein options: Eggs, yogurt
• Cooking methods: Slow cooking, steaming, blending

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Challenges and Criticisms

Economic barriers including food affordability

Cultural barrier: traditional food preferences e.g., roast beef dinner!

Availability and accessibility

Nutritional concerns: ensuring adequate nutrient intake

Equity issues: sustainability should not increase food insecurity

Breakout rooms

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Practical actions

How can we create diets that nourish both people and the planet?

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Protein debate – the high protein diet

• Rise of high-protein diets in mainstream nutrition culture
• Heavy marketing of protein-enhanced foods (snacks bars, cereals) – many of which are UPFs!

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What the evidence actually shows

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• Benefits of higher protein are context-dependent (e.g., athletes)

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• Excess protein does not automatically improve health outcomes

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• Quality & food sources matter more than sheer quantity

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• Sustainable diets prioritize:
• Plant proteins (legumes, nuts, seeds)
• Moderate animal protein where appropriate
• Dietary diversity

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Food security in Ireland

• Currently ~60 commercial field vegetable farmers compared to a larger base historically

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• For local food security:
• Increased dependence on imported foods
• Less diversity in local produce

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• Sustainability implications:
• Longer supply chains -> higher transport emissions
• Loss of local agricultural knowledge & biodiversity

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Organic Produce – Chemicals, Health & Agroecological Farming

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Organic:

• Produced without pesticides etc.
• Emphasises soil health, biodiversity & ecological balance
• EU organic certification

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Chemical exposure: what we know

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• Organic produce generally shows: lower frequency of pesticide residues

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• Lower cumulative exposure to synthetic pesticides

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• However: “Lower exposure” ≠ proven major health benefit in general populations (evidence is mixed)

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Agroecological approach (core idea)

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• Farming system that works with natural ecosystems rather than against them

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Key principles:

• Crop diversity and rotation
• Reduced external chemical inputs
• Soil regeneration and composting
• Integrated pest management (IPM)
• Focus on long-term system resilience, not just yield

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Agroecological approach (core idea)

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• Organic and agroecological systems are less about “chemical-free perfection” and more about reducing ecological harm and building resilient food systems

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• The sustainability question is not only what we avoid, but how we manage entire farming systems

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Key Messages

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Sustainable eating is about better decisions within real-world constraints, not strict rules or perfection.

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Who are we?

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A voluntary NGO and registered charity consisting of healthcare professionals and students in Ireland who aim to create awareness, interest and implement action around environment health and the impact it has on our patients’ health.

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We work alongside various NGOs, environmentalists, scientists and other organisations to educate and promote healthcare as a key issue in climate change

Learn more!

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Questions?

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References

• https://eatforum.org/eat-lancet/the-planetary-health-diet/
• Wang C, Du M, Kim H, Nguyen LH, Wang QL, Drew DA, Leeming ER, Khandpur N, Sun Q, Zong X, Gweon TG, Ogino S, Ng K, Berry S, Giovannucci EL, Song M, Cao Y, Chan AT. Ultraprocessed Food Consumption and Risk of Early-Onset Colorectal Cancer Precursors Among Women. JAMA Oncol. 2026 Jan 1;12(1):49-57. doi: 10.1001/jamaoncol.2025.4777. PMID: 41231486; PMCID: PMC12616530.

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