Linking the Puzzle Pieces of Human and Planetary Health

The year 2024 has arrived, and as every new year rolls around, many of us turn our thoughts to what we hope this brand-new year will bring.  My wish, as always, is that more people will begin to realize that increasing their intake of plant-sourced foods and decreasing animal-sourced foods is the most positive decision they can make, not only for their own health, but also for the health of our planet.

A few weeks ago, I watched a webinar from the T. Colin Campbell Center for Nutrition Studies called “The Tipping Point:  Diet and Climate Chaos”.  It brought with it food for thought and a bit of hope that the year 2024 might make a difference to the future of our Earth.  Its speakers include T. Colin Campbell PhD who, as a professor of nutritional biochemistry at Cornell University for over seventy years, has authored over 350 research papers published in peer-reviewed journals, as well as many influential books on nutrition, and participated in the development of national and international nutrition policies.  Jim Morris Hicks, an engineer, also took part.   He focused his career on searching for the optimal diet for humans and undertook a comprehensive study of what we eat from a global perspective. He has authored 3 books and over 1400 articles on healthy eating and the climate.   Mr. Hicks now concentrates on waking up the leaders of the world to the climate crisis here on Earth.  The third participant was Steven Disla who plays a prominent role in the Center for Nutrition Studies Food and Sustainability Certificate Program, and has written many articles on the environment and the climate catastrophe. Moderator and facilitator for this webinar was Dr. Michael Holly, the chairperson for the Center of Nutrition Studies medical advisory board.  The following is a synopsis of this interesting webinar along with thoughts about the effects of our own activities on climate change.


The Human Health Piece of the Puzzle

By 1980 the world scientific community, including pioneering lifestyle medical doctors, had completed enough systematic analyses to conclude with certainty that most chronic diseases could be prevented and even sometimes reversed by eating a whole food plant-based diet.

Today, vast amounts of scientific evidence exists that proves, both technically and clinically, that eating animal protein promotes cancer and a diet made up of primarily whole plant-based foods can prevent or reverse most chronic diseases including heart disease and vascular conditions, type-2 diabetes, obesity, cancer and other chronic non-communicable health conditions. (1,2,3,4,5)


The Climate Change Piece of the Puzzle

The UN’s Intergovernmental Panel on Climate Change (IPCC) concluded in 2010 that two activities have a disproportionately large detrimental effect on our planet’s life support systems.  These are;

1 – Animal agriculture, especially the raising of livestock for meat and dairy

2 – The use of fossil fuels

These two activities are on a par with each other because both rise rapidly with increased economic growth.  The UN panel further concluded that a global shift towards a completely plant-based (vegan) diet is vital to save the world from hunger, fuel poverty and the worst impacts of climate change. (6)

We hear over and over again that our dependence on fossil fuels must stop in order to lessen the inevitable escalation of global warming.  Yes, we can make our own decisions about driving an electric vehicle, using public transit, walking or riding our bicycles more often, but much of the world’s fossil fuel use is beyond our ability to alter by any great extent through our own actions.  It seems to be largely unnoticed that the UN’s panel conclusion had two activities that are equal in their ability to cause harm to the environment.  The second large driver of climate change, animal agriculture, is something upon which the daily lifestyle choices made by individual people on Earth can have a significant effect.

The portion of climate change driven by agriculture in general is at least 51%. (7)

On average, on a per calorie basis, the production of animal-based foods requires over 10 times as much land, water and energy as does that of plant-based foods.  For example, the meat and dairy industries alone use one-third of the Earth’s fresh water with a single quarter-pounder hamburger patty requiring 460 gallons of water to produce. (24)  Animal-based food production is an unnecessary use of finite natural resources and is linked to rising greenhouse gas emissions, disappearing water reserves, deforestation, topsoil loss, biodiversity reductions and species extinction. (8,9)

Almost half of all the arable land on Earth is used for agriculture.  Today, 77% of the total land used for agriculture is utilized for raising livestock but it only produces 18% of global food calories and 37% of the total protein required for the human beings living on this planet. (10)

Ten thousand years ago, at the end of the last great ice age, 6 billion hectares of forests covered 45% of the Earth.  Over the last 5000 years, 1.8 billion hectares of forest have been lost with most of the losses occurring during the last 300 years, leaving only about 30% of the Earth forested.  An estimated 75% of global forest losses today can be attributed to deforestation for agricultural expansion. Trees are ecologically important for many reasons, but not the least of them is their role in slowing climate change through the capturing of greenhouse gases like carbon dioxide, thus preventing their accumulation in the atmosphere and warming of our planet. (11)

Biodiversity means the variety and variability of all living organisms on Earth at all levels – genetic, species and ecosystem.  During the last fifty years, there has been a 68% reduction in global biodiversity.  This means a huge number of species have become extinct.  (12,26)  Biodiversity matters because it plays an enormous role in the function, stability and productivity of natural ecosystems and the services they provide.  Loss of biodiversity undermines the ability of nature to support a healthy environment.  (13)

Sadly, this ominous situation is continuing to worsen.  Our world population is now growing by 6 million people every month. (14) Economies are expanding and, over the past fifty years, meat production has more than tripled.  As incomes rise in poorer countries, so does meat consumption and the number of meat-eaters on Earth is continually increasing. (15) And, most worrying, is the absence of responsible global leadership to provide the motivation to fix it.


Connecting the Pieces of the Puzzle

We can no longer deny that climate chaos is upon us.  The increase in catastrophic weather events all over the globe are making this clear.  Temperatures are rising, species are disappearing, and human-driven greenhouse gas emissions are increasingly mounting toward the tipping point.  But there is still hope for the future of our planet, ourselves and our descendants.

In 2019, an updated report from the UN stated that the global consumption of meat must decrease exponentially if we are to curb global warming; lessen the pressures on global land and water; and improve food security, biodiversity and human health.  (16)

A major shift to plant-based diets is predicted to reduce global agricultural land use by 75%, from 4 billion hectares to 1 billion (25).  This result would be accomplished through the lower requirement of land both for grazing and for growing feed crops for the food animals. The regained land could be used for reestablishing forests that capture carbon and slow diversity loss; and for growing crops that directly feed people. (17)

Moving to diets excluding most animal products is predicted to reduce global greenhouse gas emissions by 49%. (18)

Lowering the consumption of animal-sourced products could drop global green water use (moisture stored in the root zone of the soil) by 21% and global blue water use (water found in lakes, rivers, wetlands and reservoirs) by 14%.  Eutrophication (excessive enrichment of water by nutrients spread by the run-off of nitrogen fertilizers and manure) would lessen by 49%.  (17)


Completing the Puzzle

No one believes that increasing the consumption of plant-based foods worldwide is going to be easy.  There is an extremely divided message about nutrition being broadcast out into the world from multiple conflicting interests.  This leads to such a confused mishmash of contradictory information that many people have simply ceased to listen.

For instance, meat, dairy and egg producers spend millions of dollars to fight changes in climate policies.  They have large promotional departments whose major purpose is to protect their business interests by churning out messages about the necessity for things like dairy calcium for bone health or promoting meat or egg protein as better than plant protein.  None of this information has credible science to back it up.  As well, there are companies, small and large, singing the virtues of the food supplements they are selling.  Unfortunately, their information is often skewed to promote sales of their product. Contrary to all this, plants offer a very nutritious source of every nutrient needed for health including protein and calcium. But the idea of eating only plants is very foreign to many.  (19,20)

Waking people up to the truth will take patience and time.  The connection of nutrition with both human health and planetary health needs to be publicized and to come from a credible source. It will be necessary for people to learn about specific plant-based food sources for essential nutrients such as protein; minerals such as calcium, iron and zinc; and vitamins; and to be reassured that all their nutritional needs can be met by plants.  Good communicators and a strong collaborative effort within and among countries are needed to overcome the contradictory messages coming to us from our news sources and to educate people about the health benefits of eating plant-sourced foods for both people and for the planet. (18)

There are other hurdles to conquer too.  A common perception is that plant-based eating is tasteless, time-consuming and complicated. People who adopt the plant-based way of eating know that this is not the case at all.  Cooking classes have been used very successfully at the community level to acquaint people with new cooking methods and easy tasty recipes for preparing plant-sourced food.  Free on-line courses could educate large groups of people about this new-to-them way of eating.  (18,21)

There is also a wide-held belief that eating a plant-based diet is expensive.  In fact, numerous studies have shown that eating plant-based is considerably less costly than eating the current standard western diet, especially if eating at home, emphasizing whole foods and not relying on plant-based meat substitutes as staples.  An investigation from 2021 found that healthy and sustainable dietary patterns could result in a 30% reduction in food costs for those eating completely plant-based; 14% cheaper meals for vegetarian and flexitarian eaters; and 2% lower costs for diets including fish but no meat. (22)

Further to this is the requirement for medical schools to add more and updated nutritional education to their programs.  Historically, med school curricula contain little to no education on nutrition and consequently, physicians lack the nutritional knowledge and counselling skills to guide their patients. In addition, health care professionals may have conflicts of interest and personal prejudices about plant-based eating that bias their views.  (18)

Moreover, it is important that a concerted effort is made to help current farmers transition toward plant-based farming systems.   We have to take care that what replaces our current food system is less destructive, more regenerative and viable.

The bottom line though is that our behaviour must shift.

Climate change is occurring more rapidly than originally predicted and we are running out of time even to just slow it down, let alone to stop it.  But there is the one factor that shouldn’t be overlooked.  Animal agriculture is the only cause of climate fluctuations that can be altered by individuals when they simply choose to eat mostly plant-based foods.  In 2021, a report from Stanford University stated that reducing the consumption of meat and dairy by one person, even by just a little, can have a noticeable effect. Studies have shown that if the whole population of the USA ate no meat or cheese for just one day a week, the ecological impact would be the same as taking 7.6 million cars off the road.  (24)  A 2023 investigation looking into the environmental influence of food choices found that eating fully plant-based lowered the carbon footprint of a diet by five times compared to a standard western diet and by six times compared to a keto diet. (23)

Of course, we can’t have the expectation that the whole world will suddenly stop eating animal-sourced foods completely.  It will be a gradual conversion as people learn more about the benefits of reducing animal foods and eating more plants.  And as the consequences of climatic changes become more intense, the impetus for a transition toward a way of eating that is advantageous for both human health and climate health will surely strengthen too.

What we choose to eat is the leading driver of what makes us sick.  But it is also one of the leading drivers of climate change. The power to change the world is truly in your hands.   Imagine the environmental impact if even 25% of our world’s population transitioned to a fully plant-based diet.  We can only hope that our transformation happens soon.



3 Huang T, Yang B, Zheng J, Li G, Wahlqvist ML, Li D. Cardiovascular disease mortality and cancer incidence in vegetarians: a meta-analysis and systematic review. Ann Nutr Metab. 2012;60(4):233–40.DOI:

4 Song M, Fung TT, Hu FB, et al. Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality. JAMA Intern Med. 2016;176(10):1453–1463. doi:10.1001/jamainternmed.2016.4182

5 Orlich MJ, Singh PN, Sabaté J, et al. Vegetarian dietary patterns and mortality in Adventist Health Study 2. JAMA Intern Med. 2013 Jul 8;173(13):1230–8. DOI:



9 Xu, X., Sharma, P., Shu, S. et al. Global greenhouse gas emissions from animal-based foods are twice those of plant-based foods. Nat Food 2, 724–732 (2021).









18  Gibbs, J., Cappuccio, F.P. Plant-Based Dietary Patterns for Human and Planetary Health. Nutrients. 2022 Apr 13;14(8):1614. Doi: 10.3390/nu14081614. PMID: 35458176; PMCID: PMC9024616.




22  Springmann, M., Clark, M.A., Rayner, M., Scarborough, P., Webb, P. The global and regional costs of healthy and sustainable dietary patterns: a modeling study. The Lancet Planetary Health. 2021;5(11):e797-e807. doi:10.1016/S2542-5196(21)00251-5.

23 Dixon, K.A., Michelsen, M.K., Carpenter, C.L. Modern Diets and the Health of Our Planet: An Investigation into the Environmental Impacts of Food Choices. Nutrients. 2023 Jan 30;15(3):692. Doi: 10.3390/nu15030692. PMID: 36771398; PMCID: PMC9919910.




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Promoting a healthy adventurous lifestyle powered by plants and the strength of scientific evidence.

My name is Debra Harley (BScPhm) and I welcome you to my retirement project, this website. Over the course of a life many lessons are learned, altering deeply-rooted ideas and creating new passions.

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