Eating for the Planet


Are you confused by all the contradictory dietary advice out there?

Should you go low fat or low carb? Vegan or paleo? Ketogenic? Mediterranean? Pescatarian?

The truth is, it’s extremely difficult to prove that there’s one universal diet that’s superior to all others, certainly in terms of its effects on health and peak performance.

One thing is clear, we shouldn’t be eating the prevailing low quality Western diet, which is high in refined sugar, processed and red meat and saturated fat. This pattern of eating has resulted in 2 billion people being overweight or obese, and has fuelled the increasing prevalence of non-communicable diseases such as type 2 diabetes, cardiovascular disease and cancer (1,2).

In reality, many people will derive significant health benefits if they stick to a few simple, evidence based food principles.

However, if we really want to answer the question of “what should we eat?” then we must also consider planetary health, as this is inextricably linked to our own health and survival.

And when we take the planet into consideration, the answer is very clear: we should eat a plant-based diet.

This is the conclusion of a number large-scale, mainstream scientific studies (3,4,5), including the recently published literature review by the EAT-Lancet Commission (1).

So why is a plant-based diet best for the planet?

To answer this we need to look at our current system of food production, which we now understand to be the single largest contributor to environmental degradation.

Food systems account for up to 30% of global greenhouse gas emissions(1,3,5). However, climate change is only part of the story. Food systems drive a range of serious environmental issues that now threaten human health and survival, including biodiversity loss, eutrophication and depletion of fresh water supplies.

Food production is the largest cause of global land-use change, with 40% of terrestrial land used for crops and grazing. This has resulted in massive biodiversity loss, to the extent that we are witnessing the Earth’s 6th Mass Extinction Event. Species are being lost 100-1000 times faster than the natural background rate. 80% of extinction threats to birds and mammals are due to agriculture (1).

The impact of humans and our agriculture is now so great that it has drastically altered the make-up of global biomass (the total weight of living matter in a given area).

Humans comprise just 0.01% of Earth’s total biomass, but our impact is disproportionately large; 96% of all mammals are either humans (36%) or our livestock (60%) – mainly cattle and pigs. Only 4% of mammals are wild. 70% of all birds on the planet are farmed poultry. Only 30% are wild (6).

Food production is responsible for 78% of eutrophication (1,5). This refers to the excessive application of nitrogen and phosphorus fertilisers, which are washed off into streams and rivers, causing algal blooms and hypoxic conditions in freshwater and marine ecosystems, which results in widespread coastal “dead zones,” devoid of aquatic life.

In areas where fish still exist, 60% of the world’s fish stocks are now fully fished, and 30% are overfished. Catches by global marine fisheries have been declining since 1996 (1).

The overall negative impacts of our food systems are very clear, but we still need to eat. So what we really want to know is: which food products are ecologically sustainable, and which are harmful.

To answer this, Joseph Poore and Thomas Nemecek performed the largest study to date of the impacts of agriculture on the environment, and their results were published in Science in 2018 (5).

They undertook a global analysis of data from 38,700 farms in 119 countries, looking at 40 food products, in terms of their effects on five key environmental indicators: greenhouse gas emissions, land use, acidification, eutrophication and freshwater withdrawals.

They found that even the most sustainable animal products exceed the average impacts of plant protein. As a result, if we were to switch to a plant based diet, it would reduce land use by 76%, greenhouse gas emissions by 49%, acidification by 50%, eutrophication by 49% and freshwater use by 19%.

In countries such as the UK, Australia and the USA, where meat consumption is 3 times the global average, the effects would be even greater.

The authors concluded that moving from a meat-based to plant-based diet has “transformative potential” and that avoiding meat and dairy is the single biggest way we can reduce our ecological impact.

But what exactly should we eat? What does a diet that is both healthy and ecologically sustainable look like?

This key question was finally addressed by EAT-Lancet Commission (a joint project by the Norway based NGO EAT and the Lancet Medical Journal), which undertook an extensive literature review and published its results earlier this year (1).

They came up with a universal healthy reference diet, or Planetary Diet, which is predominantly plant-based, provides 2500 kcal per day, and consists largely of vegetables, fruits, whole grains, legumes, nuts and unsaturated oils. It specifies a low to moderate amount of seafood and poultry, and no or low amounts of red meat, processed meat, added sugar, refined grains and starchy vegetables.

In practice, the Planetary Diet is similar to a Mediterranean or Okinawan Diet, which for many Europeans represents quite a shift in the way they eat. It would involve a 77% reduction in red meat consumption (by allowing only 1 beef burger per week), 15 times more intake of nuts and seeds, 2 servings of fish per week, 1-2 eggs per week, and 1 glass of milk per day (or 250g of full fat milk products).

So, having read this, are you now going to adopt the Planetary Diet, or perhaps go completely vegan? Maybe not…

Behavioural change is notoriously difficult. Even if there was widespread acceptance of the problems associated with our current level of consumption of animal products, awareness of an issue is no guarantee that people will adopt a more sensible path, as most health practitioners will attest.

This is certainly true for plant-based dietary change, probably because for many societies, eating animal products is the traditional, dominant eating pattern. A rejection of meat represents a rejection of social norms. It’s also important to appreciate that food confers much more than nutritional needs. It’s a source of pleasure, personal identity and economic status. In many developing countries eating meat is aspirational and symbolic of wealth. For some people, meat is associated with masculinity.

This is borne out by studies of public perceptions surrounding food impacts and dietary change, which suggest that there can be scepticism of the scientific evidence, resistance to the concept of reducing meat intake, and that non-food related behaviour change is deemed more acceptable (7).

However, eventually a threshold is usually reached, beyond which our resistance to change is overpowered by the realisation of the gravity of a situation, accompanied by a sense of urgency; such as when a patient receives a diagnosis of a life-threatening condition and finally feels compelled to make radical lifestyle changes. Perhaps as a society we are approaching that point with environmental degradation and non-communicable diseases.

Recently it feels as if the tide may be turning, with the global support for Greta Thunberg and the climate strikes, the Extinction Rebellion protests, and the increasing cultural acceptability of plant-based eating.

Make no mistake, we have very little time left to limit climate change to a survivable level and prevent further irreversible biodiversity loss. We urgently need to make transformative changes if we hope to do this, and there is no doubt that a global shift towards healthy, plant-based diets represents a very powerful tool.

If you still need some convincing, or are finding it difficult to make the leap to a more plant-based lifestyle, here are a few tips and suggestions:

First, watch the movie “Cowspiracy” (you can find it on Netflix).

Start experimenting with plant-based eating. There are now tonnes of resources out there (even confirmed omnivorous chefs such as Hugh Fearnley-Whittingstall and Jamie Oliver are jumping on the bandwagon). The key is to find a tribe that suits you.

Personal favourites:

  • River Cottage Veg Everyday and Much More Veg
  • The Happy Pear
  • Thug Kitchen (Eat like you give a f*ck)

Get inspired and check out some incredible plant based athletes, for example:

  • Rich Roll
    • Ultra-endurance athlete
    • Author of Finding Ultra
    • Host of The Rich Roll Podcast
  • Scott Jurek
    • Elite US ultrarunner
    • Author of Eat and Run


  1. Willett W, Rockström J, Loken B, Springmann M, Lang T, Vermeulen S, et al. Food in the Anthropocene: the EAT–Lancet Commission on healthy diets from sustainable food systems. The Lancet. 2019 2019/02/02/;393(10170):447-92.
  2. Afshin A, Sur PJ, Fay KA, Cornaby L, Ferrara G, Salama JS, et al. Health effects of dietary risks in 195 countries, 1990–2017: a systematic analysis for the Global Burden of Disease Study 2017. The Lancet. 2019;393(10184):1958-72.
  3. Aleksandrowicz L, Green R, Joy EJM, Smith P, Haines A. The Impacts of Dietary Change on Greenhouse Gas Emissions, Land Use, Water Use, and Health: A Systematic Review. PLOS ONE. 2016;11(11):e0165797.
  4. Clark M, Tilman D. Comparative analysis of environmental impacts of agricultural production systems, agricultural input efficiency, and food choice. Environmental Research Letters. 2017 2017/06/01;12(6):064016.
  5. Poore J, Nemecek T. Reducing food’s environmental impacts through producers and consumers. Science. 2018;360(6392):987.
  6. Bar-On YM, Phillips R, Milo R. The biomass distribution on Earth. Proceedings of the National Academy of Sciences. 2018;115(25):6506.
  7. Macdiarmid JI, Douglas F, Campbell J. Eating like there’s no tomorrow: Public awareness of the environmental impact of food and reluctance to eat less meat as part of a sustainable diet. Appetite. 2016 2016/01/01/;96:487-93.


Doctors as environmental advocates

By Tim Smith

As we destroy nature, we destroy ourselves. It’s a selfish thing to want to protect nature

– Yvon Chouinard (American climber, environmentalist and businessman)

Humans are not separate from nature, but part of it. As a society, we urgently need to relearn this concept, for the sake of our health.

It’s well established that our survival depends on intact ecosystems and biodiversity (the variety of life on earth). They provide us with essential life-support services such as food, clean air and water, healthy soil, medicines and disease regulation.

However, we don’t just need nature to survive, we also need it to thrive: there is now a growing evidence base to support what we intuitively already know; that our physical and mental health and wellbeing are dependent on interacting with a healthy natural environment.

Despite this, our society tends to treat the natural world solely as a resource to be exploited for our benefit. This shortsighted, extractive philosophy has resulted in the numerous environmental crises we face today: climate breakdown, ecosystems collapse, air and water pollution, biodiversity loss, deforestation, industrial fishing, intensive agriculture and plastic waste. These are all detrimental to human health and some threaten our very survival.

Air pollution for example, is a massive global public health issue. Pollutants from vehicle emissions, industry and fossil fuel combustion are responsible for millions of deaths worldwide from cardiovascular disease, asthma and lung cancer. It is also thought to be a risk factor for neurodevelopmental problems in children and neurodegenerative diseases in adults.

Climate change is said to be the biggest global health threat of the 21st Century, causing food and water insecurity, morbidity and mortality from heat waves, droughts and floods, and mental health problems arising from such extreme events.

Biodiversity loss is a less well-publicised, yet incredibly important health problem. Biodiversity refers to the huge variety of life on earth; not simply species, but also genes and ecosystems.

It’s estimated that there are about 15 million species on Earth; so far we’ve identified approximately 1.9 million. The background or natural extinction rate of species is approximately 1 per million per year, however the current extinction rate is thought to be 100-1000x greater than this due to human activity.

This level of global biodiversity loss is massive and unprecedented. We are in the throes of the earth’s 6th mass extinction event, however for the first time it is caused by human activity: mostly by habitat destruction on land and in the oceans through deforestation, bottom trawling, damning and dredging of rivers and drainage of wetlands. There are other human caused drivers such as pollution, the introduction of invasive species and climate change, which is likely to exceed habitat loss as the most significant threat in the not too distant future.

Why should all this matter to us, aside from the fact that we have a moral obligation to act as stewards of the natural world?

Biodiversity underpins ecosystem function and is therefore essential for providing all the life-support services mentioned above. It also represents a huge, mostly untapped source of potentially life-saving drugs and medical research. Over half of all drugs developed over the past 25 years are either derived directly from, or modeled after natural compounds: morphine, aspirin, warfarin, antibiotics, chemotherapy drugs, ACE inhibitors and AZT, to name but a few.

Despite the many medical breakthroughs we’ve derived from nature, we’ve barely begun to scratch the surface of what it has to offer mankind, yet we continue to allow our greatest repositories of biodiversity to be degraded or even lost forever. Rainforests are being cleared at alarming rates for agriculture, cattle ranching and timber; 17% of the forest in the Amazon has been lost over the past 50 years. Coral reefs are being destroyed by ocean warming and acidification, as a result of climate change. Who knows how many potentially life-saving discoveries have been wiped permanently from existence?

When we start to view environmental problems in this way (i.e. as a public health emergency), it becomes clear that those of us in the healthcare industry have a responsibility to start addressing environmental degradation.

As healthcare practitioners, we are ideally placed to educate our patients, students and the public about the inextricable links between the environment and human health; to promote sustainable, low carbon behaviour; and to convince policy makers that robust environmental legislation is urgently required, as is health promoting infrastructure, such as active travel networks and access to urban green spaces.

If we’re going to start engaging in environmental advocacy, then we’ll have to adopt an evidence-based approach where possible, as we do for the rest of our practice. However, in the face of life threatening problems, it is inappropriate to postpone preventive measures while we wait for full scientific certainty. This is known as the precautionary principle, and it is a key component of environmental decision-making.

Having said that, much evidence now exists to support the assertion that our physical and mental health depend on our interaction with nature. A variety of studies suggest that contact with nature reduces mortality from all causes, alleviates stress, improves mood and self esteem, increases levels of physical activity, increases concentration, reduces symptoms in mental health patients and children with ADHD, and reduces indicators of physiological stress such as pulse rate, blood pressure and cortisol levels.

Urban greenspace (i.e. any vegetated land such as parks, gardens, woods and wetland within an urban area) has also been shown to increase social interaction, reduce health inequality, reduce crime rates, and improve air and noise quality. Interestingly, it’s thought that as the species richness of an area increases, so do the psychological and physical benefits.

At this stage, although extensive, the evidence is of varying degrees of quality. Some of it is short term, with surrogate end points, sampling bias and self reporting. Most of it is correlational. It also tends to be biased towards higher latitudes (ie. North America and Europe) and Western Societies. Clearly there is more work to be done, however, the overwhelming majority of these studies show a positive association between interaction with natural environments and human health measures.

Of course, if health professionals are going to take a leadership role in advocating environmental protection and promoting sustainable, healthy, low-carbon behaviour, then we also need to get our own house in order. The NHS is a major emitter of CO2, and is responsible for approximately 25% of total public sector emissions. It also generates huge amounts of waste, the vast majority of which ends up in landfill.

The healthcare industry has the opportunity to set an example to the rest of the population:

We could build energy efficient hospitals powered by renewable sources, incorporating green space for patients, staff and the local community to use for exercise, rest and relaxation. We must significantly reduce our waste through more appropriate procurement, waste segregation and recycling. Hospital should be sourcing healthy, seasonal, local food; promoting active travel and public transport for staff and patients; and providing incentives for staff to reduce their ecological footprint.

I’ll leave you with a final quote to ponder:

The future will be green, or not at all

– Bob Brown (Australian politician, environmentalist and doctor)

Rewilding Scotland – can we live with the big, bad wolf?

Rewilding can be a pretty divisive issue, particularly when it involves top predators such as wolves and lynx. As you might expect environmentalists are generally enthusiastic, whereas many rural landowners oppose this alternative approach to land use. The general public appear to be fairly ambivalent, and understandably it’s not at the top of many people’s priority list.

However, it’s a fascinating subject and it’s importance is arguably under appreciated.

Rewilding is already occurring in many parts of the world. In mainland Europe, in recent years, there’s been the spontaneous and supported return of many previously threatened species such as bears, wolves, beavers, lynx, ibex and eagles. In North America, wolves were reintroduced to Yellowstone National Park in 1995, after a 70-year absence.

However, these changes have not been met with universal approval, and in certain areas have resulted in conflict and controversy.

So, can the age-old antipathy between wolves and humans be overcome in the UK? Could we see wolves roaming the Scottish Highlands in the not too distant future?

What is rewilding?

The idea behind rewilding is that reintroducing large predators back into ecosystems that they once inhabited, allows those ecosystems to regenerate.

This finding is based on the concept of trophic cascades. A classic example of which is the changes that were observed in the landscape when wolves were returned to Yellowstone:

As predicted, the wolves started to prey on the elk, which reduced their numbers and hence their grazing pressure. Understandably, elk also started to avoid areas where they were likely to be eaten, such as next to streams. This led to increased growth of riverside species such as aspen and willow, which in turn led to reduced riverbank erosion and allowed bird and beaver populations to increase, which led to a rise in fish and otter numbers, and so on through the ecosystem.

Given these impressive regenerative effects and the fact that our neighbours are all at it, why not do the same in the UK? Indeed, why doesn’t rewilding already form a part of mainstream conservation policy?

Rewilding the UK

The UK is in many ways an ideal candidate for rewilding. Its upland areas have undergone centuries of degradation, thanks to clearing of native forest and overgrazing by sheep (in England and Wales) and deer (in Scotland). This has resulted in a fairly barren landscape of heather moorland, lacking in biodiversity and depleted of ecosystem services.

Rewilding would have different aims and strategies in various parts of the UK, but in Scotland it means the return of native Caledonian Forest, ideally replete with wild boar, lynx, beaver and of course, wolves.

In terms of feasibility, Scotland is the only area of the UK that could support a wolf population. One study calculated that, given the minimum viable population number to maintain genetic variability for wolves needs to be around 200, and based on a typical wolf population density of 2 per 100km2, then an area of at least 10,000km2 of suitable habitat would be required.

This exists in the Scottish Highlands, but unlike Yellowstone, much of this land is in the hands of private estate owners who run deer and grouse shooting businesses, and thus may not take too kindly to this new addition to their property.

Having said that, deer numbers are so great in the Highlands that culling is required in order to meet Deer Commission targets; so by preying on deer, wolves may even be of economic benefit to these estates.

In terms of human population and road densities in the Highlands, both are comparable or lower than those in European and North American areas where wolves exist.

Other reasons to reintroduce wolves…

In addition to the ecosystem benefits, there are several other justifications that could be used to help win over a sceptical Scottish public:

Wolf-spotting ecotourism: research shows that the economic benefits to local communities of eco-tourism exceed traditional land management practices, such as agriculture and deer stalking.

Moral obligation: do we have a moral duty to restore extirpated species to their natural habitats? This is a philosophical argument, and many would counter that wolves don’t actually care that they’ve been removed from the UK.

Human Health: there is now a great deal of evidence that links environmental degradation with adverse effects on human health. Restoration of ecosystem services through rewilding would provide clean air, clean water, healthy soil, reduce the risk of flooding and help mitigate climate change, all of which are vital for our health and wellbeing.

Despite these benefits, opinions about wolves are mixed. In North America, the majority of the general public do support wolf reintroduction, with approximately 60% in favour. In Europe however, this is not the case, with a paltry 36% of the UK being supportive. In rural communities, support is even lower.

Resistance is most likely to be due to three things:

1. Conflict with vested interests (threats to livestock):

Farmers and other landowners have been the most vocal group in their criticism of rewilding in Europe and North America.

In the Pyrenees, thanks to depopulation of rural areas, coupled with government conservation projects, previously threatened species now thrive, such as bears, wolves, beaver, marmots, feral goats and deer.

Unfortunately, but somewhat inevitably, these wild animals have entered farms, grazed, preyed on livestock and spread disease. These effects, coupled with the fact that many of these animals are now protected species, have resulted in the perception that conservation and ecotourism are valued above the welfare of local communities.

In Sweden and Norway, the wolf population died out in the 1960’s through hunting, but the area was then naturally recolonised from Finland in the 1980’s, and now a Scandinavian population of around 380 exists.

Despite being a protected species according to the Bern Convention on the Conservation of European Wildlife and Habitats, it is estimated that 50% of wolf mortality here is due to poaching. The source of conflict is moose hunting, a popular activity in Sweden. Wolves prey on moose and reduce their numbers, but also kill the hunting dogs, which makes them deeply unpopular amongst many Swedes.

Farmers would probably be the biggest losers if wolves were re-established in Scotland, as there would undoubtedly be attacks on livestock, as has occurred in Europe. However, in countries where wolves have been reintroduced, it has been estimated that they are only responsible for around 1% of livestock deaths, and compensation schemes have been set up which remunerate farmers whose livestock are killed in this way.

2. Cultural attitudes (threats to humans):

The negative folklore and mythology that surrounds wolves should not be underestimated as a barrier to their reintroduction. We do not have to look far for evidence of the wolf’s image problem. Consider the sayings “a wolf in sheep’s clothing,” or “keeping the wolf from the door,” and fairytales such as Little Red Riding Hood and The Three Little Pigs. We are conditioned from childhood to believing that wolves are our mortal enemy.

However, this reputation is not backed up by evidence. Wolves have been known to kill humans, but these events are so rare that the risks are difficult to quantify. Attempts at quantification usually invoke comparisons with the chances of being struck by lightning or killed by a vending machine.

3. Old fashioned, entrenched policy:

One of the many interesting things about rewilding is that it makes you look at familiar landscapes through a new lens. The Scottish Highlands are portrayed by conservation groups, guidebooks and the media as one of the last remaining areas of wilderness in Europe. However, the reality is they are anything but wild, having been intensively managed by humans for centuries. How have we allowed this misconception to be perpetuated?

According to George Monbiot, it’s because of ‘Shifting Baseline Syndrome.’ Each generation perceives the state of ecosystems they experienced in their youth as normal, and thus the benchmark to be maintained, when in fact, they were already in a state of severe degradation.

In the UK, this has resulted in conservation groups going to great lengths to maintain a landscape that, in terms of biodiversity, is fairly barren and monotonous, when compared with its former glory that rewilding seeks to restore.

So what is the solution in the UK?

Many of our neighbours in Europe and North America are living with wolves, bears and lynx, and are actively pursuing further rewilding goals.

Australians are certainly no stranger to co-existing with potentially dangerous species such as snakes and spiders, crocodiles, sharks and jellyfish. Why are we reluctant to follow suit in the UK, given the potential benefits described above?

I think we have become used to living in our safe, green and pleasant land, with rolling hills, intensive agriculture, sheep, deer and not much else. But it was not always this way and does not have to remain so. We could re-introduce wolves fairly quickly if the will was there, but this would require a number of things to happen first:

There needs to be government support for wolf reintroduction, and for rewilding to become official environmental policy.

There must also be genuine support from the general public. To achieve this, wolves will need an image makeover, through effective campaigns that present an exciting new vision of a rewilded Britain.

Crucially, there needs to be cooperation from farmers and estate owners in the Scottish Highlands. There is some evidence that estate owners are less opposed to rewilding than farmers, as they may even benefit financially through eco-tourism and negation of the need for costly deer culls.

Convincing farmers and the National Farmers Union may prove to be the most challenging aspect, and this would certainly include providing financial compensation for any livestock that were killed by wolves.

However, providing incentives is equally important, and it’s been suggested that instead of receiving subsidies for grazing sheep, farmers could be paid for rewilding services such as planting native trees.

Personally, I would be happy to see wolves reintroduced to my native country, not only for the reasons given above, but also simply because it would be thrilling to have them here. I regularly explore the Highlands to walk and climb, and the idea of wolves being out there only makes the landscape seem more appealing.

From a purely rational viewpoint, if done properly, rewilding with wolves could have widespread benefits: ecosystems regenerate, biodiversity thrives, local communities prosper from eco-tourism, farmers are rewarded, our guilt is assuaged, flood risk is decreased and carbon dioxide is sequestered!

However, I totally appreciate that not everyone shares these sentiments!

What do you think? Could you live with the big, bad wolf?