What is the planetary health diet?
The term ‘planetary health’ was first coined in 2015 to reflect the realisation that natural systems play an important part in the health and long-term survival of the human population. The Planetary Health Diet (PHD) takes this one step further, linking diet with human health and the sustainability of the planet. The principle goal of the PHD is to pave the way for a sustainable food system which supplies healthy, nutritious food to an expanding global population.
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Where did the PHD originate?
The PHD is the result of three years work by the Eat-Lancet Commission and was funded by the Wellcome Trust. Made up of 37 leading scientists from 16 countries, the members of the Commission represent disciplines such as agriculture, environment and public health. The Commission set out to reach a scientific consensus by defining targets which would reflect both sustainable food production and a diet which would promote health.
What are the basics of the diet?
The PHD is best described as a flexitarian diet which is predominantly:
- Plant-based but may include modest amounts of fish, meat and dairy.
- Encourages variation in vegetable and fruit intake by promoting different colours.
- Focuses on unsaturated rather than saturated fats.
- Limits refined grains, highly processed foods, added sugars and starchy vegetables (including potatoes).
- Supplies an optimal calorific intake, which for the average adult is 2500kcal per day, but varies dependent on age, gender and activity levels.
What does a typical PHD plate look like?
In order to illustrate how this might look on a day to day basis the PHD sets out a reference diet as follows:
Protein (daily amount/possible range)
- Nuts (50g/0-27g)
- Beans, chickpeas, lentils etc (75g/0-100g)
- Fish (28g/0-100g)
- Eggs (13g/0-25g)
- Red meat i.e. beef, lamb, pork (14g/0-28g)
- Poultry (29g/0-58g)
- Dairy (250g/0-500g)
Carbohydrates (daily amount/possible range)
- Wholegrains i.e. rice, wheat, oats (232g)
- Starchy vegetables i.e. potatoes (50g/0-100g)
- Vegetables (300g, equivalent to 3-4 portions/200-600g)
- Fruit (200g, equivalent to 2.5 portions/100-300g)
- Added sugars (31g/0-31g)
Fats (daily amount/possible range)
- Unsaturated (40g/20-80g)
- Saturated (11.8g/0-11.8g)
What this means in real terms is you might enjoy one beef burger and two servings of fish per week with the remainder of your protein derived from beans, pulses and nuts. You may include a glass of milk or some cheese or butter each day and just under two eggs per week.
At a typical meal, approximately half of your PHD plate would be covered with vegetables and fruit of different colours; a third made up of wholegrains, followed by plant proteins (beans, pulses), some unsaturated oils with optional but modest amounts of animal protein and dairy and some added sugars and starchy vegetables.
What does the research say?
Adopting a predominantly plant-based diet has been, and continues to be, a well-trodden path, but the PHD is the first study to attempt to formulate a dietary plan which combines the benefits of such a diet for the environment combined with human health.
In evaluating the health benefits, the Commission analysed the potential benefits of dietary change on diet-related disease and mortality and concluded that adopting a diet, such as that outlined by the PHD, may prevent approximately 11 million deaths each year.
It’s widely documented that increasing plant-based foods in your diet offers numerous health benefits. The additional fibre found in plants supports gut health and acts as an important fuel source for the microbes that live there. The lower levels of sugar and refined carbohydrates proposed by the PHD may reduce the incidence of certain metabolic diseases, including type 2 diabetes and heart disease.
That said, the PHD has not been without criticism, with some industry experts suggesting the findings are based on outdated research. An example being the limitations on the consumption of saturated fats, which appear to lie at the crux of the health recommendations to reduce red meat, eggs and dairy.
Others have criticised the diet for proposing unrealistic and dangerously small portions of optional animal-source protein, which poses the risk of nutritional deficiencies. The deficits in question include levels of vitamin B12 as well as retinol, vitamin D and calcium. In response, the Commission claims the PHD is an omnivore diet with approximately two servings of animal-sourced protein per day and they acknowledge that levels of vitamin B12 may need to be supplemented or fortified foods included.
Another important aspect of a healthy diet involves eating food sources of essential fatty acids (omega 3 and omega 6) in optimal balance. The higher levels of plant oils combined with low levels of fish in the PHD is more likely to suggest an unhealthy omega-6 to omega-3 ratio.
In response to these and other criticisms, the Commission cites that they used the best available evidence on diet and human health, and that their conclusions are based on consistent evidence from a wide collection of studies. These include randomized controlled feeding studies, randomized trials assessing weight, randomized trials assessing the risk of a specific disease, and long-term epidemiology studies involving hundreds of thousands of people over a number of decades. However, they note that in certain instances only a limited number of studies were available, such as for randomized trials looking at the risk of specific diseases. This is because of the inherent problem with nutritional research in that clinical trials on diet and human health are often not possible because they need people to adhere to an assigned diet for a long period of time, which has ethical implications.
It’s also worth noting that the Commission emphasises that the reference diet does not imply the global population should eat the same foods, nor does it prescribe an exact diet with the associated potential for nutritional deficits. Instead, it outlines food groups and ranges of food intakes, which when combined in a diet, would support human health.
In this way, the Commission claims the PHD encourages local interpretation so that the culture and demography of the population is reflected. However, in countries like the UK, where average meat consumption is rising, the PHD would require a significant change to dietary habits. This is relevant because for the PHD to achieve its goals, it relies on a large number of the global population to adopt its guidelines.
It’s worth bearing in mind that the reference diet set out in the PHD is aimed at an average moderately active adult and is not relevant to children under two years, older people, pregnant or breast-feeding women and in some cases pre-menopausal women. As with any dietary change, it’s best to speak to your doctor before making any changes, especially if you have an underlying health condition or are on medication.
Want to learn more? Read the summary report.
Keen to try it out? Try these recipes…
Spring greens with lemon dressing
Fennel & celery salad
Herb & garlic baked cod with romesco sauce & spinach
Baked falafel & cauliflower tabbouleh with avocado, pea & feta smash
Cauliflower crust pizza
Aubergine & chickpea stew
Spinach kedgeree with spiced salmon
This article was published on 1 October 2020.
Kerry Torrens BSc. (Hons) PgCert MBANT is a registered nutritionist with a post graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including BBC Good Food.