What is the planetary health diet?
We delve into the planetary health diet – what it is, where it originated and what it means for us and the planet
What is the planetary health diet?
The term ‘planetary health’ was first coined in 2015, referring to the natural systems that play a crucial role in the health and survival of the human population. The Planetary Health Diet (PHD) takes this one step further, linking diet with our long-term health and the sustainability of the planet. The principal goal of the PHD is to pave the way for a sustainable food system which supplies healthy, nutritious food to an expanding global population.
Where did the PHD originate?
The PHD was created by the Eat-Lancet Commission and 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 targets that were to take into account both sustainable food production and a healthy diet.
How does the PHD work?
The PHD is best described as a flexitarian diet that 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 depending on age, gender and activity levels
How to follow the PHD
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’s the evidence for the PHD?
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 that combines the benefits of such a diet for the environment in tandem with human health.
The Commission claimed the potential benefits included preventing approximately 11 million deaths each year, caused by diet-related disease.
Is the PHD healthy? Our nutritionist’s view….
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 randomised controlled feeding studies, randomised trials assessing weight, randomised 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 randomised 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.
Does the PHD work for weight loss?
The PHD has not been designed for weight loss. The main objective of the diet is to combine the sustainability of the planet with a diet that maintains human health.
Who should not follow the PHD?
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.
You can learn more from the summary report.
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This article was reviewed on 23 October 2023 by Kerry Torrens.
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.
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