Trilemma - a quandary posed by three alternative courses of action.


“Agriculture is having increasingly strong global impact on both the environment and human health, often driven by dietary changes.”

This is the opening sentence of an article written by the two scientists, David Tilman and Michael Clark. In their paper they don’t present new research data they generated. Instead, they present a thorough analysis of existing data, a collection of 50 years of data from 100 nations regarding dietary trends and the inter- relations of diet, health and the environment.

So, why did the prestigious magazine, Nature find it important to publish this article? The reason is the strong conclusions of their analysis about the projections of the dramatic impact of diet on human health and health of the environment. Diet – Health Linkage Tilman and Clark compared three alternative diets:
  1. Mediterranean diet – centered on fruits, vegetables, seafood, olive oil, grains
  2. Vegetarian diet – grains vegetables, fruits, eggs, dairy.
  3. Pescetarian diet – a vegetarian diet that includes seafood

And a reference diet: Omnivorous diet – a conventional global diet.

Relative to the conventional omnivorous diet, Tilman and Clark found a substantial decrease in the incidence of several chronic diseases of people on the three alternative diets. For example, incidence rates for type 2 diabetes were reduced by 16% (Mediterranean diet) and 41% (vegetarian); relative rate of mortality from coronary diseases was down by 20-26%; cancer 7-13% and all-cause mortality was down by 0 – 18% as compared to the reference diet.
All three alternative diets, as compared to the conventional diet are rich in fruits and vegetables, nuts, legumes and are low in meat and refined sugar. Global changes towards these alternative diets can have a significant positive impact on our environment.
Diet – Planet Linkage  

Global agriculture and food production is responsible for about 25% of green house gases (GHG) emission. About one half of ice-free land is used for food production. The amount of GHG emission linked to meat production is dramatically higher than for plant –based food products. Tilman and Clark found that production of one pound of beef protein causes 250 times the GHG emission as compared to the production of one pound of legume-derived proteins. Or another way for comparison, 20 servings of vegetables correspond to less GHG emission than one serving of beef. 

Diet Changes --> Health --> Environmental Impact
 Changes towards healthier diets can have a significant positive effect on the health of our environment.
Tilman and Clark added all key factors that may contribute to GHG emission if the current cultural and diet trends continue to 2050. During this period, increase in global population by 36%, together with increase in dietary shift towards meat consumption, will cause an increase of estimated 80% in GHG emission from food production.

This increase in emission is equal to the total 2010 global transportation emission. Furthermore, a substantial increase in land needed for agriculture will be necessary. A global shift from the omnivore diet to the alternative plant-based diet can dramatically slow down this trend.

The Scientists estimate that this global diet change with several other changes (such as reduced wastage of fresh produce) will reduce agriculture derived GHG emission by 30-60 % and reduce land usage by 20-30%.

And as predicted before: 

Nothing will benefit human health and increase chances for survival of life on Earth as much as the evolution to a vegetarian diet.   
Albert Einstein 

  1. David Tilman and Michael Clark, “Global diets link environmental sustainability and human health”, Nature, 515, 518 (2014)
  2. Elke Stehfest, “Food choices for health and planet”, Nature, 515, 501 (2014)
Image credit: ‪