It might seem like a virtuous choice - but munching lettuce is worse for the planet than eating bacon, a study claims.
Researchers say the amount of energy and water used - and the level of greenhouse gases produced - is far greater per calorie for lettuce than pork.
The US study took into account environmental costs associated with planting, growing, processing, transporting and storage.
The findings, from Carnegie Mellon University in Pittsburgh, prompted dismay from environmentalists who insist farming livestock harms the atmosphere more than growing crops. Critics claimed the comparison is unfair - because you would need to eat a carrier bag full of low-calorie lettuce to match the energy found in four rashers of bacon.
Richard Bennett, dean of food research at Reading University, said: "The calorie is not the most sensible functional unit of comparison."
The study, in the journal Environment Systems and Decisions, claims fruit, vegetables, dairy products and seafood require more resources to produce the same amount of calories than most forms of meat.
Author Professor Paul Fischbeck said: "Eating lettuce is over three times worse in greenhouse gas emissions than eating bacon."
But the study conceded that eating fewer calories would lead to better public health, benefiting the environment and cutting energy use.
- Daily Mail