There has been much debate about quantifying the environmental impact of diet, especially in terms of meat and dairy consumption, with estimates of the proportion of global greenhouse gas emissions resulting from livestock ranging from about 10% to about 51%. Some experts have said that growing awareness of the environmental impact of dietary choices has been a major driver of vegetarianism and meat reduction among consumers.
As part of a special edition in the journal focused on diet and environmental sustainability, Dr Jennie Macdiarmid of the Rowett Institute of Nutrition and Health in Scotland examined whether nutrition advice corresponded with messages about the environmental impact of dietary choices.
She says that while consumption of plant-based protein has increased by 5% in the UK from 1990 to 2006, consumption of meat and protein from animal sources has also increased – by 11%.
“Moving towards a more plant-based diet could have benefits for health and the environment, but changing well established dietary habits dominated by animal-based products will not be easy,” she wrote.
Where health and sustainability collide
She acknowledges that it is challenging to define what exactly constitutes a healthy diet, but previous research has suggested that a healthy, environmentally sustainable diet is possible without eliminating meat and dairy products. However, healthier diets do not always mean more sustainable diets, she said, and a specific conflict exists with recommendations for fish consumption and concerns about future fish stocks.
“Integrating guidance to reduce the environmental impact of the diet with dietary recommendations for health adds a level of complexity but addressing these issues together is essential to ensure clear and consistent dietary messages are given to consumers,” Macdiarmid wrote, adding that efforts to increase sustainable fish supplies, for example, should be coordinated with dietary messages.
Misconceptions
“The most commonly cited diet-related behaviours that people think would be beneficial to the environment are avoiding excessive packaging, purchasing locally produced food, eating organic food and reducing food waste,” she wrote. “Significantly fewer people think changing their diet could have an impact.”
In the context of nutrition, one of consumers’ main concerns about consuming less meat is whether a more plant-based diet would provide enough protein, but relatively very few people in developed countries consume less than the dietary requirement for protein. In the UK, mean daily protein intakes are 88 g for men and 65 g for women, compared to dietary reference values of 55 and 45 g a day respectively.
“Despite these higher than adequate intakes there is a perception among a significant proportion of the population that they should be eating more protein,” she wrote, citing research that found 49% of the US population was trying to boost their protein intake.
“These beliefs need to be changed as they pose a significant barrier to achieving a healthy and sustainable diet.”
Source: Proceedings of the Nutrition Society
2013, Vol. 72, pp. 13–20 doi:10.1017/S0029665112002893
“Is a healthy diet an environmentally sustainable diet?”
Author: Jennie I. Macdiarmid