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A review published in Science has examined the consequences of a high meat diet and says future changes in global meat consumption will have major effects on both the environment and its help.
Dr Cristina Cleghorn, a senior research fellow at the University of Otago says the consumption of processed meat is associated with a higher risk of colorectal cancer and processed and red meat may also increase the risk of cardiovascular disease and type 2 diabetes.
Reducing consumption of processed and red meat could reduce the substantial health loss and costs to the New Zealand health systems those diseases currently caused.
"This new review reports transitioning from high meat to more plant-based diets might reduce global mortality rates by 6% to 10%."
It was possible for people to meet their nutritional needs without consuming meat and substantial reductions in meat intake would have a net positive effect on health, Dr Cleghorn said.
The World Cancer Research Fund recommended people who ate red meat should consume less than 500g a week while the Global Burden of Disease project suggested people eat no more than 100g a week.
New Zealand was economically invested in the production of meat which might be slowing the progress being made towards reducing average meat consumption, she said.
"There is an opportunity for New Zealand to contribute to the production of new plant-based meat alternatives and start the shift away from animal-based agriculture."
Fiona Greig, the head of nutrition at Beef + Lamb New Zealand, said the Charles Godfray paper acknowledged red meat provided a good source of nutrients and diets low in meat might have negative health effects when meat substitutes were not available.
In New Zealand, that reinforced beef and lamb provided an efficient and sustainable source of essential nutrients to the diet which could address nutrient intake needs and nutrient deficiencies including zinc, iron and vitamin B12.
The body of evidence supported a moderate amount of lean red meat within a healthy diet, reinforced by the World Cancer Research Fund report. Overall dietary and exercise patterns were more important than individual foods.
"This underpins the Ministry of Health’s eating and activity guidelines that included 500g of cooked red meat per week."
One of New Zealand’s best known scientists, Dr Mike Joy, now a senior researcher at Victoria University’s school of government, said the Science article contained an interesting section of choices concerning changing diets.
The section on economic assessment using the value of animal agriculture for different countries notably included only gross income and ignored the much more important net income and the cost of externalities.
"The most glaring omission though, was the role of fossil energy in agriculture, not just on on-farm but transport and processing, and especially the massive input of fossil fuel energy in artificial fertilisers."
The huge population growth enabled by the so-called "green revolution" was almost completely driven by fossil fuel-derived nitrogen fertilisers, Dr Joy said.
The vast majority of humans on the planet were dependent on fossil fuel-derived fertilisers and meat production was an inefficient way of transferring the fossil energy to humans.
"The omission of fossil energy is crucial because, notwithstanding the other issues in the paper, feeding 9billion people with meat-based diets anything like today will be impossible, given fossil fuel declines."
University of Otago PhD candidate Garrett Lentz said the consumption of meat, at least when viewed from a global perspective, was one of the most environmentally damaging day-to-day behaviours humans performed.
Mr Lentz’s research is examining the attitudes of New Zealanders to the environmental impacts of meat consumption.
The environmental damage was due to the vast range and severity of impacts tied to the raising of animals for food, including land and water degradation, habitat and biodiversity loss and contribution to pollution, ocean dead zones and climate change.
No matter the driver for change — whether it be for environmental sustainability, improved public health or animal welfare — reduced meat consumption would result in a more efficient food system feeding more people with fewer resources, he said.
Based on findings from his research, it seemed people were unaware of the range and severity of meat’s environmental impacts — at least in comparison with other food behaviours.
Environmental sustainability, as a motivation for reducing meat consumption, was a low priority for the majority of consumers, at least in comparison with other motivations such as monetary and health considerations, he said.
Also, it seemed attitudes and feelings of attachment towards meat were strongly correlated with willingness and intentions to reduce meat in the diet.
There was agreement with potential policy measures that could be implemented to promote reduced meat diets across larger society.
"Based on these results, we believe the next step is to investigate how motivations, attitudes, meat attachment and agreement with policy measures might be shifted among consumers in order to promote reduced-meat diets for environmental sustainability benefits," Mr Lentz said.
University of Otago Department of Human Nutrition Associate Prof Sheila Skeaff took a different approach.
She asked herself why, as a 57-year-old woman living in New Zealand with a PhD in human nutrition and a keen interest in sustainability, she still regularly consumed meat.
"I don’t need to eat meat because I get plenty of nutrients from other foods, such as my morning egg, cereals, plenty of fruits, vegetables and dairy products.
"But I do like meat for all the reasons mentioned in the article."
Prof Skeaff said she did not feel the need to eat meat substitutes because she knew eating a diet high in plant foods, including legumes, was associated with many health benefits.
She had not given up eating meat for the planet, just yet. She still flew around the world and drove a car. She did have a compost bin and recycled as much as she could, trying not to waste food.
As an educated nutritionist, the primary way Prof Skeaff tackled the issue was to eat less meat and fish — rarely for lunch and three to four times a week for dinner.
Little steps, she said.