December 27, 2018

‘Food Forum’ brings experts together to tackle sustainable diets

‘Food Forum’ brings experts together to tackle sustainable diets

What makes a diet sustainable? Participants at the National Academies of Sciences, Engineering and Medicine (NASEM) Food Forum tackled this question at a two-day workshop in August. Proceedings of this workshop have now been published by NASEM, and the brief report sheds light on how food system experts view sustainability.

Two major themes come across in the proceedings. First was the view that no one food item is perfectly sustainable in all ways (environmentally, healthy-wise and economically). Second was the need for experts to work closely with policy makers to quickly respond to shifts in the food system.

One animal scientist was among the speakers: Frank Mitloehner of the University of California, Davis. Mitloehner spoke on day two and provided crucial context to the data showing the impact of animal agriculture on the environment.

The workshop was split into four sessions. The first session focused on the “complexities and compromises” needed in the move toward sustainable diets. Adam Drewnowski, University of Washington, kicked off the session by emphasizing that a truly sustainable diet is not just healthy and environmentally friendly but also economically sustainable. Few foods check all the boxes for sustainability. Drewnowski used sugar as an example, noting that while sugar production is environmentally friendly, sugar is clearly not as healthy as other foods. He advocated a closer look at overall eating patterns, rather than the sustainability of individual foods.

Parke Wilde, Tufts University, wrapped up session one with his perspective on how to balance the different demands of sustainability. He said food prices are a big factor driving decisions around sustainability. “For example, decisions surrounding land conservation (e.g., whether to withhold land from agricultural production) are easier to determine in a low-priced environment, whereas decisions about incentives to reduce food waste are easier to conduct in a high-priced environment,” reports NASEM.

For session 2, participants focused on how we can measure sustainable diets—from production through consumption. One issue that came up was the possibility of a shift toward more plant-based diets. Updated research on animal contribution to environmental pressures were not discussed in depth until day two of the workshop.

Ashkan Afshin, Institute for Health Metrics and Evaluation, University of Washington, began with an overview of his work, which seeks to estimate fruit, red meat, and other dietary intakes at the population level in regions around the world. These estimates can reveal interesting consumer behavior, such as how people replace a food in their diet when it is recommended that they reduce their consumption of that item.

David Tilman, University of Minnesota, took a close look at the environmental pressures of plant-based diets versus diets with more animal products. He said more needs to be done to reduce pollution into waterways from animal feed production and animal facilities. Water pollution and greenhouse gas emissions are already driving climate change, he said, but the effects could be mitigated with a shift to more plant-based diet, according to data he shared from several studies.

Speaker Mark Rosegrant, International Food Policy Research Institute (IFPRI), again touched on the economic aspects of sustainable diets. He discussed a modeling system that suggests that while meat consumption is expected to increase, driving up prices worldwide. The system could be more sustainable if people in currently high-meat-consuming countries reduce their intake, he said, which would reduce meat prices in countries with a growing demand.

The third session focused on how policy and program changes can drive sustainability and healthy diets. Marco Springmann, Oxford University, presented his research using a modeling system that suggests that while balancing environmental and health needs is possible in many high- and middle-income countries by 2030, “even with advances in technology, it would be practically impossible in much of the rest of the world to reduce diet-related premature mortality while also reducing environmental impacts.”

Even in countries where sustainability is possible, policymakers and scientists can’t drive sustainability alone. Jennie Macdiarmid, University of Aberdeen, said it is "absolutely key” to consider the reality that people don’t just choose foods based on health or environmental sustainability—instead, we eat what we like to eat. In the same session, Janet Ranganathan, World Resources Institute, highlighted the need to appeal to people based on their existing food habits. For example, marketers have figured out that they can sell more soy milk by putting it on the shelf next to in the refrigerated section, where people already go for their milk—even though soy milk does not need refrigeration.

The fourth session focused on the innovations needed to support sustainable diets. The session began with a closer look at animal production. Frank Mitloehner, University of California, Davis, shared a “fact or fiction” presentation on the environmental impact of the livestock industry. He explained that reports like the 2006 paper Livestock’s Long Shadow have not used the same measurements to compare livestock greenhouse gas emissions to car emissions, for example (livestock emissions for example were measured from the start of the production cycle to consumption, while car emission data did not account for emissions from the production process). He also pointed out that while livestock production does use a large amount of farmland worldwide, much of this space is classified as “marginal” for crop production.

With this data put in context, Mitloehner said a lot can be done to make livestock more efficient in developing countries. For example, a dairy cow in the United States produces about 20 times more milk per year than a dairy cow in India. Innovations in animal science and production could address that inefficiency. “The more efficient you are in agricultural production,” Mitloehner said, “the relatively smaller your environmental footprint.”

Another innovation presented was work from Nicole Tichenor Blackstone, Tufts University, looking into the impact of strengthening local supply chains, which would reduce the environmental pressures of transporting foods. Blackstone also pushed for more research into using food waste in animal feed to further improve the sustainability of meat production.

The workshop concluded with a panel moderated by Eric Olson, Natural Resources Defense Council.

A free pdf of the workshop proceedings is available at