4 Food for Thought: Moving Toward Sustainable Dining

Dr. Leah Bendell

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BISC 472/854: Ecotoxicology


30 fourth-year and graduate students specializing in Environmental Science or Environmental Toxicology, a fourth-year/graduate-level course; generally taught every second year as an optional course; second-year Ecology and third-year Environmental Toxicology are recommended prerequisites.

Instructor’s Perspective

Central to my teaching philosophy is the conviction that one learns by doing. I believe that one key to learning is the application of knowledge to real-life situations such that what is being taught is directly relevant to the individual who is learning.

Ecotoxicology includes the study of the fate and effects of contaminants within our ecosystems. One approach to understanding this subject is to study the movement or fate of a contaminant through a food web, such as the food web of fish-eating birds of prey, which stretches from algae to zooplankton to fish to the apex predator. This study is then followed by an analysis of the effect of the contaminant on the top predator. The pesticide DDT is a classic example of a contaminant that occurs in almost non-detectable amounts within algae, then biomagnifies with each level of the food web such that toxic effects are observed in the apex predator, resulting in eggshell thinning.

Another approach is to consider the food chain of which humans are the top predator and to follow the fate and effects of contaminants as in the example involving birds of prey—with the difference that the source of the food and the effects are now interpreted within the context of human health. Using this approach, students become engaged in two ways. First, they become aware of the origin of their food and the cost (in terms of energy) of obtaining that food from source to table; in other words, they construct their own food web. Second, they become aware of the contaminant burden that particular foods carry. The direct feedback and understanding that students gain are the potential impact that their food choices have on their health (effect), as well as the true energy cost of bringing a food item from source to table (fate).

Key principles are taught through students’ direct experiences. For example, they may consider the following:

  • Which foods are the most contaminated and why?
  • What are the most prevalent contaminants and what are their health effects?
  • Where does their food come from and how does each food item fit within the concept of a food chain?
  • How much does it cost in terms of energy consumption to bring the dinner to the table?

The format of the course is described below from a student’s perspective. The learning outcomes are provided at the end of the student narrative.

The Experiential Learning Activity

The experiential learning activity involved two potlucks. For the first one, students prepared their favorite potluck dishes with no regard to energy costs or contaminant burden. They worked in teams of four or five, and for each food item each team had to calculate the energy cost of preparing the meal and the contaminant burden that the meal carried. In doing so, they learned the science of ecotoxicology. For example, lipid-rich foods were highest in contaminants such as DDT because of their tendency to partition into fat, whereas leafy vegetables such as spinach contained metals such as cadmium. The students were then challenged to prepare a second dish for which the contaminant burden and energy cost were lower than for the original dish. One student thought he had the edge on this as he had a freezer of moose meat tucked away. However, once he calculated the cost of freezing the meat for the season, it was no longer an energy-efficient source of protein. Ever resourceful, this student rode his bike to the local inlet, borrowed a friend’s rowboat and crab trap, and provided an energy-free, relatively contaminant-free appetizer (cooked crab meat) for his second meal.

Consistent with the goal of providing an engaging learning environment, the very act of participating in a potluck provided a tremendous social element in which students discussed their findings with each other, comparing their dishes with respect to energy costs and contaminant burdens. The exercise created a very interesting dinner conversation indeed in which students exchanged information on just how contaminated or how bad their choice of food was. Such dialogue provided an opportunity for students to exchange the information they had gained through the preparation of their dish. In this way the students learned from each other.

Students’ Perspective

As humans, we are exploiting our natural resources beyond our global capacity, and our current energy demands far exceed a sustainable level. Change is necessary on a global, national and individual scale to prevent the earth from becoming an uninhabitable environment for future generations. As North Americans, we consume the most energy on a per capita basis, and one of the less obvious contributions to our energy burden is the type of food we eat. We take for granted the processes and energy required to produce a wide variety of food and the possible contamination levels present within food products. These processes all require energy and contribute to our over-consumption. The objective of the Ecotoxicology class was to prepare a meal and to calculate the energy and contaminant burden associated with producing that meal. Following this we prepared a second dinner where the goal was to practice sustainable dining; in other words, to lower the energy and contaminant burden as much as possible while maintaining nutritional requirements. By comparing the dinners, we hope to provide people with ideas on how to eat sustainably, and therefore make changes on an individual level towards building a healthier planet.

Students’ Approach

We prepared two potluck dishes; the first dish without any consideration for either energy or contaminant burden, the second with the objective to produce a dish with the lowest energy cost and contaminant burden possible. The energy associated with the production, transportation, storage, packaging and preparation were calculated. The size and diversity of the food industry made it impossible to learn everything about a specific food item. Therefore certain assumptions were made to provide a framework and put logistical limits on the information. One of the concepts included in the assumptions was that of “free energy.” Energy, and therefore a good, was considered “free” if it did not require manufactured energy inputs for production; for example, wild meat, fish, water and home-grown organic goods were considered to involve free energy. It was also assumed that human energy inputs such as manual labour, walking and bicycling were free. Energy was calculated as specifically as possible for each food item, and therefore an assumption was made that the energy required to transport and store each item was proportionate to its weight and size.

The energy and contaminant information was collected from many different sources. Food manufacturers, suppliers and growers were contacted and questioned regarding their energy use to grow or make a specific food item.  Suppliers, such as grocery stores, were investigated to identify the origins of the food products. Transportation companies were questioned to identify the routes they used and the quantities and types of fuel consumed. Literature searches were done to identify the contaminant loading of food items. Online Canadian and international food health information was consulted, along with scientific journals and industry information.

Students’ Findings and Conclusions

One important point learned from this experience was the importance of supporting locally produced food, whether harvested from our own gardens and community gardens or purchased from our local farmers’ market. Locally grown products reduce high transportation costs and energy inputs. Buying goods that are “in season” also helps to support more sustainable agricultural practices. Packaging costs, associated with many ready-made or processed goods, also contribute significantly to the total energy bill of a meal. Plastics, a common ingredient in most commercial packaging, are derived from fossil fuels. The process of producing various plastic wraps, containers and bottles is, in itself, energetically expensive.

Currently, in North America, our total intake of animal protein exceeds what can be indefinitely sustained on a global level. Animal proteins are energetically expensive to produce, as they require large feed, water and commercial fertilizer inputs. Some of these costs can be mitigated, however, if producers choose to raise their stock in a more sustainable manner. Unfortunately, there is little incentive for producers to adopt these less energy-intensive practices as they are currently more expensive economically. In addition to being energetically expensive, meat, seafood and milk products can have extremely high contaminant burdens. This is in part due to the sequestration of persistent organic contaminants in the fatty tissues and the metal accumulation in the organ tissues of animals. When eaten, a portion of this body burden transfers to the consumer. Contaminant loads in a meal can be reduced by consuming less meat, by choosing dairy products with a lower fat content, and by avoiding the consumption of organ meat.

Certain plant crops may also be contaminated when pesticides are applied directly or, depending on their locale, by drifting industrial pollutants. Some plants will uptake and store heavy metals if they are present in the soil. Often, exposure to these various contaminants can be reduced by simply removing the skin or peel. Consumers who are concerned about their contaminant load from food sources need to educate themselves as to how they should limit their intake of certain goods. Unfortunately, clear sources of unbiased contaminant information are not easily found.

Vancouver Sun article

Vancouver Sun article

An Outcome: What Did the Students Take Away from This Course?

To the surprise of all, one outcome of this Ecotoxicology course was an article in Vancouver’s major media outlet, the Vancouver Sun. The article, titled “How Much Energy Does Your Meal Really Take?”, appeared in the science section of the paper and highlighted some of the experiences of the students.

One student commented, “Most of us were surprised. We didn’t think about what we were eating. I know I didn’t think about it at all.” For another student it was more a matter of information and the lack thereof: “People need to take more time to look for the information to eat locally and sustainably. If there was more information and it was more available, especially to people in cities, it would mean a more sustainable community.”


leahbendellDr. Leah Bendell, Professor, Department of Biological Sciences, Simon Fraser University, bendell@sfu.ca




Read, Nicholas (2007). How Much Energy Does Your Meal Really Take? Vancouver Sun.

Update as of January 28 2016

Dr. Bendell did not use the potluck project with subsequent classes primarily because she thought it was too expensive for the students to carry out. Another significant reason for not continuing to use this project is because the idea is no longer novel – the 100 Mile diet has become a more common idea. Dr. Bendell also believes that teaching is dynamic and she changes the way she approaches her courses each time she teaches.

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