U.S. agriculture has long known the value of science, helping increase productivity, combat pests and diseases and guide rational regulation. Of increasing interest, however, are cultural values different people attach to the way food is produced, marketed and consumed.

The recent appointment of Angela Tagtow as executive director of the U.S. Department of Agriculture’s Center for Nutrition Policy and Promotion (see related story on Page 18) may bring this issue to the fore again, this time in connection with the Dietary Guidelines. Should those guidelines reflect just nutrition science? Should they extend to broader issues, like how food is produced? Or should they reach to how some people want their food produced? Finding the right mix of science and cultural values is a challenging task.

Healthy eating

One aspect of that challenge is illustrated by Ancel Keys’ research a half century ago, which claimed to establish a causal link between high cholesterol foods and heart disease. Time magazine put him on its cover, and public health policy for decades steered us away from red meat, whole milk, eggs and cheese, among other foods. Now we are learning that Keys’ research used data selectively and discounted contrary evidence. Subsequent science has put many of those “bad” foods back on our plates.

Obesity research offers similar opportunities for selectivity. Many biophysical, social and economic factors interact in modern society to drive rising rates of obesity. Singling out specific ingredients — like sweeteners — or foods — like calorie-dense ones — may be part of the causal network, but such single factors are incomplete explanations. More science and fewer cultural warriors will help bend and reverse this trend.

Animal welfare

Protecting the health and well-being of food-producing animals also has become an area where science and values have come into conflict. Many ideas have been advanced for improving animal welfare — including cage-free poultry, grass-fed beef or breeding sows with room to move around. Measuring scientifically the results of such alternatives to conventional practices is difficult. How should trade-offs be made across multiple effects, such as sanitation, cost, injuries, contamination of products, etc.? With uncertainties and multiple considerations to weigh, the science becomes more challenging (and expensive), leaving room for cultural values to drive or displace science.

If non-scientific value judgments are going to play a growing role in the food system, which certainly is happening in most developed countries, then research that captures the full dynamics of the system will become more critical for well-informed decisions by regulators, consumers and producers. What all should want is science-driven value judgments, not value-driven science.

Sustainable agriculture

Sustainability already has become an elusive and ill-defined concept. To some, it means what the dictionary says — processes that can continue for a long time. To others, it means what they want to see happen, often based on emotions or cultural values rather than sound science.

Which path will be followed has become more topical with the announcement July 8 of “Field to Market,” the Alliance for Sustainable Agriculture. This is a multi-stakeholder initiative that focuses on U.S. crops, traces impacts at field and regional levels and supports claims about supply chain practices. Involved are input providers, farmer organizations, handlers and processors, food manufacturers and retailers and a broad range of conservation and environmental organizations.

Field to Market, as well as other sustainability initiatives, face at least three challenges. The first is to measure effects accurately, identify mitigation and adaptation strategies that are cost-effective and account for all effects of a strategy — intended and unintended.

Second, sustainability needs to be seen in a global context, taking account of America’s role in the global food system. This introduces a spatial dimension to the assessment, as practices that protect soil and water in one locale through lower output/less intensity of production may force other regions to stress their land or water resources more. The alternative — not producing enough to feed people — is unacceptable.

Third, the issue of climate change poses a temporal dimension to sustainability assessments. Producing enough to feed our current population without compromising future generations’ capacities to meet their needs is made more complex by the uncertainties of future moisture, temperature and pest/disease conditions as against the adaptability of the global food system over time.

All these sustainability dimensions — comprehensiveness, spatial effects and inter-generational consequences — pose complex issues for scientific assessment and cultural trade-offs.

Genetic engineering

G.M.O.s have become almost the poster child for science versus value conflicts. Most academies of science and regulatory scientists who have looked at the issue conclude that the genetically-engineered foods approved for use are safe. Yet G.M.O.s remain virtually absent from Western Europe, are excluded from U.S.D.A. Certified Organic products and are opposed by several consumer groups in the United States.

Opponents often cite unknown future risks as justification for their position. The result, again, is conflict between the science behind food safety and cultural perceptions of what “safe” should mean.

Food is necessary to human existence. As incomes rise and consumers are further separated from food production processes, however, value preferences become a more prominent part of the food system. Advocates spring up to defend specific values, but the science behind their conclusions may not be as sound as it ought to be. As these issues gain traction, it will become increasingly important that researchers are transparent about their assumptions, comprehensive about the evidence considered and the effects measured and forthcoming about what was not considered.