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The Center for Food in Community and Culture

Category Archive: Nutrient Content of Foods

Nutrient Quality of Food Affected by Agricultural Practices

Dr. Debra Pearson’s presentation at NEWfare focused on how agricultural practices influence the nutrient content of the fruits and vegetables we grow and the livestock we raise. An examination of the USDA’s food database since the 1950s indicates that there has been a decline in some nutrients over a range of fruits and vegetables.1 There are still many unanswered questions and controversies about why there has been a decline in the nutrient content of produce, but research suggests 3 reasons for this decline: 1) monoculture farming, 2) selection for yield, and 3) plant defenses. Techniques of plant breeding, selection and genetic modification, fertilizer, pesticide and herbicide practices, crop and livestock management differ markedly between sustainable/organic farming and industrial farming, and these differences impact the nutrient profiles of crops and livestock.

For a number of reasons relating in part to uniformity of produce to make machine planting and harvesting easier, the varieties of any given crop grown has sharply declined over the decades. We used to grow many more varieties of apples, corn, potatoes, broccoli etc, but in recent decades for most of these crops we have drastically decreased the number of varieties. One of the basic tenants of good nutrition is “variety”. The greater the variety of foods in our diet the better our chances for obtaining the wide array of nutrients we need. The minute we reduce the variety of foods, it becomes harder to obtain the full range of needed nutrients. Along with a reduction in the variety of crops grown, industrial farming has emphasized yield – selecting and breeding plants for bigger yields. Scientists theorize that plants have a somewhat fixed amount of resources, and if the plant is bred to grow rapidly and/or produce larger fruit (more dense head size in the case of broccoli) then the plant has fewer resources to direct to vitamin synthesize or mineral acquisition, thus nutrient density is compromised. We have seen this happen for instance, in the wheat cultivars we grow. We have both reduced the variety of wheat cultivars grown and selected for larger wheat yields. This then has reduced the mineral content of several minerals in the modern wheat cultivars grown versus the historical varieties that used to be grown.2

Plants synthesize a wide variety of phytochemicals (over 8000 have been identified) that protect plants from viruses, fungal diseases, UV/oxidative damage, and help in plant growth and maturation. Humans obtain these important beneficial phytochemicals when we eat plants. Also, livestock – if allowed to graze in the fields – obtain these phytochemicals as well, which means their meat, eggs, and milk are enriched with these phytochemicals. Industrial farming, with its heavy reliance on pesticides and fertilizer practices that don’t support the maintenance of a rich organic soil matrix seem to dramatically decrease the amount of phytochemicals the plants produce.3,4

What we feed livestock directly impacts the nutrient and phytochemical content of the meats, milk and eggs we eat. Grass-fed cattle and free-range chickens produce milk and eggs that are lower in overall fat content, higher in omega-3 fatty acids, higher in conjugated linoleic acid, higher in vitamins such as vitamin E and higher in phytochemicals. To reverse the decline and increase the nutrient density of foods, Dr. Pearson concluded that we need to research, develop, and encourage the use of agricultural practices that promote high quality, nutrient dense foods.

Davis et al J Am Coll Nutr, 2004, 23, 669
Murphy et al Euphytica, 2008, 163, 381
Wang et al JAFC, 2008, 56, 5788
Mitchell et al JAFC, 2007, 55, 6154

Are We Restoring or Destroying Our Health? Agriculture from the Ground Up

Science faculty members from the Center for Food in Community and Culture participated in a panel discussion, entitled “Are We Restoring or Destroying our Health? Agriculture from the Ground Up,” 5:00-6:15 p.m., Thursday, November 19th in Mary Ann Cofrin Hall 208.  Joanne Gardner, Vicki Medland, Debra Pearson, and Angie Bauer-Dantoin focused on various impacts of agricultural and food production practices on human health.

Registered dietitian and nutrition consultant, Joanne Gardner introduced the panel discussion with an overview of some of the problems confronting contemporary agricultural and food production practices with regard to human health. She pointed out that sustainable high quality food is rooted in fertile soil, ample clean water, biological diversity, and predictable climatic conditions, each of which has been negatively impacted by high productivity demands on energy and water use; fertilizer and pesticide inputs of industrialized agriculture and food processing; and post production outputs, such as manure runoffs and pesticide residues.  Diets, shaped by political, economic, and social factors, as well as by advertizing, ethics, and taste preferences, in turn shape our health. In the United States, our agriculture and food policies are designed, in part, to assure a supply of cheap food, much of it in the form of highly processed sugars and grains, have led to increased obesity and Type 2 diabetes.  In the developing world, on the other hand, over a billion people go hungry, and population increases put ever greater pressure on agrifood production and the productive capacities of natural resources and the environment. All of these processes challenge the very elements upon which our lives depend.

Vicki Medland, biologist and Associate Director of the Cofrin Center for Biodiversity, spoke on Agrobiodiversity with a focus on the biological diversity of potatoes. Dr. Medland noted that although there may be as many as 5000 varieties of potato concentrated in its original area of domestication in the Andean region of South America where the varieties are adapted to diverse micro-environmental zones.  In the United States, however, we rely on only a few commercial varieties. The Russet Burbank constitutes 80% of U.S. potato production and dominates because of its preferred qualities for processing into French fries for fast food restaurants, particularly for McDonald’s.  U.S. production is concentrated in the state of Idaho where potatoes are typically grown as monocultures using industrialized agricultural practices, including extensive irrigation and repeated applications of pesticides in an attempt to control pests like the Colorado potato beetle and late blight fungus. Over-use of pesticides has led to a decline in the biodiversity of beneficial species and has contributed to pesticide resistance in both Colorado potato beetles and late blight. However, recognition of these problems has resulted in innovative opportunities for farmers to increase production while maintaining biodiversity. In Wisconsin, some farmers are using precision agriculture and integrated pest management to reduce the use of the most toxic pesticides and have instituted requirements for restoring surrounding habitats.  Significantly, McDonald’s has also committed itself to reducing pesticide residues as their shareholders apply pressure on management.  Finally, the International Potato Center in Peru has received grants for local farmers to preserve the biodiversity of potatoes and the cultural diversity of growers.

The impact of agricultural practices on the nutrient qualities of food was the subject of Debra Pearson’s presentation. Dr. Pearson, who is Co-Director of the Center for Food in Community and Culture and Associate Professor of Human Biology and Nutritional Sciences, compared the pre-harvest nutrient profiles of foods produced using conventional industrial agriculture with those grown using sustainable farming practices. She cited a study that shows a decline in nutrients—protein, calcium, phosphorus, iron, and vitamins A, B2, B3, and C–in 43 crops from 1950 to 1999. One theory about why this decline has occurred is that growing crops for maximum yield per acre tends to dilute the levels of nutrient in these crops. Another theory is that industrial agriculture has selected varieties for qualities like size, uniformity, machine harvestability, and shelf life that do not necessarily provide the most nutrients. Also, extensive use of energy, water, fertilizers and pesticides inputs may make “life easier for the plants” such that they do not have to produce the same level of phytochemicals to protect themselves from oxidative stress or pest attack. The net result for humans are produce with lower levels of important health-promoting phytochemicals.

Thousands of these phytochemicals are used by plants to defend against fungal, viral, bacterial, and insect attack; to protect against UV light damage; and to promote growth, ripening, and coloration.  New research is being conducted on various food crops, such as blueberries and tomatoes, to assess the impact of specific phytochemical on the promotion of consumer health. Other studies indicate that meat, milk, and eggs from animals that are grass-fed and free range have higher levels of phytochemicals, higher omega 3 fats, lower omega 6 fats, and more CLA (conjugated linoleic acid). Much research indicates that westerners are not getting enough omega 3 fats and getting too many omega 6 fats. A return to animals products that are grass grazed can help correct this imbalance in omega 3 and omega 6 fats in our diets. Pearson concluded that more research on these issues is vital, and that consumers need more information upon which to select foods with the highest nutrient profiles.

Angie Bauer-Dantoin, Associate Professor and Chair of Human Biology, reported on the impact of endocrine disrupting chemicals on human health and the potential impact of agricultural practices on prevalence of these chemicals in well water in ten wells in four northeastern Wisconsin counties, including Brown County.  Dr. Bauer-Dantoin started by noting the pervasiveness of endocrine disruptors from bisphenol A and nonylphenol in plastics and PCB contamination of the waters of the Fox River to herbicides, pesticides, and hormones from agricultural production and human waste. Endocrine disrupting chemicals are a cause for concern about human health, having been linked to infertility, intersexed conditions, low sperm counts, and hormone-sensitive cancers such as prostate and breast cancers.  Her chemical analyses of well water found samples with unsafe levels of coliform, E. coli, and enterococci bacteria as well as nitrates.  Well waters in the region are especially vulnerable to contamination from manure and artificial fertilizers because of their permeability. She and her graduate student Sarah Wingert also found some samples with estrogenic activity that generated breast cancer cell proliferation under laboratory conditions.  Further studies are being planned to attempt to identify the source of the estrogenic contaminants.