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By Susan T. Marcolina, MD, FACP
As more evidence reveals a correlation between what we eat and how much we eat and the likelihood of developing cancer and other chronic diseases, the old adage "you are what you eat" takes on new meaning as we make daily choices about our food intake.1,2
Large areas of the planet, however, including countries in Southeast Asia and Sub-Saharan Africa, have the highest population growth, the highest food poverty, and little choice about food intake. Food poverty also exists for many people in economically developed nations.3 As a result, many agricultural practices developed over the past 60 years, such as the use of synthetic pesticides, fertilizers, and hormones (livestock raising) and most recently the introduction of genetically modified organisms (GMOs), have been incorporated into conventional farming as a means to augment the necessary crop yields to feed the growing global population.
With limited resources available in many third world countries, it is important to decide which practices not only will provide increased crop yields while maintaining the sustainability of land they are grown upon, but also will augment the health of those who consume these crops. The resurgence of organic farming practices may be another means by which to address both the quality and quantity of food production and health promotion. This paper will provide an overview of the risks and benefits associated with both conventional and organic farming, focusing on perspectives both local and global. It is a topic that is timely as well as emotionally charged.
Agrichemical Pesticide Use
Each year, 750 million pounds of pesticides are used on farms in the United States.4 Nitrates, pesticides, and industrial chemicals used in agriculture are found in both surface and ground water in 46% of all U.S. counties.5 These substances move up the food chain, then are concentrated and stored in adipose tissue where they have cumulative effects on our health. Table 1 outlines some of the health effects attributed to agricultural pesticides.6,7
Children are at particular risk for adverse effects from exposures to pesticide residues. Children are more vulnerable to toxin exposure due to smaller size, higher metabolic rate, developmental vulnerability, hand-to-mouth activity, and increased consumption of water and food associated with multiple pesticide residues. A National Academy of Sciences’ study, published in 1993, determined that the Environmental Protection Agency (EPA) exposure tolerances underestimate toxicity to children because EPA tests were conducted primarily on adult males or animal species exposed to one chemical at a time.8 Table 2 gives the Environmental Working Group’s (EWG’s) current list of produce grown with the heaviest pesticide applications.9
Ames et al, however, contend that the widespread belief of U.S. consumers that pesticide residues on food pose a serious cancer risk is grossly exaggerated. He explains that part of the reason for the exaggeration has been that the major source of information of carcinogenic effects of synthetic pesticides on humans comes from high-dose rodent cancer tests. Such testing, he believes, requires the use of both qualitative extrapolation from effects on rodents to effects on humans and quantitative extrapolation from the high dose given to rodents to the much lower pesticide residue actually measured annually by the Food and Drug Administration (FDA) in the annual Total Diet Study, which measures dietary pesticide residues in table-ready food. In other words, Americans are more likely to develop cancer from exposure to cigarette smoking, genetic susceptibility, and dietary deficiencies than from pesticide residues on their food.10
Organic Agriculture: Statistics
The market for organic foods has increased 40-fold from 1986 to 1996 and is expected to grow at a rate of 24% per year. Sales of organic food in the United States totaled $7.8 billion in 2000.11
Organic Farming: Origins and Practices
Sir Albert Howard, imperial economic botanist to India at the turn of the 20th century, is credited with the initial development of modern organic methods of agriculture. Since the East Indian farmers with whom he worked could not afford imported synthetic fertilizers and pesticides, Sir Albert developed ways to recycle natural nutrients from locally available animal manure and waste plant materials. Such composting enriched and replenished the soil and diminished problems with erosion, all of which increased crop yields.5
In the past decade in the United States, there has been a resurgence of interest in the implementation of sustainable agriculture methods to help farmers avoid the use of chemical pesticides and petroleum-based fertilizers. Such methods are governed by the principles of crop rotation (planting different crops in the same field during different seasons), renewal of the soil tilth (the soil’s texture, nutrients, and ability to hold water) with composting, and the planting of cover crops such as peas, oats vetch, and clover. These cover crops fix nitrogen, provide habitat for beneficial insects that prey on destructive pests, crowd out noxious weeds, and prevent runoff and erosion of the soil. Crops grown utilizing these principles have yields comparable to those of conventionally grown crops with less adverse environmental impact and the market for their goods is steadily growing.4,12
Organic: What’s in a Name?
The U.S. Department of Agriculture (USDA) has clarified the definition of organic with standards published in October 2002. These labeling rules help consumers know the exact organic content of the foods they purchase. Organic food is produced without using pesticides, synthetic fertilizers, sewage sludge, bioengineering, or ionizing radiation. A farm cannot be certified as organic until it has performed organic practices for three years. The companies responsible for handling and processing of organic food also must be certified.
"Natural" is not synonymous with organic, nor is hormone-free or free-range, although such claims, if truthful, can be used on food labels. Fines for illegal organic labeling run $10,000 per violation.13
Nutritional Benefits of Organic Produce
Serious limitations exist in the quality and quantity of nutritional data from comparative studies of organic and conventionally grown produce. The reviews compiled by Woese et al and Worthington show a trend for increased nutrient content and decreased nitrate and water content of organically produced foods.14,15 Asami et al, however, found higher levels of total secondary phenolic metabolites and ascorbic acid (P < 0.05) in strawberries, marionberries, and corn produced using organic and sustainable agricultural methods versus conventional agriculture methods.16
Prior to the Asami study, there had been concern that levels of some phenolics were lower in foods grown utilizing conventional agricultural practices since the pesticides and fertilizers disrupt the natural production of phenolic metabolites in the plant. These phenolic metabolites protect the fruits from insect predation, photo-oxidation, and bacterial and fungal infections. Evidence has demonstrated a wide range of activity for these phenolic compounds in humans including potent antioxidant, anticancer, and inhibition of platelet aggregation functions, which have important implications for health.17
Organic goods can cost 20-100% more than conventionally produced goods, depending upon the location and the product sold. This is because organic farming is more labor intensive, involving hand weeding, tilling, planting of cover crops, composting plant waste, and hand harvesting of certain heirloom crops.18
Organic Farming Yields
In a 21-year study of agricultural and economic performance of biodynamic, bio-organic, and conventional farming systems in central Europe, Mader et al found that, although crop yields were about 20% lower in the two organic systems compared to the conventional farming system, the input of fertilizer and energy was 34-53% lower and pesticide use was decreased by 97%. The soils in the organically farmed plots also were healthier with greater aggregate stability, which was positively correlated with more numerous, biodiverse populations of nutrient-recycling microbes.19
It is a common misconception that organic food are at greater risk of contamination by E. coli due to animal manure applications. Organic standards impose strict guidelines for manure use in organic farming: Manure must be first composted or applied at least 90 days prior to harvest, which allows plenty of time for breakdown of any microbial pathogens.20
Genetically Modified (GM) Crops: Seeds of Discontent?
Genetic manipulation has been used in farming for many thousands of years. Native Americans developed corn by selective breeding over a period of generations to create a more productive, tasty variety. Within the past 20 years, however, genetic engineering techniques have resulted in the development of crops containing specific single-gene transfers that cause predictable changes in the plants and produce immediate results.
GM crops are extensively tested with regard to their composition, safety, growth, nutrition profiles, and environmental effects prior to introduction into the marketplace. Evaluations take place under the auspices of four federal regulatory agencies, including the FDA, the National Institutes of Health, the EPA, and the Animal Plant Health Inspection Service of the USDA.18 At present there exist few data suggesting direct harm to humans who eat genetically modified foods, yet public perception is often at odds with this fact.21
GM Technology: History and Development
GM crops were first grown commercially in the United States in 1996. Currently four countries (USA, Argentina, Canada, and China) account for 99% of the total global area of GM crops. Although more than 50 biotechnology crop products have passed the regulatory review process and been commercialized, the four main GM crops are soy, cotton, oilseed rape, and maize, which account for 99% of the total global GM acreage.
The U.S. company Monsanto dominates the GM market and is responsible for 91% of the total GM acreage. Sixty percent of the processed food products in the United States contain GM ingredients, represented almost entirely by corn and soybeans.22
GM crops have been engineered with two traits. One set (RoundUp Ready soy, oilseed rape, and maize) is resistant to the particular herbicide RoundUp such that it can still be applied to the field for weed control while the crop plants are growing. The other set (Bt maize and Bt cotton) contains the gene from the soil bacteria Bacillus thuringiensis (Bt).
Naturally occurring Bacillus thuringiensis has been used as a selective biological control in organic farming for 40 years. The bacterial spores are applied in spray form during the intermittent infestations of pest larvae throughout the growing season. Its potency degrades after three days. The Bt transgenes in GM crops, however, are active throughout the plant and during the entire growth cycle. Such Bt organisms have been modified to express "Cry," a class of insecticidal proteins, which destroys the digestive tract of the European corn borer and other harmful caterpillar larvae, but is harmless to humans, mammals, and birds.18,19 As a result of this persistent, widespread exposure, however, insects with a natural immunity have survived and formed the basis of a resistant population. Although Bt cotton has successfully reduced the overall use of insecticides for bollworms and budworms, these effects have varied widely in different states.
With regard to the herbicide-tolerant crops (like RoundUp Ready soybean varieties), most farmers have to apply herbicides several times throughout the life cycle of the crops. Susceptibility to glycosate (Round-Up) varies among species of weeds and shifts are occurring in the genetic composition of field weeds as a result of the introduction of herbicide-resistant crops.21,22
A genetically modified rice cultivar, "golden rice," which produces both beta-carotene and iron via incorporation of two genes from a daffodil, one from a bacterium, and one from a bean species, has been developed by Zeneca Agrochemicals but is not yet commercially available. There is potential that this bioengineered product, in conjunction with other dietary interventions and a commitment to improvement of socioeconomic status, could alleviate blindness and complications of anemia that occur in billions of people in developing countries who suffer from vitamin A and iron deficiency.
However, these nutritional problems are complex. Many people who could benefit from this rice have concomitant protein-calorie malnutrition and intestinal infections that interfere with absorption of beta-carotene and its conversion to vitamin A. Their diets do not contain the fat and vitamin C necessary to absorb the nutrients supplied by this type of rice. Further re- search may illuminate a way to incorporate such biotechnological improvements into comprehensive aid programs that will improve health in third world nations.23
GM Crops: Economic Problems
Overall, U.S. farmers have sustained losses with GM crops because GM seeds are significantly more expensive than non-GM seeds, and they cannot be saved to grow the subsequent year’s crop. Despite the fact that herbicide prices have declined, the GM crops attract lower market prices than those available for non-GM crops. Indeed, guaranteed GM-free crops command significant price premiums, especially in the European markets where there are strict import restrictions for GM produce.21
GM Crops: Contamination Problems
Genetically altered crops have caused widespread contamination of the non-GM varieties of oilseed rape, corn, and soybeans. This contamination occurs in several ways, including accidental seed mixing, the use of soiled planting and harvesting machinery, and gene transfer through cross-pollination by wind or insects.
The StarLink Bt maize was a notorious case. In September 2000, it was discovered that taco shells manufactured by the Kraft Food Company contained the Cry9C transgene protein. This GM maize had been approved by the FDA only for animal feed, due to concerns about the possibility of allergic sensitization. Despite the fact that only 1% of the 2000 U.S. corn harvest contained StarLink, this mixed with and contaminated almost 50% of the national maize supply.22
As depicted in Table 1, cumulative effects of pesticide exposure have been associated with significant health problems. Curl et al have shown statistically significant higher concentrations of organophosphate pesticide residues in the urine of preschool students consuming a diet composed primarily conventional foods versus students consuming a diet composed of organically derived foods.24
Adequate data to predict the long-term effects of ingestion of GM-derived foods have yet to be generated. However, the FDA has received reports of more than 50 allergic reactions to StarLink-modified corn, ranging from mild skin rashes and gastrointestinal symptoms to life-threatening anaphylaxis.19
Although such potential risks must be kept in mind and more fully evaluated, the benefits of a diet high in fruits and vegetables are well-established and should be encouraged. Proper cleansing of produce and peeling, where appropriate, can enhance the safety profile of many non-organic foodstuffs.
Dose estimates generated from urinary pesticide metabolite levels suggest that organic diets can reduce the level of pesticide exposure that children receive, thereby lessening potential health risks. Such a dietary change is a relatively simple way for parents to reduce children’s exposure to potential toxins. Patients can minimize expenses by prioritizing organic purchases to the foods listed in Table 2. With the new USDA guidelines for organic product labeling, it will be easier to verify that we are really getting what we pay for.
Although the potential benefit in the fight against global hunger is great, more research needs to be done in order to determine whether GM foods will indeed help safely increase crop yields to provide food, enhance the health and well-being of a growing world population, and end world hunger.
Organic farming methods offer ways to sustainably grow crops with a potentially more favorable environmental impact. The exposure of children to pesticide residues can be minimized with an organic diet. The adoption of such a diet can be cost effective when organic purchases are restricted to fruits and vegetables with the highest pesticide loads when grown conventionally. While promoting these specific types of organic produce, however, health care practitioners should continue to recommend that patients eat five properly washed and prepared servings of fruit and vegetables per day, even if grown conventionally, to promote optimal health.
Dr. Marcolina is a board-certified internist and geriatrician in Issaquah, WA.
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