Part B.
Does organically-grown food contain more or better nutrients - vitamins, minerals and phytonutrients - than conventionally grown food?

AFSIC Research Guide
Compiled by:
Mary V. Gold
Alternative Farming Systems Information Center

October 2008

Answer: Unclear at this point in time

Issues and references:

1. U.S. organic standards and certification do not address food quality. They denote method of production and handling only and were implemented to provide a credible marketing claim for organic producers, processors and retailers. [Find out more]
   
   
2. Valid scientific research comparing organic and conventional foods is scant and what has been done focuses on very specific foods and conditions. Across studies done so far, however, some general trends have been noted: on average, organic foods contain slightly higher levels of trace minerals, vitamin C, and antioxidant phytonutrients than conventionally grown crops. [Find out more]
   
   
3. Research criteria and parameters to do valid research of this type are extremely difficult to create and are demanding and expensive to implement. [Find out more]
   
   
4. There is no real definition of "conventional" agriculture. Conventionally produced foods come from a broad range of farming and food processing practices, challenging any science-based comparison between systems. [Find out more]
   
   
5. Measuring the nutrient content of food is only partly indicative of the "healthfulness" or nutritive value of foods. Assessing the effects of eating organic and conventional foods requires complicated, long-term dietary surveys involving human subjects. [Find out more]
   
   
6. Studies have found higher levels of some phytonutrients in organically grown foods. Research has linked consumption of some phytonutrients to health benefits, but when and how these substances affect human health is still unclear. Research on phytonutrients is still in its early stages. [Find out more]
   
   
7. There is evidence that some fruits and vegetables today contain lower levels of some vitamins, minerals and other elements important to human health than they did 50 years ago. Have farm soils become "depleted" of essential nutrients over the years, and, if so, 1) are they to blame for differences in food values and, 2) does organic farming address these concerns? [Find out more]
   
   

*See also related parts of this information series:

Question and answer fact sheets:

• Should I purchase organic foods? Introduction

• A. Where are background resources? [A-3 sections]

• B. Does organically-grown food contain more or better nutrients – vitamins, minerals and phytonutrients – than conventionally grown food? [B-7 sections]

• C. Are there fewer pesticide residues on organic foods than on conventionally grown foods? Are there fewer antibiotic and hormone residues in organic meat, eggs and dairy products than in conventional animal products? Is organic food safer to eat? [C-5 sections]

• D. Are organic foods more environmentally friendly than non-organic foods? Do organic farming practices have fewer negative impacts on soil resources, water quality and climate change than conventional practices? Are organic farms more sustainable? [D-in progress]

Bibliographies:

• Organically Produced Foods: Nutritive Content. Citations for research publications to 2000 (2000), Full text: http://www.nal.usda.gov/afsic/AFSIC_pubs/srb0003.htm and citations for research publications, 2000-July 2008 (2008). Full text: http://www.nal.usda.gov/afsic/AFSIC_pubs/srb0003.htm

• Organically Produced Foods: Food Safety Issues. Citations for research publications, 2000-July 2008 (2008). Full text: http://www.nal.usda.gov/afsic/pubs/srb0803.shtml#ref25

• Organic Agriculture's Conservation Focus: Selected Research Publications 2005-2006 (2006). Full text: http://www.nal.usda.gov/afsic/pubs/orgconserv2006.shtml

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B. Does organically-grown food contain more or better nutrients - vitamins, minerals and phytonutrients - than conventionally grown food? Find Out More: Issues and References, number 1.

1. U.S. organic standards and certification do not address food quality. They denote method of production and handling only and were implemented to provide a credible marketing claim for organic producers, processors and retailers.

United States Department of Agriculture (USDA) National Organic Program (NOP) oversees all labeling and marketing claims for "certified organic" products sold in the U.S.

"The NOP is a marketing program housed within the USDA Agricultural Marketing Service. Neither the OFPA [Organic Food Production Act] nor the NOP regulations address food safety or nutrition." National Organic Program: Background Information, 2008. Full text: http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELDEV3004443&acct=nopgeninfo

"100% Organic," "Organic" or "Made with Organic Ingredients" are labels regulated by federal law. The label claims are verified through inspections and documentation requirements administered at the production and processing level by USDA-accredited certifying agents.

"The Organic Foods Production Act (OFPA) and the National Organic Program (NOP) assure consumers that the organic agricultural products they purchase are produced, processed, and certified to consistent national organic standards. The labeling requirements of the NOP apply to raw, fresh products and processed products that contain organic agricultural ingredients. Agricultural products that are sold, labeled, or represented as organic must be produced and processed in accordance with the NOP standards.

"Except for operations whose gross income from organic sales totals $5,000 or less, farm and processing operations that grow and process organic agricultural products must be certified by USDA-accredited certifying agents. Excerpt: Organic Labeling and Marketing Information, USDA, National Organic Program, 2008. Full text: http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELDEV3004446&acct=nopgeninfo

Suggestions that a food composition component for "certified organic" be part of the certification and/or marketing process are being considered, especially in Europe. Laboratory analysis that can prove "product authenticity" of organic food claims are being researched.

"In spite of research work carried out on different aspects of organic food, there is not yet a method/methods for routine use in authentication of organic food products. Research work to support and meet the needs of farmers and markets concerning claims on authenticity, safety and nutritional values of organic crops is necessary." Excerpt: "Need for Research to Support Consumer Confidence in the Growing Organic Food Market," by Yona Siderer, Alain Maquet and Elke Anklam, Trends in Food Science and Technology, vol. 16, no. 8 (2005):332-43. Abstract: http://dx.doi.org/10.1016/j.tifs.2005.02.001

"As a result [of consumer concerns], some researchers have begun to look for ways to test organic products for authenticity. Alison Bateman of the University of East Anglia in Norwich, UK, is developing a test based on the higher proportion of the isotope nitrogen-15 in organically farmed soil. This is because nitrogen-fixing plants accumulate more of this heavy isotope than is present in synthetic fertilizers. Other researchers are investigating whether concentrations of trace elements such as calcium, boron, magnesium and selenium differ between organic and conventional produce." Excerpt: "Organic FAQs," Nature 28 (2004): pp. 796-798. Full text: http://www.nature.com/nature/journal/v428/n6985/full/
428796a.html

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B. Does organically-grown food contain more or better nutrients - vitamins, minerals and phytonutrients - than conventionally grown food? Find Out More: Issues and References, number 2.

2. Valid scientific research comparing organic and conventional foods is scant and what has been done focuses on very specific foods and conditions. Across studies done so far, however, some general trends have been noted: on average, organic foods contain slightly higher levels of trace minerals, vitamin C, and antioxidant phytonutrients than conventionally grown crops.

There appear to be many scientific research papers offering evidence as to the nutritional superiority - one way or the other - of organic and conventional foods. Some scientific papers conclude that certain organic foods are more nutritious than conventional ones; however, other studies find no difference or that conventional foods, are, in some cases, more healthful. When examined carefully, though, very few of the studies, regardless of their conclusions, meet basic criteria for good science. As in any field of science, it is necessary to evaluate the validity of each research project's design, objective and methodology, and to weigh evidence across a range of published research. Research should also be evaluated for organizational bias.

Across studies done so far, there are some general conclusions that can be made about nutrient content of organic crops: On average, they contain higher levels of trace minerals, vitamin C, and antioxidant phytonutrients than conventionally grown crops. But the evidence is mixed and often specific to one crop or product. In other words, the definitive study has yet to be done, and the verdict regarding the overall "winner" in terms of nutritional superiority may not be known for some time.

Given the above caveat, here are references to recent reviews with links to abstracts and/or full text (all sites successfully accessed Aug. 10, 2008). Each review provides information on science and consumer issues, evaluates research, makes research recommendations and points to individual research in the field:

1. Benbrook, Charles, Xin Zhao, Jaime Yanez, Neal Davies and Preston Andrews, New Evidence Confirms the Nutritional Superiority of Plant-Based Organic Foods. (State of Science Review) Organic Center, 2008. 53p. Full text: http://www.organic-center.org/science.nutri.php?action=view&report_id=126

2. Brandt, Kirsten and Jens Peter Molgaard, "Organic Agriculture: Does it Enhance or Reduce the Nutritional Value of Plant Foods?" Journal of the Science of Food and Agriculture, vol. 81 (2001): pp. 924-931. Abstract: http://dx.doi.org/10.1002/jsfa.903

3. Heaton, Shane, Organic Farming, Food Quality and Human Health: A Review of the Evidence. The Soil Association, 2001. 88p. Full text: http://www.soilassociation.org/web/sa/
saweb.nsf/24ffc96e2350a4e680256ab10047def0/de88ae6e5aa94aed80256abd00378489!
OpenDocument

4. Magkos, Faidon, Fotini Arvaniti and Antonis Zampelas, "Organic Food: Buying More Safety or Just Peace of Mind? A Critical Review of the Literature." Critical Reviews in Food Science and Nutrition, vol. 46, no. 1 (2006): 23-56. Abstract: http://dx.doi.org/
10.1080/10408690490911846

5. Winter, Carl K. and Sarah F. Davis, "Organic Foods." Journal of Food Science, vol. 71, no. 9 (2006): R117- R124. Full text: http://members.ift.org/NR/rdonlyres/A5367812-A6CF-46C0-80B9-B1EF39A0BCC4/0/OrganicFood.pdf

6. Worthington, Virginia. "Nutritional Quality of Organic versus Conventional Fruits, Vegetables, and Grains," The Journal of Alternative and Complementary Medicine, vol. 7, no. 2 (2001): 161-173. Abstract: http://dx.doi.org/10.1089/107555301750164244 Full text: http://www.ioia.net/images/pdf/orgvalue.pdf

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B. Does organically-grown food contain more or better nutrients - vitamins, minerals and phytonutrients - than conventionally grown food? Find Out More: Issues and References, number 3.

3. Research criteria and parameters to do valid research of this type are extremely difficult to create and are demanding and expensive to implement.

It is impossible to cover all of the issues related to research methodology that need to be addressed in comparative studies related to food composition. Plants and animals are very sensitive to countless elements in their production environment, and each element affects the harvested "final product" - vegetables, fruits, meat, eggs and dairy products. In order to obtain credible research data, each element or variable must be accounted for, analyzed, controlled and weighed. Variables may be anything from pre-existing soil conditions to time and method of harvest to livestock housing and feed.

"The definitive study has not been done, mainly because of the multitude of variables involved in making a fair comparison between organically grown and conventionally grown food. These include crop variety, time after harvest, post-harvest handling, and even soil type and climate, which can have significant effects on nutritional quality." Excerpt: Frequently Asked Questions about Organic Food and Farming, Organic Farming Research Foundation. Full text: http://ofrf.org/resources/organicfaqs.html

"Kika de la Garza researcher Gene Lester [USDA ARS] argued that one of the biggest challenges facing organic farming research is the need to put more rigor into the science. 'We need to make sure the science is done right,' he said.. 'Creating a good head-to-head comparative study takes time, money, and good planning.' Before sharing his results comparing organic and conventional grapefruit production, Lester presented all the variables that were controlled and documented, including percentage soil organic matter, mineral uptake efficiency, micro-environments, system inputs, and year-to-year records." Excerpt: "Organic Research Slowly Gaining Funds, Practitioners and Publicity," by Skip Connett. New Farm, March 2005. Full text: http://www.newfarm.org/depts/talking_shop/2005/0305/
tx_research.shtml

"To ascertain possible quality differences and develop a definitive data base, direct comparative studies of organic vs. conventional produce, require that rigorous guidelines be followed which include: 1) appropriate study approaches (retail market vs. farm vs. research center studies); and 2) standardized preharvest production site, harvest procedural, postharvest handling, and analytical methodology constraints." Excerpt, abstract: "Organic vs. Conventionally Grown Produce: Quality Differences and Guidelines for Comparison Studies," by Gene E. Lester. HortScience, vol. 41, no. 2 (2006):296-300.

"In plant foods, genetics, husbandry and storage are major sources of variation. Water content is particularly affected by storage conditions, and changes in water content are associated with changes in all other constituents, primarily as a result of changes in nutrient density. Husbandry conditions, geochemistry (soil composition) and fertilizer use alter vitamin and mineral contents, especially of trace elements; levels of illumination affect sugars, organic acids, carotenoids and vitamin C levels. The level of phytochemicals in plant foods varies even more than nutrient levels because it is heavily dependent on factors such as pests and pesticides (Eldridge and Kwolek, 1983)." Excerpt: "Guidelines for the Use of Food Composition Data" Chapter 11, Food Composition Data: Production, Management and Use, by H. Greenfield and D.A.T. Southgate. Food and Agriculture Organization of the United Nations, 2003. Full text: http://www.fao.org/docrep/008/y4705e/y4705e16.htm

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B. Does organically-grown food contain more or better nutrients - vitamins, minerals and phytonutrients - than conventionally grown food? Find Out More: Issues and References, number 4.

4. There is no real definition of "conventional" agriculture. Conventionally produced foods come from a broad range of farming and food processing practices, challenging any science-based comparison between systems.

Non-organic agricultural products, that is, anything not "certified organic," defaults to many farming and food processing options. "Conventional" and "industrial" are the two primary terms used to describe non-organic systems. These labels do not come with standards and auditing systems as does the U.S. organic label. The terms "sustainable," "natural" and "integrated," usually used to describe more environmentally-friendly practices, also have no comparable legal definitions when it comes to agricultural production or food products.

The clearest differences between organic and the non-organic systems, in terms of the composition and food safety of plant and animal food products, are these:

Scientific research usually focuses on specific farm practices, e.g. fertilizer application or livestock feed content, in order to qualify and measure definable impacts on food composition. Some research efforts have evaluated intermediate levels of "non-organic" management, e.g. "integrated pest management" as well as more intense pesticide or fertilizer applications, in their comparisons with organic.

*U.S. agencies that approve materials used in agriculture/food production include the Environmental Protection Agency (EPA), Food and Drug Administration (FDA) and the Department of Agriculture (USDA).

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B. Does organically-grown food contain more or better nutrients - vitamins, minerals and phytonutrients - than conventionally grown food? Find Out More: Issues and References, number 5.

5. Measuring the nutrient content of food is only partly indicative of the "healthfulness" or nutritive value of foods. Assessing the effects of eating organic and conventional foods requires complicated, long-term dietary surveys involving human subjects.

The challenges in documenting real differences in the healthfulness of organic vs. non-organic diets are enormous.

"The ultimate test of nutritional quality is the capacity of a food to support health, growth and reproduction. Relevant, then, are studies that assess the health of animals or people fed organically or non-organically grown food." Excerpt: "Assessing Organic Food Quality: Is It Better for You?" by Shane Heaton. UK Organic Research 2002: Proceedings of the COR Conference, March 26-28, 2002, Aberystwyth, Wales. pp. 55-60. Full text: http://www.organic.aber.ac.uk/library/Assessing%20organic%20food%20quality.pdf

"All current data are on content of food; needed data are on health effects in consumers -the only research gap that counts for nutrition; it would take huge groups over many years to derive answers if we could have people consuming organic vs. conventional products for study of chronic disease endpoints or intermediate biomarkers." Excerpt: David M. Klurfeld, Nutrition Issues for Organic Food (presentation). USDA, Agricultural Research Service, 2007. Full text: http://www.ars.usda.gov/SP2UserFiles/Program/216/Klurfeld-NAREEEABOct2007.pdf

"There are many difficulties in assessing the nutritive value of organic vs. conventionally produced foods. The first is that the difference in terms of health effects is not large enough to be readily apparent. In other words, if people stayed well on an organic diet but got violently ill as a result of consuming food grown with chemical fertilizers and pesticides, then the difference would be perfectly obvious; however, this is not the case, and a more subtle difference, such as an 8% increase in the incidence of allergies, for example, is much more difficult to detect and easier to overlook." Excerpt: "Is Organically Grown Food More Nutritious?" by Virginia Worthington. The Co-op Connection, 2001. Full text: http://www.mindfully.org/Food/Organic-More-Nutritious-WorthingtonNov01.htm

The challenges in conducting controlled studies of dietary intake require strict attention to selection of participants - for age, health, diet history, motivation, long-term availability, etc. - as well as development of well defined goals and methods for statistical analysis. To date, very few studies have attempted to correlate organic and conventional foods with human or animal health indicators, especially in terms of nutrient content. Some studies have looked at the fate and effects of pesticide residues on conventional vs. organic foods in humans. There are also some interesting studies documenting laboratory animal preferences for organic vs. conventional feeds.

"A team of Swiss and Austrian scientists recently concluded a 21-year study of organic wheat production. As an "integrative method" for assessing quality, they gave lab animals a choice of biscuits made from organic or conventional wheat. The rats ate significantly more of the former. The authors call this result remarkable, because they found the two wheats to be very similar in chemical composition and baking performance." Excerpt: "Organic, and Tastier: The Rat's Nose Knows," by Harold McGee. New York Times, October 3, 2007. Full text: http://www.nytimes.com/2007/10/03/dining/03curi.html?ref=dining

[Cited study: "Wheat Quality in Organic and Conventional Farming: Results of a 21 Year Field Experiment," by P. Mader, D. Hahn, D. Dubois, L. Gunst, T. Alfoldi, H. Bergmann, M. Oehme, R. Amado, H. Schneider, U. Graf, A. Velimirov, A. Fliessbach and U. Niggli. Journal of the Science of Food and Agriculture 87, no. 10 (2007): pp. 1826-1835. Abstract: http://dx.doi.org/10.1002/jsfa.2866]

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B. Does organically-grown food contain more or better nutrients - vitamins, minerals and phytonutrients - than conventionally grown food? Find Out More: Issues and References, number 6.

6. Studies have found higher levels of some phytonutrients in organically grown foods. Research has linked consumption of some phytonutrients to health benefits, but when and how these substances affect human health is still unclear. Research on phytonutrients is still in its early stages.

Phytonutrients, or phytochemicals, are substances that plants produce to protect themselves from diseases and pests.

"Levels of phytochemicals and other plant defence compounds are modulated by many genotype-independent factors such as light, water, CO2, oxygen and ozone, nutrient supply, pesticides, levels of diseases and herbivore damage. Therefore different production methods for crops (conventional, low input and organic) have the potential to significantly affect the levels of the phytochemicals in the crops, and subsequently affect health and nutrition in the consumers.

"Based on the various factors that can affect phytochemical levels and profiles it is obvious that differences in cultivation conditions will have effects. Conventionally-grown crops live a life of 'luxury' receiving both high nutrient inputs and chemical control of pests and diseases, whereas organically-grown crops receive nutrients through potentially slower but more natural processes and control of pests and diseases is done via non-chemical processes (e.g. biocontrol). In the case of organically-grown crops there could be a higher level of stress (due to increased pest and disease damage) and therefore a higher level of certain phytochemicals. It is clear that further research is needed to determine the pros and cons of the different production methods in relation to animal and human health and nutrition." Excerpt: Phytochemicals under Organic and Low Input Crop Production Systems - Potential Influences on Health and Nutrition in Humans and Animals, by R.N. Bennett and E.A.S. Rosa. Organic Eprints, 2004? http://orgprints.org/7883/01/bennett.doc

"The term 'phyto' originated from a Greek word meaning plant. Phytonutrients are certain organic components of plants, and these components are thought to promote human health. Fruits, vegetables, grains, legumes, nuts and teas are rich sources of phytonutrients. Unlike the traditional nutrients (protein, fat, vitamins, minerals), phytonutrients are not 'essential' for life, so some people prefer the term 'phytochemical'. "What are phytonutrients and where are they found?" Phytonutrient FAQs, USDA Agricultural Research Service, Human Nutrition Research Center, Full text: http://www.ars.usda.gov/Aboutus/docs.htm?docid=4142

"Population studies have linked fruit and vegetable consumption with lowering the risk for chronic diseases including specific cancers and heart disease. However, media and consumer interest in phytonutrients and functional foods is far ahead of established proof that documents the health benefits of these foods or food components for humans. Phytonutrients research is experiencing remarkable growth. Hopefully, more specific information on phytonutrient consumption and human health will be forthcoming in the near future. For now, it appears that an effective strategy for reducing risk of cancer and heart disease is to increase consumption of phytonutrient-rich foods including fruits, vegetables, grains and teas." Excerpt: "What is the present state of phytonutrient research?" Phytonutrient FAQs, USDA Agricultural Research Service, Human Nutrition Research Center, Full text: http://www.ars.usda.gov/Aboutus/
docs.htm?docid=4142

"Despite their wide distribution in plants, the health effects of dietary polyphenols have come to the attention of nutritionists only rather recently. Until the mid-1990s, the most widely studied antioxidants were antioxidant vitamins, carotenoids, and minerals. Research on flavonoids and other polyphenols, their antioxidant properties, and their effects in disease prevention truly began after 1995. Flavonoids were hardly mentioned in textbooks on antioxidants published before that date. The main factor that has delayed research on polyphenols is the considerable diversity and complexity of their chemical structures." Excerpt: "Polyphenols: Antioxidants and Beyond," by Augustin Scalbert, Ian T. Johnson and Mike Saltmarsh. American Journal of Clinical Nutrition, vol. 81, no. 1 (2005): 215S-217S. Full text: http://www.ajcn.org/cgi/content/full/81/1/215S

See also:

Antioxidants, Phytochemicals and Functional Foods. All About Foods, USDA National Agricultural Library, Food and Nutrition Information Center. Full text: http://fnic.nal.usda.gov/nal_display/index.php?info_center=4&tax_level=3&tax_subject=358
&topic_id=1610&level3_id=5947&level4_id=0&level5_id=0&placement_default=0

"A Daily Dose of Antioxidants?" Agricultural Research, March 2008. Full text: http://www.ars.usda.gov/is/AR/archive/mar08/fruit0308.pdf

Phytochemical Databases, compiled by Jae B. Park, USDA Agricultural Research Service. Web site: http://www.pl.barc.usda.gov/home.cfm

Three searchable databases: 1. Phytochemicals - search phytochemicals by using their names or using an alphabetical list; 2. Biological Activities - all biological activities of phytochemicals are classified into several disease conditions so that their medicinal uses are quickly searched; 3. Phytochemical Classes - representative chemical groups and phytochemical classes are chosen and indexed for searching phytochemicals easily on basis of their chemical structures.

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B. Does organically-grown food contain more or better nutrients - vitamins, minerals and phytonutrients - than conventionally grown food? Find Out More: Issues and References, number 7.

7. There is evidence that some fruits and vegetables today contain lower levels of some vitamins, minerals and other elements important to human health than they did 50 years ago. Have farm soils become "depleted" of essential nutrients over the years, and, if so, 1) are they to blame for differences in food values and, 2) does organic farming address these concerns?

Comprehensive analysis of food nutrient content, in the form of Food Composition Tables, has been collected and updated over many years in the U.S. Many studies have attempted comparisons between historical and current data. Comparisons are muddied, however, by at least two significant factors: a) testing methodology for measuring food composition has changed since the first tables were compiled - valid comparisons between tables requires care; b) food plant varieties and livestock breeds have changed a great deal over the years - research has found that this factor, unaccounted for in food composition tables, is an important one in terms of changes in food composition.

"During the last century there were dramatic reductions in the mineral contents of fruit and vegetables according to [UK] government-reported Composition of Food Tables. There were statistically significant reductions between the 1930s and 1980s in the levels of Ca, Mg, Cu and Na in vegetables and Mg, Fe, Cu and K in fruit. In the USA, similar reductions have also been reported for US Composition of Foods Tables. It is only now that these reductions are being taken seriously by governments. The causes and consequences of the reductions are still not known. There are several possibilities for the causes and these include changes to the choice of varieties of fruit and vegetables being used, changes to the soil environment and changes to agricultural practice or mere anomalies of sampling and measurement. The consequences for human nutrition are also still not clear and could be small and restricted to a few individuals or the tip of an iceberg of far-reaching health problems." Excerpt, Summary: "Historical Changes in the Mineral Content of Fruits and Vegetables: A Continuing Controversy," by Anne Marie Mayer. Paper presented at Quality Low Input Food Congress 2005: Organic Farming, Food Quality and Human Health, Jan. 6-9, 2005. Full text: http://www.qlif.org/qlifnews/april05/con2.html

Agricultural crops (including vegetables, fruits and pasture plants that support animals) do interact with the soil that they grow in, removing and transforming elements as they grow. Good farming practices - both organic and conventional - address this phenomenon through fertilization and cultural practices that replace or regenerate these elements on an ongoing basis.

A recent study looked at nutrient decline in vegetables and concluded that soil quality was not a major factor.

"We postulate that the median declines in nutrient concentration reflect primarily unintended side effects of increased yields (environmental and genetic dilution effects), whereas the increases in some individual foods and nutrients reflect primarily genetic variability associated with changes in cultivated varieties. Many studies show marked genetic variability in nutrient concentrations...We doubt that inadequate soil minerals can explain most of our findings. Nitrogen, phosphorus, and potassium are routinely added to soils if needed. Yet we find median declines for all three associated nutrients-protein, phosphorus, and ash (-6%, not quite statistically significant)." Excerpt: "Trade-offs in Agriculture and Nutrition," by Donald R. Davis. FoodTechnology, vol. 59, no. 3 (2005): 120.

Organic farming practices deal directly with soil quality and care. Relevant sections of the regulatory text include:

Title 7: Agriculture - Part 205 - National Organic Program -

§205.203 Soil fertility and crop nutrient management practice standard)

§205.205 Crop rotation practice standard

§205.206 Crop pest, weed, and disease management practice standard

For full text: Electronic Code of Federal Regulations (e-CFR): http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?type=simple;c=ecfr;cc=ecfr;
sid=4163ddc3518c1ffdc539675aed8efe33;region=DIV1;q1=national%20organic%20program;
rgn=div5;view=text;idno=7;node=7%3A3.1.1.9.31

Soil building is the most important component of any organic cropping system. In addition to soil management, organic farming practices also influence crop variety selection and crop harvest date. These are both factors with potential impact on food nutrient content that have been noted in the "nutrient decline" debate. Selection of disease and pest resistant varieties favored by organic growers, and the longer period that some crops require until maturity under organic regimens, are topics targeted for future food composition research.