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Nutritional Superiority of Organic Foods
Nutritional Superiority of Organic Foods
Nutritional Superiority of Organic Foods
Nutritional Superiority of Organic Foods
Nutritional Superiority of Organic Foods
Nutritional Superiority of Organic Foods
Nutritional Superiority of Organic Foods
Nutritional Superiority of Organic Foods
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Nutritional Superiority of Organic Foods

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Yes, organic plant-based foods are, on …

Yes, organic plant-based foods are, on
average, more nutritious.

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  • 1. The Organic Center www.organic-center.org The Organic Center Critical Issue Report Page March 2008 Nutritional Superiority of Organic Food A State of Science Review: Nutritional Superiority of Organic FoodsNew Evidence Confirms theNutritional Superiority ofPlant-Based Organic Foodsby Charles Benbrook, Xin Zhao, Jaime Yáñez, Neal Daviesand Preston Andrews March 2008
  • 2. The Organic Center Critical Issue Report Page March 2008 Nutritional Superiority of Organic Food Btable of contentsForeword ........................................................................................................................................... AI. Executive Summary .............................................................................................................. 1II. The Importance of Nutrient Content......................................................................... 6A. The Dark Side of the American Diet ........................................................................................ 7B. The Plant Physiology Behind Nutrient Density........................................................................ 9C. Two Basic Questions ...................................................................................................................12D. Key Caveats..................................................................................................................................... 9III. Overview of Published Studies and LiteratureReviews Comparing the Nutrient Content ofOrganic and Conventional Food...................................................................................16A. Published Studies Comparing the NutrientContent of Conventional and Organic Food.................................................................................16B. Review Articles Assessing Studies of Organic Food Quality..............................................17C. Methodological Issues in Comparing Nutrient Levels inOrganic and Conventional Foods...................................................................................................21IV. Screening and Selection Criteria toIdentify Valid Matched Pairs .............................................................................................23A. Agronomic Practices and Experimental Design ...................................................................25B. Analytical Methods Screen ........................................................................................................28C. Outlier Values ................................................................................................................................32D. Criteria for Selecting the Matched Pairs froma Study for Inclusion in Cross-Study Analyses...........................................................................32V. Differences in the Nutrient Content of Organicand Conventionally Grown Foods ................................................................................36A. Nutrient Density Comparisons for Valid Matched Pairs......................................................36B. Conclusions....................................................................................................................................37Appendix 1.Bibliography of Studies ..........................................................................43Bibliography .................................................................................................................................49About the Co-authors of the Nutirent Content SSR ..........................................50
  • 3. The Organic Center Critical Issue Report Page March 2008 Nutritional Superiority of Organic Food CForewordBy Andrew Weil, MDDeveloping a healthy lifestyle requires information and motivationto apply it. Your everyday choices about eating, physical activityand stress management, for example, all influence how you will feeltomorrow and your health risks later in life. It is our choices thatindividually and collectively determine how gracefully you will age.Adopting healthy routines, and sticking to them, is key. A practicaltip I often give is to spend more time in the company of people whohave those routines down. If you want to improve your diet, eat withpeople who know about and are in the habit of making healthy food choices. Eating well is afoundation of good health. It can help you feel well, give you the energy you need, and copewith routine ailments, from colds to lack of sleep. Long term, it will reduce the risk and delaythe onset of the chronic age-related diseases.For years I have urged people to include several servings of fresh organic fruits and vegetablesin their daily diets, and to choose produce that covers all parts of the color spectrum. The medicalevidence linking fruits and vegetables to good health is overwhelming. And now, so too is the newevidence that organic fruits and vegetables deliver more nutrients per average serving, includingthe all-important protective phytonutrients like polyphenols and antioxidant pigments.Getting in the habit of choosing organic food whenever you can will ensure that you and your familyget the nutritional benefits nature provides. It is a cornerstone on which to structure a lifestyle thatwill promote and maintain health lifelong.Andrew Weil, MDBoard Member, The Organic CenterDirector of the Program in Integrative MedicineUniversity of ArizonaMarch 2008
  • 4. The Organic Center Critical Issue Report Page March 2008 Nutritional Superiority of Organic Food 1I. Executive Summary“We just don’t know…” or In the six years since 2001, more than forty new studies have been published, increasing the number of peer-reviewed studies comparing the“There is not enough high quality data to reach nutritional quality of organic and conventionalconclusions” have been the common answers foods to over 100. Figure 1 shows the steadygiven over the last few years when nutritionists increase in the number of studies published perand agricultural scientists have been asked the year over the last three decades.question on the minds of many consumers -- “Areorganic foods more nutritious?” Not only has the number of studies doubled since 2000, the quality of the studies has also improvedIn fact, this sort of ambivalent answer accurately immensely, as has the sensitivity of the analyticalreflects, for the most part, the major conclusions methods used to measure nutrients contained inreported in five published scientific literature foods.reviews of studies comparing the nutritionalquality of organic and conventional food. These Most studies in the 1980s focused simply onreviews all appeared between 2001 and 2003. mineral and vitamin levels, while almost all studiesThe most recent of the five reviews came out in published since 2000 include measures of2003 and covered comparative studies through minerals, vitamins, and health-promotingthe end of 2001. polyphenols and total antioxidant capacity. Figure 1. Increase in the Number of Studies Published per Year Comparing the Nutrient Content of Organic and Conventional Foods 7 Average Number 6 of Studies 5 Published per Year 4 3 2 1 0 1980s 1990s Since 2000
  • 5. The Organic Center Critical Issue Report Page March 2008 Nutritional Superiority of Organic Food 2A Fresh Look and exclusion criteria and a rating system. The criteria were chosen to help restrict our analysis ofWe identified all peer-reviewed studies published nutrient levels across multiple studies to just thosein the scientific literature appearing since 1980 experiments producing the highest quality data.comparing the nutrient levels in organic and We believe our screening method achieved thisconventional foods and screened them in two objective, but acknowledge that there are manyways for scientific validity. We assessed how the alternative ways to accomplish the same goal.studies defined and selected organic andconventional crops for nutrient level comparisons. There were 135 study-crop combinations coveredFrom 97 published studies, we identified 236 in the 97 studies. Based on our screen, 70% ofscientifically valid “matched pairs” of the study-crop combinations were deemedmeasurements that include an organic and a “acceptable” or “high quality” (94 out of 135), andconventional sample of a given food. hence “valid”, while 41 were deemed “invalid” for the purposes of this study.Our first screen took into account the experimentaldesign of each study, the need for the same We also screened the 94 valid study-cropcultivars to be planted in both the organic and combinations for the accuracy and reliability ofconventional fields, the degree of differences in the analytical methods used to measure nutrientsoil types and topography, the focus of the study levels. This screen factored in the base resolution,and where it was carried out, the definition of standard deviations, and reliability of theorganic farming, and years the organic field in a chromatographs and other measurementmatched pair had been managed organically. techniques. Fifty-five study-crop-analytical method combinations were deemed “invalid” for aFor each crop addressed in a given study, we specific nutrient measurement. (Other nutrientdetermined whether the study was “high quality,” measurements from the same study-crop“acceptable” or “invalid” based on explicit inclusion combination could be deemed valid).
  • 6. The Organic Center Critical Issue Report Page March 2008 Nutritional Superiority of Organic Food 3Seventeen criteria and decision rules were also and antioxidants in about three-quarters of the 59established and adhered to in selecting the most matched pairs representing those fourappropriate matched pairs from a given study to phytonutrients. Increasing intakes of theseinclude in our cross-study comparisons of nutrient nutrients is a vital goal to improve public healthlevels. We needed these criteria because some since daily intakes of antioxidants and polyphenolsstudies reported results on a dozen or more are less than one-half of recommended levels.different combinations of production systemalternatives, variable rates of fertilizer, different Matched pairs involving comparisons ofharvest dates, and alternative food formulations potassium, phosphorous, and total protein levels(i.e. fresh, dry, frozen, pureed). accounted for over three-quarters of the 87 cases in which the conventional samples wereWe used these 17 decision rules to select the nutritionally superior. While a positive finding,matched pairs from a given study-crop these three nutrients are clearly of lessercombination that most closely reflected food in its importance than the other eight nutrients because,fresh form, grown using routine or typical organic in general, these nutrients are adequately suppliedand conventional practices. in the average American diet.As a result of these screens and selection criteria, The magnitude of the differences in nutrient levelswe had an adequate number of valid matched strongly favored the organic samples. One-pairs (at least eight) to compare the levels of 11 quarter of the matched pairs in which the organicnutrients in organic and conventional foods. The food contained higher levels of nutrients exceedednutrients included: the level in the conventional sample by 31% or • Four measures of antioxidants (total more. Only 6% of the matched pairs in which the phenolics, total antioxidant capacity, conventional sample was more nutrient dense quercetin, kaempferol), exceeded the levels in the organic samples by • Three precursors of key vitamins 31% or more. (Vitamins A, C, and E), • Two minerals (potassium and phosphorous), • Nitrates (higher levels are a nutritional disadvantage), and • Total protein.Key FindingsThere were 236 valid matched pairs across the11 nutrients. The organic foods within thesematched pairs were nutritionally superior in 145matched pairs, or in 61% of the cases, while theconventional foods were more nutrient dense in87 matched pairs, or 37%. There were nodifferences in 2% of the matched pairs.The organic samples contained higherconcentrations of the very important polyphenols
  • 7. The Organic Center Critical Issue Report Page March 2008 Nutritional Superiority of Organic Food 4For five nutirents, Figure 2 shows the percent of averaged 25%. The differences documented intotal matched pairs for which the orangic sample this study are sufficiently consistent and sizablenutrient level exceeded the conventional sample to justify a new answer to the original question–level by eleven percent or more. Almost one-halfof the 57 organic samples in these matched pairs Yes, organic plant-based foods are, onexceeded the conventional sample nutirent level average, more nutritious.by 21% or more. Over the next few years another 20-30 studiesAnother perspective reinforces the basic point. will likely be completed and published. TheAbout 22% of the 145 matched pairs in which the Organic Center will add the results of theseorganic samples were more nutrient dense fell studies to our database, subject them to the samewithin a difference of only 0% to 10%, which can sort of scientific-merit screens, and then updatebe regarded as minor. Almost two-thirds of the and refine the analysis reported herein.conventional matched pairs found to be morenutrient dense fell within the 0% to 10% difference Soon, there will be enough high quality studies torange. reach the threshold of eight valid matched pairs for several more nutrients. Greater numbers ofAcross all 236 matched pairs and 11 nutrients, matched pairs for primary nutrients likethe nutritional premium of the organic food antioxidants and Vitamin C will allow estimation ofFigure 2. Percent of Total Matched Pairs for a Nutrient in Which the Organic Sample Nutrient Levels Exceeded the Conventional Samples by % of Matched Pairs with Organic More than 10% Higher by 11% or More 100% 80% 60% 40% 20% 0% Total Phenolics Total Quercetin Vitamin C Vitamin E Antioxidant Capacity Individual Nutrients
  • 8. The Organic Center Critical Issue Report Page March 2008 Nutritional Superiority of Organic Food 5differences in key nutrients by crop and food – the For every farm and agricultural region there areaverage difference, for example, in the total unique combinations of genetics, soils, climate,antioxidant capacity of organic and conventional and practices waiting to be discovered that haveapples, or Vitamin C in oranges. the potential to produce exceptionally nutrient dense and flavorful foods. These are the kinds ofOver time the Center’s database will grow to the fruits and vegetables needed to lure children —point where we can explore linkages between and adults — away from high-fat, sugar-ladenspecific organic and conventional production foods, and in the course of doing so set the stagepractices and the nutrient density of foods. This for sustained improvement in public health.will open an exciting chapter in the continuousimprovement of organic farming systems.

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