Thanks to the Price-Pottenger Nutrition Foundation for access to this article!
by Virginia Worthington, ScD
This article is a summary of a study entitled:
Effect of Agricultural Methods on Nutritional Quality:
A Comparison of Organic with Conventional Crops
Alternative Therapies Health Med 1998 (Jan); 4 (1): 58–69
Since the 1920s, when chemical fertilizers were first used commercially on a large scale, there have been claims that agricultural chemicals produce less healthful and less nutritious food crops. By the 1940s, the organic farming movement had begun, in part due to this belief that food grown using more traditional, chemical-free methods was more healthful. Foods grown by these methods came to be known as “organic.” Today, this notion has continued in the alternate health arena, and some alternative treatments, such as the Gerson cancer therapy, rely on food grown organically.
But the question remains: is organically grown food more nutritious? There are several reasons why there has not been a solid answer to this question. 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.
A second reason is that it is difficult to conduct and interpret agricultural research investigating nutrient content. Factors such as sunlight, temperature and rainfall, which influence the nutrient content of plants, vary from year to year. Additional changes in the nutrient content of a crop can occur during storage and shipping. For these reasons, it is difficult both to plan effective studies and to make sense of the results. Furthermore, these considerations often make it difficult to compare the results of different studies.
Finally, many of the studies that have been done are relatively old and not performed according to modern standards. In particular, the older studies do not include a rigorous statistical analysis. This factor alone can make these studies difficult to evaluate. As a result, these studies have been dismissed by some as valueless.
What is the evidence? There are more than 30 studies comparing the nutrient content of organic crops and those produced conventionally with chemical fertilizers and pesticides. In these studies, various individual nutrients in individual crops were compared, such as zinc in organic versus conventional carrots, or vitamin C in organic versus conventional broccoli. In the more than 300 comparisons performed in these studies, organic crops had a higher nutrient content about 40% of the time, and conventional crops had a higher nutrient content only about 15% of the time. Overall, organic crops had an equal or higher nutrient content about 85% of the time. These results suggest that, on average, organic crops have a higher nutrient content.
While the overall outlook is favorable for organic crops, there is too little data for most individual nutrients to say anything at all. But for three individual nutrients - vitamin C, nitrates and protein quality – there is enough evidence to suggest that organic crops are superior to conventional ones. Compared to crops grown with chemical fertilizers and pesticides, organically grown crops generally have a higher vitamin C content, a lower content of carcinogenic nitrates and better protein quality. Further work is needed on other nutrients before any definitive conclusions can be drawn. While this nutrient content data is interesting, it does not tell us anything about the health of people and animals that consume these crops.
The most relevant studies then, are not those that simply assess nutrient content, but are those that feed organic or conventional feed to animals and then look at how healthy they are. There are 14 such animal studies that have been performed over the last 70 years. In ten of these, the organically fed animals fared better; in one, the animals fed organic feed came in second among several chemically fertilized feeds; and 3 studies showed no difference, possibly due to weaknesses in the study designs.
The ten positive studies are summarized in Table 1. Again, these results support the notion that organically produced crops may be more conducive to good health and hence more nutritious. The positive effects are most striking in sick or otherwise vulnerable animals such as newborns and in sensitive areas of reproduction such as sperm motility. It is particularly interesting to see that the fertility of animals fed fodder grown with chemical fertilizers and pesticides declined over several generations. This recalls the progressive decline in health that Dr. Pottenger saw in each succeeding generation of cats fed a less than optimal diet.
In summary, from the research that has been done, it appears that organically grown crops may have, on average, a higher nutrient content than crops grown with chemical fertilizers and pesticides. In addition, animal evidence supports the thesis that organically produced foodstuff can produce a better health outcome over the long term, particularly in the area of reproduction. These studies support a return to traditional, organic farming methods.
Table 1. Summary of Results from 10 Animal Studies:
Comparisons of Organic with Conventional Feed
|Impact on Reproduction
Higher ovum production in rabbits (6 versus 3 eggs per dam) & chickens (192 versus 150 eggs per hen).
|Males: Testes in better condition in mice; sperm motility greater in bulls.
Fewer perinatal deaths & other deaths prior to weaning in rabbits (mortality rate of 27% versus 51%) in mice (mortality rate of 9% versus 17%) and rats
|Overall: Fertility rate of rabbits remained constant over 3 generations in organically fed rabbits and declined in rabbits fed conventionally produced feed
|Impact on Weight Maintenance & Growth
- Lower percentage weight loss (22.4% versus 37.4%) & longer survival (50 versus 33 days) in birds with polyneuritis.
- Better weight maintenance in lactating female rats.
- Higher percentage weight gain in young rats (77% versus 51.4%) and in chickens.
- Better weight gain after coccidial illness and fewer incidents of illness in chickens.
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