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Invited Commentary
October 22, 2018

Organic Foods for Cancer Prevention—Worth the Investment?

Author Affiliations
  • 1Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
  • 2Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
  • 3Channing Division of Network Medicine, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
JAMA Intern Med. Published online October 22, 2018. doi:10.1001/jamainternmed.2018.4363

In 2015, the International Agency for Research on Cancer1 classified 3 pesticides frequently used in agriculture—glyphosate, malathion, and diazinon—as carcinogenic to humans (group 2A) based on evidence from studies of occupational exposure in humans and laboratory studies in animals. Through occupational exposure (primarily in agricultural settings), malathion is associated with prostate cancer, diazinon is associated with lung cancer, and all 3 pesticides are individually linked to non-Hodgkin lymphoma.1 In the general population, low-level pesticide exposure is widespread, and the primary route of exposure is diet, especially intake of conventionally grown fruits and vegetables.2 In the United States, more than 90% of the population have detectable pesticides in their urine and blood.3 Organic foods are produced without synthetic pesticides and are less likely to contain pesticide residues than conventionally produced, nonorganic foods.4 Crossover trials have shown that switching from consuming conventionally grown foods to organic foods decreases urinary concentrations of pesticide metabolites, suggesting reduced exposure to pesticides.4 Nevertheless, the health consequences of consuming pesticide residues from conventionally grown foods are unknown, as are the effects of choosing organic foods or conventionally grown foods known to have fewer pesticide residues.

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    2 Comments for this article
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    Food choices and Organic Food Consumptions.
    Jonathan Harris, PhD Chemistry. | Indepdendent
    I wonder if the authors and commentators have considered the possibility that beyond the food choices addressed by the study, those who consume organic foods likely have more subtle differences in diet from those who don't. For example the choices within each food group could be altered by the relative availability and cost of organic options of specific items. Since foods contain a large number of different natural chemicals, it would not be ridiculous for variations in these natural chemicals to play a role in cancer risk.
    CONFLICT OF INTEREST: None Reported
    More questions than answers in this study about organic food consumption
    Guy Pelouze, MD MSc |
    1/ The volunteers of the study represent a very highly biased population as 78.0% of 68 946 participants were women. Only 22% of male volunteers is by itself a great explanation of the results.
    2/ 1340 first incident cancer cases were identified, with the most prevalent being 459 breast cancers (34.3%), 180 prostate cancers (13.4%), 135 skin cancers (melanoma and spinocellular carcinoma) (10.1%), 99 colorectal cancers (7.4%), 47 non-Hodgkin lymphomas (3.5%), and 15 other lymphomas (1.1%).
    3/ The reduction of risk associated with organic food consumption is only about postmenopausal breast cancer, non-Hodgkin lymphomas, and all lymphomas (62 cases) /> For non-Hodgkin lymphoma and lymphomas, the risk reduction with organic food consumption is not linear and in lymphomas, the Q3 has a trend of higher risk!
    Non-Hodgkin lymphoma
    1 [Reference]
    0.80 (0.35-1.81)
    1.21 (0.61-2.43)
    0.27 (0.07-0.96)
    .23
    0.75 (0.60-0.93)
    .009
    All lymphomas
    1 [Reference]
    0.56 (0.27-1.17)
    0.97 (0.54-1.74)
    0.23 (0.08-0.69)
    .05
    0.75 (0.60-0.93)
    .03
    4/ Among the participants consuming organic food, physical activity and alcohol consumption are different. But we those factors are  important and more important than pesticides in cancer promotion and development.
    5/ In the figure, several unlikely findings are against all other evidence in the literature.
    - Sex. In men who do have a higher rate of cancers, there is no difference between the Q4 vs Q1.
    In women who do have a lower rate of cancers the  women in Q4 do have a lesser risk than those in Q1. This suggestion is that organic food consumption lowers the risk in women only.
    - Age. Q4 vs Q1. Organic food consumption is associated with a lesser risk only in post-median age participants. This means that in the time interval cancers which are the slowest to develop, Thus, cancers in older people would have been reduced and the others that grow faster in younger people wouldn't be.
    - BMI ≤25 0.81 (0.66-0.99)
    BMI >25 to <30 0.66 (0.48-0.90)
    BMI ≥30 0.57 (0.35-0.93)
    It is very improbable that people with BMI >30 would have been "protected" when consuming organic food in the Q4, considering the evidence about the link between obesity and cancer.
    - That organic food consumption does have an undifferentiated effect in non-smokers and former or current smokers is very unlikely, given what is known about smoking and cancer and the quantitated effect of carcinogens.. 

    For these reasons, people should be advised to implement a healthy lifestyle based on efficient measures:
    No smoking,
    Moderate to high physical activity.
    Normal weight and hip/waist ratio even at old age.
    Fewer carbohydrates and especially added sugars.
    Less processed foods including processed meats.
    CONFLICT OF INTEREST: None Reported
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