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Adjunct Faculty, Research Investigator, Bastyr University, Seattle, WA
Dr. Pantuso reports no financial relationships relevant to this field of study.
SYNOPSIS: In this prospective cohort study, high amounts of organic food consumption were associated with a significant decrease in the risk of overall cancer, particularly postmenopausal breast cancer, non-hodgkin lymphoma, and other lymphomas.
SOURCE: Baudry J, Assmann KE, Touvier M, et al. Association of organic food consumption with cancer risk: Findings from the nutrinet-santé prospective cohort study. JAMA Intern Med 2018;178:1597-1606.
In 2018, the estimated number of new cancer cases was more than 17 million worldwide.1 Although it has not been well-researched, environmental risk factors include exposure to pesticides.2 There is a growing body of evidence demonstrating an association between pesticide exposure and the development of cancer.2,3
The authors of this population-based cohort study investigated the association between an organic food-based diet and the risk of cancer in 68,946 French adults. This study is part of a larger research project called the NutriNet-Santé study, which is investigating the associations between nutrition and health and other determinants of dietary behaviors and nutritional status in France.4 Adults 18 years and older were recruited into the NutriNet-Santé study using a web-based platform. Of the 68,946 participants, 78% were female, with a mean age at baseline of 44.2 years. After registration, participants were followed through a website that was designed specifically for this purpose with an online, secure HTML interface.
At enrollment, participants completed a set of questionnaires investigating sociodemographics, health status, lifestyle, physical activity, anthropometrics, and diet. These questionnaires were pilot tested and either objectively validated or compared against traditional assessment methods. At two months post enrollment, participants provided information on their consumption of 16 groups of organic products. These 16 groups of organic products included vegetables; fruits; soy-based products; dairy products; meat and fish; eggs; grains and legumes; bread and cereals; flour; vegetable oils and condiments; ready-to-eat meals; coffee, tea, and herbal tea; wine; biscuits, chocolate, sugar and marmalade; other foods; and dietary supplements. The authors calculated the frequency of organic foods using the following categories: 1) most of the time, 2) occasionally, 3) never (“too expensive”), 4) never (“product not available”), 5) never (“I am not interested in organic products”), 6) never (“I avoid such products”), 7) never (“for no specific reason”), 8) “I don’t know.” For each category, points were allocated to each response, with two points being allotted to “most of the time,” one point for “occasionally,” and zero for the “never” categories. The 16 categories of food with frequency of consumption data (points) were summed to provide an organic score from 0 to 32 points.
Baudrey et al also evaluated the participants’ dietary intake at baseline using three random, 24-hour diet diary recalls during a two-week period. This period included two weekdays and one weekend day, and was separate from the organic food intake information the participants provided.
Participants recorded all foods and beverages eaten, and estimated portion sizes by looking at photographs from a previously validated picture booklet, or by weight, volume, or the purchased unit. Seafood intake was measured by a specific frequency question. The authors accounted for ultra-processed food and assessed it using the NOVA classification system. Nutrient intake was assessed from individual food consumption calculated using the NutriNet-Santé food composition table. The authors excluded under-reporters of food intake.
The authors also assessed diet quality using a modified version of the validated Programme National Nutrition Santé Guideline Score (PNNS-GS) without the physical activity component, reflecting adherence to the official French National Guidelines. The French National Guidelines recommend a diet high in fruits and vegetables, whole grains, legumes, and potatoes, with moderate consumption of dairy, eggs, and meat.5 Currently, the French National Guidelines are under review, and an update will be released in 2021.6
In this study, participants self-declared medical health events annually. When patients reported a case of cancer, the clinical research study physician requested to be provided the medical records. An independent medical expert committee reviewed all major health events. Medical records were obtained in 90% of all self-reported cancer cases. The study included all new primary cancers, with the exception of basal cell carcinoma, diagnosed between study initiation and Nov. 30, 2016. The authors used the COX proportional hazards regression model to calculate hazard ratios and 95% confidence intervals (CI), and P < 0.05 was considered statistically significant.
During the follow-up period of 4.56 years, the researchers identified 1,340 first-incident cancer cases, including 459 breast cancer cases, 180 prostate cancers, 135 skin cancers, 99 colorectal cancers, 47 non-Hodgkin lymphomas (NHL), and 15 other lymphomas.
High organic food scores were associated linearly and negatively with the overall risk of cancer (hazard ratio [HR] for fourth quartile vs. first quartile, 0.75; 95% CI, 0.63-0.88, P trend = 0.001). The authors also removed early cancer cases and found that the overall association remained significant for fourth quartile vs. first quartile (0.70; 95% CI, 0.56-0.88; P trend = 0.004). When analyzing the results by cancer site, the authors found a decreased risk of postmenopausal breast cancer (P = 0.03), NHL (P = 0.049), and lymphomas (P = 0.02) in patients with high-frequency organic food consumption. The authors did not report any worsening of health outcomes or adverse events.
Since this study is part of a the larger NutriNet-Santé Study, the authors controlled for overall diet quality calculated from 24-hour food recall questionnaires. The authors found that when combined with a high-quality diet or a low-quality diet, organic food consumption was associated with a reduced risk of overall cancer. Although this finding was not significant, it suggests that high-frequency organic food consumption is a major factor in the reduction in the risk of overall cancer.
There is limited epidemiological research investigating the association between cancer risk and organic food consumption, which makes this study important. It is one of the first studies to examine the frequency of organic food consumption and cancer risk while incorporating detailed information on pesticide exposure and controlling for diet quality. The sample size for this study was large, and the authors performed a stratified analysis on cancer sites, indicating a decreased risk of postmenopausal breast cancer, NHL, and lymphomas with increased organic food consumption. The authors also used detailed questionnaires on organic food frequency, and clinical research physicians reviewed the cancer cases.
The authors of The Million Women Study, carried out with 623,080 women in the United Kingdom, found that organic food consumption was not associated with a reduction in overall cancer incidence.7 They also found that women who reported usually or always eating organic food had a small increase in breast cancer incidence compared to women who reported never eating organic food. Interestingly, The Million Women Study authors did find that increased organic food consumption was associated with a 21% lower risk of NHL than nonconsumption of organic food.7
More recently, the authors of the Sister Study found a lower risk of breast cancer with higher frequency of organic food consumption in 39,563 women.8 The Sister Study is a research study investigating the environmental and genetic risk factors for breast cancer in the United States. The authors found that any organic food consumption was inversely associated with breast cancer (HR, 0.87; 95% CI, 0.80-0.95), particularly estrogen receptor-negative cancer (HR, 0.77; 95% CI, 0.61–0.98).8
Since the Million Women Study, the Sister Study, and the NutriNet-Santé study have differing results regarding the risk of breast cancer and organic food consumption frequency, more research studies with longer follow-up periods are needed. The Million Women Study had a follow-up period of 9.3 years, the Sister Study had a 9.0-year follow-up, and the NutriNet-Santé study had a follow-up period of 4.56 years. The Million Women Study authors suggested that future prospective studies investigating the role of organic food consumption and cancer risk, particularly with NHL, should enroll 500,000 participants with a follow-up period of at least a decade.7
There are a number of limitations to this study and to research in organic food consumption in general. Specific limitations include the self-selected participants who may be more likely to be concerned about their health. In addition, the participants were mostly female, exhibited healthier behaviors (e.g., higher quality diet and decreased smoking), and had a higher education level than the general population in France, limiting the generalizability of the findings.9 The follow-up time for this study was 4.56 years, which may not be long enough to capture nuances of cancer causation. Further limitations to commenting on causation result from this being a prospective cohort study rather than a controlled trial. In general, organic food consumption information has been obtained from responses on food frequency questionnaires, limiting the reliability.
Individuals who regularly consume organic food also tend to have healthier dietary pattering, eating less meat and more fruits, vegetables, and whole grain products.3 In addition, consumers who purchase organic foods are also less likely to smoke and are more likely to be physically active.3 The NutriNet-Santé Study previously demonstrated that individuals who consumed increased amounts of organic food had a decreased risk of obesity, hypertension, type 2 diabetes, and hypercholesterolemia compared to those who consumed low amounts.8 They also found that men had a decreased risk of cardiovascular disease with increased frequency of organic food consumption.10 Although the authors controlled for numerous confounding variables (physical activity, smoking status, alcohol intake, family history of cancer, body mass index, energy intake, fiber intake, processed meat intake, red meat intake, postmenopausal status, hormone treatment for menopause, and oral contraceptives), there may be other unknown risk factors.
More research is needed to further delineate the risk of cancer and whether to eat organic food, which may be related to pesticide residue on food. Organic food has been found to be higher in beneficial nutrients, such as antioxidant compounds in fruits and vegetables and higher omega-3 fatty acids in meat and dairy products.11,12 There is also a lack of long-term interventional studies researching the link between organic food and human health, making it difficult to assess the effect of organic food consumption on health.3
These prospective cohort studies are an important first piece of the puzzle to spur more research with trial designs that are properly powered to infer causation. In the meantime, there are benefits to supporting organic farming, such as the health and environmental benefits associated with decreasing or eliminating pesticide use. Decreasing the use of pesticides in farming through organic farming is more sustainable for the environment, it decreases the risk of occupational pesticide exposure, and it decreases pesticide residues on food. Organic food often is more expensive than conventionally grown food, which may be unaffordable for some patients. The Environmental Working Group produces a Shopper’s Guide listing fruits and vegetables that the group recommends for people to purchase organic.13 This list is determined by the USDA reports on pesticide testing.13
Bottom Line: There may be health benefits with eating organic food, as shown by the decreased risk of certain cancers in this observational analysis. Provided that the extra cost is not prohibitive and there is reasonable availability of organic food, clinicians can recommend a focus on these foods for all demographics. Future research will hopefully both clarify the specific benefits of these foods, as well as the mechanisms of action.
Financial Disclosure: Integrative Medicine Alert’s Executive Editor David Kiefer, MD; Peer Reviewer Suhani Bora, MD; Relias Media Associate Editor Journey Roberts; Editorial Group Manager Leslie Coplin; and Accreditations Manager Amy M. Johnson, MSN, RN, CPN, report no financial relationships relevant to this field of study.