Baudry J, Assmann KE, Touvier M, et al. Association of frequency of organic food consumption with cancer risk: findings from the NutriNet-Santé Prospective Cohort Study. JAMA Intern Med. 2018;178(12):1597-1606.
To investigate the association between organic food consumption and cancer risk in a large prospective study
This was a prospective cohort study of 68,946 French adults who reported their frequency of organic food consumption. Volunteers were asked to provide information on their consumption frequency of 16 organic products (fruits; vegetables; 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). Dietary intake was assessed using three 24-hour records randomly allocated over a 2-week period, including 2 weekdays and 1 weekend day. Participants were followed for a mean of 4.5 years.
The data were adjusted for confounding factors such as sociodemographics, lifestyle, and dietary patterns. Baseline age, sex, occupation, educational level, marital status, monthly income per household, number of children, and smoking status were collected.
Participants self-declared health events through a yearly health status questionnaire or an interface on the study website. Medical records were obtained for more than 90% of self-reported cancer cases. The French national health insurance system database and the French mortality epidemiology database were used to collect and verify reported health records and mortality data.
There were 68,946 participants, 78% of whom were female. Mean age at beginning of the study was 44.2 years.
Study Parameters Assessed
The authors assessed both the frequency of organic food consumption and the quality of the food consumed; quality of the diet was based on nutrient density.
An organic food score was computed based on the participant reports, ranging from 0 to 32 points. Consumption frequencies were reported with the following options: (1) most of the time; (2) occasionally; (3) never “too expensive”; (4) never “product not available”; (5) never “I’m not interested in organic products”; (6) never “I avoid such products”; (7) never “for no specific reason”; and (8) I don’t know.
Nutrient intake was derived from the self-reported diet diaries and was calculated using the NutriNet-Santé food composition table. To assess dietary quality, these intake values were compared to the official French nutritional guidelines.
The primary outcome measure was the number of incident cancer cases in the follow-up period.
A total of 1,340 first incident cancer cases were identified during follow-up; the most prevalent were breast cancer (459; 34.3%), prostate cancer (180; 13.4%), skin cancer (135; 10.1%), colorectal cancer (99; 7.4%), non-Hodgkin lymphoma (47; 3.5%), and other lymphomas (15; 1.1%). High organic food scores were inversely associated with the overall risk of cancer (hazard ratio for the fourth quartile compared to the first quartile, 0.75; 95% confidence interval [CI]: 0.63-0.88; P for trend=0.001; absolute risk reduction, 0.6%; hazard ratio for a 5-point increase, 0.92; 95% CI: 0.88-0.96).
Higher organic food scores were linearly and inversely associated with the overall risk of cancer. Significant risk reduction was seen for non-Hodgkin lymphoma (hazard ratio for a 5-point increase, 0.75; CI: 0.6-0.93; P=0.009) and for other lymphomas (hazard ratio for a 5-point increase, 0.75; CI: 0.6-0.93; P=0.03). There were trends of risk reduction for post-menopausal breast cancer (hazard ratio for a 5-point increase, 0.91; CI: 0.83-1.01; P=0.07), and skin cancer (hazard ratio for a 5-point increase, 0.89: CI: 0.78-1.01; P=0.06).
Accounting for other additional dietary factors did not modify the factors.
Higher organic food scores were positively associated with female sex, monthly income, education level, physical activity, and former smoking status. Higher organic food scores were also associated with a healthier diet rich in fiber, vegetable proteins, and micronutrients (ie, a higher intake of fruits, vegetables, nuts, and legumes), and with a lower intake of processed meat, other meat, poultry, and milk.
This large cohort study of French adults provides strong epidemiological evidence that a higher frequency of organic food consumption is associated with a decreased risk of developing cancer, specifically non-Hodgkin lymphoma, other lymphomas, and postmenopausal breast cancer.
This study contradicts a prior publication by Bradbury and colleagues from 2014. Bradbury’s prospective study of 623,080 women in the United Kingdom found that organic food consumption was not associated with a reduction in overall cancer risk. In fact, there was a significant increased risk of breast cancer among women with high organic food intake.1 The 2014 study had a longer follow-up period than the present study (9 years vs 5 years), and it also looked at nearly 10 times more people (though all participants were women). The different demographics, size, duration, and locations (United Kingdom and France) of the studies, as well as differences in assessment methods and statistical analysis, could all contribute to the conflicting results. It is interesting that while the 2014 study did not show overall cancer risk reduction, both studies did show a reduction in the risk for non-Hodgkin lymphoma with organic food consumption.
Another confounding factor is that the definition of the term 'organic' varies from country to country, which makes comparisons between studies challenging.
One of the limitations of the present study is selection bias: the participants were volunteers, and likely more health-conscious than people who would not volunteer. Another major limitation is the relatively short follow-up time (mean of 4.5 years). Would the results change with longer follow-up time? There is no way to predict this. Certainly more research needs to be done to validate these results, increase the follow-up time, and expand the demographic to other parts of the world. Another confounding factor is that the definition of the term “organic” varies from country to country, which makes comparisons between studies challenging.
Participants of higher socioeconomic status who ate a diet rich in a variety of plant foods (vegetables, nuts, legumes, fruits), and thus high in fiber and micronutrients, had higher organic food scores. While dietary patterns were controlled for, the independent benefits of eating a high-quality diet rich in polyphenols, nutrients, and fiber cannot be discounted. Given that those who ate more organic food also ate higher amounts of beneficial foods in general, the “organic” label may be a surrogate parameter for overall intake of plant-based foods.
With a growing body of research indicating certain pesticides are carcinogenic, many studies have assessed occupational exposures to various pesticides.1-5 The most well-established link is between occupational exposure to pesticides and incidence of non-Hodgkin lymphoma.6 The present study corroborates this causative link. Future studies should assess the chronic effects of dietary low-dose pesticide residue exposure on the general population. This is a complex endeavor, but a worthy one because it reflects real-life exposure to nonorganic foods.
Even with its limitations, the present study suggests that organic diets have the potential to reduce the risk of developing cancer, findings that should be considered when we make dietary prescriptions for patients. Although there may be a short-term increased financial cost to purchasing organic food, it could be financially beneficial in the long-term due to the potential decreased risk of developing cancer, which can be a huge financial burden. Given that there is no risk of eating organic foods and perhaps significant benefits, it seems like a rational approach to incorporate organic foods whenever possible.