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Baudry J, Assmann KE, Touvier M, et al. Association of organic food consumption frequency with cancer risk: results of the NutriNet-Santé prospective cohort study.JAMA Intern Med. 2018;178(12):1597-1606.
Objective
To examine the association between organic food consumption and cancer risk in a large prospective study
Draft
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 spices, convenience foods) to-eat meals; coffee, tea and herbal teas; Wine; biscuits, chocolate, sugar and jam; other foods; and nutritional supplements). Dietary intake was assessed using three 24-hour recordings randomly distributed over a 2-week period, including 2 weekdays and 1 weekend day. Participants were followed for an average of 4.5 years.
The data was adjusted for confounding factors such as sociodemographics, lifestyle and dietary habits. Baseline age, gender, occupation, education level, marital status, monthly income per household, number of children and smoking status were collected.
Participants self-declared health events via an annual 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 review reported medical records and mortality data.
Participant
There were 68,946 participants, 78% of whom were female. The average age at the start 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; Diet quality was based on nutrient density.
Based on participants' reports, an organic food score was calculated, ranging from 0 to 32 points. Consumption frequencies were reported using the following options: (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 “without a special reason”; and (8) I don't know.
Nutrient intake was derived from self-reported food diaries and calculated using theNutriNet-SantéFood composition table. To assess diet quality, these intake values were compared with the official French nutritional guidelines.
Target parameters
The primary endpoint was the number of new cancer cases during the follow-up period.
Key insights
A total of 1,340 first-incidence cancer cases were identified during follow-up; the most common were breast cancer (459; 34.3%), prostate cancer (180; 13.4%), skin cancer (135; 10.1%), colon cancer (99; 7.4%), and non-Hodgkin's lymphoma (47; 3.5%). and other lymphomas (15; 1.1%). High organic food scores were inversely associated with overall cancer risk (hazard ratio for the fourth quartile compared to the first quartile, 0.75; 95% confidence interval [CI]: 0.63-0.88;Pfor 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 overall cancer risk. A significant risk reduction was observed in non-Hodgkin's 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 in risk reduction for postmenopausal 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).
Consideration of other additional dietary factors did not change the factors.
Higher organic food scores were positively associated with female gender, monthly income, education level, physical activity, and previous smoking status. Higher organic food scores were also associated with healthier diets rich in fiber, plant proteins, and micronutrients (i.e., higher intakes of fruits, vegetables, nuts, and legumes) and with lower intakes of processed meats, other meats, poultry, and milk.
Practice implications
This large cohort study of French adults provides strong epidemiological evidence that a higher frequency of organic food consumption is associated with a reduced risk of developing cancer, particularly non-Hodgkin's lymphoma, other lymphomas and postmenopausal breast cancer.
This study contradicts a previous publication by Bradbury and colleagues in 2014. Bradbury's prospective study of 623,080 women in the United Kingdom found that eating organic food was not associated with a reduction in overall cancer risk. In fact, there was a significantly increased risk of breast cancer in women with a high intake of organic foods.1The 2014 study had a longer follow-up period than the current study (9 years versus 5 years) and it also examined almost 10 times more people (although all participants were women). The different demographic characteristics, size, duration and locations (UK and France) of the studies, as well as differences in assessment methods and statistical analysis, could all contribute to the contradictory results. It's interesting that while the 2014 study didn't show a reduction in cancer risk overall, both studies showed a reduction in the risk of non-Hodgkin's lymphoma from eating organic foods.
Another confusing factor is that the definition of organic varies from country to country, making comparisons between studies difficult.
One of the limitations of the present study is selection bias: participants were volunteers and were likely to be more health conscious than people who would not volunteer. Another major limitation is the relatively short follow-up period (average 4.5 years). Would the results change with longer follow-up? There is no way to predict this. Certainly, more research needs to be done to validate these results, extend the follow-up period, and expand the demographics to other parts of the world. Another confusing factor is that the definition of organic varies from country to country, making comparisons between studies difficult.
Participants with higher socioeconomic status who ate diets rich in plant-based foods (vegetables, nuts, legumes, fruits) and therefore high in fiber and micronutrients had higher organic food scores. While dietary habits were controlled, the independent benefits of a high-quality diet rich in polyphenols, nutrients and fiber cannot be ignored. Given that those who consumed more organic foods also generally consumed more healthy foods, the “organic” label may be a surrogate parameter for overall plant-based food intake.
With a growing body of research indicating that certain pesticides are carcinogenic, many studies have evaluated occupational exposure to various pesticides.1-5The best established link is between occupational exposure to pesticides and the occurrence of non-Hodgkin's lymphoma.6The present study confirms this causal relationship. Future studies should evaluate the chronic effects of exposure to low-dose dietary pesticide residues on the general population. This is a complex undertaking, but a worthwhile one as it reflects real-world exposure to non-organic foods.
Despite its limitations, the present study suggests that organic diets have the potential to reduce cancer risk, findings that should be taken into account when prescribing diets to patients. Although purchasing organic food may have a higher financial cost in the short term, it could be financially beneficial in the long term as there may be a lower risk of developing cancer, which can be a huge financial burden. Given that there are no risks and potentially significant benefits to eating organic food, it seems like a sensible approach to use organic food whenever possible.