Australian nutritionists have choked on suggestions that consumption of organic foods may have a causal link to lower cancer risk.
A French population-based study of nearly 69,000 adults found a significant reduction in the risk of cancer among people who ate a lot of organic food.
The prospective cohort study calculated organic food consumption based on self reports of 16 products between 2009 and 2016. During the study period 1340 first incident cancer cases were identified with the most prevalent being 459 breast cancers, 180 prostate cancers, 135 skin cancers, 99 colorectal cancers, 47 non-Hodgkin lymphomas, and 15 other lymphomas.
High organic food scores were inversely and significantly associated with the overall risk of cancer, with a hazard ratio of 0.75 between the highest and lowest quartiles of organic food consumption. The absolute risk reduction for highest versus lowest intakes of organic food was 0.6%.
Writing in JAMA Internal Medicine, the study authors conclude that “promoting organic food consumption in the general population could be a promising preventive strategy against cancer.”
But Peter Clifton, Professor of Nutrition at the University of South Australia, says the paper did not show that the lower cancer rates were actually due to the organic foods.
“Cancer has a very long development period so to assume causation these people would need to have been consuming organic foods for many years, possibly longer than it has been available,” he said.
“The major failing in relation to organic food is a lack of convincing biological causation-the herbicides and pesticides avoided need to have been shown to cause cancer in animals at human doses in reproducible studies and to cause DNA defects in human consumers.”
“We also need to see a relationship between urinary levels of the putatative cancer causing agents and cancer rates.”
Dr Rosemary Stanton a Public Health Nutritionist and Visiting Fellow, School of Medical Sciences, University of New South Wales, said the absence of synthetic fertilisers and pesticide in organic foods might provide a mechanism to explain reduced cancer risk, but the study didn’t measure levels of pesticide residues in participants.
“As well as the differences in what is added during production, organically-grown products may involve different varieties with different flavour profiles, often harvested only when fully ripe. Such details means that many organically grown products cost more. This will affect consumption patterns. Other positive health behaviours may also be relevant for those with less socio-economic stress,” she said.