One day, it may be necessary to be content with swallowing seeds to be sure to eat completely healthy food. And even. An American study comparing the dietary habits of 160,000 people and their impact on mortality suggests that pesticide residues could cancel out the health benefits of fruits and vegetables. This work, published in January in the journal Environment International, were carried out by a prestigious team of researchers from the departments of nutrition, epidemiology and environmental health at Harvard University, in Boston (United States). They are the first to focus so precisely on the question of the links between the consumption of plants with pesticide residues and health effects. But does this mean that all the products in our shopping cart are organic to be healthy?
The answer is not only complex, but also polluted by an extreme polarization of the debate, as with that on glyphosate. The fierce opposition between the newspapers The world, who has first mentioned the Harvard study, and Point, contesting his resultsas well as the controversy that followed on social networks, constitute a perfect example of these tensions. Defenders of conventional agriculture are rarely hesitant to accuse studies that do not agree with them of suffering from major biases, of being financed by lobby groups or of being produced by scientists they consider to be too committed. The defenders of organic gladly return the same arguments to them. Finally, scientific results are often drowned in a political debate. Hardly surprising since supporting theses likely to modify an agricultural strategy is, in essence…political; with important economic interests. And what does science say about it? For the moment, it does not yet make it possible to settle these questions definitively, but it does pose some benchmarks.
Too few studies and data
First, it is useful to recall the points on which the researchers agree. First, eating less meat – especially red meat and cold cuts – while favoring fruits and vegetables is definitely good for our health, but also for that of the planet. The National Agency for Food Safety advises the French in particular to reduce their consumption of charcuterie to 150 grams per week – against 280 currently – in order to reduce “the excess risk of colorectal cancer”. And according to a report by the World Resources Institute, not exceeding 230 grams of beef weekly – two small slices of steak – can reduce greenhouse gas emissions, therefore limiting global warming. Secondly, “People with a diet based more on a more vegetable than animal base have overall more intake of certain micronutrients and fibers and are between 30% and half less obese or overweight”, adds Denis Lairon, biochemist , nutritionist and research director emeritus at Inserm, which participates in the vast NutriNet-Santé program bringing together more than 170,000 French people regularly monitored to assess the relationship between nutrition and health. Third, processed products – pizzas, sodas, prepared meals, sweets – whether organic or not, should be avoided. Finally, more generally, a good diet involves the diversification of foods, not eating too much fat or too much sugar, without forgetting to exercise regularly. So much for the certainties.
But is the consumption of organic fruits and vegetables rather than those from conventional agriculture better for your health? Is the consumption of non-organic vegetables bad for your health? “We still lack epidemiological data to decide, summarizes Bernard Salles, former director of the Toxalim laboratory at Inra, professor in toxicology emeritus at the University of Toulouse, and co-author of a colossal report “Pesticides and effects on health” by Inserm (1036 pages). And even so, when a strong link between a pathology and a pesticide is demonstrated, it is still necessary to explain the causality by finding the mechanism of action.” To make matters worse, modern pesticides contain molecules in such large numbers – and their formulas are so frequently changed – that analyzes remain extremely difficult to perform.
“Are organic fruits and vegetables better for your health than conventional ones? I prefer to ask myself if these foods are chemically different, continues the researcher. And there we have information.” First, organic plants have more antioxidants and water-soluble vitamins, whose health benefits have been demonstrated. This major difference could be explained by the fact that they are less protected by pesticides and are led to produce more antioxidants such as polyphenol in order to fight against stress induced by insects or diseases. “However, factors other than organic could come into play, such as the quality of the soil, the variety of the plant, but also the farming methods involving the maturity of the plant at the time of harvest, the travel time to to the various shops, etc.”, specifies the toxicologist, who believes that short circuits, organic or not, have a real advantage.
Organic vs conventional: 1 – 0?
Then there is another strong argument in favor of organic fruit and vegetables, demonstrated by numerous studies and by the European Food Safety Authority: they undeniably contain much less pesticide residues. A finding that is not necessarily so logical, since organic farmers also use pesticides – like copper – or sometimes cultivate near conventional crops. But are people who eat plants containing less pesticide residue necessarily healthier? “The NutriNet-Santé cohort has demonstrated that heavy consumers of organic fruit and vegetables have less pesticide residues in them, certifies Denis Lairon. Our scientific studies also show that heavy consumers of organic (between 60 and 70% of their diet) are less obese and in better health, with less risk of cardiovascular disease, type 2 diabetes and certain cancers – breast in postmenopausal women and lymphoma – after adjusting the variation factors, such as age, gender, income level, smoking and alcohol consumption.” Furthermore, the Ministry of Health recommends, in its national health nutrition programto favor organic vegetable foods.
Does this allow us, then, to conclude that the consumption of fruits and vegetables from conventional agriculture is bad for your health or would partially cancel out its benefits? “We have not demonstrated it”, recognizes Pr. Lairon. The researcher also regrets the lack of studies and funding on the subject. “Why is public health not better protected and why the CAP in France does not favor organic farming?, he is indignant. Look at what is happening in pharmacovigilance, where extremely monitored can be very quickly withdrawn in the event of a problem. This is without comparison with the monitoring of pesticides, the ban of which is sometimes expected for decades.
For the biochemist, the study published by Harvard therefore represents a great scientific advance. “This team is very serious and their results are particularly relevant. The sample size is spectacular, with three large cohorts that they have been following for decades,” he continues. While he acknowledges that this work has biases – indicated by the authors themselves – he recalls that the same is true for all the cohorts, including that of NutriNet-Santé. “Indeed, we rely on the statements of the participants [qui dans l’absolu pourraient mentir, NDLR], he explains. But the forms are extremely precise and dieticians check the answers with great rigor: a 70-kilogram person claiming to consume 1000 calories a day without declaring a diet is not taken into account, for example.” Conclusion, if the results of Harvard are for the moment too isolated to mark the end of the scientific debate – they will have to be confirmed by several studies in the coming years – they go in the direction of a “little music” suggesting that the consumption of fruits and vegetables with few pesticides is more beneficial than that of plants from conventional agriculture.
However, while there is a lack of data on the effects of the consumption of food contaminated by pesticides and the effects on health, the converse is true: there is little information on the potential negative effects of organic farming. . “Certain productions could, for example, contain mycotoxins – such as aflatoxin – caused by fungi which are difficult to treat without pesticides, advances Bernard Salles. There are none in France, but it is a big problem in Africa. In France, for example, there is the fungus (fusarium) which can contaminate the ears of cereals and produce Don, a fungal mycotoxin causing effects on the immune system. And there are many other examples. I’m not saying will necessarily happen, especially since our standards are strict, but we must be vigilant and compare conventional and biological approaches for each risk.” Organic vegetables and fruits have not finished making controversy.