A recently published study was good news for those who eat organic foods. The large French study (about 69,000 people) found a significantly lower risk of getting cancer (25% lower) in people who ate a lot of organic food - when compared to people who rarely or never ate organic food. The participants in the study were followed for an average of 4.6 years. Cancers with the greatest decreased risk were breast cancer (especially in postmenopausal women) and all lymphomas, especially non-Hodgkin lymphoma.
The researchers summarized the findings as: "In a population-based cohort study of 68 ,946 French adults, a significant reduction in the risk of cancer was observed among high consumers of organic food." and "...if the findings are confirmed, promoting organic food consumption in the general population could be a promising preventive strategy against cancer." This could be an easy way to cut cancer risk! (Other organic food benefits.)
Of course the pesticide and conventional agriculture industry went nuts attacking the study - this finding goes against their message that pesticides are fine and necessary, don't worry about pesticide residues in food, and that antibiotics and other medicines are safe when given routinely to animals. Unfortunately, research finds that a number of pesticides used in conventional farming are considered carcinogenic (cancer causing), and pesticide residues are found in conventionally grown foods. Eating conventional foods every day results in chronic low-dose pesticide residue exposure. The researchers suspect the pesticide residues in foods is the reason for the higher cancer risk. [Note: those pesticides are not allowed to be used in organic farming.]
What foods did the researchers ask about? They asked people about the consumption of 16 types of labeled organic food 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. In other words, all the foods we eat daily.
But what I found really interesting was a review of the study by Dr. Charles Benbrook (Visiting Scholar in the Bloomberg School of Public Health, Johns Hopkins University, and a Visiting Professor at the Univ. of Newcastle in the UK). He correctly points out that the results are big news and a big deal. Excerpts from Environmental Health News:
No study is perfect—but recent findings that organic food consumption cuts cancer risk highlights an opportunity to tackle a deadly, expensive health crisis.
More than 1.7 million Americans will be newly diagnosed with cancer in 2018, and 35 percent of these cases will prove fatal. A little less than $150 billion was spent fighting cancer in 2017. ....
There is a new paper in JAMA Internal Medicine by a team of French scientists that reports a 25 percent decrease in overall cancer risk from relatively high levels of organic food consumption, compared to little or no organic food consumption, in a large, prospective epidemiological study.
Sizable reductions in prevalence were also seen for breast cancer, non-Hodgkin lymphoma (NHL), and all lymphomas. (Check out a written summary of the study methods or this 2-minute video focused on key findings).
The French scientists suspect that the reduction in pesticide dietary exposure among study participants reporting a high-level of organic food intake is the key factor driving these encouraging results. The team did all it could to control for several confounding factors. They stressed the study's limits and the clear need for more precise measures of pesticide dietary exposures. They emphasized the need for all consumers to eat more fruits and vegetables, conventional and/or organic.
True believers in organic food and farming systems see proof and vindication in this paper, while defenders of the pesticide-status quo are generally dismissing it, citing one or more weaknesses from a long list of widely acknowledged shortcomings in this sort of study.
Does the study prove organic food will reduce cancer rates by 25 percent? No, of course not. Epidemiology studies cannot prove cause and effect. Could the study have been improved? Yes, of course, as can any study.
But for people wondering whether to take this study's encouraging results seriously, the question that really matters is did the weaknesses of the study likely inflate the health benefits of organic food?
Weakness #1: Self-reported diets. Study participants used a validated, online form to submit detailed dietary intake data across 16 major food groups.
Yes, multiple studies report that people do not always accurately recall, or report, what they actually ate. But deviations from actual intakes across the near-70,000 people in this study were likely comparable across all participants, regardless of how frequently they reported consuming a particular type of organic food. So, were self-reported dietary intakes a source of inaccuracy -- yes. Were they a source of major bias in results -- not likely.
Weakness #2: Self-reported organic food intake frequency across the 16 food groups. There were three responses taken into account in calculating an aggregate "organic food score" for each study participant across each of the 16 food categories: (1) Two points when a participant reported buying organic brands "most of the time", (2) One point when organic brands were "occasionally" consumed, and (3) no points for all other responses ("never" or "I don't know").
A close look at the data by quartile suggests clearly that the "low-intake of organic" group reliably contained people eating essentially no organic food, while the high-intake group included all, or nearly all of the people regularly consuming organic brands across at least a few categories of the 16 foods studied.
So, regardless of some degree of over- and under-reporting of organic food intake, the comparison of new cancer cases in the high versus low-intake group amounts to a comparison of people eating some, to a lot, versus no organic food.
Weakness #3: Failure to fully take into account all confounding variables. There has never been, and will never be, an epidemiological study that meets this threshold. So, unless one is willing to dismiss the entire field of epidemiology and all insights gained from well-designed studies, dealing with confounding factors is part of the process. Major source of bias? Not likely.
After adjusting as fully as possible for confounding factors, they reported their main result in the studied cohort of 70,000 French citizens -- a 25 percent reduction in the risk of being diagnosed with a new case of cancer within four years after study enrollment in the high-organic food intake group, compared to the low (and essentially no) organic food intake group.
The site The Conversation discusses the study in 2 articles. The first is written by Tim Spector, Professor of Genetic Epidemiology at Kings College, London: Organic food and cancer risk – gut microbe expert on latest research
The second article is by a nutritionist, Rosemary Stanton: Research Check: can you cut your cancer risk by eating organic?