Research Check: can you cut your cancer risk by eating organic?

Study links organic foods to a reduced cancer risk, but what do the academics say?

Can you cut your risk of cancer by eating organic?

Rosemary StantonUNSW

The science isn’t clear on whether organic foods can lower your risk of cancer. But eating plenty of fruit and veg – however it’s grown – can reduce your risk. 

A recent study has shoppers wondering whether it’s worth paying more for pesticide-free organic food.

The research, published in JAMA Internal Medicine, found those who chose more organically grown foods over 4.5 years had slightly lower rates of cancer, and in particular, lymphoma and postmenopausal breast cancer.

But while there is a correlation between eating organic foods and lower rates of cancer, it doesn’t necessarily mean one caused the other. People who choose organic foods are likely to be healthier, wealthier and better educated, all factors known to impact risk of cancer.

Read more: Clearing up confusion between correlation and causation

As the researchers note, this is the first study of its kind. The findings need to be confirmed in other studies before organic food can be proposed as a preventive strategy against cancer.

Past research has found, however, that higher intakes of fruit, vegetables and wholegrains – however they’re grown – and lower intakes of processed and red meats can decrease your risk of cancer.

So, if you don’t want to buy organic produce or can’t afford it, it’s fine to buy conventionally grown plant foods, especially if this means you eat more fruit and veg.

How was the research conducted?
This research was part of the French NutriNet-Santé study and included almost 70,000 volunteers who were free of cancer.

At the beginning of the study, each participants’ diet was assessed based on the French nutritional guidelines and their food and drink consumption recorded in three 24-hour snapshots over two weeks.

Two months into the study, the participants were asked to provide specific information about their consumption of 16 categories of organically labelled foods. This included fruits, vegetables, soy-based products, dairy products, meat and fish, and so on.

The study included nearly 70,000 volunteer participants. Alyson McPhee

The participants were then given an “organic food score”. If they chose organically produced foods in all 16 categories, they would get a maximum score of 32.

The health of each participant was assessed each year and monitored for a median period of 4.5 years. When any cases of cancer occurred, details were independently confirmed with the individual’s hospital or treating physician.

What did they find?
The participants’ organic food scores ranged from 0.7 to 19.4. These were used to divide the group into equal quartiles.

The overall cancer risk was 25 per cent lower in those who had the highest organic food score.

Read more: Interactive body map: what really gives you cancer?

Cancers showing the greatest correlation with decreased risk were breast cancer (especially in postmenopausal women) and lymphomas (especially non-Hodgkin’s lymphoma).

No correlation appeared with prostate or colorectal cancers, although the relatively short time frame would have made any change unlikely.

What do we need to take into account?
As previous studies with this group had shown, people who choose organically grown products tend to have higher income, higher levels of education and healthier diets. So the researchers adjusted for these factors.

They also made adjustments for other factors that could affect the outcome: age, sex, the month the participants were included in the program, marital status, physical activity, smoking status, alcohol intake, family history of cancer, body mass index, height, energy intake, and the intake of dietary fibre and also red and processed meat.

For women (who made up 78 per cent of the study group), they also adjusted for the number of children they had, oral contraception use, postmenopausal status and use of hormonal treatment for menopause.

But although the researchers tried to adjust their results for these confounding factors, when so many are relevant in those who consumed more organically grown products, it’s hard to be definite about the validity of the findings.

Consumers of organic food tend to have healthier diets. Henrique Félix

Participants with a high organic food score also had generally healthier diets with higher intake of fruits and vegetables and lower consumption of red and processed meats. They also had lower levels of obesity.

So was it pesticides in conventional products that are related to some cancers, as the researchers hypothesised? Or is it that those who choose organic products over conventional foods have better diets and healthier lifestyles?

This research doesn’t, and can’t, tell us the answer.

Read more: Organic, grass fed and hormone-free: does this make red meat any healthier?

Confirmation in future studies
This is the first study of its kind. The only study with some resemblance was a 2014 British study that asked women if they ate organic foods “never, sometimes, usually or always”.

The British researchers found 21per cent less non-Hodgkin’s lymphoma in women who “usually or always” ate organic food. It also noted organic food eaters had a very slight increase in breast cancer (but the participants also drank more alcohol and had fewer children – both factors that can increase the risk of breast cancer).

In 2015, the International Agency for Research on Cancer classified some pesticides as “probably carcinogenic to humans”. This means there is limited evidence of a link between pesticide use and cancer in humans, but sufficient evidence of a link between pesticide use and cancer in experimental animal studies.

Read more: Stop worrying and trust the evidence: it's very unlikely Roundup causes cancer

There’s also evidence that people who consume more organically grown products have lower levels of pesticide residue in their urine and some research showing that self-reported intake of organic produce can be used to predict urinary levels of metabolites of some pesticides. So it’s an area worthy of more research.

The French study may have told us more if it included more accurate measurements of the various organically grown foods that were consumed and also the levels of particular pesticide residues in the participants’ urine.

An ideal way to study this issue in future would be to monitor rates of cancer in a group of similar people. Half would be given set amounts of organically grown foods; the other half would have the same amount of the same foods grown using conventional agriculture.

Their urinary levels of pesticide residues and the incidence of cancer over some years could then be assessed more accurately.

But the time and costs to conduct such a study make it unlikely to happen. – Rosemary Stanton

Blind peer review
The article is a fair, balanced and accurate assessment of the research study. – Tim Crowe

Read more: Research Check: will eating 'ultra-processed' foods give you cancer?

Research Checks interrogate newly published studies and how they’re reported in the media. The analysis is undertaken by one or more academics not involved with the study, and reviewed by another, to make sure it’s accurate.The Conversation

Rosemary Stanton, Nutritionist & Visiting Fellow, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.



    To make a comment, please register or login

    23rd May 2019
    If insecticides and pesticides can kill other species they can kill people too.
    23rd May 2019
    Same as I was thinking Jackie. Not only vegetables either. I was brought up on a farm and remember the hormones we used to inject into poultry, geese etc to make them plump quickly. This was in the 1950's so I hate to think what happens now.
    23rd May 2019
    Casey, I am shocked that was happening in the 1950s. Roast chicken was a luxury back then.

    Many homes kept chooks and ducks back then. Ours were grain fed and helped themselves around the yard.
    24th May 2019
    Yes Jackie and they do it slowly by effecting your hormones, liver and other organs, and accumulating in the body, but you also have to protect yourself from outside chemicals, including body products and house cleaners, what we breath and what we put on our bodies is just as or even more harmful.
    25th May 2019
    casey and jackie, hormone supplements have not been used in poultry raising in Australia in over 50 years. Selective breeding has given us a breed of chickens that naturally grow quickly.
    Everyone of us over the age of around 50 has measurable levels of DDT in our bodies. It was a very effective and safe pesticide that accumulates in our internal fat deposits. It poses no danger to a normal healthy person. It may cause some adverse reaction in the CNS if a person goes on an extreme diet.
    Please read up on the methods of actions of the various pesticides. Some are very species specific and no identifiable effects have been found in non-target species.
    As an example of species specific action, the venom of the Sydney Funnel web spider only has the same toxicity as on humans on three day old chickens and one species of monkey.
    23rd May 2019
    What bothers me is that in this country as far as I know there is no government mandated body that is authorised to certify through regulation that this product is "organic" and this one is not. So anyone can put up a product for public consumption and charge 10 times the price. As such, at present I refuse to buy anything labeled organic. There was also that famous study in the Lancet about 4 years ago (meta-analytic, multi-centre, huge patient cohort, that concluded that there was no evidence (as yet) that eating things labeled organic was proved to be in way better for one's health.
    23rd May 2019
    Digby, when I can’t grown my own organic I buy it. The taste tells the difference.
    24th May 2019
    Clearly Jackie, my sense of taste is not as refined as yours, I just can't taste the difference. And yes I have tried, and probably will keep on trying.
    27th May 2019
    I think you're throwing out the baby with the bath water, Digby, though I hear where you're coming from. I saw something in the supermarket yesterday called "Organic ..." but I couldn't see a "Certified Organic" label anywhere on the packet. Unfortunately, food labeling laws in Australia allow this, because the product was organic as opposed to plastic, for example. It must have the label "Certified Organic" if you want real organic.

    The same food labeling laws allow honey called "100% pure honey" to have water & sugar syrup added to it. I call it false advertising, because there's nothing pure or 100% about it, but our sloppy laws kowtow to chemical companies, just as they do in the USA. Europe has a much better record, banning glyphosates like what we call "Round Up". The main reason it was banned was because it was associated with bee colony collapse (as well as a mite) & bees are responsible for at least 33% of pollination of our food harvest.

    My otherwise very healthy mum died very suddenly in her early 80's from an aggressive non-Hodgkin’s lymphoma. On the flight to see her (in hospital, but unfortunately she died before I arrived), I sat next to a Naturopath on the plane, who told me non-Hodgkin’s lymphoma was strongly associated with farm chemicals such as Round Up. To my horror, when my siblings & I were sorting through mum's home (of 40 years), there was a 20 litre jerrycan of Round Up in the "living room", as we called it. Mum wasn't using that part of the (4 bedroom) house, but that room was next to the kitchen, with only a sliding door as a barrier.

    I've just decided to go 100% organic.
    27th May 2019
    HooHoo, good on you for going organic, sad about your mum, here is a petition to stop Bunnings selling the dangerous Round up:

    Trouble is they already have another nasty replacement ready.
    24th May 2019
    These kinds of studies have way too many variants. You don't have to have a high income to eat organic, I have been purchasing organic for years on a low income,they taste better, I buy mostly in season, plus I don't buy from supermarkets who charge too much. The best way to stay healthy is just to eat more fruit, veg and wholefoods, as fresh as possible. First choice should be grow your own, second from farmers markets (choosing organic if they are available), then organics and lastly conventional. If you only buy conventional then learn to wash them correctly to minimize chemicals and stay away from the worst and heavily sprayed.
    27th May 2019
    Good advice, musicveg.
    I grow my own lawn, limes, mandarins, herbs, tomatoes & salad greens without using chemicals, but I can't stop the drift of poisons from careless suburban neighbours, farms or the nearby golf course.
    I think I'll have to move near the local communes, where at least there are larger pockets of unpolluted air.
    I agree it doesn't have to be too much more expensive to eat organic, but it does require a lot of organisation, effort, travel & time, something very difficult for time-poor people who are working full time, like me.
    27th May 2019
    Great you grow your own, can I come for lunch, I eat lots of salad green's, I think it does not take much to grow a few greens in a pot or plot, some grow like weeds, in fact there are some weeds you can eat too.

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