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Mediterranean Diet: reporting from a recent study

The Mediterranean Diet, reporting from a recent study

WHAg Director, Karen Seyersted shares her views on on the latest research released on the much acclaimed MedDiet. 

“Don't dig your grave with your own knife and fork”

I was early introduced to the idea that medical “truths” have short lifespans. Growing up, many family friends were medical doctors, and health, food, and food as medicine were regular topics around the dinner table. In the 1960ies and 70ies, honest medical doctors I knew used to say that the “truths” their profession built their practice upon lasted for an average of five years. Fifty years later, the life span of a medical “truth” may be even shorter.

In whatever way we choose to approach the subject of what health and a healthy diet really is, there can be no question that this topic is complex, and that there probably is more than one answer. The science of biology is built on a whole system of simple and complex organisms communicating and interacting with each other. Everything is linked. As we all inhabit a world where toxins have entered the food chain and thus affected both plant, animal, human and environmental health in various ways, it would be really helpful to define some universal guiding principles. One solution I have been introduced to is to eat only what our grandparents and great grandparents considered to be food, but is it as simple as that, and is such food still available, and if so: where to find it? 

Trying to understand what is good for us and the health of the planet, based on what is presented in the media, is definitely not for amateurs. As a consumer and (hopefully) an informed citizen, I must not only decide what to eat, what is good for me (which may, by the way, differ from what is good for you) and where to shop; in addition, I should consider how the food is produced, its environmental impact and the food´s “carbon footprint”. As an integrated health practitioner, I have also learnt that it is important to listen to the signals from our own bodies. It is indeed hard to make the right choices and to know what is best advice. 

So, when I read about healthy diets or indeed someone tells me they have a healthy diet, I often wonder; do we need clearer guidelines and a more nuanced truth? And is the truth that there may in fact be parallel, and not universal truths in this matter? Norwegian philosopher and founder of the deep ecology movement, Arne Naess, claimed that there are indeed parallel truths. Renee Descartes famously said that “a common rule is that everything which is clearly perceived are all true”. Clearly.

The Mediterranean Diet (MedDiet)

I was first introduced to the MedDiet when studying in Montpellier in southern France in the late 1970ies. During my student days in my early twenties, on a budget of 70 francs a week, I lived on onions, garlic (daily), fresh fruit and vegetables, baguettes, salads, olives, cheese, occasionally some fish and meat, and very cheap local wine (also daily) and did not catch a cold or a flu once in three years. And even if the climate in South France attracts tourists, winter months with five degrees, rain and wind does feel cold, even in Southern Europe. And houses are cold; very cold for Norwegians who are used to well insulated and heated houses. I remember we often discussed in my group of fellow Scandinavian students what was keeping us so healthy during those years; it was certainly not regular sleep and exercise, nor a stress-free life; the French education system seemed mainly to be designed to allow teachers to get revenge for the way they were treated by their teachers during their student days, and exam failing rates were high. 

Which leaves mainly the diet. Many years after leaving France, I learnt that the diet we enjoyed is called the MedDiet and that, according to experts, it is supposed to be one of the healthiest diets on the planet. 

A recent article in the American Journal of Clinical Nutrition by Leonidas Rempelos et al: “Diet and food type affect urinary pesticide residue excretion profiles in healthy individuals: results of a randomized controlled dietary intervention trial” states that replacing a “western” diet of highly processed foods with a conventional MedDiet of chemically-grown fruits and vegetables triples exposure to toxic pesticides

The article reports from a study conducted by a team of researchers from the University of Oslo. It is a randomised study with 27 healthy young British volunteers. The study lasted for five weeks with an objective to evaluate:

1) the effects of herbicide/ pesticide/ fungicide residue in urine when changing from a conventional western diet to a Med Diet and 

2) what measurable differences there would be in the organic versus non-organic Med Diet groups during the two-week intervention period. 

The composition and pesticide residue profiles in foods eaten were also measured as the students kept food journals throughout the study. Participants were aware of group assignment, but the study assessors were not.

Before starting the active intervention period, the participants were home in England and were eating what the researchers call a regular Northern European diet. They registered everything they ate for one week and after a week, urine tests were taken and analysed for environmental toxins used in farming such as plant growth regulators, synthetic herbicides like glyphosate, insecticides and fungicides, and used these data to determine which pesticides would be tested in urine. The food they were eating was also tested for such toxins.

The students were then sent to a farm on the Greek island of Crete and split into two groups. One group followed the Med Diet, with foods grown and raised conventionally. The other group also followed the Med Diet, but organically grown and raised. The food was analysed for environmental toxins, and urine samples were taken. After another week, back home in England, eating their regular diet again, another urine test followed. The results showed that consuming a conventional versus an organic Med Diet increased pesticide levels in urine by three-fold. For organophosphate insectisides in particular, levels increased nearly 4x. Individuals that ate organic had 91% lower pesticide residue in their urine than those consuming foods produced conventionally. Interestingly, the researchers found that the pesticide residue mainly came from conventionally grown fruit, vegetables, and whole grain cereals.

“There is growing evidence from observational studies that the health benefits of increasing fruit, vegetables and whole grain consumption are partially diminished by the higher pesticide exposure associated with these foods. For the Mediterranean diet and also a more plant based diet to be a healthier option, the produce we eat needs to be organically grown”, the study team from the University of Oslo concludes.

Chris Seal, PhD, co-author of this study, says it “provides clear evidence that both our diet and the way we produce food may affect the level of exposure to synthetic chemical pesticides and ultimately our health.” This clearly indicates that the claim (however well intended) by some environmentalists and others, that we should eat more plant based foods, without considering the way it is grown, requires further scrutiny.

There are many studies to confirm that eating organic lowers pesticide and herbicide residue levels in one’s body. A 2015 study based on self-reported food intake found much lower levels of organophosphate insecticide metabolites in the urine of people who eat organic foods. Another intervention study on children found that switching to an organic diet decreased organophosphate metabolites in urine by 50% and 2,4-D by 25%.This has been confirmed in study after study, for a variety of pesticides and herbicides. 

More importantly, these levels have implications for health. Higher levels of insecticides were more likely to score high on reported behavioural problems, such as inattention and hyperactivity, in a 2013 study. The good news is that recent data suggest that children who eat higher amounts of organic food score higher on cognitive tests.


In toxicology, we learn that one plus one is not always two, it may indeed be ten or more. The toxic load which is already stored in the body and its organs, plus one more toxic drop, may all of a sudden trigger acute disease. The so called “cocktail effect” makes it impossible to know when an additional intake of pesticides and/ or herbicides through food, drinks or air pollution will represent a danger for an individual. Not infrequently, symptoms develop gradually and over time, leading to chronic disease, which is even harder to understand. When determining safe limits of pesticides and other residues in food, the cocktail effect is unfortunately not taken into consideration. The practical consequence is that there is no such thing as a universal and safe limit for everyone, and that what is safe for you depends on what is already stored in your body, and also on your ability to eliminate toxins and other waste products. This ability is individual, and largely depends on the health and condition of mainly your gut, liver and kidneys, and your lifestyle. 

All the questions about health and healthy food lead to further and bigger questions: Do we urgently need a whole new way of approaching health, where also “seven generation thinking” is included? Has time come for the departments of agriculture, health, education and finance to work more closely together? How many observational and other studies are needed before politicians and policy makers react? Can diets which benefit both human, environmental and planet health be combined? And what about ethics such as animal and farmer welfare, and cost efficiency for the farmers? What about the (not uncommon) close links between politicians and agrochemical/ pharmaceutical industries? Lastly; is developing and supporting organic farming practices (as a consumer and educated citizen; through our food choices) and a whole systems approach to health the only intelligent way to go? 

As a final note, everyone I, until now, have asked the question: “How can we as citizens contribute to healthy changes?” have replied: “From the choices we all make”. 

Eating is indeed a political act.

Further reading:

MedDiet study
Rempelos, L, et al (2021). Diet and food type affect urinary pesticide residue excretion profiles in healthy individuals: results of a randomized controlled dietary intervention trial. American Journal of Clinical Nutrition

Observational studies review
Human health implications of organic food and organic agriculture: a comprehensive review. Environmental Health, 16. 

Arne Naess and deep ecology
Scwartz, W (2009). Ethical and green living. Arne Naess. The Guardian

Karen Seyersted

About the author: A physiotherapist and registered homeopath with an MSc in Integrated Healthcare, Karen is keen to investigate, understand, and promote best practice to achieve whole health.

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