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Monday, March 31, 2014

Organic food does not protect against cancer

The Soil Association[1] was founded in 1946 and today is the main body for the certification of organic farms in the UK. It’s website has a section on pesticides, which states the following: “Around 31,000 tonnes of chemicals are used in farming in the UK each year to kill weeds, insects and other pests that attack crops. There is surprisingly little control over how these chemicals are used in the non-organic sector and in what quantities or combinations. What we do know is that 150 of the available 311 pesticides commonly used have been identified as potentially causing cancer and many of us would have been exposed to these pesticides before we were born”. It then goes on to state: ”Even food that we think is healthy, such as non-organic Cox's apples, can be sprayed 18 times. The most dangerous chemicals used in farming, such as organophosphates, have been linked with a range of problems including cancer, decreasing male fertility, foetal abnormalities, chronic fatigue syndrome in children and Parkinson's disease”. This linking of organic food with a reduced exposure to so-called cancer-causing pesticides is a widely held belief among organic food advocates.
That view within the organic movement is unlikely to be changed by a recent study refuting this belief but the majority of people who are made to worry about this alleged pesticide-cancer link will take solace from its findings. The paper, published in the British Journal of Cancer[2] was based on data from The Million Women study, which was based on a million women screened for breast cancer, followed these women over a 12 year period with questionnaires on lifestyle completed at baseline and at years 3, 8 and 12. In the year 3 questionnaire, women were asked about their consumption of organic food within categories, “never”, “sometimes”, “usually” or “always”. A total of 751,975 provided data on their organic food intake in year 3. In this particular study part of the study, women were excluded if they had changed their diet in the previous 5 years because of an illness. That then left the researchers with data on 623,080 women.

At the outset of the study, 30% of women reported never consuming organic food, 63% sometimes consumed organic food and 7% reported always or usually eating organic food. During the follow up period of almost 9 years, a total of 53,769 women were diagnosed with some form of cancer. The authors looked at the relative risk of 16 cancers across the frequency of use of organic food. They controlled for age, area of residence, body mass index, smoking, physical activity, alcohol intake, age at first birth, fibre intake and type of meat intake. Compared to women who never consumed organic food, there was a 9% greater incidence of cancer among women who usually or always consumed organic food. The one exception was Non-Hodgkin Lymphoma (NHL) where those who usually or always consumed organic food had a 21% lower risk of NHL than women who never consumed organic food.

Already the organic movement is claiming that the 21% reduction in NHL is proof that pesticides are a causative factor in cancer. However, NHL in the UK accounts for just 4% of all cancers. Thus there were 161,215 cases of cancer among UK women in 2011 of which 155,358 or 96% of all cases did not involve NHL with cancer of the breast, bowel, lung, uterus and ovaries accounting for 62% of all cancers[3]. No matter what way the organic advocates dredge the data, the simple fact remains that the consumption of organic food had no overall protective effect against cancer (indeed it was 9% higher in the organic food consumers).
Plants maintain a natural defence system against pests and thus the overall load of exposure to natural pesticide is enormous concerned to our exposure to pesticides used in agriculture whether for commercial or organic agriculture. Data shows that using the rodent carcinogenic model, of the plants natural pesticides, 55% were positive carcinogens and 45% were not[4]. All available data show that about half of all naturally derived chemicals are positive in the rat carcinogenic model. The figure for all synthetic chemicals is also about 50%. Natural doesn’t equate with safety. Think of hemlock, magic mushrooms, opium, caffeine and nicotine to name a few.

People make all sorts of decisions about their lifestyle including diet. Some opt to be vegetarian. Some prefer to eat organic food. Some choose food based on a perceived allergy. The reasons are endless. So live and let live but please don’t preach about the health virtues of organic food to consumers who are not so inclined for whatever reason. Enjoy your food whatever your choice and let others enjoy theirs. There are many great challenges facing us in terms of public health nutrition. This paper, the first of its kind, has binned the claim of the organic food movement that consuming conventionally farmed foods can lead to exposure to cancer causing pesticides.

[2] Bradbury KE et al 2014 March 24 (e print ahead of publication)
[4] Ames BN & Gold LS (1997) FASEB J. 1Nov;11(13):1041-52

Friday, March 7, 2014

Food outlets, schools and obesity related outcomes

Understandably, there is a very strong focus in obesity research on the diets of schoolchildren with many schools now attempting to implement healthy eating policies.  Equally, there has been considerable concern about the existence of food retail outlets nearby to schools to which the schoolchildren have access. A group at the University of Oxford has recently published a meta-analysis of all relevant studies, which set out to examine the relationship between obesity outcomes and the proximity of food retail outlets to schools[1].

The authors completed a search of 10 on-line library databases and identified several thousand studies but, as ever, in meta-analyses, many of the initial studies were rejected for a variety of reasons leaving the authors with 30 full studies which met all of the a priori inclusion criteria. Each study had to have defined exactly what was meant by the retail food environment and to have measure quantitatively the relationship between food purchase patterns and obesity-related outcomes. Most of the papers were published between 2011 and 2013 and most were cross-sectional with children ranging in age from five to seventeen years. More than three quarters had sample sizes of over 1,000.

Of the 30 studies, the majority used a defined “buffer zone” around the school but some used route maps between the pupil’s home and school. GIS (Geographic Information Systems) software was the main source of information on retail outlets either within the designated buffer zone or school route. In general the buffer zone applied a distance of between 0.1 to 3.0 miles while the route approach generally used distances of 50 to 100 meters from the road travelled to and from school. The main outcome studied was the child’s BMI (kg/m2). The second most frequent measure of outcome was food intake but this appeared generally to be related to a narrow range of foods: fruit and vegetables, soda drinks or fast food. Some of course used several measures and just three used the overall diet quality index of the schoolchildren which would have included all sources of foods at all times of the day.

One study focused on fast food purchases and found a statistically significant positive association between fast food purchasing and the density of fast food outlets.  Ten studies examined the relationship between food outlets in general  and the consumption of sugar sweetened beverages and of fast food, including crisps, sweets, biscuits, fried food, sugar sweetened beverages and fast foods. Within these 10 papers, a total of 54 associations were examined and only two of these showed a statistically significant association. Four papers examined the association between fruit and vegetable consumption and food retail outlets and within these a total of 32 associations were examined. Only three showed statistically significant associations. Within the 30 studies, only three had data on the overall quality of the pupil’s diet and food retail outlet density. Two of these showed a significant association between diet quality of food outlets. In one case, the data showed a significantly higher diet quality index among pupils attending a school where the nearest retail outlet was greater than 1 km away as compared to those where the distance was less than 1km away. The second study found that the greater the distance to the nearest grocers the better was the overall diet of the pupils.

This is an important paper for several reasons. Firstly, it is a very well conducted study published in a high impact journal. Secondly, it highlights how the existence of evidence is happily ignored by those policy makers who want to place restrictions on the availability of food outlets within the vicinity of schools. Thirdly, it shows that the outcome variables which are easy to measure such as fruit and vegetable intake, soda intake or BMI yield fairly useless conclusions since they do not relate the one aspect of the determinants of food choice (school associated food outlets) to the totality of the effects of all food choice in terms of overall daily nutritional quality. Once again, we see a majority of studies in what is a very important area of public health nutrition, bedevilled by bad design. In the three studies, which did look at the overall quality of the pupil’s diet and density of food retail outlets two showed some significant associations. Now do two swallows make a summer?. No, but they point the way forward for the conduct of scientifically rigorous studies in this very important area of public health nutrition. To discover that the proximity of food outlets influenced specific food intake is of zero importance in public health nutrition. We need to know the full accurate daily nutrient intakes and only then can we judge whether any aspect of the obesigenic environment id truly influencing overall nutritional quality.

[1] [1] Williams J et al (2014) Obesity reviews Jan 13th (e pub ahead of print)