We're obese. We know it and we know about the risks of junk food, poverty and mothers' diets. But if we think organic food can cut our obesity rate, we could be swallowing a whole lot of dodgy – and costly – ideas

The headline in the New Zealand Herald's Element magazine last month certainly hit its targets: "Feeding the nation – obesity, poverty and how to get New Zealand eating its greens". But from pointing out that we are one of the world's most obese nations (30% of us classed as obese, another 34% overweight), the feature moved to junk food, poverty and onto the dangers of pesticides and the benefits of eating organic – preferably heritage – food.

'You are what you eat' seemed to be the central and overt message, and few would disagree. It was the covert messages that were more concerning.

Obesity has many causes behind the obvious ones such as what you put in your mouth and how much activity you perform.

Professor Sir Peter Gluckman, the Prime Minister’s Chief Science Advisor is clear in his research findings that maternal diet can have an impact on a child’s weight gain later in life. So what is eaten by the mother affects the diet tendencies of the child. These are exacerbated by the socio-economic environment in which the child is raised, and Element reported that one in four children in New Zealand lives in poverty.

What wasn’t pointed out is that in New Zealand ‘poverty’ is defined (by The Children’s Social Health Monitor) as less than 60% of the national median income; the median is the middle point in a ranking of everybody’s income from top to bottom – it is the numerical value that separates the higher half of incomes form the lower half.

This definition of poverty is not related to the necessities of life.

Junk food was identified as part of the problem because it is "often cheaper than healthy food". Research that supports the alternative view wasn't presented. It is true, however, that the fast food intake in New Zealand has escalated. A World Health Organisation study of intake between 1999 and 2008 released last week placed New Zealand fourth in increased fast food consumption, and first place in increasing Body Mass Index.

Combined with the actual data on obesity – the look isn’t pretty….

Having dealt with obesity and poverty the magazine went on to getting people to eat their greens – with an alert on pesticides, a message that organics is better and the suggestion that heritage apples have eight times more nutrients than their supermarket counterparts. ""Grow your own and if you can't grow your own then go to a farmers market and ask questions", was advocated.

Organic sounds natural and therefore good, right? In 2012 the Hartman Group reported that an ‘absence of’ residue from agricultural production techniques was the major reason for people purchasing organic food. In the same vein, a Nielsen report released in August 2010 indicated that the  biggest reason consumers gave for buying organic was that it was ‘healthier’ (76% ), followed by avoiding pesticides (53%) and ‘more nutritious’ (51%). The study concluded that consumers are driven to organic food purchases because they believe they are healthier choices; socially conscious reasons such as ‘it’s better for the environment’ and ‘the right thing to do’ are less important. Similarly in 2012 the Hartman Group reported that ‘absence of’ residue was the main reason for purchasing organic food.

The ‘healthier’ concept is hugely debated, however. Last year scientists at Stanford University released a report on the results of four decades of research involving 237 trials comparing organic and conventional foods. They concluded that fruits and vegetables labelled organic were, on average, no more nutritious than their conventional counterparts; variables such as ripeness were reported to have a greater influence on nutrient content than production method. Organic produce was not less likely to be contaminated by bacteria such as E. coli; composting animal manure, which is often associated with organic systems, increases likelihood of contamination.

Conventional fruits and vegetables did have more pesticide residues than organic produce, but the levels were almost always under the allowed safety limits. The Food Safety Authority in New Zealand (now part of the Ministry for Primary Industries) reports that New Zealand has among the lowest levels of pesticide residues in the world.

The Stanford researchers found no obvious health advantages to organic meats and though they did find that that organic chicken and pork was less likely to be contaminated by antibiotic-resistant bacteria, the overall incidence of contamination was low. In New Zealand antibiotics to promote growth are forbidden; antibiotics are used only for animal health. 

The same research reported that organic milk (which comes from cows on pasture for at least 120 days a year during which their diet is at least 30% pasture) contained more omega-3 fatty acids than conventional milk (which comes from cows in barns). In New Zealand animals have far more access to pasture than do organic cows in America, and as a consequence we have a natural advantage in omega-3s.

Overall, New Zealand has world leading food safety whatever the production system involved; the supermarkets have standards for what is on their shelves.

These standards involve testing organic food for residues of chemicals such as copper sulphate and lime sulphur, which are permitted in organic production systems in New Zealand to control fungi such as brown spot or mildew, and neem and pyrethrins, which are permitted in organic production systems for use against insects.

Organic production systems do not mean pesticide- or chemical-free, but the limited range of chemicals that are allowed means that control of pests is not as effective as compared with traditional systems. This is part of the reason that organic food is generally more expensive than conventionally produced food. Research by AgResearch has shown that organic sheep and beef farms tend to be operating at 60% of the production of conventional farms. Lincoln, Otago and Massey Universities have shown that organic dairy farms operate at 70-80%. Horticulture is somewhere between 0 and 100% depending on the season and pest and disease pressure.

Look at that research as a whole, and you'll see that concerns food is less nutritious than it used to be are not supported by facts.

A large study in America of analysis of nutritional changes between 1950 and 1990 of 43 fruits and vegetables concluded that any changes were more to do with modern day cultivars than production systems. This meta-analysis corrected for water content of the fruit and vegetables analysed – which is not always done. Modern day varieties have often been bred to be ‘juicy’ and for keeping quality, which improves desirability and decreases nutritional deterioration. When combined with preservation techniques, such as controlled atmosphere chilling and snap freezing, the quality of what is available has improved markedly over the years.

The covert message in Element was that modern day food is bad for you. In excess that may well be true. Research commissioned by the World Cancer Research Fund and American Institute for Cancer Research reports that food is absolutely linked with health and disease… through obesity. But it is what humans choose to put in their mouths in terms of quantity (including sugar, salt and fat), not how the food is produced on farms, that has health impacts.

And when you consider the impact of poverty on our health, consider also that articles implying more expensive organic food is better for you put further burden on stretched purses for no proven gain.

In New Zealand nutritious, healthy food is produced by farmers using modern technologies, and thanks to those technologies that food will be an smaller proportion of the household income almost every year. My next post will discuss the data.