Comment: Soil scientist Dr Jacqueline Rowarth examines the claims that organic food is healthier than food grown conventionally.

Availability of food produced in an organic production system, where synthetic chemicals are not used, has increased markedly over the past few decades. Most people buy some food that is organic, sometimes because they are pursuing the label, and sometimes because the coffee or whatever that they like happens to be organic. Marketing associated with the organic movement suggests that buying organic food means 'healthier, without chemicals, friendlier towards the environment, non-GMO, supporting local/small farms'.
This article examines the claims that organic food is 'healthier' than food grown conventionally.

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The Facts

• There is no consistent scientific evidence that food grown under organic principles is any 'healthier' than food grown in conventional systems


• Development of modern cultivars and the increasing carbon dioxide concentration in the atmosphere has resulted in small changes in nutrient composition of some fruit and vegetables

• Switching to an organic diet has not been shown to reduce incidence of cancer

• Food safety in New Zealand is monitored irrespective of the production system

The Concern


It is easy to find articles on the internet suggesting reasons for purchasing food grown organically. 'Better for you and your family' is a consistent theme (with the other suggested benefits in environment and local support).

In 2010, a Nielsen study reported that 76% of organic food purchasers did so because they are believed to be healthier. This figure was confirmed in a Pew Research Centre report in 2016. In the general population, however, only 55% of the population thought organic food was better for health. By 2018, 68% of organic food consumers and only 45% of the total surveyed thought there were health benefits.

In reality it is difficult to compare the effect of production system on food because so many variables are involved. The variables include effect of environment, cultivar, harvesting (particularly the stage of ripeness at harvest), processing and storage. Despite this, the belief persists that food was more nutritious before the advent of agrichemicals.

In America research investigating changes in food composition for 43 garden crops over a 50-year period concluded that 'any real declines are generally most easily explained by changes in cultivated varieties between 1950 and 1999, in which there may be trade-offs between yield and nutrient content'. Further research has indicated that at least part of the apparent decline is due to increased carbon dioxide in the atmosphere - carbohydrate has increased without increase in minerals.


Comparing results of current food produced in different production systems has been attempted through reviews of published research. Reports where only scientifically credible and paired studies are included are rare. American research published in 2012 is still the most comprehensive examination. Over 230 studies were involved and the authors concluded that 'fruits and vegetables that met the criteria for 'organic' were on average no more nutritious than their far cheaper conventional counterparts'.

Dr Jacqueline Rowarth. Photo / Supplied
Dr Jacqueline Rowarth. Photo / Supplied


Investigating human health is even more difficult because of the confounding factors of lifestyle choices. Cancer Research scientists from Oxford University in the UK studied over a quarter of a million women over 9 years. They reported in 2014 that eating only organically produced food did not affect the likelihood of being diagnosed with cancer in comparison with eating conventionally produced food

Similarly, a large study in Norway concluded that there was no substantive evidence to suggest that food produced by different systems is inherently 'better for you' than any other.

Organic milk and meat have been shown to have increased conjugated linoleic acid (CLA). CLAs have been variously suggested to assist with controlling the onset of cancer and arteriosclerosis, and to improved immunity and anti-inflammation in consumers. However, it is the grass diet, rather than the organic production system per se, that resulted in the increased CLA. (Milk and meat produced in New Zealand is mostly grass-fed and more than meets the feed definition for organic in the northern hemisphere.)

Antibiotics and growth hormones

Use of antibiotics and growth hormones in farm animals has become a matter of concern. New Zealand is the third lowest user of antibiotics (active ingredient per kg of animal weight) in the world, and antibiotics are used only under veterinary prescription. This is not necessarily the case overseas where antibiotics are used in animal feedlots as a prophylactic. Growth hormones for animals are also in common use overseas, but not in New Zealand.

In all cases in developed countries the resulting food has to meet food safety standards.


The Ministry for Primary Industries and Food Safety Authority, as well as the Environmental Protection Authority are active in keeping consumers safe. They help guard the international reputation of New Zealand food products, as well as setting and monitoring food standards. Testing of food safety occurs irrespective of production system and country of origin.

The take home message is that New Zealanders have choice in the type of food they buy and can rest assured that fresh food is safe and nutritious to eat, whatever production system has been used.

- Dr Jacqueline Rowarth CNZM CRSNZ HFNZIAHS has a PhD in Soil Science and has held various academic and government positions across the environment, agriculture and business spectrum. She has worked on organic and conventional farms in the UK and New Zealand.