Organic and non-organic foods are compositionally different, says new study

Date: Jul-14-2014 A new analysis appears to refuel the debate about the nutritional value

of organic versus conventional foods, by finding that organic crops and crop-based foods contain

up to 69% more of certain antioxidants, are four times less likely to contain pesticide residue,

and have significantly lower levels of the toxic heavy metal cadmium.

Led by Newcastle University in the UK, the international team of experts reports its findings

in the British Journal of Nutrition. In what is thought to be the largest study of its

kind, the researchers describe how they pooled and analyzed data from 343 studies comparing the

compositional differences of organic and conventionally grown fruit, vegetables and cereals.

Researchers say organic foods contain more antioxidants and less pesticide residue than conventionally grown crops.

Study leader Carlo Leifert, professor of ecological agriculture at Newcastle University, says

the evidence is "overwhelming," and shows that:

"[...] choosing food produced according to organic standards can lead to increased intake of

nutritionally desirable antioxidants and reduced exposure to toxic heavy metals. This constitutes

an important addition to the information currently available to consumers which until now has

been confusing and in many cases is conflicting."

Prof. Leifert and colleagues say their findings suggest that by switching to organically grown

crop foods, and foods made from them, people would consume additional antioxidants equivalent to

eating between one and two extra portions of fruit and vegetables per day.

They would also be consuming less cadmium, one of the three metal contaminants - the other two

being lead and mercury - for which the European Commission has given maximum permitted levels in

food.

In their analysis, the team found cadmium levels were nearly 50% lower in organically grown than

conventionally grown crops.

For a crop to qualify as "organic," the grower is not allowed to protect it with synthetic

chemicals or feed it with certain mineral fertilizers (for example, nitrogen compounds, potassium

chloride and superphosphate). This is in order to reduce environmental impact from nitrates and

phosphorous, and to avoid pesticide contamination in groundwater.

Instead, organic crop growers are expected to give regular feeds of organic fertilizers, such

as manure and composts, to enrich the nitrogen in the soil by rotating legume crops, and use

non-chemical crop protection methods, such as crop rotation, mechanical weeding and biological

pest control.

Findings contradict two earlier important studies

The findings contradict those of two important studies - one published in 2009 and the other

in 2012 - that have found no substantial differences or nutritional benefits in organic over

conventionally produced foods.

The 2009 study - which was commissioned by the UK Food Standards Agency (FSA) - was the first systematic review of the

literature on organic food versus non-organic food. Researchers from the London School of

Hygiene and Tropical Medicine concluded there was currently no evidence to justify selecting

organically over conventionally produced foods on the basis of nutritional superiority.

The 2012 study was also a

literature review on organic versus conventionally produced food. There, researchers from

Stanford University School of Medicine also concluded that - apart from "weak evidence" of higher

phenol levels in organic produce - there was no significant evidence pointing to nutritional

benefits linked to the consumption of organic foods.

Prof. Leifert says research on organic versus conventionally produced food has been slow to

take off the ground and more studies have been published since these reviews:

"We benefited from a much larger and higher quality set of studies than our colleagues who

carried out earlier reviews."

For example, more than half the studies in the Newcastle-led analysis were not available to

the team that carried out the 2009 FSA-sponsored study. Prof. Leifert and colleagues also argue

that the Stanford study incorporated less than half the number of comparisons for most health-promoting nutrients.

Plus, because of the much larger quantity of data available, they were able to "use more

appropriate statistical methods to draw more definitive conclusions regarding the differences

between organic and conventional crops," says meta-analysis expert Dr. Gavin Stewart, a lecturer

in Evidence Synthesis at Newcastle.

Nutritional benefit of organic food is yet to be studied

The study did not investigate the nutritional benefits of organic food, it compared the

composition of organic food against conventionally grown food and found:

Concentrations of antioxidants such as polyphenolics were between 18-69% higher in

organically grown crops.
Organic crops contained, on average, 48% lower levels of the toxic heavy metal cadmium.
Concentrations of total nitrogen were 10% lower, nitrate 30% lower and nitrite 87% lower in

organic compared with conventional crops.
Pesticide residues were four times more likely to be found in conventional crops than organic

ones.

Prof. Leifert says while the findings show without doubt there are compositional differences

between organic and non-organic crops, there is now an urgent need for well-controlled human

studies that pinpoint and quantify the health impact of switching to organic food.

Critical reaction says 'the evidence is unconvincing'

Meanwhile, there has been a critical reaction from some experts about the new findings. One of

these is Dr. Alan Dangour, reader in Food and Nutrition for Global Health at the London School of

Hygiene & Tropical Medicine, and first author of the 2009 FSA paper.

Dr. Dangour says the new review mixes good quality data with bad quality data in a way that is

"highly problematic" and in his view significantly weakens the researchers' conclusions.

In an "expert reaction"

published by Science Media Centre, he also says the new study has overstated the significance of

its findings, because there is no good evidence to support the idea that consuming more

antioxidants and polyphenols has important benefits for public health, and there is no robust

evidence that having more of them in the human diet reduces the risk of cardiovascular disease,

cancer and other chronic conditions.

"All natural products vary in their composition for a wide variety of reasons," says Dr.

Dangour, adding that the paper "provides no convincing evidence to refute our earlier finding,"

which he says were fully supported by the 2012 Stanford study, that there are "no important

differences in nutrient content between organically and conventionally produced foods."

The study was funded jointly by the European Framework 6 programme and the Sheepdrove

Trust.

Written by Catharine Paddock PhD

View all articles written by Catharine, or follow her on:

Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.