Features
Good for nature, good for you
On June 26, Irish Times' science columnist Prof William Reville wrote that the "claimed nutritional superiority of organically produced food has no scientific basis'. Was he correct?
Last year an EU funded study - the largest ever of its kind - found that organic fruit and vegetables contain 40 per cent more antioxidants than conventional varieties. The figure was 60 per cent for organic milk, while organic produce was also found to be richer in iron and zinc. Professor Carlo Leifert, the project's co-ordinator, concluded that the nutritional advantage of organic produce was such that it might be even sufficient to eat four portions of organic fruit and vegetables a day rather than the traditionally recommended five.
Positive studies
A research review conducted by the University of California found that, on average, organic produce contains up to 27 per cent more Vitamin C, 21 per cent more iron, and 29 per cent more magnesium than conventional equivalents, while a 10 year study at the same university found that organic tomatoes are richer in two flavinoid compounds that are linked with reduced levels of heart disease and some forms of cancer.
Another study found that organic vegetable soup contains six times as much salicylic acid as non-organic varieties. Salicylic acid is an ingredient in aspirin and helps to prevent hardening of the arteries and bowel cancer. It is produced naturally in plants as a defence against stress and disease, providing a possible explanation as to why plants protected with artificial pesticides produce less of it.
Scientists differ
Despite these results, the overall picture isn't conclusive. Some scientists point out that while organic foods might be richer in certain compounds, these might not necessarily confer any health benefits. For example, the health effect of antioxidants is often exaggerated in the media, with a string of lab studies on antioxidant supplements concluding that they don't offer any protection against disease. Other scientists, however, says that antioxidant supplements are digested too quickly to be effective, but that antioxidants bound in fibrous fruits and vegetables take longer to digest and thus have more time in the gut to neutralise disease-causing compounds.
Accurate research comparing the nutritional differences between organic and non-organic produce can be difficult, as variations in soil type, climate and other conditions between farms mean it is often difficult to say exactly which factor is responsible for any nutritional differences. Some studies have painted a disappointing picture for organic produce. Research comparing conventionally and organically grown wheat concluded that they were nutritionally indistinguishable. This study was noted for its strict quality control - rather than just comparing wheat crops that had already been grown, the research team used the same strain of wheat and grew them with the exact same inputs, the only difference being whether the fertiliser was organic or not. Equally, a 2002 review of previous studies concluded that organic food was not nutritionally superior, and the UK's Food Standards Agency disregarded a study that found that organic milk contains more omega-3 fatty acids, stating that these fatty acids aren't as beneficial to health as omega-3 oils.
Excessive residues
One thing health-conscious consumers can be certain about is that organic food is far less likely to contain pesticide residues than conventional produce. While legal safety limits mean that most fruit and vegetables are low in pesticides, the Pesticide Action Network said in 2006 that more than 5 per cent of foods tested in the UK posed an "appreciable" health risk to consumers due to their pesticide content. According to the group, one pesticide exceeded safety limits in 79 per cent of oranges, and overall 1.6 per cent of fresh produce was found to contain excessive pesticide residue, meaning someone eating a healthy diet could expect to eat fresh produce exceeding the limit five or six times a year.
Cocktail effect
The group says that eating organic produce is "perhaps the way in which one can be most confident of avoiding pesticide residues in food", stressing that the "public are exposed to a daily diet of a mixture of pesticides, and scientists have very little understanding of how these cocktails may act inside the human body." However, pesticide residues aren't always found in conventional produce - a 2000 study commissioned by the BBC found that conventionally grown carrots were pesticide free. In Britain, just under a third of conventional produce tested contained pesticide residues, which are very rarely found in organic produce. Here in Ireland the Department of Agriculture's pesticide control service monitors food to ensure pesticide residue content remains within legally set safety limits, though critics question whether these limits are sufficiently strict.
Fresh is better
One thing that isn't in doubt is that once fruit and vegetables are harvested, their nutrient content can decline rapidly. This gives organic produce - which is often grown locally and sold via markets, local shops or box schemes soon after harvesting - a potential health advantage over a lot of conventional fruit and vegetables, which often spends more time in storage and transit, though obviously this isn't always the case.
While the evidence isn't conclusive - few things in science are - more independent research is clearly needed. But while it was once thought that there was no nutritional difference between organic and conventional food, there is now a substantial body of scientific evidence suggesting that isn't the case.
