Today

There is now a significant body of scientific evidence from around the world that organic vegetables, fruit and milk generally contain more nutrients than non-organic food.

In 2001, an independent review of the evidence found that organic crops had significantly higher levels of all 21 nutrients analysed compared with non-organic produce.

This included statistically significant higher levels of iron (21 per cent more), magnesium (29 per cent), phosphorus (14 per cent) and Vitamin C (27 per cent), and significantly less nitrate (a toxic compound). Organic spinach, lettuce, cabbage and potatoes showed particularly high levels of minerals.

The Soil Association, in 2001, also conducted a review of the evidence on mineral and vitamin content and found that, on average, organic food contains higher levels of minerals such as calcium, magnesium, iron and chromium, as well as more vitamin C, and a higher dry matter content, than non-organic food.

Higher levels of minerals in organic produce are explained by the improved bioavailability of minerals in the soil of organic farm systems. Organic farming is based around the maximisation of soil biology to optimise nutrition pathways from soil to crops.

Since then, there has been much more research published, confirming the conclusion that organic food is more nutritious for a wider range of crops - tomatoes, apples, peaches and kiwis. This research found that these organic foods have higher levels of both Vitamin C and a range of secondary metabolities including anti-oxidants, which play a role in preventing cancer.

Studies published during 2006 and 2007 include:

• A University of California, Davis, study concluded that organically grown kiwis had significantly higher levels of vitamin C (14 per cent) and polyphenols (17 per cent).
• A Polish study found that organic apple puree contained more phenols, flavonoids and vitamin C in comparison to non-organic apple preserves.
• A further Polish study found that organic tomatoes contained more dry matter, vitamin C, B-carotene and flavonoids, while non-organic tomatoes were richer in lycopene and organic acids. (Previous research has found organic tomatoes have higher levels of vitamin C, vitamin A and lycopene.)
• A French study found that organic peaches have a higher polyphenol content.
• A controlled 10-year study by the University of California, Davis, found that organic tomatoes contain almost double the level of two antioxidant flavonoids, quercetin and kaempferol, which were on average 79 and 97 per cent higher respectively than in non-organic tomatoes and are believed to reduce heart disease.

Secondary metabolites or polyphenols - a category to which vitamins belong - are produced by plants as a protective mechanism in response to external stress and disease, and thus are part of plants defence mechanisms. Consumed in the human diet, these polyphenols are antioxidants that have an important role to play in cancer prevention. Researchers have suggested that the pesticides used in conventional growing practices may discourage or disrupt the production of phenolic metabolites in the plant, perhaps due to the reduced need for the plant to produce its own biochemical defences. This would explain the higher levels found in organic food.

At the same time, scientific evidence has now emerged against the use of artificial vitamin supplements. Since the 1950’s, research had shown that natural vitamins protect against certain cancers, neuro-degenerative diseases and heart disease. It was assumed that synthetic vitamins would do the same, and so the vitamin supplements industry was born and boomed. However, in August 2006, the New Scientist reported on reviews of years of studies into Vitamin A and E supplements which found that, opposite to expectations, they are increasing mortality. So, it now appears that actually only a natural food source of these vitamins has health benefits. This makes the higher vitamin A and E levels of some organic foods even more significant.

Milk
In total, six studies have now found that organic milk has more fat-soluble nutrients - omega-3 fatty acid, Vitamin E and beta-carotene - than non-organic milk, as well as a healthier omega 3:6 ratio (skimmed milk does not have these nutrients). The most recent and scientifically robust study is by Glasgow and Liverpool Universities, which found that UK (whole) organic milk has on average 68 per cent higher levels of the essential fatty acid omega-3 and a healthier omega-3:6 profile than non-organic milk.

The details above were provided by the Soil Association, the group which campaigns for organic farming. For more information about organic food and drink, visit www.soilassociation.org or www.whyorganic.org.

Britain's organic food and drink market was worth around £1bn in 2005, according to figures from consumer research group Mintel. Looking ahead, Mintel forecasts that the organic market will reach a value of £2bn by 2010.