According to a study by Dr Richard Dewhurst and colleagues at Wales's Institute of Grassland and Environmental Research Organisation in Aberystwyth, organic milk contained two thirds more omega-3 essential fatty acid than industrial milk.

On the whole, the UK population does not consume sufficient omega-3, which protects against a wide range of illnesses including heart disease and arthritis, and promotes brain development, improves concentration and reduces behavioural problems in children.

See also Organic crops more nutritous

Organic soups can contain almost six times as much salicylic acid as non-organic vegetable soups.* The average level of salicylic acid in eleven brands of organic vegetable soup on sale in Britain was 117 nanograms a gram (ngm/gm) compared with 20ngm/gm in the 24 non-organic soups analysed. The highest concentration of the acid, 1040ngm/gm, was found in a carrot and coriander soup made by Scottish company Simply Organic.

Having infamously rubbished the possibility of organic crops being more nutritious a few years ago, the UK Food Standards Agency promised to study the new evidence.

The biotech industry was furious. Not only did it dismiss the study's methods as unscientific, it also warned that exposure to excessive levels of salicylic acid (Ed. - here it actually means neat synthetic salicylic acid as in aspirin) may cause bleeding problems or gastric ulcers and should be avoided by pregnant women, women who are breastfeeding and children under twelve. It then went on to recommend Government Health Warnings on organic foods and wines, warning that three or more glasses of organic wine a day on top of an organic diet could be fatal for vulnerable people.

Ed.- (i) The obvious difference between organic and non-organic crops is the richness of the soil on which they are grown, but it may also be linked to exposure to pesticides. Salicylic acid is produced naturally in plants as a defence mechanism. Possibly plants whose protection is augmented by pesticides are evolving to produce less natural defence.

(ii) Salicylic acid is the main anti-inflammatory component of aspirin, which is widely prescribed to reduce the risk of heart attacks by reducing hardening of the arteries. Research also suggests that salicylic acid may combat bowel, breast, and lung cancer and Alzheimer's disease.

(iii) Earlier research by John's team discovered significantly higher concentrations of salicylic acid in the blood of vegetarian Buddhist monks compared to that of meat-eaters.

* John Paterson and colleagues from the Dumfries and Galloway Royal Infirmary and the University of Strathclyde

In Obesity: the solution under our nose, Paula Baillie-Hamilton explains why organic foods taste so much better. Firstly, it is thought that synthetic fertilisers and pesticides interfere with plants' metabolisms, reducing natural sugar levels. Organic produce tends to contain approximately 21% higher levels of natural sugars. Secondly, pesticide residues in and on the food appear to affect our senses of taste and smell, either altering or reducing it. Common pesticides like carbamates leave a metallic or bitter taste (Schiffman,SS et al. Pharmacology, Biochemistry and Behaviour 1994;52(1)189-94).