Organic vegetables and fruits are usually better, but may not be treasure troves of necessary minerals either. Organic means that no poisonous or commercial fertiliser has been used in the past two or three years. This may protect consumers, as well as farmers, against potential causes of cancer, but there is nothing about being ‘organic’ to ensure that food is grown on mineral-rich soil.

If the soil in which crops are raised has been fed only NPK for decades before organic treatment began, the food is still likely to be mineral-deficient. Levels of some of the desirable nutrients in organic food are still, on average, 75 per cent too low (Australas Health Healing, 1995; Aug/Oct: 43-5). Weathered manure helps those organic farms where it is used, provided the animals are grassfed rather than grainfed, or raised in countries like the US, which mandate that farm animals are fed all needed minerals.

Although there have been more than 40 studies in this area, comparing results is difficult since the studies are a mixed bag of organic vs conventionally grown food or comparisons between various farming systems. Organic consumers may be healthier in other ways, and organic food may be stored differently, but even different weather can affect nutrient content. Nevertheless, when all the data are reviewed together, there was a clear trend supporting the notion that organic foods are more nutritious (J Alt Complement Med, 2001; 7: 161-73).

One study found that organic fruits and vegetables in the samples tested were better than what we usually get at the supermarket. In this test, organic foods offered up to four times more trace elements, 13 times more selenium, and 20 times more calcium and manganese than supermarket foods. And organic contained 40 per cent less aluminium, 29 per cent less cadmium, 25 per cent less lead and 28 per cent less rubidium - elements commonly associated with disease (J Appl Nutr, 1993; 45: 35-9).

However, the difference in nutrient content between organic and conventional produce could also be explained by the difference in water content between the two types of produce (Alt Ther Health Med, 1998; 4: 58-69).

As a result of the fertilisers used in modern farming practices, conventional crops have a higher proportion of water than organic foods. The higher amount of water in conventional crops may well dilute available nutrients, resulting in less nutrient-dense food (Alt Ther Health Med, 1998; 4: 58-69, Knorr D et al., ‘Quantity and quality determination of ecologically grown foods’, in Sustainable Food Systems, Westport, CT: AVI Publishing, 1983: 352-81).

Is organic produce better for you? Yes, of course it is. But the claim for the superiority of organic foods should not be based on nutrient content alone. Indeed the nutrient-content argument may even be misleading as it is not what’s in organic foods, but what’s not in them that makes the crucial distinction.