I attended a very interesting talk by Matthew Adams of The Good Gardeners Association in Leeds on 26th May 2009. His thesis was that, in order to provide food which was sufficiently nutritional for good health, it was not enough simply to avoid using artificial fertilisers and pesticides; we have to avoid digging the soil to ensure that the plants can get all of the nutrients required. The reasons for this are both simple and complex. The complexity comes from the nature of the soil food web; this is an amazing structure, containing vast quantities of bacteria, protozoa, nematodes, arthropods, gastropods, fungi, and earthworms. Below is a much-simplified mindmap showing the main elements of the soil food web.
The nutritional value of most fruit and vegetables has declined since the early 1940s, and the document A study on the mineral depletion of the foods available to us as a nation over the period 1940 to 1991 by McCance & Widdowson makes disturbing reading. In summary, their finding show that vegetables show on average:
a loss of 49% of their Sodium content
a loss of 16% of their Potassium content
a loss of 24% of their Magnesium content
a loss of 46% of their Calcium content
a loss of 27% of their Iron content
and a massive 76% loss of their Copper content
"Perhaps two of the most concerning results relate to two regularly used vegetables in the British diet, ‘Old’ Potatoes and ‘Old’ Carrots. During the 51 year period Carrots lost 5% of their Magnesium , 48% of their Calcium, 46% of their Iron and 75% of their Copper, whilst our traditional ‘spud’ lost 30% of its Magnesium, 35% of its Calcium, 5% of its Iron and 47% of its Copper and you would need to have eaten 10 tomatoes in 1991 to have obtained the same copper intake as one tomato would have given you in 1940. "
All of these "trace" elements are essential in the human diet.
Further reading:
The book Teaming with Microbes is highly recommended.
