There is, however, no scientific proof for this assertion. On the contrary, the Danish Veterinary and Food Administration’s monitoring programme shows that the vitamin and mineral content of foods remains remarkably stable. There are very few systematic changes for the better or the worse, and these are only of a limited magnitude of 10-20%, so there is no sign that the soil is becoming exhausted.
10-20% may sound like a lot, but when we remember that vitamin and mineral contents may vary by 300-400% between two varieties of the same fruit or vegetable, this 10-20% is not of major significance.
The Danish Veterinary and Food Administration’s monitoring programmeFrom 1983 to 1999, the Danish Veterinary and Food Administration implemented systematic monitoring of the nutritional content of Danish and imported foods.
At five-year intervals, each of the major food groups (fruit and vegetables, bread and grain products, dairy products, meat and fish) were examined for a wide range of vitamins and minerals. The sampling process was carefully planned so that the entire Danish market was covered – e.g. all major potato varieties, the most popular varieties of vegetables and apples, bread from all major producers and from the retail trade, fish from several different waters, dairy products from all over the country etc.
The results have been evaluated on an ongoing basis with a view to the nutritional consequences and published piecemeal, most recently in the report “Nutrients: food monitoring system 1993-1997”.
ResultsIn the case of vitamins A, D, B1, B2 and B6 there have been no major changes at all. Folate (folic acid) levels also remain constant.
There has been a systematic increase in the vitamin C content of apples from about 7 mg to around 11 mg per 100 g. This rise is due to the fact that the Spartan variety has gradually fallen from favour in Denmark, and Spartan is known for its low vitamin C content. Major changes were not seen in other foods.
The calcium content has not changed over the 15-year period, nor has magnesium changed to any extent, though a significant drop of 10% in oatmeal has been noted.
The iron content of oatmeal and rye bread has fallen.
Zinc levels fluctuate a good deal. Most recently we have seen a significant drop in the content of zinc in cheese and pork, resulting in a daily intake reduction from 11.5 mg to 10.5 mg. This is a declining trend which should continue to be monitored.
Levels of iodine and sodium have not changed to any extent.
The potassium content has fallen in almost all bread and grain products. This is difficult to explain, since Danish soil has plentiful reserves of potassium. In this case also, only time will tell whether this is a temporary fluctuation.
Certain food groups have therefore been found which show minor reductions in the content of individual minerals, and the explanation for this is not immediately apparent.
Major variations between varieties
In the implementation of such studies of fruit and vegetables it is important to take account of varietal variations, which can readily generate differences of up to 300-400%. Conditions of cultivation, climate, soil and transport also exert their influence on the nutrient content. Surveys dealing with nutrient levels in both fruit and vegetables and other food groups should therefore be regarded in a critical light before deciding which products are best.
Organic and conventional foods
The Danish Veterinary and Food Administration has not undertaken systematic studies of the differences in vitamin and mineral content between organic and conventionally-produced foods, though the Administration has reviewed the literature in this field on a number of occasions. For vegetables – though not for fruit – certain studies exist that suggest that dry matter, vitamin C and dietary fibre levels may be 10-20% higher in organic than in conventional products, while the B1 and carotine content may be 10-20% lower in organic products than their conventional counterparts. However, bearing in mind varietal variations of 300-400%, a variation of 10-20% is of no major nutritional significance.