Chemistry researchers R.A. McCance and E.M. Widowson were commissioned by the Medical Research Council to produce a report entitled the 'Chemical Composition of Food' in 1940. Periodically, these same authors were recruited by The Ministry of Agriculture, Fisheries and Food (MAFF) and the Royal Society of Chemistry to repeat the exercise. In 1991, they were asked to compare their current results with those of 1940. These results offer a stark view of the hugely diminishing nutritional quality of vegetables, fruits and even meat over just 50 years.
Although the analytical procedures have changed over the years between 1940-1991, the methods were 'no less accurate than the modern automated ones, but they took a much longer time', the authors wrote.
During this time, they examined 28 raw vegetables and 44 cooked vegetables, 17 fruits and 10 types of meat, poultry and game. Here's a sample of the greatest individual mineral losses, measured in mg per every 100 g sample).
Food type Loss
Carrots 75 per cent less magnesium, 48 per cent less calcium, 46 per cent less iron and 75 per cent less copper
Broccoli (boiled) 75 per cent less calcium
Spring onion 74 per cent less calcium
Spinach (boiled) 60 per cent less iron and 96 per cent less copper
Swede 71 per cent less iron
Watercress 93 per cent less copper
Potatoes 30 per cent less magnesium, 35 per cent less calcium, 45 per cent less iron and 47 per cent less copper.
All meats 41 per cent less calcium and 54 per cent less iron
All fruits 27 per cent less zinc
Apples and oranges 67 per cent less iron
As the authors point out, you'd have to eat 10 tomatoes in 1991 to obtain the same amount of copper from one tomato in 1940, and three oranges to get the iron you got 50 years ago.
Even more worrying, seeding the soil with only certain minerals (sodium, phosphorus and potassium) has drastically altered the ratios between minerals which naturally occur in food.
For instance, in 1940, there was a two-to-one ratio between phosphorus and calcium. Now, this ratio is one-to-one, which means that the phosphorus content of many foods has increased. Swedes now contain 110 per cent of the phosphorus they once did. Given that there are critical ratios of certain minerals in the human physiology (such as between calcium and phosphorus or calcium and magnesium), these artificially created new ratios could have profound effects on the body's chemistry.