Nutrients declining in food supply.

In the January/March issue of The Food Magazine, British nutritionist David Thomas reports that the mineral content of meat and milk products has declined significantly in the past 60 years. Analyzing food nutrient data from 1940 and 2002, Thomas found that the iron content in 15 different meat items fell on average 47 percent, though some products showed a decline as high as 80 percent. The iron content of milk dropped by more than 60 percent, while the loss for cream and eight different cheeses was over 50 percent. Thomas concluded that a transition to high-fat, high-calorie, and highly processed foods lacking in micronutrients has caused people to be simultaneously overfed and undernourished.

Other research has found that while the "bad" fat and calorie content in meat and poultry is increasing, the beneficial fat in these foods is decreasing. A 2004 study from London Metropolitan University revealed that eating the same weight of chicken today compared to 30 years ago yields twice as many calories but one-third to one-eighth the omega-3 fatty acids (the "good" fats). The shift to more intensive animal production has led to an increase in energy content in meat that may have contributed to higher obesity levels in industrialized countries.

Earlier U.K. and U.S. analyses showed substantial nutritional losses in every food sub-group investigated. Possible reasons for the nutrient declines include mineral depletion of the soil itself, changes in plant varieties, and loss of soil microorganisms. But American researcher Donald R. Davis believes that large-scale industrial farming plays a key role. Davis notes that yield-enhancing methods like fertilization and irrigation may in fact reduce concentrations of some nutrients by creating a "dilution effect."

Changes in mineral composition of milk, 1940 to 2002

            1940    2002    Change
             milligrams

Sodium       50      43     -14%
Potassium   160     155      -3%
Phosphorus   95      93      -2%
Magnesium    14      11     -21%
Calcium     120     118      -2%
Iron          0.08    0.03  -62%
Copper        0.02   >0.01  gone

Sources: McCance and Widdowson, 1940 and 2002.