why a ‘healthy diet’ isn’t so healthy any more.
Hundreds of years of farming have depleted the soil of the minerals we need in our food.
Plants need these mineral for their own healthy growth, and we need them for our own health when we eat plants. Our need for minerals is part of our evolution during our prehistoric beginnings.
The fruit, vegetables and cereals which form the bulk of our diet have been found to be deficient in a range of minerals and trace elements compared to those 50 years ago. Similar findings were found in animal-derived foodstuffs, including meat and dairy produce. A detailed, well controlled experiment measured a range of minerals and trace elements in a variety of vegetables, fruit meat and dairy products. They also calculated certain critical ratios of the minerals that are important to human physiology.
The collection of this data began in 1940 and finished in 1991, so represent a 50 year gap. The soil at the beginning of the trial was very different to what it was at the beginning of the 20th Century.
Intensive farming, and the use of inorganic fertilisers, has gone on since the 1920’s, but these fertilisers consist mainly of nitrogen, phosphorus and potassium. calcium, in the form of lime, and iron are sometimes added. The essential trace elements are never deliberately replaced.
Vegetables are probably the best indicators of change to mineral content, because of their rapid growth and short life cycles.
Analysis showed severe depletion in the mineral content of the vegetables (see Table).
Perhaps the most concerning results relate to the mineral loss in two of the West’s main vegetables, potatoes and carrots. The latter lost 75% of its magnesium content, 48% of its calcium, 46% of its iron and 75% of its copper, with similar losses in potatoes. Calculation of critical ratios: Ca:P, Na:K, Mg:Ca and Fe:Cu found a significant change in all these ratios, which will have a significant influence on our body’s biochemistry. This example shows that we don’t know what a ‘healthy diet’ consists of any more.
Fruit, because only a small part of the plant is harvested, the longevity of the fruit tree and generally deeper roots than vegetables the mineral depletion is not so severe. Nevertheless there were significant overall losses in mineral content. Meats and Dairy products also showed a general depletion.
Table summarising changes in mineral content of different types of vegetables (27 varieties), fruit (17 types) and meat (10 cuts) measured between 1940 and 1991.
There are many reasons why minerals and trace elements have been diminished. This includes the depletion of the soil itself by long-term farming, excessive use of NPK fertilisers, (trace elements are never deliberately added), changes in varieties of plants grown and loss of micro-organisms in the soil.
This deficiency in our diet is made even worse by radical changes to our eating habits. There has been a massive increase in manufactured, convenience foods, often referred to as ‘junk food’. These are high in saturated fats, sugars and processed carbohydrates. These foods have, over the last 30 years, as the norm and there is a generation of children who have eaten little else and regard it as an appropriate diet. Consequently, we have created a society which is overfed but malnourished of micro-nutrients. These factors have contributed to the rise in certain diseases, such as diabetes, obesity, cardiovascular disease and osteoporosis.
Many of the minerals and trace elements missing from our food are essential for healthy living. For example magnesium is required for 300 enzyme reactions and zinc for 200.
Chemical substances derived from the diet also affect human behaviour. A recent study demonstrated that proving the recommended daily allowance (RDA) of micronutrients assisted in the correction of ant-social behaviour of juveniles.
In the West we over indulge in poor quality food with a low intake of essential micronutrients. Greater intake of fresh, preferably home grown or organic vegetables, and perhaps dietary supplements will help to redress the balance.
This article is based on the paper ‘A study on the mineral depletion of the foods available to us as a nation over the period 1940 to 1991’ by David Thomas. Nutrition and Health 2003; 17: 85-115.