Nitrogen is the building block of life - it is the basis of protein both in plants and in our bodies. If there is more nitrogen in the soil, farmers can grow more crops in the same soil but greater use of the same soil makes it poorer in minerals unless farmers replace them.

Minerals are simple inorganic chemicals required by living organisms. They act as catalysts for vital processes. Plants usually obtain their mineral salts and trace minerals from the soil while animals obtain theirs from food. Magnesium is used by plants for photosynthesis while humans use it, together with zinc, for the production of hormones and maintaining strength levels. There are many trace minerals which we know are important to human nutrition but do not know exactly how.

Minerals came to my attention many years ago when I received an audio cassette in the mail from somebody network-marketing supplements. I had tried taking vitamins but had not noticed any difference except my urine turned a different color, so had dismissed the idea of nutritional supplementation.

The cassette contained the famous lecture 'Dead Doctors Don't Lie' by Joel Wallach. Its premise is that we all suffer from a deficiency of minerals and that the medical profession profits from our malnutrition. This is an extreme view of the medical profession; that it has an interest in the population remaining malnourished. You do not have to subscribe to this viewpoint to agree that our diet is deficient in minerals. It is deficient because our food production is industrialized. Michael Pollan, in his excellent book 'A History Of Four Meals', gives us a short history that helps us understand why minerals lost out in the effort to harvest nitrogen.

Before the invention of nitrogen-fixing, the supply of nitrogen on Earth was severely limited even though 80% of the Earth's atmosphere is nitrogen. Until then, the only way to capture nitrogen and put it in the soil ('fix' it) so it could feed plants, and therefore end up in our bodies, was to plant legumes in the fields. The amount of grains that farmers could grow was severely limited by the amount of nitrogen available in the soil. Farmers had to rotate crops so that corn could only be grown every other year, interspersed with years of growing legumes to put back nitrogen and other nutrients. They would also graze farm animals and spread manure from livestock in the fields to put back more nutrients.

In 1909, a German chemist called Fritz Haber invented a process to fix nitrogen from the atmosphere and convert it into ammonia which could then be used to make ammonium nitrate. He developed this technology for the purpose of manufacturing nitrates for explosives for the German war effort in the First World War. He was also responsible for the development of such poison gases as ammonia, chlorine and Zyklon B which was used in Hitler's concentration camps. Only later did his invention find a use in agriculture.

Michael Pollan identifies 1947 as the year when the era of the industrialization of food production began. A munitions factory at Muscle Shoals, Alabama which used the Haber-Bosch (Bosch commercialized the process) nitrogen-fixing process had a huge surplus of ammonium nitrate, the main ingredient in making explosives. In order to use up this surplus, it switched over to making chemical fertilizer. The Department of Agriculture decided to use the ammonium nitrate as fertilizer on farmland.

Once farmers could buy fertility in the form of bags of ammonium nitrate fertilizer, the old methods of crop rotation, growing vegetables and grazing animals to restore nitrogen and other nutrients to the soil became unnecessary.

If Haber had not found this way of artificially supplementing the nitrogen in farm soil, the population explosion associated with industrial expansion could not have happened. Pollan refers to a book by Vaclav Smil, Enriching The Earth, that estimates that two out of every five humans alive today would not be alive without Haber's invention. He rates the invention of fixing nitrogen as the most important of the twentieth century.

The end of crop rotation and the constant, highly intensive cultivation of one or two crops (usually soybeans and corn) made possible by the use of ammonium nitrate fertilizer mean that minerals are taken out of the soil and, if put back, are only put back artificially and incompletely by farmers. Typically, apart from the nitrogen in ammonium nitrate, they only put back a few minerals, the main ones being potassium and phosphorus. They may also put calcium, sulfur, magnesium and sometimes boron, manganese, iron, zinc, copper and molybdenum. They certainly do not put back all the minerals that the human body requires.

Therefore, what we have gained in the availability of nitrogen and the quantity of food that we can grow, we have lost in nutritional value from essential minerals. We cannot rely on industrial food to provide the minerals we need.