Boron is a non-metallic element that is essential for the growth of plants but is not yet officially regarded as an essential trace mineral for animals and man. It is present in the earth’s crust in a proportion of only 10 mg per kg, but its distribution throughout soils is variable.
Boron occurs naturally in minerals such as borax, boracite and colemanite and is found in high concentrations near volcanic sites and hot springs.
Boron deficiency has long been recognised as a factor in crop failures. Widespread use of NPK fertilisers (containing nitrogen, phosphorus and potassium) reduces the bioavailability of boron in soil.
The mineral’s function in plants is not known. Brown algae are known to accumulate boron but no metabolic process has yet been attributed to it.
Like all minerals boron comes ultimately from the soil and the quantities present in plants are related to levels in the soil where they are grown. The highest concentrations of boron occur in vegetables, but cereals and dairy products also supply significant quantities.
Meat, fish and poultry provide less boron than vegetable foods so a vegetarian diet will supply higher levels of boron than one which contains meat. On the whole, boron intake will depend to a large extent on soil levels in the locations where vegetable foods are grown.
Hence the intake derived from an average diet will vary across the world with high intakes of boron (6 – 8 mg) in Israel and certain parts of Australia and New Zealand, medium intakes (1 – 2 mg) in the UK, USA, South Africa and other parts of Australia and New Zealand and low intakes (0.5 mg) in Mauritius and Jamaica.
As a general rule the lower the dietary intake of boron the higher the incidence of arthritis in that community.
No specific symptoms have been attributed to lack of boron.
As boron is supplied entirely by the diet the levels of the mineral in the food determine the quantities in the body. It is not known at what level the mineral could be classed as deficient in the body.
In rats, guinea pigs and chicks borate is antagonistic to the metabolism of riboflavin. It inhibits the binding of the vitamin to serum proteins and increases its excretion in the urine. In addition, a study demonstrated that riboflavin protected animals against the toxic effects of borate, which was given at high levels.
As boron appears to function partly by stimulating the production of the individual’s own hormones, extra calcium can help to replace the mineral that is lost through the condition osteoporosis.Vitamin D deficiency increases the requirement for boron in animals.