Europe Reviews Ban On
BST Hormone Use In Dairy Cattle
By Alex Kirby
BBC News Environment Correspondent
Presenter of BBC Radio Four's 'Costing the Earth'
By Alex Kirby BBC News Environment Correspondent Presenter of BBC Radio Four's 'Costing the Earth' 5-4-99
It has an eerie echo of BSE, the initials which now mean mad cow disease. But BST is not an illness. It is a drug.
It is an artificial hormone, a copy of one that occurs in nature. And just as natural bovine somatotropin, to give it its full name, promotes lactation, so artificial BST does the same.
Cows injected with BST produce 10%, sometimes even 15% more milk than they would do otherwise. But there is a downside.
Painful infection
BST causes increased health problems in animals injected with it. They include higher infertility rates, more mastitis - a painful infection of the teat - and a much higher incidence of lameness.
Despite that, the drug has been cleared for use in the United States, where between a quarter and a third of all dairy cows are thought to be injected with it.
Milk from them and from non-BST animals is mixed together haphazardly, and there is no way of knowing whether dairy products in the US - or exported from it - contain BST milk.
Five-year ban
The European Commission imposed a five-year ban on the sale and use of BST in 1994, on what it called socio-economic grounds. That ban is now under review.
Veterinary surgeons in both Britain and Canada say that BST should remain banned to protect animal welfare. The Canadian Government agreed that the drug presented an unacceptable threat to the safety of dairy cows.
But there are also concerns over possible implications for human health. One centres on the increased use of antibiotics to treat the increased disease that BST causes, and the risk that they could find their way to humans.
Cancer link
Another worry is the fact that the milk of cattle injected with BST contains up to five times more of a substance called IGF-1, insulin-like growth factor one, than normal milk.
IGF-1 has been linked with the development of some cancers of the breast, colon and prostate.
Professor Donald Broom, of Cambridge university, is one of a team of senior vets advising Brussels on BST.
He told the BBC that "the IGF-1 increase could possibly lead to a very small increase in the occurrence of some cancers in humans - a very small risk, but a real risk".
Dr David Challacombe, a consultant paediatrician in Somerset, says these higher levels could over a long period help to trigger the growth of malignant tumours.
Clean bill of health
BST does have its supporters. One influential group that has given it a clean bill of health is JECFA, the Joint Expert Committee on Food Additives.
JECFA's members are appointed by and answerable to two United Nations agencies, the World Health Organisation and the Food and Agriculture Organisation.
The drug's critics say the longest examination of its possible toxicological effects, a 90-day study involving thirty rats, showed significant impacts on the animals.
The US Food and Drug Administration did approve BST for use, but says it did not consider the rat study in reaching its decision.
But the chairman of JECFA, Professor Jock MacLean of Swinburne University of Technology in Melbourne, says his committee did consider the study.
Insignificant role
He points out that the levels of IGF-1 present in milk from BSE cows are only a minute fraction of the amount produced naturally by the human body, which led JECFA to conclude that it plays no significant role.
However, a Japanese study suggests that IGF-1 from BST milk persists in the digestive tract long enough to pose a far greater risk than the natural version.
The European jury is still out on BST. But it has heard evidence to show that there is cause for concern.