A National Institutes of Health scientific panel yesterday gave a clean bill of health to the use of genetically engineered growth hormone in the production of milk, rebutting the claims of consumer groups that the hormone poses a potential threat to humans and animals.
After reviewing published scientific studies on the effect of bovine growth hormone (BGH) on milk production, the nutritional quality of milk, and human and cow health, the panel of 13 veterinarians, toxicologists, pediatricians and statisticians concluded that none of the available scientific data suggests that milk from BGH-treated cows should be a cause for alarm.
"The evidence clearly indicates that overall composition and nutritional quality of milk and meat from BGH-treated cows is equal to that from untreated cows," said panel chairman Melvin Grumbach, chairman emeritus of pediatrics at the University of California at San Francisco.
Panel members, however, acknowledged that their assessment of BGH will not be the final word on the subject, because the product is still under review by the Food and Drug Administration (FDA) and because a portion of the data relating to the product's safety was not available to the committee for review.
Critics of BGH, who have attempted to orchestrate a public campaign against use of the hormone, also raised questions about the panel's conclusions, punctuating the final public session of a conference yesterday with frequent angry outbursts against the scientists' statements.
"We remain unconvinced," said Michael Hansen of the Consumer Policy Institute, which earlier this week called on the FDA to stop public sales of milk from cows being treated experimentally with BGH. "We are seriously concerned that the data now in public hands may not present a complete picture of human and animal health problems."
BGH is a genetically engineered copy of a hormone that occurs naturally in cows. When fed to dairy cattle, it can increase milk production by as much as 20 percent. Currently, four U.S. drug firms have applied to the FDA for permission to sell the hormone to farmers.
Since the synthetic version of BGH is virtually indistinguishable from natural BGH found in milk, scientists say there is little concern about any direct effect on humans of giving extra amounts of the hormone to cows. Bovine growth hormone, unlike human growth hormone, is not recognized by the human body, meaning that it has no metabolic effect on milk drinkers.
The indirect effects of BGH, however, are less clear. For example, some experts have worried that BGH-treated cows might be less healthy than untreated animals, and in particular, more prone to the most common bovine ailment, swelling of the udders. This would mean that BGH-treated animals might have to be treated with more antibiotics and that those drug residues would show up in their milk, making it marginally less safe than normal milk.
"There is widespread disease throughout the U.S. dairy herd because of the demands put on each cow to produce abnormally high quantities of milk," Robert A. Brown, a BGH opponent, told the panel yesterday. "If you use BGH to increase milk production even further, you will get more disease, more veterinary drug use, and more drug residues in our food supply."
However, the panel found no evidence to suggest that BGH made dairy cows sicker.
The panel did recommend further research on the finding that milk from BGH-treated cows appeared to have slightly higher amounts of another hormone called insulin growth factor than milk from untreated cows. But panel members stressed that their concern was slight, since insulin growth factor already circulates in the bloodstream and saliva of children and adults in concentrations far greater than those found in treated cows' milk.