- It was the confluence of two important
events that made Carol Baxter start buying organic milk about five and
a half years ago. Her oldest daughter had just turned 1 and soon would
move from breast milk to cow's milk. And American dairy farmers had just
received approval to inject their cows with recombinant bovine growth hormone,
a genetically engineered hormone that increases milk production.
- Ms. Baxter, who lives in Palisades, N.Y.,
knew of environmental groups' claims that treated cows got more infections
and needed more antibiotics, which could then enter their milk. And she
learned that some scientists had raised the possibility of an increased
cancer risk in people who drank the milk. "Milk is such an important
part of a child's diet," she said. "I didn't want my child to
be a guinea pig."
- The Food and Drug Administration has
long dismissed such concerns. In the journal Science in 1990, two agency
scientists concluded that "no toxicologically significant changes"
were seen in rats that ingested the hormone. The agency's approval of the
hormone in 1993 rested on the strength of that 90-day rat study, which
was commissioned by Monsanto, the manufacturer.
- Safety questions about the hormone never
went away among health-conscious consumers, and recently the old questions
have resurfaced in light of new research and a fresh examination of the
- Last week, the Canadian government said
that it would not approve the synthetic hormone. Canadian scientists reviewed
unpublished data from the study and found health effects that had not been
cited in the Science report. Canada's decision leaves the United States
the only major country to permit use of the synthetic hormone.
- In its analysis of the Monsanto rat study,
the Canadian scientists found that 20 percent to 30 percent of the rats
that ingested high doses of the hormone developed antibodies to it, a sign
that it was active in the bloodstream. And some of the male rats developed
cysts on their thyroids and abnormalities in their prostates.
- In December, after the Canadian researchers
released their findings, Sens. Patrick Leahy and James Jeffords, both of
Vermont, asked Health and Human Services Secretary Donna Shalala to investigate
whether the =46DA overlooked evidence in the case. Dr. Shalala has not
- In addition, in December, 21 dairy farmer
associations and consumer groups in the United States said they would file
suit against the FDA for failing to require additional safety studies of
the hormone. "The 90-day rat study doesn't show that recombinant bovine
growth hormone is a human health hazard," said Dr. Michael Hanson,
a research associate for the Consumer Policy Research Institute, a division
of the Consumers Union, one of the groups. "But neither does it show
that there is no possibility of any health hazard, as FDA claimed. It's
clear that FDA has grossly misled us."
- The agency is writing a response to the
concerns, said Dr. Stephen Sundlof, director of its Center for Veterinary
Medicine. He acknowledged that the agency had not reviewed the antibody
data in the approval process "for reasons I can't explain."
- He said the agency had seen the information
on the thyroid and prostate effects, but considered them "biologically
meaningless" because they were no more prevalent in rats fed high
doses of the hormone than in those fed low doses. Ordinarily, if a substance
like a drug affects the body, the effects increase as the dose increases.
"Consumers have no reason to be concerned about the milk," he
- Monsanto said its product, called Posilac,
is safe. Extensive evaluations have established that the hormone supplements
for cows do not change the composition and wholesomeness of milk, Dr. David
Kowalczyk and Dr. Robert Collier, Monsanto scientists, wrote in a statement
released Jan. 12. The scientists point out that the United Nations Joint
Expert Committee on Food Additives, which determines the safety of residues
from veterinary drugs in foods, affirmed in March that the growth hormone
- Besides the Canadian investigation, two
studies published last year rekindled longstanding worries about a possible
increased risk of cancer from consuming milk from hormone-treated cows.
Reports from two continuing Harvard-based studies, the Physicians' Health
Study and the Nurses' Health Study, found that insulin-dependent growth
factor 1, a protein that is elevated in the milk of hormone-treated cows,
is a strong risk factor for breast cancer and prostate cancer.
- Researchers in the study say this protein
circulates naturally in the human body at such high levels that the added
amount in treated milk is unlikely to be noticed. Also, it occurs in breast
milk in higher amounts than in the milk of hormone-treated cows. And, the
researchers say there is no evidence that consuming the substance in food
contributes to cancer risk.
- Last January, scientists with the Physicians'
Health Study reported in Science that men with the highest levels of IGF-1
in their blood were four times as likely to develop prostate cancer as
men with the lowest levels. In May, scientists with the Nurses' Health
study reported in The Lancet that premenopausal women with high levels
of IGF-1 had up to a seven-fold increase in breast cancer risk over those
with low levels. They said the findings suggest "that the relation
between IGF-1 and risk of breast cancer may be greater than that of other
established breast-cancer risk factors," except for family history
and dense breast tissue.
- Dr. Michael Pollack, who was involved
with both studies, noted that the difference between the IGF-1 in milk
from untreated cows and treated cows is relatively small. Levels range
from 1 to 9 nanograms per milliliter of milk from untreated cows and 1
to 13 nanograms per milliliter of milk from treated cows, the FDA said.
And because levels in human milk are slightly higher, "if there's
a biological difference, one would be most concerned with human milk,"
said Pollack, a professor of medicine and oncology at McGill University
- He said that, according to Canadian scientists,
the amount of IGF-1 that people consume in cow's milk is less than 1 percent
of the total amount of IGF-1 that naturally circulates in the body, regardless
of what people eat.
- Still, he said he could not rule out
the possibility that daily exposure to the small additional amounts of
IGF-1 in milk over a lifetime could increase a person's cancer risk. "It's
a hypothetical concern," he said.
- =46or one thing, scientists cannot tease
out the human health risk of IGF-1 from foods until they know how much
of it remains active in the body after digestion. But that point is also
- "When you consume any peptide, like
IGF-1, very little of it is absorbed in an active form," said Dr.
Carolyn Bondy, chief of the developmental endocrinology branch of the National
Institute of Child Health and Human Development. Dr. Bondy's research found
a connection between abnormal mammary gland growth in female monkeys and
high levels of IGH-1 given to the monkeys, but these IGF-1 levels were
far greater than people get from drinking milk, she said.
- Even though the increased amount of IGF-1
in treated milk is small, Hanson said the possible health effects could
not be dismissed. He cited a 1995 study in the Journal of Endocrinology
showing that the breakdown of IGF-1 in rats is slowed in the presence of
casein, a protein in milk. "If casein increases the half life of IGF-1,
the effects could be dramatic," he said.
- Several experts agree with the Consumers
Union and the other parties in the planned lawsuit against the FDA that
more testing is needed to establish whether bovine growth hormone supplementation
is safe. "More studies need to be done," said Dr. Marion Nestle,
director of the department of nutrition at New York University, who opposed
the approval of the hormone as a representative on the drug agency's advisory
panel that approved it.
- "The science on the effects of oral
ingestion of IGF-1 is incomplete," the American Medical Association
said in a statement last month, in response to a reporter's questions.
- In the climate of uncertainty, one thing
is for sure. Many consumers want milk without added hormones and antibiotics.
Sales of organic milk nearly doubled to almost $31 billion in 1997, from
about $16 million in 1996, according to dairy industry figures.
- And Wendy Gordon, executive director
of Mothers and Others for a Livable Planet, said demand was strong for
its list of milk manufacturers, organic and nonorganic, whose dairies pledge
not to use the synthetic hormone.