GENTECH archive


Synthetic Hormone in Milk Raises New Concerns (NY Times)

        January 19, 1999

        Synthetic Hormone in Milk Raises New Concerns


           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

        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

        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 rat study. 

        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        scientists reviewed unpublished data from the study and found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 FDA overlooked evidence in the case. Dr. Shalala has
not yet responded. 

        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 said. 

        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 was safe. 

        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

        For 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 in dispute. 

        "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. 

              Copyright 1999 The New York Times Company