Alarming News on rBGH--IGF-1 Increases Cancer Risks

Sept. 11, 2002

Web Note from Dr. Michael Hansen <> of the Consumers
Union, a noted expert and critic of Monsanto's controversial recombinant
Bovine Growth Hormone, now being injected into 15% of all US dairy cows.

Dear all,

This [Reuter's article] is important stuff. Although there had been a study a
couple of years ago in the American Dietetic Assn journal that found that increased
milk consumption lead to a 10% increase in IGF-1 levels blood serum, this study
is stronger because it is larger and is more prestigious as the famous
nurses study from Harvard and Brigham and Women's Hospital. Also it clearly
makes the link between IGF-1 and cancer (of lung, breast, and colon)--in a
pull quote no less ("Higher levels of insulin-like growth factor 1, or
IGF-1, have been associated with increased risk of colon, lung and breast
cancer")--and suggests that it may be the mechanism for reduced rates of
breast and colon cancer in women who've had multiple pregnancies, who show a
15% increase in serum IGF-1 levels compared to women who haven't been
pregnant ("Pregnancy is known to protect against several cancers such as
breast and colon cancer. It is possible that the mechanism of this
protection could be through lowering IGF-1 levels"). It also points out
that serum IGF-1 levels are higher in women who drink a lot of milk and even
says "This association raises the possibility that diet could increase
cancer risk by increasing levels of IGF-1 in the blood stream." This data
jives very well with the Am Dietetic Assn journal study as that was a
controlled study where the diets were iso-caloric (e.g. same calorie intake)
and where consumption of 3 glasses of milk per day increased serum IGF-1
levels by about 10% compared to those that didn't drink milk. The
iso-caloric point is important as it is known that larger calorie intake is
associated with increased secretion of IGF-1 (which is also known to help
with digestion).

In fact, a study publilshed in 1997 in the British journal Cancer
Research found that mice on calorie restricted diets (20% lower calories
than normal diet) had far fewer tumors than mice on a normal diet (these
mice had been dosed with a known bladder carginogen); the calorie
restriction appeared to protect them from the tumors. If the calorie-
restricted mice were given a tiny quantitiy of IGF-1 to restore the
IGF-1 levels to what they were in a full calorie diet, the protective effect
disappeared, which implicated IGF-1 as the agent that promoted the tumors.
Overall, the British study suggested that perhaps some of the diet-related
links to cancer may be mediated by IGF-1: "Diet contributes to over
one-third of cancer deaths in the Western world, yet the factors in the diet
that influence cancer are not elucidated. A reduction in caloric intake
dramatically slows cancer progression in rodents and this may be a major
contribution to dietary effects on cancer. . . In conclusion, DR [dietary
restriction] lowered IGF-1 levels [by 24%], thereby favoring apotosis [cell
death; was 10-fold higher DR-treated mice than mice with normal diet] over
cell proliferation [6-fold higher in hyperplastic foci in mice with IGF-1 +
DR] and ultimately slowing tumour progression. This is the first
mechanistic study demonstrating that IGF-1 supplementation abrogates the
protective effect of DR on neoplastic progression" (Dunn et al., 1997:

When you combine this study (and the Am Dietetic Assn study) with
the 1997 Japanese study (which used radioactively labeled IGF-1) that found
that 9% of IGF-1 fed to mice survived digestion and could be pulled intact
out of the bloodstream and that this figure increased to 67% when the IGF-1
was fed along with casein (the major milk protein) (Kimura et al., 1997), it
provides very strong circumstantial evidence that increased levels of IGF-1
in milk from rbGH-treated cows could have a potential negative impact on
human health. And it suggests that the arguements that milk consumption
can't have an impact on serum IGF-1 levels (becauses the levels in milk are
in the 3-6 ng/ml range, while the level in serum is in the >100ng/ml range)
and that IGF-1 doesn't survive digestion (both FDA and Monsanto arguements)
don't hold water. Indeed, this study seems to vindicate the arguments that
we have been making for over the past decade. Any possibility that this
could lead to some kind of legal action on rbGH?

Michael Hansen

Milk, Pregnancy, Cancer May Be Tied

Study culls data from long-term analysis of 1,000 nurses

WASHINGTON, Sept. 10 < Pregnancy may lower a woman¹s risk of cancer
but drinking milk could raise it, researchers reported on Tuesday. Both factors,
as well as the use of hormone replacement therapy, affect levels of a
hormone that may influence the development of some cancers, a team at
Brigham and Women¹s Hospital and Harvard Medical School in Boston found.

Higher levels of insulin-like growth factor 1, or IGF-1, have been
associated with increased risk of colon, lung and breast cancer.

THE FINDING could explain why women who have had children have
a lower risk of cancer < something doctors have noticed but been unable
to explain, Dr. Michelle Holmes, who led the study, said. Pregnancy,
HRT use and milk drinking all affect levels of insulin-like growth factor
1 or IGF-1, a hormone linked to an increased risk of cancer, Holmes
and colleagues report in the journal Cancer Epidemiology Biomarkers
& Prevention, which is published by the American Association for
Cancer Research.

This is the first study to report that the more pregnancies a women
had, the lower was her blood level of IGF-1,² Holmes said.
"Pregnancy is known to protect against several cancers such as breast
and colon cancer. It is possible that the mechanism of this protection could
be through lowering IGF-1 levels."

Women who had four or more pregnancies had IGF-1 levels that were on
average 15 percent lower than in women who had never been pregnant, the
researchers found.


Using data from a large, long-term study of more than 1,000 nurses who
record their diets carefully and who are then watched for changes in health,
Holmes' team also found that those who drank the most milk had higher levels
of IGF-1
IGF-1 is important to the growth and function of many organs, but
higher levels have been associated with an increased risk of prostate,
colon, lung and breast cancer.

" We concluded that greater milk consumption was associated with
higher levels of IGF-1," said Holmes. "This association raises the
possibility that diet could increase cancer risk by increasing levels of
IGF-1 in the blood stream. However, more research must be done
to determine whether milk consumption itself is directly linked to
cancer risk."

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