recent editorial in the British Medical Journal, several experts from
the University of Bristol in England write about the substantial and
still growing body of evidence implicating insulin-like growth
factor-I (IGF-1) in cancer.
They note that the role of IGF-1 in promoting cancer
has been investigated for many years, but recently the quality and
quantity of evidence has increased
They note that several prospective
studies have used stored blood collected up to 14 years before the
onset of cancer have shown associations between IGF-1 and prostate
cancer, premenopausal breast cancer, and colon cancer.
According to the editorial,
"The risk of cancer is higher
among people with raised concentrations of insulin-like growth
In addition, "it is lower among those
with high concentrations of insulin-like growth factor binding
protein-3 (the main binding protein)."
Research suggests that the observed
relation between cancer and IGF-1 is not due to the release of the
growth factor by the cancer itself.
"The effects are sizeable
and stronger than the effects seen in relation to most previously
reported risk factors" they state.
In addition to the increasing direct
epidemiological evidence, there is a significant amount of
- Acromegaly, in which high
concentrations of growth hormone stimulate production of high
concentrations of IGF-1, has been associated with an increased risk
of colorectal cancer and breast cancer in some studies and less
consistently with prostate, thyroid, and hematological malignancies.
- In many studies anthropometric
markers of the activity of insulin-like growth factor-I, such as
height and leg length, are associated with cancer incidence,
particularly with the cancers for which risk increases with rising
concentrations of insulin-like growth factor-I.
- In animals, calorie restriction
reduces the risk of cancer primarily by reducing the circulating
concentrations of insulin-like growth factor-I" the editorial notes.
Some of the potential mechanisms of
the way in which IGF-1 increases cancer risk are as follows:
- IGF-1 could be a surrogate for the
activity of sex steroid hormones, which in turn influence the risk
- IGF-1 may increase cell turnover
and the susceptibility of cells to malignant transformation both
directly and by modulating the effects of sex steroids.
- IGF-1 might increase the
risk of cancer by preventing the programmed death of cells that have
been transformed, thus interrupting an important process, which
retards the development of cancer.
"Given the increasing
evidence of the risk of cancer, caution should be exercised in the
exogenous use of either insulin-like growth factor-I or substances
that increase concentrations of it," they
Medical Journal October 7, 2000;321:847-848
DR. MERCOLA'S COMMENT:
Many may not realize that when you drink milk you are consuming IGF-1,
along with many other growth factors.
Milk from cows treated with synthetic growth hormones such as rBGH
have especially high levels of IGF-1. This is one of the many
reasons why I advise avoiding milk. You can click on the links below
for the others.
It is also interesting to note that the
growth hormone that is so strongly promoted by many anti-aging
clinicians may in fact have adverse effects by raising insulin-like
growth factor-I. It is probably best for most to avoid the use of
growth hormone and rely on more proven and less risky interventions,
like a good
diet which reduces insulin levels and also weight training which
can increase growth hormone.
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