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Chroomsuppletie wordt steeds gevaarlijker
Supplementen bevatten chroom III, en niet het gevaarlijke chroom VI. Maar als natuurlijke
enzymen in het lichaam stoffen als glucose omzetten, kunnen ze het ongevaarlijke chroom III
daarbij veranderen in het kankerverwekkende chroom VI. Dat ontdekten Australische onderzoekers.
Hoewel supplementenmakers en fabrikanten van veevoer chroomverbindingen al in hun producten
stoppen, is nog niet bekend hoe de stoffen zich in de spijsvertering gedragen. Het onderzoek
van de Australiërs met kunstmatige spijsverteringssappen was bedoeld om die leemte op te vullen.
Met de door hen ontwikkelde methoden gaan ze nu de chroomingrediënten in supplementen screenen.
De onderzoekers hebben zich geconcentreerd op chroompropionaat, een gedoodverfde opvolger
van het omstreden chroompicolinaat. Die stof is bij in vitro-studies een krachtige oxidant
gebleken. De veevoerindustrie maakt in sommige landen al dankbaar gebruik van chroompropionaat.
De verandering van chroom III naar chroom VI trad overigens ook op bij andere chroomverbindingen,
zoals chroompicolinaat.
Irma Mulyani, Aviva Levina, Peter Lay.
Chromium (III) complexes used as nutritional supplements: structures and reactivities.
Journal of Inorganic Biochemistry 96 (2003) 196.
Weight pills may boost cancer risk
The Australian
Leigh Dayton
September 17, 2004
THEY'RE touted as a legal route to weight loss and big muscles, not to
mention a treatment for some forms of diabetes. But commonly used chromium
supplements may in fact boost the risk of cancer.
The warning comes from University of Sydney researchers who found in
laboratory tests that the harmless form of chromium in the supplements --
chromium(III) or chromium picolinate -- is likely to be converted into
cancer-causing chromium(VI) in the body.
"I don't want people to panic that taking small amounts will cause cancer,
but taking large amounts (of the supplements) over large periods of time
may not be a wise thing to do," said team leader Peter Lay, a bioinorganic
chemist.
Chromium is a trace mineral found in many foods, including yeast, whole
grains, nuts, and vegetables such as broccoli and potatoes.
It's unlikely that healthy people are chromium-deficient. And, as
Professor Lay said, there is a "very vigorous debate" among scientists
about whether chromium is essential for good nutrition.
Experts do agree, though, that chromium helps insulin control blood sugar
levels, although other compounds can also do that.
Chromium supplements became popular in the mid-1980s when the mineral was
-- like anabolic steroids -- linked to effects such as increased muscle
mass and reduced body fat. A range of supplements containing chromium are
widely available in Australia, and worldwide they are a
billion-dollar-a-year business.
Although there is scant evidence that chromium supplements are effective,
manufacturers claim they're beneficial for heart disease and depression,
as well as for slimming, building muscles and controlling type 2 diabetes.
In the US the Federal Trade Commission cracked down on manufacturers that
made unsubstantiated claims about the benefits of chromium supplements.
Last week, Professor Lay informed Australia's federal regulator, the
Therapeutic Goods Administration, of the worrisome findings.
The TGA did not respond to The Australian's request for comment.
In contrast, Britain's food-safety watchdog, the Food Standards Agency,
concluded last year that chromium(III) could potentially cause cancer, and
advised consumers against taking it.
Although separate groups in the US previously suggested that chromium
supplements might trigger genetic mutations, and thus, cancer, they didn't
know how they caused the harm.
But in the latest edition of the German journal Applied Chemistry,
Professor Lay, and his colleagues Aviva Levina, and Irma Mulyani report
that chromium(III) interacts with naturally occurring compounds called
oxidants, which convert it into dangerous chromium(VI). They hope to
follow up their findings.
[Link]
Does the activity of chromium in "slimming agents" stem from the formation of cancer-causing substances?
Chemie.de
08/30/2004
It is a widespread but disputed doctrine that the trivalent form of
chromium is an essential trace element playing an important role in
glucose and fat metabolism.
What is certain is that chromium in its penta-
and hexavalent forms is toxic, carcinogenic, and causes genetic mutations.
Are the popular "slimming agents" and muscle-building dietary supplements
based on chromium(III) compounds harmless, or not?
While there is yet to
be a definitive answer to this question, recent results on the in vitro
reactions of the dietary supplements with enzymes provide strong
indications that the dietary supplements could be converted from
chromium(III) into carcinogenic chromium(VI) by our bodies.
It is undisputed that special complexes of chromium(III) demonstrate an
insulin-intensifying effect. They are therefore under consideration as
potential drugs for diabetes (apart from their widespread use in dietary
supplements), even though the mechanism of their effect is not known.
In a
project funded by the Australian Research Council, Peter Lay, Irma
Mulyani, and Aviva Levina have now developed a novel explanation. First,
they throw out the current notion that chromium(III) cannot be converted
into chromium(VI) in the body. In immune reactions, for example, the human
body releases very strong oxidizing agents, such as hydrogen peroxide,
which were demonstrated to oxidize chromium(III), even under physiological
conditions. "It is postulated that it is the resulting chromium(VI) and
chromium(V) species that then interfere with our metabolism," explains
Lay.
When insulin is released by the pancreas, it docks onto a receptor on the
surface of cells. Afterwards, a phosphate group attaches onto the
receptor, which releases a signal cascade that orders the cell to take up
glucose from the blood. When the insulin is gone, an enzyme, tyrosine
phosphatase, splits the phosphate groups off the receptor, returning the
cell to its original state.
This is where, according to the Australian
researchers, the chromium(V) or chromium(VI) species step in: they inhibit
the tyrosine phosphatase, intensifying the effect of the insulin.
Chromium(III) species, in contrast, are not tyrosine phosphatase
inhibitors.
The trouble is that chromium(VI) has long been established as a human
carcinogen, as highlighted in the film Erin Brokovitch. "In light of our
new findings," stresses Lay, "the safety of chromium(III) compounds as
nutritional supplements or drugs should be re-examined very carefully,
particularly for heavy users of the supplements, such as elite athletes."
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[Definitie:] "An ergogenic aid is any substance or phenomenon that enhances performance."
(Wilmore and Costill) 
