a259  1803  12 Feb 88
AM-Diet-Cancer,0639
Researcher Finds Foods Loaded with Natural Carcinogens
By PAUL RAEBURN
AP Science Editor
    BOSTON (AP) - Many foods contain very high levels of natural
cancer-causing agents, suggesting that intense efforts to control
industrial carcinogens may be misplaced, a researcher said Friday.
    Apples, for example, contain high levels of formaldehyde, which is
considered to be a potent carcinogen, said Bruce Ames, chairman of
the biochemistry department at the University of California,
Berkeley.
    Broccoli contains a substantial amount of a substance that is
chemically similar to dioxin. Peanut butter is unavoidably
contaminated with a fungus that is highly carcinogenic.
    ''Does that mean we're being done in by vegetables? Well, that's
what the reality is turning out to be,'' Ames said at the annual
meeting of the American Association for the Advancement of Science.
    Ames said he does not, in fact, believe that the cancer-causing
agents in food are causing us harm, because we have evolved to defend
ourselves against those agents.
    He believes, however, that the defenses we have evolved also protect
us against industrial carcinogens, which cause cancer in the same
ways as do natural carcinogens.
    Peter Preuss, director of the Office of Health and Environmental
Assessment at the U.S. Environmental Protection Agency said, ''I
think there's a great deal of importance in what Professor Ames
said.''
    He was critical, however, of many of Ames's calculations. ''While
the idea is important, I'm disturbed by the details. I think there's
a lot of rigor that has to be introduced into that science before
it's accepted.''
    He noted, for example, that the dioxin-like substance in broccoli
might act differently than dioxin. ''There are a lot of things that
are like that, but, nevertheless, dioxin is unique,'' he said.
    Ames said most of the natural carcinogens in plants evolved as a
natural defense mechanism.
    ''Plants don't have teeth, they don't have claws, they can't run
away,'' he said. ''All plant evolution is plants developing new and
better toxins to fight off predators.''
    Ames began his talk by saying that the world is full of carcinogens
but that they are not as harmful as people believe.
    One line of evidence to support that, he said, is that, with a few
exceptions, rates of cancer have not increased in the industrial era.
    ''Except for lung cancer, which is due to cigarette smoking, rates
of cancer are staying steady or going down,'' he said.
    While that is true for some cancers, Preuss said, others have gone
up. They include melanoma, lymphoma and cancer of the testes,
prostate and kidney.
    Ames was critical of the use of rats and mice to test whether
substances are carcinogenic. ''It's reasonable to think that
chemicals that are carcinogens in mice and rats would be carcinogens
in people - but the hook is, at that dose.''
    Rats are given the maximum dose that won't poison them, he said, but
such doses can kill cells in the body and may lead to cancer simply
through the disruption they cause. If that were the case, the
substances would not be expected to cause cancer at the low doses
that humans might be exposed to, he said.
    Ames is the developer of an alternative test that uses bacteria to
identify possible carcinogens.
    Ames presented dozens of examples of carcinogens in plants. Celery,
for example, contains psoralens, which become carcinogenic when
exposed to light. The levels are so high that celery pickers often
develop a rash on their hands and arms as a result, Ames said.
    Potatoes have high levels of solanine and chaconine, which block the
action of a human enzyme called cholinesterase, he said.
Organophosphate pesticides are considered dangerous, said Ames,
because they do the same thing - block cholinesterase.
    
 
 
AP-NY-02-12-88 2049EST
***************

a060  0515  13 Feb 88
PM-Diet-Cancer,0341
Researcher Finds Foods Loaded with Natural Carcinogens
By PAUL RAEBURN
AP Science Editor
    BOSTON (AP) - Many foods contain very high levels of natural
cancer-causing agents, suggesting that intense efforts to control
industrial carcinogens may be misplaced, a researcher said.
    Apples, for example, contain high levels of formaldehyde, which is
considered to be a potent carcinogen, said Bruce Ames, chairman of
the biochemistry department at the University of California,
Berkeley.
    Broccoli contains a substantial amount of a substance that is
chemically similar to dioxin. Peanut butter is unavoidably
contaminated with a fungus that is highly carcinogenic.
    ''Does that mean we're being done in by vegetables? Well, that's
what the reality is turning out to be,'' Ames said Friday at the
annual meeting of the American Association for the Advancement of
Science.
    Ames said he does not, in fact, believe that the cancer-causing
agents in food are causing us harm, because we have evolved to defend
ourselves against those agents.
    He believes, however, that the defenses we have evolved also protect
us against industrial carcinogens, which cause cancer in the same
ways as do natural carcinogens.
    Peter Preuss, director of the Office of Health and Environmental
Assessment at the U.S. Environmental Protection Agency said, ''I
think there's a great deal of importance in what Professor Ames
said.''
    He was critical, however, of many of Ames's calculations. ''While
the idea is important, I'm disturbed by the details. I think there's
a lot of rigor that has to be introduced into that science before
it's accepted.''
    He noted, for example, that the dioxin-like substance in broccoli
might act differently than dioxin. ''There are a lot of things that
are like that, but, nevertheless, dioxin is unique,'' he said.
    Ames said most of the natural carcinogens in plants evolved as a
natural defense mechanism.
    ''Plants don't have teeth, they don't have claws, they can't run
away,'' he said. ''All plant evolution is plants developing new and
better toxins to fight off predators.''
    
 
AP-NY-02-13-88 0805EST
***************