Pramesh Ru
Wed, May-16-07, 17:16
http://www.eurekalert.org/pub_releases/2007-05/jotn-mu051007.-
php
MEMO TO THE MEDIA Liz Savage Press Release: Heavy Multivitamin
Use May Be Linked to Advanced Prostate Cancer
J. Natl. Cancer Inst. 2007 99: 741
Heavy multivitamin use may be linked to advanced
prostate cancer
The embargo has been lifted at the request of the
submitting PIO.
While regular multivitamin use is not linked with early or
localized prostate cancer, taking too many multivitamins may
be associated with an increased risk for advanced or fatal
prostate cancers, according to a study in the May 16 issue of
the Journal of the National Cancer Institute.
Millions of Americans take multivitamins because of a belief
in their potential health benefits, even though there is
limited scientific evidence that they prevent chronic disease.
Researchers have wondered what impact multivitamin use might
have on cancer risk.
Karla Lawson, Ph.D., of the National Cancer Institute in
Bethesda, Md., and colleagues followed 295,344 men enrolled in
the National Institutes of Health-AARP Diet and Health Study
to determine the association between multivitamin use and
prostate cancer risk. After five years of follow-up, 10,241
men were diagnosed with prostate cancer, including 8,765 with
localized cancers and 1,476 with advanced cancers.
The researchers found no association between multivitamin use
and the risk of localized prostate cancer. But they did find
an increased risk of advanced and fatal prostate cancer among
men who used multivitamins more than seven times a week,
compared with men who did not use multivitamins. The
association was strongest in men with a family history of
prostate cancer and men who also took selenium, beta-carotene,
or zinc supplements.
"Because multivitamin supplements consist of a combination of
several vitamins and men using high levels of multivitamins
were also more likely to take a variety of individual
supplements, we were unable to identify or quantify individual
components responsible for the associations that we observed,"
the authors write.
In an accompanying editorial, Goran Bjelakovic, M.D., of the
University of Nis in Serbia, and Christian Gluud, M.D., of
Copenhagen University Hospital in Denmark, discuss the
positive and negative health effects of antioxidant
supplements. "Lawson [and colleagues] add to the growing
evidence that questions the beneficial value of antioxidant
vitamin pills in generally well-nourished populations and
underscore the possibility that antioxidant supplements
could have unintended consequences for our health," the
authors write.
http://jnci.oxfordjournals.org/cgi/content/full/99/10/742
EDITORIALS Goran Bjelakovic and Christian Gluud Surviving
Antioxidant Supplements
K. Natl. Cancer Inst. 2007 99: 742-743; doi:10.1093/jnci/djk21
An association between healthy diet and good health has been
noted since Hippocrates (460-377 BC)-and in fact long before
(1). Our diet provides numerous vitamins and trace elements
that are essential to good health. Observational studies have
shown that there is a positive association between a healthy
diet, especially high intake of fruits and vegetables, and
delayed aging, reduced risk of cancer, and reduced risk of
cardiovascular diseases (2,3). Fruits and vegetables contain
numerous micronutrients, including -carotene (a precursor of
vitamin A), vitamin C, vitamin E, and selenium. These organic
components have antioxidant potential and are defined as
essential micronutrients (4). Because our body cannot
synthesize them, they must be consumed.
In spite of intensive research, it is still not clear exactly
which specific dietary constituents of fruits and vegetables
might be beneficial. Antioxidant vitamins and elements have
attracted most attention in this regard. It is assumed that
antioxidants may prevent oxidative damage to cellular
components, a potentially important function given that
oxidative stress might play a role in aging and the
pathogenesis of number of diseases, including cardiovascular
diseases and cancer, the leading causes of death in
high-income countries (5).
Hypotheses as to the role played by oxidative stress in human
disease have stimulated interest in the preventive potential
of antioxidant supplements. Worldwide, institutions have been
created to study antioxidants, and many resources have been
allocated to this area. Consumption of antioxidant supplements
in high-income countries has become widespread-it is estimated
that about one-third of adults in high-income countries
consume antioxidant supplements (6). A large number of primary
or secondary prevention randomized trials have been conducted
to assess the benefits and harms of antioxidant supplements
versus placebo or no intervention. Systematic reviews and
meta-analyses of these randomized trials have not demonstrated
that -carotene, vitamin A, and vitamin E in the administered
dosages lead to decreased mortality, and some analyses have
suggested the possibility of increased mortality (7-11). As to
vitamin C and selenium, the verdict is still out (11).
There are several possible explanations for the potential
negative effect of antioxidant supplements. Reactive oxygen
species in moderate concentrations are essential mediators of
reactions by which the body gets rid of unwanted cells. Thus,
if administration of antioxidant supplements decreases free
radicals, it may interfere with essential defensive mechanisms
for ridding the organism of damaged cells, including those
that are precancerous and cancerous (12). Thus, antioxidant
supplements may actually cause some harm (7-11,13). Our diets
typically contain safe levels of vitamins, but high-level
antioxidant supplements could potentially upset an important
physiologic balance (7-11,13).
The amounts of antioxidants that may afford protection are not
known and may differ among individuals. People exposed to
increased oxidative stress may have elevated antioxidant
requirements. Furthermore, antioxidants could be beneficial in
people with innate or acquired high baseline levels of
reactive oxygen species but be harmful in people with lower
innate levels
(12). It is important to keep in mind that antioxidant
supplements are synthetic and possess prooxidant
properties as well (14). These factors could explain a
possible increase in the risk of cancer (8,9,13) and
cardiovascular diseases (7). Meta-analyses of randomized
clinical trials have not shown that antioxidant
supplements reduce cancer incidence (8,9,13,15).
In this issue of the journal, Lawson et al. (16) report the
results of a prospective observational study. They
investigated the association between multivitamin use and
prostate cancer risk in 295344 men enrolled in the National
Institutes of Health (NIH)-AARP Diet and Health Study (16).
The men were clinically cancer free at enrollment. The authors
found that use of multivitamins more than seven times per
week, when compared with never use, was associated with a
doubling in the risk of fatal prostate cancer (relative risk =
1.98, 95% confidence interval = 1.07 to 3.66). The study of
Lawson et al. (16) is observational, and therefore confounding
by indication and other confounding cannot be excluded. But
the sample studied is very large, which reduces random errors,
and the study seems well conducted. The results are in accord
with the results of systematic reviews and meta-analyses of
randomized clinical trials (7-11,13). The findings lend
further credence to the possibility of harm associated with
increased use of supplements, including increased rates of
cancer (8,9,13,15) and cardiovascular mortality (7).
Lawson et al. (16) add to the growing evidence that questions
the beneficial value of antioxidant vitamin pills in generally
well-nourished populations
(13) and underscore the possibility that antioxidant
supplements could have unintended consequences for our
health. There are still many gaps in our knowledge of the
mechanisms of bioavailability, biotransformation, and
action of antioxidant supplements. How much fruit and
vegetables do we have to eat to obtain an optimal amount
of these nutrients? Why is it not possible to take a
vitamin pill to obtain the same effect as a balanced
diet? Antioxidant supplements in pills are synthetic,
factory processed, and may not be safe compared with
their naturally occurring counterparts (17-21). a
possible explanation for the negative effects of
antioxidant supplementation observed in trials is that
the studies were conducted in middle- and high-income
countries among populations already well saturated with
vitamins and trace elements (11). The American diet
provides 120% of the recommended dietary allowances for
-carotene, vitamin A, and vitamin C, and dietary vitamin
E deficiency has never been reported in the United States
(17-21). Whether oxidative stress is a primary cause of
chronic diseases and the aging process itself or merely a
secondary phenomenon is another question that deserves
debate and scrutiny (22).
Results of ongoing clinical trials and further studies will be
required to extend our knowledge of the impact of antioxidant
supplements on health. Is oxidative stress the cause of
disease or rather a consequence? Is it wise to artificially
modulate the delicate balance between oxidative stress and
antioxidants in our cells? Ideally, we should have more data
to address these questions.
One way to extend our knowledge about the effects of
supplemental vitamins on health would be to test for benefits
and harms of supplements before they come to the market. This
would entail fair testing of all commercial ingested products
with claimed health benefits, as we intend to do with
pharmaceutical drugs (23,24). What happens in a petri dish or
in preclinical assays may not happen in people
(http://www.jameslindlibrary.org; http://www.cochrane.org).
Public investment in independent clinical research will be
needed to adequately test hypotheses generated in the
laboratory.
http://jnci.oxfordjournals.org/cgi/content/abstract/99/10/754
Karla A. Lawson, Margaret E. Wright, Amy Subar, Traci Mouw,
Albert Hollenbeck, Arthur Schatzkin, and Michael F. Leitzmann
Multivitamin Use and Risk of Prostate Cancer in the National
Institutes of Health-AARP Diet and Health Study
J. Natl. Cancer Inst. 2007 99: 754-764
Background: Multivitamin supplements are used by millions of
Americans because of their potential health benefits, but
the relationship between multivitamin use and prostate
cancer is unclear.
Methods: We prospectively investigated the association
between multivitamin use and risk of prostate cancer
(localized, advanced, and fatal) in 295344 men enrolled in
the National Institutes of Health (NIH)-AARP Diet and Health
Study who were cancer free at enrollment in 1995 and 1996.
During 5 years of follow-up, 10241 participants were
diagnosed with incident prostate cancer, including 8765
localized and 1476 advanced cancers. In a separate mortality
analysis with 6 years of follow-up, 179 cases of fatal
prostate cancer were ascertained. Multivitamin use was
assessed at baseline as part of a self-administered, mailed
food-frequency questionnaire. Relative risks (RRs) and 95%
confidence intervals (CIs) were calculated by use of Cox
proportional hazards regression, adjusted for established or
suspected prostate cancer risk factors.
Results: No association was observed between multivitamin use
and risk of localized prostate cancer. However, we found an
increased risk of advanced and fatal prostate cancers (RR =
1.32, 95% CI = 1.04 to 1.67 and RR = 1.98, 95% CI = 1.07 to
3.66, respectively) among men reporting excessive use of
multivitamins (more than seven times per week) when compared
with never users. The incidence rates per 100000 person-years
for advanced and fatal prostate cancers for those who took a
multivitamin more than seven times per week were 143.8 and
18.9, respectively, compared with 113.4 and 11.4 in never
users. The positive associations with excessive multivitamin
use were strongest in men with a family history of prostate
cancer or who took individual micronutrient supplements,
including selenium, -carotene, or zinc.
Conclusion: These results suggest that regular multivitamin
use is not associated with the risk of early or localized
prostate cancer. The possibility that men taking high levels
of multivitamins along with other supplements have increased
risk of advanced and fatal prostate cancers is of concern and
merits further evaluation.
CONTEXT AND CAVEATS
Prior knowledge
Previous epidemiologic studies have suggested that
multivitamin supplement use may be associated with more rapid
prostate cancer progression.
Study design
In a prospective cohort study, demographic data and
information pertaining to multivitamin and individual
supplement use were obtained via questionnaire; information on
prostate cancer diagnosis was accessed via certified cancer
registries.
Contribution
This large study was confirmatory of previous reports of an
association between multivitamin use and advanced prostate
cancer. It also found potential associations of various
individual vitamins and mineral supplements with prostate
cancer that should be investigated further.
Implications
Despite the perceived health benefits of multivitamin
supplements, the risks associated with their use need to be
explored further.
Limitations
Differences between heavy users of multivitamins and nonusers
that may not be controlled for in a study of this type may
obscure the true relationship between multivitamin use and
prostate cancer.
--
Pramesh Rutajit - p297tongue6221@newsguy.com - Remove
tongue to reply.
php
MEMO TO THE MEDIA Liz Savage Press Release: Heavy Multivitamin
Use May Be Linked to Advanced Prostate Cancer
J. Natl. Cancer Inst. 2007 99: 741
Heavy multivitamin use may be linked to advanced
prostate cancer
The embargo has been lifted at the request of the
submitting PIO.
While regular multivitamin use is not linked with early or
localized prostate cancer, taking too many multivitamins may
be associated with an increased risk for advanced or fatal
prostate cancers, according to a study in the May 16 issue of
the Journal of the National Cancer Institute.
Millions of Americans take multivitamins because of a belief
in their potential health benefits, even though there is
limited scientific evidence that they prevent chronic disease.
Researchers have wondered what impact multivitamin use might
have on cancer risk.
Karla Lawson, Ph.D., of the National Cancer Institute in
Bethesda, Md., and colleagues followed 295,344 men enrolled in
the National Institutes of Health-AARP Diet and Health Study
to determine the association between multivitamin use and
prostate cancer risk. After five years of follow-up, 10,241
men were diagnosed with prostate cancer, including 8,765 with
localized cancers and 1,476 with advanced cancers.
The researchers found no association between multivitamin use
and the risk of localized prostate cancer. But they did find
an increased risk of advanced and fatal prostate cancer among
men who used multivitamins more than seven times a week,
compared with men who did not use multivitamins. The
association was strongest in men with a family history of
prostate cancer and men who also took selenium, beta-carotene,
or zinc supplements.
"Because multivitamin supplements consist of a combination of
several vitamins and men using high levels of multivitamins
were also more likely to take a variety of individual
supplements, we were unable to identify or quantify individual
components responsible for the associations that we observed,"
the authors write.
In an accompanying editorial, Goran Bjelakovic, M.D., of the
University of Nis in Serbia, and Christian Gluud, M.D., of
Copenhagen University Hospital in Denmark, discuss the
positive and negative health effects of antioxidant
supplements. "Lawson [and colleagues] add to the growing
evidence that questions the beneficial value of antioxidant
vitamin pills in generally well-nourished populations and
underscore the possibility that antioxidant supplements
could have unintended consequences for our health," the
authors write.
http://jnci.oxfordjournals.org/cgi/content/full/99/10/742
EDITORIALS Goran Bjelakovic and Christian Gluud Surviving
Antioxidant Supplements
K. Natl. Cancer Inst. 2007 99: 742-743; doi:10.1093/jnci/djk21
An association between healthy diet and good health has been
noted since Hippocrates (460-377 BC)-and in fact long before
(1). Our diet provides numerous vitamins and trace elements
that are essential to good health. Observational studies have
shown that there is a positive association between a healthy
diet, especially high intake of fruits and vegetables, and
delayed aging, reduced risk of cancer, and reduced risk of
cardiovascular diseases (2,3). Fruits and vegetables contain
numerous micronutrients, including -carotene (a precursor of
vitamin A), vitamin C, vitamin E, and selenium. These organic
components have antioxidant potential and are defined as
essential micronutrients (4). Because our body cannot
synthesize them, they must be consumed.
In spite of intensive research, it is still not clear exactly
which specific dietary constituents of fruits and vegetables
might be beneficial. Antioxidant vitamins and elements have
attracted most attention in this regard. It is assumed that
antioxidants may prevent oxidative damage to cellular
components, a potentially important function given that
oxidative stress might play a role in aging and the
pathogenesis of number of diseases, including cardiovascular
diseases and cancer, the leading causes of death in
high-income countries (5).
Hypotheses as to the role played by oxidative stress in human
disease have stimulated interest in the preventive potential
of antioxidant supplements. Worldwide, institutions have been
created to study antioxidants, and many resources have been
allocated to this area. Consumption of antioxidant supplements
in high-income countries has become widespread-it is estimated
that about one-third of adults in high-income countries
consume antioxidant supplements (6). A large number of primary
or secondary prevention randomized trials have been conducted
to assess the benefits and harms of antioxidant supplements
versus placebo or no intervention. Systematic reviews and
meta-analyses of these randomized trials have not demonstrated
that -carotene, vitamin A, and vitamin E in the administered
dosages lead to decreased mortality, and some analyses have
suggested the possibility of increased mortality (7-11). As to
vitamin C and selenium, the verdict is still out (11).
There are several possible explanations for the potential
negative effect of antioxidant supplements. Reactive oxygen
species in moderate concentrations are essential mediators of
reactions by which the body gets rid of unwanted cells. Thus,
if administration of antioxidant supplements decreases free
radicals, it may interfere with essential defensive mechanisms
for ridding the organism of damaged cells, including those
that are precancerous and cancerous (12). Thus, antioxidant
supplements may actually cause some harm (7-11,13). Our diets
typically contain safe levels of vitamins, but high-level
antioxidant supplements could potentially upset an important
physiologic balance (7-11,13).
The amounts of antioxidants that may afford protection are not
known and may differ among individuals. People exposed to
increased oxidative stress may have elevated antioxidant
requirements. Furthermore, antioxidants could be beneficial in
people with innate or acquired high baseline levels of
reactive oxygen species but be harmful in people with lower
innate levels
(12). It is important to keep in mind that antioxidant
supplements are synthetic and possess prooxidant
properties as well (14). These factors could explain a
possible increase in the risk of cancer (8,9,13) and
cardiovascular diseases (7). Meta-analyses of randomized
clinical trials have not shown that antioxidant
supplements reduce cancer incidence (8,9,13,15).
In this issue of the journal, Lawson et al. (16) report the
results of a prospective observational study. They
investigated the association between multivitamin use and
prostate cancer risk in 295344 men enrolled in the National
Institutes of Health (NIH)-AARP Diet and Health Study (16).
The men were clinically cancer free at enrollment. The authors
found that use of multivitamins more than seven times per
week, when compared with never use, was associated with a
doubling in the risk of fatal prostate cancer (relative risk =
1.98, 95% confidence interval = 1.07 to 3.66). The study of
Lawson et al. (16) is observational, and therefore confounding
by indication and other confounding cannot be excluded. But
the sample studied is very large, which reduces random errors,
and the study seems well conducted. The results are in accord
with the results of systematic reviews and meta-analyses of
randomized clinical trials (7-11,13). The findings lend
further credence to the possibility of harm associated with
increased use of supplements, including increased rates of
cancer (8,9,13,15) and cardiovascular mortality (7).
Lawson et al. (16) add to the growing evidence that questions
the beneficial value of antioxidant vitamin pills in generally
well-nourished populations
(13) and underscore the possibility that antioxidant
supplements could have unintended consequences for our
health. There are still many gaps in our knowledge of the
mechanisms of bioavailability, biotransformation, and
action of antioxidant supplements. How much fruit and
vegetables do we have to eat to obtain an optimal amount
of these nutrients? Why is it not possible to take a
vitamin pill to obtain the same effect as a balanced
diet? Antioxidant supplements in pills are synthetic,
factory processed, and may not be safe compared with
their naturally occurring counterparts (17-21). a
possible explanation for the negative effects of
antioxidant supplementation observed in trials is that
the studies were conducted in middle- and high-income
countries among populations already well saturated with
vitamins and trace elements (11). The American diet
provides 120% of the recommended dietary allowances for
-carotene, vitamin A, and vitamin C, and dietary vitamin
E deficiency has never been reported in the United States
(17-21). Whether oxidative stress is a primary cause of
chronic diseases and the aging process itself or merely a
secondary phenomenon is another question that deserves
debate and scrutiny (22).
Results of ongoing clinical trials and further studies will be
required to extend our knowledge of the impact of antioxidant
supplements on health. Is oxidative stress the cause of
disease or rather a consequence? Is it wise to artificially
modulate the delicate balance between oxidative stress and
antioxidants in our cells? Ideally, we should have more data
to address these questions.
One way to extend our knowledge about the effects of
supplemental vitamins on health would be to test for benefits
and harms of supplements before they come to the market. This
would entail fair testing of all commercial ingested products
with claimed health benefits, as we intend to do with
pharmaceutical drugs (23,24). What happens in a petri dish or
in preclinical assays may not happen in people
(http://www.jameslindlibrary.org; http://www.cochrane.org).
Public investment in independent clinical research will be
needed to adequately test hypotheses generated in the
laboratory.
http://jnci.oxfordjournals.org/cgi/content/abstract/99/10/754
Karla A. Lawson, Margaret E. Wright, Amy Subar, Traci Mouw,
Albert Hollenbeck, Arthur Schatzkin, and Michael F. Leitzmann
Multivitamin Use and Risk of Prostate Cancer in the National
Institutes of Health-AARP Diet and Health Study
J. Natl. Cancer Inst. 2007 99: 754-764
Background: Multivitamin supplements are used by millions of
Americans because of their potential health benefits, but
the relationship between multivitamin use and prostate
cancer is unclear.
Methods: We prospectively investigated the association
between multivitamin use and risk of prostate cancer
(localized, advanced, and fatal) in 295344 men enrolled in
the National Institutes of Health (NIH)-AARP Diet and Health
Study who were cancer free at enrollment in 1995 and 1996.
During 5 years of follow-up, 10241 participants were
diagnosed with incident prostate cancer, including 8765
localized and 1476 advanced cancers. In a separate mortality
analysis with 6 years of follow-up, 179 cases of fatal
prostate cancer were ascertained. Multivitamin use was
assessed at baseline as part of a self-administered, mailed
food-frequency questionnaire. Relative risks (RRs) and 95%
confidence intervals (CIs) were calculated by use of Cox
proportional hazards regression, adjusted for established or
suspected prostate cancer risk factors.
Results: No association was observed between multivitamin use
and risk of localized prostate cancer. However, we found an
increased risk of advanced and fatal prostate cancers (RR =
1.32, 95% CI = 1.04 to 1.67 and RR = 1.98, 95% CI = 1.07 to
3.66, respectively) among men reporting excessive use of
multivitamins (more than seven times per week) when compared
with never users. The incidence rates per 100000 person-years
for advanced and fatal prostate cancers for those who took a
multivitamin more than seven times per week were 143.8 and
18.9, respectively, compared with 113.4 and 11.4 in never
users. The positive associations with excessive multivitamin
use were strongest in men with a family history of prostate
cancer or who took individual micronutrient supplements,
including selenium, -carotene, or zinc.
Conclusion: These results suggest that regular multivitamin
use is not associated with the risk of early or localized
prostate cancer. The possibility that men taking high levels
of multivitamins along with other supplements have increased
risk of advanced and fatal prostate cancers is of concern and
merits further evaluation.
CONTEXT AND CAVEATS
Prior knowledge
Previous epidemiologic studies have suggested that
multivitamin supplement use may be associated with more rapid
prostate cancer progression.
Study design
In a prospective cohort study, demographic data and
information pertaining to multivitamin and individual
supplement use were obtained via questionnaire; information on
prostate cancer diagnosis was accessed via certified cancer
registries.
Contribution
This large study was confirmatory of previous reports of an
association between multivitamin use and advanced prostate
cancer. It also found potential associations of various
individual vitamins and mineral supplements with prostate
cancer that should be investigated further.
Implications
Despite the perceived health benefits of multivitamin
supplements, the risks associated with their use need to be
explored further.
Limitations
Differences between heavy users of multivitamins and nonusers
that may not be controlled for in a study of this type may
obscure the true relationship between multivitamin use and
prostate cancer.
--
Pramesh Rutajit - p297tongue6221@newsguy.com - Remove
tongue to reply.