The
information in this column is intended for informational
purposes only, and does not constitute medical advice or
recommendations by the author. Please consult with your
physician before making any lifestyle or medication changes, or if you
have any other concerns regarding your health.
VITAMIN
E, VITAMIN C
& SELENIUM DO NOT PREVENT
CANCER
These past 5 years have seen
the dashing of the hopes of many cancer physicians and researchers who,
like me,
had hoped that antioxidant vitamin supplements would prove to be potent
cancer
prevention agents. These
hopes were
built up over the previous decade as multiple clinical and laboratory
studies
reported encouraging results with Vitamin E, Vitamin C and selenium in
the
prevention of breast cancer, prostate cancer, and other types of cancer. However, most of these
studies were performed
using research methods that are far less rigorous than the “gold
standard”
prospective, randomized, placebo-controlled clinical trial.
Most
of the previous research
studies performed in this area have relied upon dietary questionnaires,
tests
of human cancer cells growing in laboratory Petri dishes, and the
injection of
human tumor cells into mice that have been genetically altered to have
a faulty
immune system. While
research studies such
as these occasionally yield results that are subsequently reproduced
and
confirmed in humans, the results of the vast majority of such
“low-powered” research
studies are, unfortunately, not validated by “Level 1” prospective,
randomized
clinical research trials in humans.
However, for most of the past decade, all that has been
available in
terms of cancer prevention research studies have been these relatively
weak
research studies. Over
the last 5 years,
however, several very large placebo-controlled prospective clinical
cancer
prevention trials have reported their results, and the news from these
trials
has been uniformly disappointing.
This
week, two more
long-awaited large prospective placebo-controlled cancer prevention
trials have
reported their preliminary results in the Journal
of the American Medical Association.
The
first of these two
studies is the SELECT Trial (Selenium and
Vitamin E Cancer Prevention Trial), which was a huge prostate cancer
prevention
study that enrolled more than 35,000 middle-aged men.
In the SELECT Trial, study volunteers were
secretly randomized to one of 4 different groups.
One group received placebo (sugar) pills,
only, while the remaining groups were assigned to receive selenium
alone,
Vitamin E alone, or both selenium and Vitamin E.
All men were clinically free of prostate
cancer when they joined this enormous multi-center research study.
The
SELECT Trial, the largest prospective
cancer prevention research study ever conducted, was originally planned
to
continue for as long as 12 years, but was prematurely ended after an
interim
review of the research data raised significant concerns. Half of the 35,533 men
participating in this
study had been observed for just over 5 years, while the remaining half
had
been observed less than 5 years, when the study was shut down.
Among
the men randomized to
secretly receive Vitamin E alone, the risk of developing prostate
cancer was actually
13 percent higher than what was
observed in the group of men who received only placebo tablets. The men who received only
selenium
supplements experienced a 5 percent greater risk of prostate cancer
when compared
to the men in the placebo group.
Finally, the men who were secretly randomized to receive both Vitamin E and selenium supplements
experienced an identical risk of prostate cancer when compared to the
men in
the placebo group. (The
slight increase
in prostate cancer risk that was observed in the groups receiving only
selenium
and only Vitamin E did not, however.)
Not only was there no apparent reduction in prostate
cancer risk among
the men who received Vitamin E and/or selenium in this study but,
importantly,
there was also no difference in the risk of other types of cancer
observed among
the 4 groups of study volunteers.
Although
additional years of
observing the more than 35,000 men who participated in this clinical
trial may
reveal additional findings, the interim results of this huge and
extremely well
conducted prospective cancer prevention trial are disappointing, to say
the
least. However, the
preliminary findings
of the SELECT trial join a growing number of other large-scale
prospective,
randomized, placebo-controlled cancer prevention and cardiovascular
disease
prevention research trials that have recently revealed absolutely no
disease
prevention effects associated with the most commonly used antioxidant
vitamin
supplements.
The
SELECT Trial, like other
recent large and very expensive “gold standard” disease prevention
research
trials, raises serious questions about the clinical utility of
individual
antioxidant vitamin supplements, and takes us back to our much earlier
view
that there is likely to be little, if any, benefit associated with
taking extra
doses of dietary antioxidants outside of a well-balanced diet. I have previously included
these same
antioxidant vitamins, and other antioxidant dietary supplements, in my
own
little plastic tray of vitamins and supplements.
However, with the advent of several recent
very large prospective, randomized clinical trials showing no health
benefits
associated with most of these supplements, and with several of these
clinical
trials actually showing an increase
in serious illnesses, and even death, associated with some of these
same
dietary supplements, I have recently updated my secret little tray of
supplements. To my
wife’s relief, the
number of plastic vitamin and supplement bottles crammed into her
kitchen
cabinets has been on the decline, recently.
Now, let me discuss the second cancer prevention trial
also published in
the current issue of the Journal of the
American Medical Association.
The
results of the second large
prospective cancer prevention study, The Physicians’ Health Study II,
have also
been much anticipated. In
this study,
14,641 clinically healthy male physicians, aged 50 years and older,
were
secretly randomized to receive Vitamin E supplements every other day,
Vitamin C
supplements every day, or identical placebo (sugar) tablets. The average duration of
follow-up for this
large number of healthy middle-aged men was 8 years.
During this nearly decade-long period of
follow-up, 1,943 cases of cancer were diagnosed, including 1,008 cases
of
prostate cancer.
Compared
with the men who were
secretly randomized to receive the placebo pills, there was absolutely
no
difference in the incidence of prostate cancer, or of any other type of
cancer,
observed among the men who secretly received either the Vitamin E or
the Vitamin
C supplements.
The
results of this large
prospective clinical trial, as with the SELECT Trial and other recently
published large cancer prevention studies, shows that Vitamin E or
Vitamin C
supplementation has no apparent impact on the incidence of any type of cancer in otherwise healthy
adults.
These
two powerful prospective
clinical research trials, which provide the highest available level of
clinical
research data among all types of clinical or laboratory research
studies, are
showing us, over and over again, that Vitamin C and alpha-tocopherol
(the most
common form of Vitamin E) supplements, when given in typical doses,
appear to
have absolutely no impact on cancer and cardiovascular disease risks in
adults
who eat a balanced diet. Moreover,
recently published prospective clinical trials have actually found an increased risk of lung cancer among
smokers taking beta-carotene (a member of the Vitamin A family), and an
overall
4 to 5 percent increase in the risk
of death among healthy research volunteers who were randomized to
receive 400 International
Units per day of Vitamin E.
The
newly published results of
these two very large cancer prevention trials, along with similarly
negative
results from other large prospective cancer prevention trials, should
prompt
all of us to reconsider the notion, based upon earlier and much less
rigorous
research, that taking supra-normal doses of vitamins and other dietary
supplements are going to significantly decrease our risk of cancer, and
other
serious diseases, beyond the disease reduction benefits that have long
been
associated with eating a healthful and balanced diet.
There is no question, based upon decades of
epidemiological studies, that a diet low in fat (and very low in red
meat and
processed meats, in particular), and rich in fresh vegetables and
fruits, can
lower not only our risk of many of the most common cancer killers, but
as an
added bonus, can also lower our risk of cardiovascular diseases as well.
As
the disappointing results
related to Vitamins A, C and E continue to pile up, I often receive
messages
from readers more or less condemning these studies and their negative
results. I
generally remind these readers that I have
sat in their midst for a couple of decades now, popping a
rainbow-colored
assortment of nearly every dietary antioxidant known to mankind. However, when the Level 1
clinical data
starts coming in, and all of it is bad news, sometimes you just have to
accept
these findings, make an adjustment, and move on….
The good news is that, despite
the accumulating disappointing news about dietary antioxidants as
cancer
prevention agents, between 60 and 80 percent of all cases of cancer can
be
prevented with judicious and fairly moderate lifestyle, diet and other
behavioral strategies. My
forthcoming
book, “A Cancer Prevention Guide for the Human Race,” is based upon an
exhaustive, global review of, literally, thousands of cancer prevention
and cancer
screening research studies. Despite
all
of the bad news about antioxidants, you can still tremendously reduce
your
lifetime risk of developing cancer by using an evidence-based approach
that
will also significantly reduce your risk of cardiovascular diseases at
the same
time. Look for this
new cancer
prevention book to arrive in the fall of 2009!
POSTSCRIPT:
A POSSIBLE CURE FOR DOWN’S SYNDROME
I have
received numerous inquiries regarding last
week’s column on Down’s syndrome, also known as trisomy 21. In that column, I
described the rather
miraculous improvements in learning abilities observed in newborn mice
born
with a trisomy disorder that mimics Down’s syndrome.
Prior to their birth, the pregnant mothers of
these young trisomy mice were treated with two neuroprotective proteins. Following their birth,
these young trisomy mice
were found to do as well with several types of learning as young mice
without
trisomy.
I
wrote to the authors of this study at the National
Institutes of Health to inquire about their plans for possible
early-phase
human clinical trials with these two proteins.
Unfortunately, I learned that, at the present time, no
human clinical
trials are in the works. I
also
contacted Dr. Steve Whitaker, who is the Chief Medical Officer for
Allon
Therapeutics, the Canadian biotechnology company that has developed
these two
experimental proteins. Dr.
Whitaker very
graciously responded after I mentioned to him that many parents of
children
with trisomy 21 have expressed a tremendous interest in participating
in a
clinical trial using these experimental proteins, after reading last
week’s
column. Unfortunately
for families and
patients with Down’s syndrome, Allon Therapeutics’ research focus, at
this
time, is pretty much limited to Alzheimer's
disease,
and cognitive impairments secondary to stroke
and schizophrenia-related cognitive impairment.
My
recommendation
to parents who would like to see the National Institutes of Health
develop an
early-phase clinical trisomy 21 trial using these peptides is that you
contact
your Congressional Representative or Senator, and ask them to propose
funding
to carry out at least a small preliminary clinical trial with these
neuroprotective proteins. It
is time to
assess the toxicity of these proteins in very carefully controlled
prospective
clinical trials and, if there is no significant toxicity associated
with these
drugs, to then proceed with actual testing of these compounds in humans
within
a placebo-controlled, randomized prospective clinical trial setting.
Disclaimer:
As always, my advice to readers is to seek the advice of your physician
before making any significant changes
in
medications, diet, or level of physical activity.
