Download Green Tea: What is the cancer connection?

Issue 2, Volume 1 • Summer 2007
Nutrition education after a cancer diagnosis
Green Tea: What is the cancer connection?
In this issue:
• Green Tea:What is the
cancer connection?
• Selenium and Cancer:
What is we recommended?
• Soy:What you need to know
• Organic Fruits and Vegetables:
Are they better?
There are four major forms
of tea – green tea, black tea,
oolong tea and white tea.
All of these forms differ in
how they are produced and in
their chemical make-up. All
tea contains polyphenols
which are found in the tea
leaves. The polyphenol group
that is of most interest to
researchers at this time is the
catechins which includes four
types - epicatechin (EC),
epicatechin-3-gallate (ECG),
epigallocatechin (EGC) and
epigallocatechin-3-gallate
(EGCG). More catechins are
available in green tea than in
black tea. Catechins are of
interest in cancer research
because they act as antioxidants which prevent damage
to DNA and other molecules
caused by free radicals.
Laboratory studies support
the anti-cancer properties of
adequate and consistent
intakes of green tea. Green tea
may be more beneficial to
some individuals than others.
A study conducted with
individuals who were at risk
for lung cancer development
found that those who were
“genetically deficient” in
GSTM1, an enzyme that
quickly eliminates carcinogens
from the body, received the
greatest reduction in lung
cancer risk from drinking
green tea. This means the
chemopreventive effects of
green tea may be restricted to
individuals who are
particularly susceptible
to oxidative stress and
oxidative DNA damage.
Experimental studies using
cell cultures and animals have
supported green tea as a
chemopreventive agent for
breast, prostate and colorectal
cancer, meaning that it has
some type of protective
effect against cancer cell
development. In laboratory
experiments green tea has
been shown to induce breast
cancer cell apoptosis (cell
death) in estrogen-receptor
negative cells and also found
to increase the effects of
tamoxifen on estrogenreceptor positive breast cancer
cells. Cell apoptosis has also
been observed in lung
cancer cells with exposure
to green tea.
Clinical trials will help determine if green tea extracts are
as effective as drinking green
tea. A recent study
conducted in individuals who
have prostate neoplasia, a
precursor of prostate cancer,
found that those who received
green tea polyphenols in
capsule form had a lower incidence of prostate cancer diagnosis after one year.
There is also more attention
being given to the amount and
type of fat in the diet and its
role in absorption of the
catechins from green tea.
In animal models those with
colon carcinogenesis that
received a high corn oil diet
did not see the same cancer
preventive effects as did the
mice that received a low fat
diet meaning that the amount
To maintain the greatest catechin
content use small, loose leaf green
tea. If you do use a teabag dunk the
bag continuously in the water to
increase the extraction of catechins.
Use boiling water and steep for two
to five minutes.
and type of fat in the diet may
influence the preventive
properties of catechins.
This type of information is
important to consider when
evaluating the health benefits
of certain foods and nutrients.
At this time it appears that
drinking about 3 to 6 cups of
green tea or decaffeinated
green tea each day may
provide health benefits such
as cancer prevention
and delayed progression
after cancer diagnosis, for
most individuals.
Selenium And Cancer: What is recommended?
Selenium is an essential mineral,
responsible for antioxidant function,
energy metabolism, and protection
against DNA damage. However, it is
considered highly toxic, with the
difference between the Recommended
Dietary Allowance (55 micrograms/day
for adults) and the upper limit of safe
intake (400 micrograms/day) relatively
narrow, compared to most nutrients.
In some parts of the world, the soil
content of selenium is very low.
Some areas in Europe and China, for
example, have a long history of
selenium deficiency because the foods
that grow in these soils pick up very
little selenium. In contrast, the soil in
the U.S. is relatively rich in selenium.
Foods grown here, and the animals that
consume those foods, are relatively
good sources of selenium. Estimates of
selenium intakes from a large
representative sample of people in
the U.S. is estimated to be about
100 micrograms per day.
Selenium has come under attention
recently because of its association with
cancer. Many studies show that an
adequate selenium intake – one that is
neither too low nor too high – may protect against certain cancers, including
prostate, colorectal, and lung. A large,
12-year study currently in progress is
studying the effects of selenium
supplementation (200 micrograms/day)
and vitamin E supplementation (400
IU/day) on the development of prostate
cancer in men. Confirmation of these
studies – many of which have been
observational vs. randomized, controlled
clinical trials – is a high priority in cancer research today.
The status of the research thus far
suggests the following:
• Selenium deficiency, as measured by
low selenium intakes or low blood
selenium concentrations, should be
corrected with a combination of diet
and supplementation.
• Selenium should be obtained, as
much as possible, from foods
rather than supplements in
order to obtain the type of selenium
that appears to be most easily
absorbed (i.e., organic
selenomethionine).
• Selenium from supplements, which
is inorganic, may not be absorbed as
well as that from foods; studies are
mixed. There is no evidence that
supplementation with selenium
above 200 micrograms per
day is protective against cancer.
Good food sources of selenium are
wheat and meat. Brazil nuts are very
high in selenium, with two nuts
providing about 200 micrograms.
Fish is relatively high in selenium, but
some reports suggest that selenium
from fish may not be absorbed in our
bodies as well as selenium found in
other foods. There are many forms of
selenium found in foods. Some forms
are being studied for their protection
against cancer growth. Research
suggests that it is best to eat a variety of
foods to obtain the health benefits of
different forms of selenium.
Selected Food
Sources of Selenium
Serving size
Micrograms/
serving
Percent DV*
Brazil nuts, dried
1 ounce (~ 6 nuts)
544
780
Tuna, light,
canned in oil, drained
3 ounces
63
95
Beef, cooked
3 1/2 ounces
35
50
Spaghetti with meat
sauce, frozen entrée
1 serving
34
50
Cod, cooked
3 ounces
32
45
Turkey, light meat,
roasted
3 1/2 ounces
32
45
Chicken breast,
meat only, roasted
3 1/2 ounces
20
30
Noodles, enriched, boiled
1/2 cup
17
25
Egg, whole
1 medium
14
20
Brazil nuts are very high in selenium.
Two nuts per day provides about
200 micrograms.
References:
1.) Finley JW. Bioavailability of
selenium from foods.
Nutr Rev 64: 146-151, 2006.
2.) Daniels LA. Selenium: does
selenium status have health
outcomes beyond overt deficiency?
MJA 180: 373-374, 2004.
3.) Dietary Supplement Fact
Sheet. National Institutes of
Health, Office of Dietary Supplements.
Available at
http://dietary-supplements.info.nih.gov/
factsheets/selenium.asp.
Accessed 3/13/07.
Adapted from: National Institutes of Health.
Office of Dietary Supplements.
http://dietary-supplements.info.nih.gov/
factsheets/selenium.asp. Accessed June 1, 2007.
*DV = Daily Value. DVs are reference numbers
developed by the Food and Drug Administration
(FDA) to help consumers determine if a food contains a lot or a little of a specific nutrient. The DV
for selenium is 70 micrograms. Most food labels
do not list a food’s selenium content. The percent
DV (%DV) listed on the table indicates the
percentage of the DV provided in one serving.
A food providing 5% of the DV or less is a low
source while a food that provides 20% of more of
the DV is high in that nutrient. It is important to
remember that foods that provide lower percentages of the DV also contribute to a healthful diet.
For foods not listed in this table, please refer to
the U.S. Department of Agriculture’s Nutrient
Database Web site: http://www.nal.usda.gov/fnic/
cgi-bin/nut_search.pl.
Soy: What you need to know
The facts surrounding soy foods and
certain types of cancers have been
presented in ways that are misleading
for many health professionals and
consumers. This has produced some
anxiety in individuals who have been
diagnosed with hormone dependent
cancers such as breast cancer and
prostate cancer.
Soy foods contain “phytoestrogens” or
soy isoflavones. The bioactive food
compounds found in soybeans that
have gained recent attention are –
genistein, daidzein and glycitein.
Most likely soy foods are most
protective when consumed in small
amounts throughout a lifetime.
Several studies in individuals who
consumed soy in small amounts over
their lifetime show reduced incidence
of breast cancer and prostate cancer
development later in life.
A recent study found that
individuals with the highest intakes of
phytoestrogens from soy foods had a
significant reduction in colorectal
cancer and lung cancer risk. Cell culture research has confirmed that soy
isoflavones inhibit growth of breast
cancer cells, prostate cancer cells and
colorectal cancer cells. Genistein
induces apoptosis (cancer cell death)
in lung cancer cell cultures.
This association exists in humans is not
known at this time, although adding soy
foods to your daily diet may have some
cancer preventive properties, as well as
other health benefits, such as reducing
the risk of heart disease.
Why do I hear conflicting
information about soy?
Because soy contains “phytoestrogens”
many people became concerned that
soy foods contained estrogen. This is
not true. Some of the phytochemicals
in soy foods do have weak estrogen-like
activity but this doesn’t mean they act
the same way as human estrogen does
in your body. In animal studies soy
foods appear to actually protect against
estrogen activity in hormone
dependent cancers.
Soy foods also contain dozens of other
compounds that appear to have many
important functions in our bodies.
The phytoestrogens in soy foods
protect cells from damage, assist with
cell apoptosis (cancer cell death) and
help control normal cell growth.
Soy supplements have not been shown
to have the same health benefits as
soy foods. Even if you have an
estrogen-receptor positive breast cancer
there has not been any research to
show that eating a modest amount of
soy promotes cancer growth. In fact,
recent studies have shown that diets
with adequate amounts of soy may
make the cancer cells more responsive
to chemotherapy and radiotherapy.
One to two servings of soy foods per day
is beneficial as part of a healthy diet.
What about a soy supplement?
At this time soy supplements have not
been shown to be effective in reducing
cancer risk or delaying progression of
disease after diagnosis. The best
evidence for health benefits has been
when a moderate amount of soy
foods have been added as part of
a healthy diet.
References:
1.) Setchell KD. Soy isoflavones Benefits and risks from nature's
selective estrogen receptor
modulators (SERMs).
J Am Coll Nutr.
20:354S-362S. 2001.
2.) Trock BJ, Hilakivi-Clarke L,
Clarke R. Meta-analysis of soy
intake and breast cancer risk.
JNCI. 2006;98:459-471.
What foods contain soy and how
much do I need?
One to two servings of soy foods per
day are beneficial as part of a healthy
diet. Dietary sources and serving sizes
of soy foods are: tofu (4 oz); soy milk
(8 fl. oz.); tempeh (1/2 cup); soy beans
or edamame (1/2 cup); soy nuts
(1/4 cup).
3.) National Library of Medicine.
Agency for Healthcare Research
and Quality. Available at:
http://www.ahrq.gov/clinic/epcsums/
soysum.htm. Accessed June 3, 2007.
Type of Soy Food
Serving size
Protein content (g)
Total isoflavone (mg)
Genistein* (mg)
Soy beans, green
(Edamame)
1/2 cup
17
12
6
Tofu
3 oz
13
20
12
Tofu yogurt
1/2 cup
5
21
12
Soy flour, defatted
1/4 cup
13
22
13
Soy milk
1 cup
10
30
17
Soy nuts
1/4 cup
15
37
19
Tempeh
3 oz
10
37
21
Adapted from: U.S. Department of Agriculture’s Nutrient Database Web site: http://nal.usda.gov/fnic/cgi-bin/nut_search.pl
Note: Nutrient content can vary by brand name.
* Genistein is a specific isoflavone that may have a role in reducing risk of heart disease and some types of cancer.
Nutrition Connections is a
pilot project funded by a grant
from UW Health.
Organic Fruits and Vegetables:
Are they better?
The primary focus of this
project is to provide up-to-date
nutrition education for
individuals after a cancer
diagnosis. Consuming adequate
nutrients in your diet may
help reduce your risk of
cancer recurrence as well as
other diseases.
All fruits and vegetables
contain a wide array of
carotenes, polyphenols and
other phytochemicals that are
important for optimal health
and protection against cancer
and cardiovascular disease.
Fruits and vegetables also
provide many vitamins and
minerals that are essential for
good health. Thousands of
studies, involving hundreds of
thousands of people all over
the world, prove that a high
intake of fruits and vegetables
is associated with improved
health. Nearly all of these
studies were conducted
using non-organic fruits
and vegetables.
To meet with a Clinical
Nutritionist at the
UW Paul P. Carbone
Comprehensive Cancer Center,
please contact Cancer Connect
at (800) 622.8922 or
(608) 262.5223.
The increase in organic
farming has raised interest in
the health benefits of organic
fruits and vegetables,
If you have moved, do not wish
to receive this publication in
the future, or have feedback for
future publications, please
return this form to:
UW Paul P. Carbone
Comprehensive
Cancer Center
Megan Waltz-Hill, MS, RD
Clinical Nutrition, Oncology
600 Highland Ave., F4/120
Madison, WI 53792-1510
(608) 263.8245
[email protected]
Kristina Penniston, PhD, RD
Clinical Nutrition, Urology
600 Highland Ave., F4/120
Madison, WI 53792-1510
(608) 265.9797
[email protected]
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particularly with respect to
nutrient content and pesticide
exposure. Some studies show
that organic vegetables do
have higher levels of vitamins
C and E, iron, magnesium,
and some phytochemicals
than those grown with
conventional methods. Other
studies show no difference.
Studies do show that people
who eat organic fruits and
vegetables have lower levels of
pesticides in their bodies than
those who eat non-organic
fruits and vegetables.
Bottom line: Eating 8 or
more servings of fruits and
vegetables every day –
whether organic or not –
protects against cancer and
promotes overall health.
If you have access to organic
fruits and vegetables, you may
Eating eight or more servings of fruits
and vegetables everyday may protect
against some cancers.
reduce your pesticide
exposure but it is uncertain
how necessary this is in
reducing risk of certain types
of cancers.
The Environmental Working
Group (http://www.ewg.org/)
has published information on
the pesticide content of
commonly-consumed fruits
and vegetables.
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