It has long been known that
severe selenium deficiency increases the risk of cancer. One double-blind
study found some evidence that selenium supplements might help prevent
cancer even in the absence of severe deficiency. The study actually designed
to detect selenium's effects on skin cancer. It followed 1,312 individuals,
half of whom were given 200 mcg of selenium daily. People participating in
the study were not deficient in selenium. The participants were treated for
an average of 2.8 years and were followed for about 6 years. Although no
significant effect on skin cancer was found, the researchers were startled
when the results showed that people taking selenium had a 50% reduction in
overall cancer deaths and significant decreases in cancer of the lung (40%),
colon (50%), and prostate (66%). The findings were so remarkable that the
researchers felt obliged to break the blind and allow all the participants
to take selenium.
beta-carotene and cancer; It
starts in the early 1980s, when the cumulative results of many studies
suggested that people who eat a lot of fruits and vegetables are
significantly less likely to get cancer. A close look at the data pointed to
carotenes as the active ingredients in fruits and vegetables. It appeared
that a high intake of dietary carotene might significantly reduce the risk
of cancer of the lung, bladder, breast, esophagus and stomach.
However, as noted above,
observational studies cannot prove cause and effect. When researchers gave
beta-carotene to study participants, the results have been impressively
Most studies enrolled people in
high-risk groups, such as smokers, because it is easier to see results when
you look at people who are more likely to develop cancer to begin with.
Beta-carotene alone is not
efficient. Fruits and vegetables contain many carotenoids (carotene-like
substances) that may be more important for preventing cancer than
beta-carotene alone. One researcher has suggested that taking beta-carotene
supplements and none other, actually depletes the body of other beneficial
carotenoids. This is the reason that the Anti-Aging Clinic first measures
the carotenoids in the tissue and follows up with testing each month testing
the clients who are taking our antioxidant blends.
Lycopene, a carotenoid like
beta-carotene, is found in high levels in tomatoes and pink grapefruit.
Lycopene appears to exhibit about twice the antioxidant activity of
beta-carotene and may be more helpful for preventing cancer.
In one observational study,
elderly Americans consuming a diet high in tomatoes showed a 50% reduced
incidence of cancer. Men and women who ate at least seven servings of
tomatoes weekly developed less stomach and colorectal cancers compared to
those who ate only two servings weekly.
In another study, 47,894 men were
followed for 4 years in an observational study looking for influences on
prostate cancer. Their diets were evaluated on the basis of how often they
ate fruits, vegetables, and foods containing fruits and vegetables. High
levels of tomatoes, tomato sauce, and pizza in the diet were strongly
connected to reduced incidence of prostate cancer. After an evaluation of
known nutritional factors in these foods as compared to other foods,
lycopene appeared to be the common denominator.
Additional impetus has been given
to this idea by the discovery of lycopene in reasonably high levels in the
human prostate, evidence from test tube studies that lycopene might slow DNA
synthesis in prostate cells and evidence that men with higher lycopene
levels in the blood have a lower risk of prostate cancer.
Several observational studies
have found a strong association between high dietary
vitamin C intake and a
reduced incidence of stomach cancer. It has been proposed that vitamin C may
prevent the formation of carcinogenic substances known as N-nitroso
compounds in the stomach.
Observational studies have also
linked higher vitamin C
in the diet with reduced risk of colon, esophageal,
laryngeal, bladder, cervical, rectal, breast, and perhaps lung cancer.
One study found that
supplementation at 500 mg or more daily was associated with a lower
incidence of bladder cancer.
Both green tea and black tea come
from the plant Camellia sinensis, which has been cultivated in China
for centuries. The key difference between the two is in preparation. For
black tea, the leaves are allowed to oxidize, a process believed to lessen
the potency of the presumed active ingredients in green tea, catechin
polyphenols. Green tea is made by lightly steaming the freshly cut leaf, a
process that prevents oxidation and possibly preserves more of the
Laboratory and animal studies
suggest that green tea consumption protects against cancers of the stomach,
lung, esophagus, duodenum, pancreas, liver, breast, and colon.
A study in Shanghai, China, found
that those who drank green tea had significantly less risk of developing
cancers of the rectum and pancreas than those who did not.
Another study in Shanghai found
similar associations for stomach cancer. Green tea drinkers were 29% less
likely to get stomach cancer than nondrinkers, with those drinking the most
green tea having the least risk.
Green tea may exert an
estrogen-blocking effect that is helpful in preventing breast and uterine
cancer and another study suggests that it might prevent the development of
tumors by blocking the growth of new blood vessels.
The main catechin polyphenol
found in green tea is epigallocatechin gallate (EGCG). Preliminary
experimental studies suggest that EGCG may help prevent skin cancer if it is
applied directly to the skin.