"The Role of Kimchi and H. Pylori in Stomach Cancer"
For decades, Japan has had the longest life expectancy
in the world, while spending just a fraction on healthcare
compared to other high-income countries.
This longevity has been attributed in part to Japanese dietary patterns,
which are thought to have contributed to their comparatively
low rates of coronary artery disease.
Japan has historically had amongst the lowest rates
of colon cancer, breast cancer, ovarian cancer, prostate cancer,
bladder and blood cancers.
Japan, however, has among the highest rates of stomach cancer.
Yes, Japanese men may have had seven times less prostate cancer
than Americans but got six times more stomach cancer.
Is there some Achilles' heel in the Japanese diet?
One of the first theories, proposed in the 1970s,
was that it was the talc used to polish white rice
to give it a glossy sheen.
That was the case with ovarian cancer, which led to billions
in damages against Johnson & Johnson's baby powder
as I detailed in a previous video,
but that did not appear to be the case with stomach cancer.
Is it just genetics? No. Studies on Japanese migrants
show that as they and their children Westernize
their diets and lifestyles,
their stomach cancer rates drop accordingly.
Well, the most well-established risk factor for stomach cancer
is H. pylori, a bacteria that infects
the lining of the stomach and causes the chronic inflammation
that can lead to cancer.
H. pylori infection is considered a Group 1 carcinogen, indicating
our highest level of certainty that it indeed causes cancer.
Korea and Japan have the highest rates of stomach cancer
and among the highest incidence of H. pylori infection.
Case closed then, right?
The mystery seemed to have been solved.
But then came the African enigma.
Countries such as Nigeria had even more H. pylori,
but only a fraction of Japan's stomach cancer rates.
Then came the Indian enigma.
H. pylori is twice as prevalent in India than Japan, yet Indians get
ten times less stomach cancer.
Obviously, H. pylori alone can't explain Japan's epidemic.
Though most cases of stomach cancer
are thought caused by H. pylori,
most people with H. pylori don't get cancer.
H. pylori is one of the most common human infections.
It's been estimated that half of the world's adult population
is infected with H. pylori, yet half of us don't get stomach cancer.
There must be some kind of co-factor in countries like Korea and Japan
that explains their elevated cancer rates.
The inflammation caused by H. pylori may just set the stage
for cancer formation, increasing the susceptibility
of the stomach lining to dietary carcinogens.
But what's so carcinogenic about Korean and Japanese diets?
Studies that have compared the dietary components
of different Asian populations with similar H. pylori rates,
but dramatically different stomach cancer rates, have suggested
preserved, salted foods—both fish and vegetables—as the culprits.
Fresh vegetables and fruits, on the other hand, were associated
with an 85% reduction in stomach cancer odds,
whereas consumption of fresh fish doesn't appear associated
with stomach cancer either way.
A review of 60 studies found the consumption
of pickled foods was associated with significantly higher rates
of stomach cancer, though more so in Korea than Japan,
perhaps because per-capita Korean consumption
of salt-fermented vegetables like kimchi
is five to eight times greater.
You can't know for sure though until you...put it to the test.
Pickled vegetable extracts can cause DNA damage in cells in a petri dish,
but what about in people?
Researchers in Vancouver fed people 30 ounces of fukujinzuke —
assorted vegetables pickled in soy sauce —
or pickled cucumbers over a three-day period.
Biopsies taken from their stomach lining before the experiment started
were normal, as were the biopsies taken after eating
fresh carrots or cucumbers.
But after just a few days of consuming pickled vegetables,
moderate to severe tissue abnormalities were found,
suggestive of stomach irritation.
The consumption of non-fermented soy foods, such as tofu, edamame,
and soymilk is linked to a lower risk of stomach cancer in Japan,
whereas no association was found with fermented soy foods,
even highly salted miso.
The protection afforded by soy foods was attributed
to the anti-inflammatory and anti-oxidant effects
of the isoflavone compounds in soybeans.
Salt itself isn't considered a direct carcinogen, but it may
damage the stomach lining, thin the protective mucus layer,
enhance H. pylori colonization, enhance the penetration
of carcinogens, and enhance the formation of carcinogens.
Even moderately high salt intake is associated with significantly
increased risk of stomach cancer, though in Japan this effect
may be limited to those already suffering from
H. pylori-induced inflammation.
H. pylori is typically treated with a cocktail of multiple antibiotics.
Is there any way to eradicate it naturally through diet?
We'll find out next.