You may have heard the expression
“knowledge is power.”
Well, today we’re going to give you more power
to control your diet and lifestyle
by giving you the facts.
Welcome to the Nutrition Facts Podcast.
I’m your host, Dr. Michael Greger.
Today we get the low- down on a bacteria
most people have never heard of.
It’s called Helicobacter Pylori, or H. pylori, for short.
And it can cause big problems in your stomach.
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,
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.
The salting and pickling of fish produces a novel DNA mutating
chemical called CMBA, which is formed from a reaction of the salt,
nitrite preservatives, and methionine,
an amino acid found concentrated in animal proteins.
The nitrites can also interact with other protein components
to form N-nitroso compounds, a powerful class of carcinogens
found in cigarette smoke.
This may explain why processed meats, such as bacon, ham, hot dogs,
lunch meat, sausage, have been tied to increased stomach cancer risk,
but this extends to fresh, unprocessed, unsalted meat as well.
But wait. I thought most stomach cancer was caused by an infection
with a stomach bacteria called H. pylori.
There's a synergistic interaction between H. pylori-induced
inflammation gastritis and diet in the formation of stomach cancer.
Check it out.
Researchers in China discovered that even genetically
vulnerable individuals infected with a particularly
pathogenic strain of H. pylori did not appear to be
at increased risk of stomach cancer unless they ate about an ounce
or more of pork per day.
An average pork chop is like about six ounces.
This is a striking example of how our diet can sometimes trump
both our genes and environmental influences
like cancer-causing infection.
But is there a way to wipe out the H. pylori in the first place?
Normally you'd use a triple antibiotic cocktail of drugs
to kill off H. pylori, but patient compliance is difficult to maintain
due to the quantity of drugs taken and the adverse side effects.
Anything we can eat to wipe them out instead?
Decades before the detoxifying and anti-cancer abilities were discovered,
sulforaphane, that remarkable compound in cruciferous vegetables,
was originally described for its antimicrobial activity.
After hearing anecdotal reports of individuals with H. pylori-induced
peptic ulcer disease experiencing dramatic
and sometimes unexpected relief after eating three-day-old
broccoli sprouts, researchers at Johns Hopkins University
and elsewhere decided to put broccoli sprouts to the test.
Not only did broccoli sprout extracts kill antibiotic-resistant strains
of H. pylori in a petri dish,
some patients who were given as little as
a third of a cup of broccoli sprouts a day for a week
were able to eradicate their H. pylori infection.
So how about a randomized controlled trial:
broccoli sprouts vs. alfalfa sprouts?
And those given two to three servings of broccoli a day worth of sprouts
were able to significantly cut down on markers of both H. pylori colonization
and stomach lining inflammation.
Though broccoli sprouts may be able to eradicate H. pylori
in the majority of patients, 56%,
the standard triple drug antibiotic therapy is much more effective,
about 90% eradication.
Still, for those who don't meet the criteria for drug treatment,
cruciferous vegetables may present a safe, natural way
to combat H. pylori and the development of stomach cancer.
A compilation of 22 population studies found that eating more
cruciferous vegetables was associated with
a significantly lower stomach cancer risk, but
broccoli has never been directly put to the test, but garlic has.
Observational studies dating back to the 1960s on Japanese migrants
have suggested that allium family vegetablesâ€”
garlic and onion family vegetablesâ€”
may be protective against stomach cancer.
To date, there have been dozens of such studies published,
and overall, eating lots of allium vegetables was indeed
associated with significantly lower stomach cancer risk.
There's evidence of publication bias though, meaning there appears
to have been other studies that maybe failed to show such an effect,
that were shelved and never published.
Even if this weren't the case, observational studies never prove
cause and effect.
Maybe low garlic and onion consumption didn't contribute
to stomach cancer, for example,
but rather stomach cancer contributed to low garlic and onion consumption.
Decades of H. pylori stomach inflammation leading up to the cancer
may have led to individuals choosing bland diets to avoid discomfort.
You can't know if garlic really helps until you put it to the test.
Louis Pasteur was evidently the first to describe
the antibacterial effect of onion and garlic juices.
Petri dish studies have shown that garlic is effective in suppressing
the growth of H. pylori at concentrations achievable
in the stomach with a single clove.
Even some antibiotic-resistant strains are susceptible.
But does this translate into stopping the growth of cancer?
A randomized, double-blind, controlled trial was launched
to find out. Thousands of individuals at high risk
for stomach cancer from 13 villages in China
were randomized into various combinations
of antibiotics, garlic supplements, and antioxidant supplements.
And just few weeks of antibiotics led to a significant decrease
in subsequent precancerous stomach growths 7 years later,
and a significant decrease in subsequent stomach cancer
by 15 years.
What about the garlic? No benefit by 7 years,
and only a non-statistically significant reduction after 15 years.
But in 2019 we got the 22-year update: 15 years after the study ended and
those who had taken the garlic did indeed have a significantly lower risk
of subsequently dying from cancer, though interestingly the protective
effect of garlic only seemed to manifest among nondrinkers.
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please go to the Nutrition Facts Podcast landing page.
There you’ll find all the detailed information you need –
plus, links to all of the sources we cite for each of these topics.
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