By Dr. Mercola
The fact that sugar and obesity are linked to an increased risk of
cancer is now becoming well-recognized. Obesity has also been linked to
an increased risk of death from all causes.
According to research published in 2013, nearly 1 in 5 U.S. deaths is associated with obesity.1
More recently, researchers published findings from a meta analysis of
239 studies covering four continents, saying excess body weight is
responsible for 1 in 5 of all premature deaths in the U.S. and 1 in 7 in
Europe.2,3,4
On
average, carrying excess weight may reduce your life expectancy by
about one year, while being moderately obese may result in a three-year
reduction in lifespan. Those of normal weight had the longest life
expectancy and the lowest risk of dying before the age of 70.
Considering facts such as these, it's no surprise that the financial burden of excessive sugar consumption is also great.
According to the Credit Suisse Research Institute's 2013 study5
"Sugar: Consumption at a Crossroads," as much as 40 percent of U.S.
healthcare expenditures are for diseases directly related to the
overconsumption of sugar, and this includes obesity, diabetes and
cancer.
So, sugary processed foods may be cheap on the front end, but they exact a hefty price tag down the line.
Diet Can Influence Your Cancer Risk in More Ways Than One
Your
diet plays a crucial role when it comes to obesity and related health
problems such as elevated blood sugar, insulin resistance and cancer.
Research suggests obesity can promote cancer via a number of different
mechanisms.
One of the key mechanisms by which sugar promotes cancer and other chronic disease is by causing mitochondrial dysfunction.
Sugar is not an ideal fuel for your body as it burns "dirty," creating
far more reactive oxygen species (ROS) than fat does when it's
metabolized.
As a result, excessive amounts of free radicals are
generated when you eat excessive sugar, which in turn causes
mitochondrial and nuclear DNA damage, along with cell membrane and
protein impairment.
So, contrary to conventional teaching,
nuclear genetic defects do not cause cancer. Rather, mitochondrial
damage happens first, and this then triggers nuclear genetic mutations.
Research6
has shown that chronic overeating in general has a similar effect, as
it places stress on the endoplasmic reticulum (ER), the membranous
network found inside the mitochondria of your cells.
When the ER
receives more nutrients than it can process, it signals the cell to
dampen the sensitivity of the insulin receptors on the surface of the
cell.
Thus continuously eating more than your body really needs
promotes insulin resistance by the mere fact that your cells are
stressed by the additional work placed on them by the excess nutrients.
Insulin resistance in turn is at the heart of most chronic disease,
including cancer.
Sugar Is a Key Contributor to Cancer
Most people who overeat
also tend to eat many sugar-laden foods, which promotes elevated blood
sugar levels and insulin resistance. So overeating sugary foods equates
to a double-whammy in terms of cancer risk, compared to overeating
whole, unprocessed fare.
In fact, recent research has identified sugar as the top contributor to the worldwide cancer surge. According to a report7
on the global cancer burden, published in 2014, obesity is responsible
for an estimated 500,000 cancer cases worldwide each year.
The
reason for this is because cancer cells are primarily fueled by the
burning of sugar anaerobically. Without sugar, most cancer cells simply
lack the metabolic flexibility to survive.
Normal, healthy cells
have the metabolic flexibility to adapt from using glucose to using
ketone bodies from dietary fats. Most cancer cells lack this ability so
when you reduce net carbs (total carbs minus fiber), you effectively
starve the cancer. This is why nutritional ketosis appears to be so
effective against cancer.
According to recent research from the
University of Texas MD Anderson Cancer Center, refined sugar not only
significantly increases your risk of breast cancer; it also raises your
risk of tumors spreading to other organs.8
It
was primarily the refined fructose in high-fructose corn syrup (HFCS)
found in most processed foods and beverages that was responsible for the
breast tumors and the metastasis.
The Role of Genetics, Proteins and Hormones
While genetic
defects are not a primary cause of cancer, genes can still play a role.
Scientists have discovered that a number of genes known to promote
cancer by influencing cell division — including a gene called AKT — also
regulate cells' consumption of nutrients.
So certain genes
actually appear to play a role in cancer cells' overconsumption of
sugar. Whereas healthy cells have a feedback mechanism that makes it
conserve resources when there's a lack of food, cancer cells do not have
this mechanism and feed continuously.
Recent research has also
found that overweight women who lost weight reduced their risk of cancer
by lowering their levels of certain proteins linked to cancer
development.9
These proteins (VEGF, PAI-1 and PEDF) promote angiogenesis,
a process your body uses to build blood vessels that tumors need to
thrive. The greater the women's weight loss, the greater their reduction
in these proteins.
Previous research suggests losing weight can reduce your risk of
breast, colon and prostate cancer by as much as 20 percent, and this
effect is thought to be due to reductions in these proteins and other
inflammatory compounds stored in fat cells.10
Obesity also triggers overproduction of certain hormones, such as
estrogen, which is associated with an increased risk for breast cancer.
Links Between Diabetes and Cancer Are Getting Stronger
Overall, insulin resistance is one of the key contributors to a
heightened cancer risk, and many studies have confirmed that type 2
diabetics are at greater risk.
One recent study, which included
more than 1 million adult cancer patients, found that those diagnosed
with type 2 diabetes were 23 percent more likely to have received a
cancer diagnosis during the decade preceding their diabetes diagnosis
compared to non-diabetics.11,12
Recent
research has also noted that a growing number of obese Americans have
poor blood sugar control, which in turn promotes rising rates of type 2
diabetes and associated health conditions. To combat this trend, the
researchers urge overweight people to consider "serious weight loss
efforts." As reported by WebMD:13
"Between 1988 and 2014, rates of diabetes rose from 11 percent to 19
percent, which was due to increases in blood sugar, the researchers
said.
The investigators found that the rate of obese adults without the
three key risk factors for heart disease — diabetes, high cholesterol
and high blood pressure — held steady at just 15 percent.
But the rate of obese adults with all three risk factors rose 37
percent — to nearly [1] in [4] ... Risk for all three factors increased
progressively from age 40 on ...
'We have two choices: letting this population get sick and provide
monies for treatment of complications and disability; or intervene early
and prevent diabetes by encouraging weight loss, leading to a healthier
and more productive life,' [Dr. Joel] Zonszein, [director of the
Clinical Diabetes Center at Montefiore Medical Center] said."
Prediabetes Also Raises Your Cancer Risk
Both of these
findings tend to strengthen previous research showing that even
prediabetes is a risk factor for cancer. More than 1 in 3 Americans aged
20 and older has prediabetes,14
a condition in which your glucose (blood sugar) levels are higher than
normal but not yet high enough to be diagnosed as full-blown diabetes.
Of those with prediabetes, 15 percent to 30 percent will develop type 2 diabetes within five years.
A meta-analysis15
published in 2014, which included data from nearly 900,000 people,
found that those with prediabetes have a 15 percent higher risk of
cancer, especially cancers of the liver, stomach, pancreas, breast and
endometrium. Other research has shown that people with the highest
insulin levels at the time of a cancer diagnosis have significantly
increased risks of cancer recurrence, as well as a greater risk of being
diagnosed with a particularly aggressive form of cancer.16
From my perspective these findings aren't the least surprising and
precisely what you would predict if you understand the mechanism of most
cancers, which are essentially being fueled by a metabolism that is
driven by sugar (glucose), generating loads of unnecessary and damaging
free radicals, as opposed to clean burning, high-quality fats that
generate far less ROS.
Ketogenic Diet May Be Key to Cancer Recovery
Nutritional ketosis is part of the answer here. In this type of diet,
you replace net carbs (total carbs minus fiber) with moderate amounts
of high-quality protein and high amounts of beneficial fat. Since cancer
cells need glucose to thrive, and carbohydrates devoid of fiber turn
into glucose in your body, cutting out net carbs quite literally starves
the cancer cells. Additionally, low protein intake tends to minimize
the mTOR pathway, which also helps restrict cell proliferation.
The
video above features Thomas Seyfried, Ph.D., who discusses how, as a
metabolic disorder involving the dysregulation of respiration, malignant
cancer (in this case brain cancer) can be managed by altering your
metabolic environment.
That said, this kind of diet (low in net carbs, moderate in
high-quality protein and high in healthy fats) will also help normalize
your weight and boost your general health for the simple reason that it
helps you convert from carb burning mode to fat burning, which helps
optimize your mitochondrial function.
How Fasting May Benefit Cancer Patients
Fasting is another strategy that helps reverse obesity and optimize
mitochondrial function, and it too can offer hope in the fight against
cancer. In fact, one research group is reportedly looking into the
possibility of getting intermittent fasting approved by the U.S. Food
and Drug Administration (FDA) as an adjunct therapy for cancer patients.17,18,19
Valter Longo, Ph.D., has published a number of studies on fasting and its impact on cancer. His most recent research, published in the journal Cancer Cell,20
found that fasting during chemotherapy boosts cancer-killing T cell
activity, thereby improving the effectiveness of the chemotherapy. As
reported by Science Daily:21
"[R]odents that received caloric restriction mimetics alone or
chemotherapy combined with a fasting-mimicking diet had smaller tumor
masses over time than those that received only chemotherapy ...
Mice with breast or skin cancers were given a low-sugar,
low-protein, high-fat, low-calorie diet and were observed for [six]
weeks while receiving doxorubicin, cyclophosphamide or no
chemotherapeutic drugs. All of the mice receiving the diet-drug
combination saw their tumors shrink to half the volume of the tumors in
mice that received chemotherapy alone."
According to Longo:22
"The biggest factor exposing cancer cells to the T cells is the effect
on the enzyme heme oxygenase-1, which is normally at high levels in
cancer cells. Fasting reduces oxygenase levels and gives rise to a
number of changes that included the increase of tumor-killing cytotoxic T
cells."
What to Eat for Optimal Health and Cancer Prevention
From my perspective, ignoring diet as a cancer prevention tool is
foolhardy at best. I'm convinced most cancers are preventable through
proper nutrition. Avoiding toxic exposures (such as pesticides) is
another important factor, and this is one reason why I recommend eating
organic foods, especially grass-fed or pastured meats and animal
products, whenever possible.
Make no mistake about it, the FIRST
thing you want to do if you want to avoid or treat cancer if you have
insulin or leptin resistance is to cut out all forms of sugar/fructose
and grain carbs from your diet. This step will optimize the signaling
pathways that otherwise might contribute to malignant transformation.
Remember,
the foundational aspect that must be addressed is the metabolic
mitochondrial defect discussed earlier, and this involves radically
reducing the net (non-fiber) carbohydrates in your diet and replacing
them with high-quality fats. Moderating your consumption of protein, and
being mindful of the quality of the protein, is also important, as
excessive protein can also trigger cancer growth. To learn more about
this, please see my previous article, "The Very Real Risks of Consuming Too Much Protein".
So,
in summary, for optimal health you need sufficient amounts of
carbohydrates, fats and protein. However, there are healthy carbs and
unhealthy ones. Ditto for fat and protein. From my review of the
molecular biology required to optimize mitochondrial function, it may be
wise to aim for a diet with the following nutrient ratios:
• Healthy fats, 75 to 85 percent of your total calories. Beneficial monosaturated and saturated fats include olives and olive oil, coconuts and coconut oil, butter made from raw grass-fed organic milk, raw nuts such as macadamia and pecans,
seeds like black sesame, black cumin, pumpkin and hemp seeds, avocados,
grass-fed meats, lard and tallow, ghee (clarified butter), raw cacao
butter, organic pastured egg yolks, animal-based omega-3 fats and small
fatty fish like sardines and anchovies.
Harmful fats that contribute to disease are primarily trans fats and
highly refined polyunsaturated omega-6 vegetable oils (PUFAs). Remember,
glucose is an inherently "dirty" fuel as it generates far more ROS than
fat burning does. But to burn fat, your cells must be healthy and
normal. Cancer cells lack the metabolic flexibility to burn fat and this
why a diet high in healthy fats appears to be such an effective anti-cancer strategy.
When you switch from burning glucose as your primary fuel to burning
fat for fuel, cancer cells must struggle to stay alive, as most of their
mitochondria are dysfunctional and can't use oxygen to burn fuel. At
the same time, healthy cells are given an ideal and preferred fuel,
which lowers oxidative damage and optimizes mitochondrial function. The
sum effect is that healthy cells begin to thrive while cancer cells are
"starved" to death. • Carbohydrates, 8 to 15
percent of your daily calories. Aim for twice as many fiber carbs as
non-fiber (net) carbs. This means if your total carbs is 10 percent of
your daily calories, at least half of that should be fiber. Fiber has a number of other health benefits, including weight management and a lower risk for certain cancers.23
I
personally believe that most would benefit from reducing net carbs (not
just fructose) to less than 100 grams (g) per day, and keeping your
total fructose intake to a maximum of 25 g per day from all sources. If
you are insulin resistant, you'd do well to make your upper fructose
limit 15 g per day.
Cancer patients would likely be best served by even stricter limits.
By reducing the amount of net carbs you eat, you will accomplish four
things that will result in lowered inflammation and reduced stimulation
of cancer growth. You will:
• Lower your serum glucose level • Reduce your mTOR level • Reduce your insulin level • Lower insulin growth factor-1 (IGF-1, a
potent hormone that acts on your pituitary gland to induce metabolic
and endocrine effects, including cell growth and replication. Elevated IGF-1 levels are associated with breast and other cancers).
I typically keep my net carbs around 50 to 60 g per day While this
may sound awfully complicated, the easiest way to dramatically cut down
on your sugar and fructose consumption is to switch to real foods, as
the vast majority of added sugar and fructose you end up with comes from
processed fare.
Excellent sources of high-fiber carbs that you
can eat plenty of include chia seeds, berries, raw nuts, cauliflower,
root vegetables and tubers such as onions and sweet potatoes, green
beans, peas, broccoli, Brussels sprouts and psyllium seed husk. • Protein, 7
to 10 percent of your total calories. Quality is important, so look for
high-quality grass-fed or pastured meats and animal products. As a
general rule, I recommend limiting your protein to 0.5 g of protein per
pound of lean body mass, which for most people amounts to 40 to 70 g of
protein a day.
(To estimate your protein requirements, first determine your lean
body mass. Subtract your percent body fat from 100. For example, if you
have 20 percent body fat, then you have 80 percent lean body mass. Just
multiply that percentage by your current weight to get your lean body
mass in pounds or kilos.)
Again, the reason for limiting protein is because excessive amounts
have a stimulating effect on the mTOR pathway, which plays an important
role in many diseases, including cancer. When you reduce protein to what
your body needs for cell repair and maintenance, mTOR remains
inhibited, which helps minimize your chances of cancer growth.
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