Add to that, doing the right thing

when it comes to preventing

and treating a chronic disease,

fighting a virus, or losing weight,

and suddenly our nutrition choices

can seem almost overwhelming.

Well, I'm here to help.

Welcome to the Nutrition Facts Podcast.

I'm your host, Dr. Michael Greger.

Today we begin a two-part series on the effects of fasting on cancer.

Do we feed cancer?

Do we starve it?

What do randomized trials tell us?

Here's our first story.

In 1974, an influential paper was published decrying

physician-induced malnutrition as the skeleton in the hospital closet ---

the fact that many patients in hospitals were malnourished,

which the editorial board of the journal of the AMA

described as shocking.

"Even a single case is one too many,"

yet still to this day the issue persists.

If anything, people with serious illness would seem to need

even more nutrition, not less, yet underfeeding

persists, involving as many as 50% of hospitalized patients.

The ethical principle of justice requires that every patient

be fed enough, given that hospital malnutrition

has been associated with increased

risk of disease and death, but is it cause and effect?

Does eating less make you sicker,

or does being sicker just make you eat less?

You don't know until you put it to the test.

But would it be ethical to randomize patients to remain starved?

I mean wouldn't nutritional support obviously help?

It turns out, no.

Not one, but 22 randomized controlled

trials involving thousands of malnourished patients

found that, sure, you can plump them up;

however, there seemed to be little effect on clinical outcomes.

In fact, sometimes it can actually make things worse.

Maybe your body is losing your appetite on purpose.

Ever since Hippocrates, fasting has been offered as a treatment

for acute and chronic diseases, based on the observation

that when people get sick, they frequently lose their appetite,

so maybe that's part of our body's wisdom and we shouldn't force it?

OK, but that was 2400 years ago.

What have we learned since?

Along with fever, decreased food consumption is indeed

one of the most common signs of infection, often regarded

as an undesirable manifestation of sickness,

but it's actually an active, beneficial defense mechanism.

Now obviously, chronic under-nutrition can impair

our defenses, but data suggest that in the short-term,

immune function can be enhanced by lowering food intake.

Some of the data are crazy, like 95% alive versus 95% dead

after the same infection,

but that was in mice starved for 48 hours.

Obviously, you can't randomize people to a fatal infection,

but what they showed is that the blood from starved mice was

nearly 8 times better at killing off the invading bacteria

in a petri dish.

It dramatically boosted

the capacity of their white blood cells to kill off the pathogens.

Why can't we just test people like that?

Indeed, we can.

Researchers fasted people for two weeks

on an 80 calorie a day diet,

and their white blood cells showed the same kind of boost

in bacteria-killing activity, a boost in antibody production,

and natural killer cell activity increased by an average of 24%.

Now that's especially interesting because our natural killer cells

don't just help clear infections, but also kill cancer cells.

In fact, that's how they measured natural killer cell activity by pitting

them against K562 cells --- those are tumor cells, human leukemia cells.

So two weeks of fasting boosted their bloodstream's ability

to kill off cancer cells by 24%.

So fasting is said to improve anticancer immunosurveillance,

or more poetically

"stimulate the appetite of the immune system for cancer.

"

So why isn't fasting used more to treat cancer?

Until recently,

fasting therapy was not considered to be a treatment option

in cancer, related to the fact that a common therapeutic goal

in palliative cancer treatment is to avoid weight loss

and to counteract the wasting syndrome known as cachexia,

which is the ultimate cause of death in many cancer cases.

Tumors are voracious, rapidly expanding,

and needing lots of energy and protein,

and so metabolically reprograms our body

to start breaking down to feed it.

It does this by triggering inflammation throughout the body.

It's not just that people lose their appetite.

The fundamental difference between weight loss

observed in cancer cachexia and that seen in simple starvation

is the lack of reversibility with feeding alone.

For example, here's the weight of a cancer patient that started to drop.

No wonder: they were only taking in a few hundred calories a day.

So in addition to giving them about 100 grams of protein a day,

they stuck a tube into a vein and infused up to 4,000 calories a day.

But it didn't matter.

They continued to lose weight.

Therapeutic nutritional interventions to correct or reverse

cachexia have met with little success.

The best treatment for cancer cachexia therefore

is to treat the cause and cure the cancer.

In fact, maybe forcing extra nutrition on cancer patients

could be playing right into the tumor's hands.

Like in pregnancy when the fetus gets first dibs on nutrients

even at the mother's expense,

the tumor may be first in the feeding line.

Maybe our loss of appetite when we get cancer

is even a protective response.

But in the 1960s, TPN was born --- total parenteral nutrition ---

where people no longer had to eat;

and you could infuse all the nutrition people needed straight

into their veins, and the modern era of nutrition support was born.

It became widely accepted and implemented,

growing into a multibillion-dollar industry.

So should it be routinely given to malnourished cancer patients?

The answer is not as obvious as one might think.

When it was put to the test in dozens of randomized trials,

the results were both disappointing and surprising.

Parenteral nutrition didn't just fail to provide any benefit

to these patients; it caused harm.

Not only did it appear to provide zero survival benefit,

there was an increase in complications and infections,

and a decrease in tumor response to chemotherapy,

presumed to be due to all those extra nutrients

stimulating tumor growth.

Similarly, oral nutritional

interventions in malnourished patients with cancer,

like giving them bottles of Ensure, found no survival advantage.

Despite the lack of demonstrated benefit, the knee jerk reaction

of many oncologists to the idea of cancer patients fasting

is the concern they're not eating enough already.

But you don't know until you until you put it to the test,

which we'll explore next.

For the past 50 years, chemotherapy has been a major medical treatment

for a wide range of cancers.

Its main strategy has been largely based on targeting cancer cells,

by means of DNA damage caused in part by the

production of free radicals.

Although these drugs were first believed to be

quite selective for tumor cells,

we now know that normal cells also experience severe

chemotherapy-dependent damage, leading to dose-limiting side effects

including bone marrow and immune system suppression,

fatigue, vomiting, diarrhea, and in some cases even death.

And if you do survive, the DNA damage to normal cells

can even lead to new cancers down the road.

There are cell-protecting drugs that have been tried

to reduce the side effects,

so you can pump in higher chemo doses,

but these drugs have not been shown to increase survival,

in part because they may also be protecting the cancer cells.

What about instead using fasting

for cellular protection during cancer treatment?

Fasting may have an unrecognized role

in cancer prevention and treatment.

Short-term fasting before and immediately after chemotherapy

may minimize side effects, while at the same time

may actually make cancer cells more sensitive to treatment.

That's exciting.

During nutrient deprivation, healthy cells switch from growth

to maintenance and repair, but tumor cells are unable

to slow down their unbridled growth due to growth-promoting mutations

that led them to become cancer cells in the first place.

This inability to adapt to starvation may represent an important

Achilles' heel for many types of cancer cells.

As a consequence of these differential responses

of healthy versus cancer cells to short-term fasting,

chemotherapy causes more DNA damage and cell suicide

in tumor cells, while potentially leaving healthy cells unharmed.

Thus, short-term fasting may protect