We have a lot of choices to make about our diet. Add to that doing the right thing when it comes to preventing or 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, a crying, physician-induced malnutrition as the skeleton in the hospital closet.

The fact that many patients in hospitals were malnourished with 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 it would 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 seem 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 end chronic diseases based on the observation, then 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.

Okay, 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 undernutrition can impair our defenses, but data suggests that in the short term, immune function can be enhanced by lower rate of disease.

...