Here's the Scoop on Fiber

Several years ago, I was sitting in Santa Fe, New Mexico, with my friends David and Ardith. We were looking west to an orange sunset from their glorious adobe home perched high amid the mountains... and strangely our long-standing debate about fiber came up.

Is fiber good for you? Or is it bad for you? How much should you eat? Does it prevent cancer?

My friends in Santa Fe are old Kellogg School of Management classmates who "retired" at the young ages of 42 and 43. They now do varied work for local charities and not-for-profits around the country. They are truly two of the brightest people I know. In fact, they can do the Sunday New York Times crossword puzzle before breakfast is finished.

David reminded me of a diatribe I'd launched in 1996 about fiber and how its health benefits were greatly overrated. At that time, he was taking fiber in spoonfuls from a Metamucil canister. He's a man all about convenience. If he could capture the benefits of life in a pill and not waste time on eating fruits and vegetables, he'd be very happy. He reminded me of my comments 11 years ago: The business and marketing of fiber had gotten far ahead of the alleged benefits of consuming it.

And he said he was happy to have me as his "doctor-insider"... events over the next 10 years had justified my position.

Recent articles in peer-reviewed medical journals show fiber is not as beneficial as once thought – especially when it comes to colon cancers. You can do some simple things to lower your risks. But sadly, many doctors don't know the truth.

How can this be? How can doctors make "scientific claims" as recently as 10 years ago... that suddenly are no longer "true."

It happens all the time.

The reason is medical schools teach our student doctors to parrot whatever is told to them and to rarely question the conventional medical authorities' wisdom. Also, knowledge evolves. You must regularly read the literature and integrate that into your practice. Sadly, not many docs out there do this.

Ask your doctor if fiber is good for preventing colon cancer, and you'll surely get a resounding YES. But guess what? It just isn't true. In fact, it may even be dangerous.

It is thought that colon cancer, more properly colorectal cancer (CRC), begins as a small mushroom-shaped tissue or polyp called an "adenoma." Over time, it develops into cancer.

CRC is a major cause of impairment and death worldwide. It is the third most common cancer in the U.S.

But CRC is rare in rural Africa. In 1971, a researcher there named Denis Burkitt proposed fiber as the reason for the low cancer rates. Thus began the marketing of high-fiber diets to prevent cancer. However, no one had ever performed a randomized clinical trial to test this theory. Thirty years later, we accept it as gospel truth, and I was even taught this in medical school. Actually, there isn't even an accepted definition of fiber, let alone proof it improves anyone's health or longevity.

Theories abound about how fiber might prevent CRC. Some claim the benefits occur because fiber reduces the amount of time digested food spends inside your colon (the so-called “reduced transit time” theory). Others claim fiber provides chemicals that turn off cancer genes. Whatever the claim, the facts are conflicting. So no one knows for sure.

In fact, one study, using the fiber ispaghula – or psyllium husk – found an increase in adenomatous polyps.

The bottom line is that fiber (however you define it) is not the panacea Western medicine would have you believe. Genetics, lifestyle, and the other foods you eat all play a role in whether you'll get CRC.

So what can you do? The answer is simple. Epidemiologic studies show it is the WHOLE food and WHOLE grains – not just one component, like fiber – that decreases your cancer risk. The fact that fiber is part of these whole forms may or may not be related.

Dietary research does offer fiber proponents some good news. It appears fiber does aid in blocking the production of cholesterol.

It turns out there are two types of fibers: soluble and insoluble. Insoluble fibers should be minimally consumed, especially if you have problems with your digestion. They can lead to bloating and gas. On the other hand, soluble fibers appear to lower cholesterol by both absorption and fermentation. Interestingly, the by-products of fermented fiber actually block cholesterol production.

Many foods have a mix of each type of fiber but some have a little more than others.

Several common foods with loads of soluble fiber include:

Several common foods with loads of insoluble fiber include:

What we currently know is that over the short term, fiber does not lower the risk of CRC. Until longer-term studies are completed, the actual benefits of fiber may truly be mythical.

What do I do?

Here's to our health,

David Eifrig, M.D., M.B.A.