Years ago, I was sitting in Santa Fe, New Mexico with two former classmates from the Kellogg School of Management.
We were looking west to an orange sunset from their glorious adobe-style home perched high amid the mountains... and, strangely, conversation turned to our long-standing debate about fiber.
Is fiber good for you? Or is it bad for you? How much should you eat? Does it prevent cancer?
One friend 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 from years before: The business and marketing of fiber – particularly supplement form – had gotten far ahead of the alleged benefits of consuming it.
But despite my conviction that fiber supplements are less valuable than folks think, it is true that almost nobody gets enough daily fiber... just 5% of Americans. Most of us get less than 60% of what we need.
Lately, we've gotten lots of questions from readers asking for a basic primer on fiber and its benefits. So today, we're going to do just that... We'll explain why not all fiber is created equal, fiber's proven health benefits, and the best ways to eat it...
What is fiber?
Fiber, sometimes called roughage, is a type of carbohydrate found in plants like fruits, vegetables, and grains.
There are two forms of fiber: insoluble and soluble. Your body can't break down insoluble fiber, but it does make stool softer and easier to pass. That helps food and waste move through your digestive system more efficiently.
Soluble fiber helps slow the absorption of sugar, meaning your blood sugar won't spike as much. One study in the New England Journal of Medicine showed the difference between high- and moderate-fiber diets. Those on a high-fiber diet had a 10% lower level of sugar in their blood compared with those on a moderate-fiber diet. In this study, high fiber meant 50 grams per day – the equivalent of about 11 apples – and moderate fiber meant 24 grams a day – the equivalent of about five and a half apples.
And the Joslin Diabetes Center – the leading source for diabetes research – adds that the key variable was soluble fiber, not insoluble. That's what helps keep blood glucose under control.
Is there danger in not eating enough fiber?
The greatest risk for those not getting enough fiber is cardiovascular disease. A 2017 review of meta-analyses published from 1980 to 2017 found that people who ate more fiber had a lower risk of cardiovascular disease than those who ate less fiber. More dietary fiber also reduced the risk of dying from a cardiovascular event, like a heart attack. Researchers noted that, on average, adding about 7 extra grams of fiber to your diet reduced your risk of cardiovascular disease by 9%.
There's also some evidence pointing to an increased risk of a digestive system disorder called diverticulitis in those who don't get enough daily fiber.
Diverticulosis is the development of little pouches in the wall of your colon. The pouches, called diverticula, form when the outer layer of the colon weakens and breaks and the inner layer pushes through. At first, these little pouches may not be problematic, but eventually they can become a more serious problem (diverticulitis), interfering with digestion... and leading to pain, irregular bowel movements, and even an infection like diverticulitis
What's startling is that, although so many folks develop these pouches, researchers haven't found the exact cause...
Some studies of different populations found an association between a lack of dietary fiber and folks developing diverticula. Diverticulitis is most common in countries with low-fiber diets. For instance, the U.S., England, and Australia have much higher rates than countries in Asia (where fiber is a staple in the diet).
Whatever the true cause (or combination of causes), fiber is vital to keep your colon healthy. Insoluble fiber relieves constipation, which is a symptom (and possible cause) of diverticulitis. So getting enough fiber can lower your risk of diverticulitis, boost your immune system, and improve your overall digestive health.
What's the difference between fiber supplements and fiber from food?
Skip the fiber supplements containing psyllium. As a study in the Lancet found, these pills lead to higher rates of precancerous colon tissue called polyps. Fiber supplements also increase your risk of constipation.
The best way to add fiber to your diet is to start including natural sources in your meals. Good sources include split peas, black beans, green peas, and oatmeal. Avoid loading up on bad sources of fiber, like processed foods and baked goods that also contain tons of starches and sugars.
Fruit also contains fiber, but don't make that your main source. Several studies over the past few years show most of the health benefits from fiber are from sources like vegetables, legumes, and grains.
How should I start adding more fiber to my diet?
The key here is to not add too much fiber too quickly. According to the Institute of Medicine, women need about 21 to 25 grams of fiber each day, while men need between 30 and 38 grams. If you're not getting enough, start adding fiber to your diet gradually over the course of a few weeks. Going too fast could lead to gas, constipation, abdominal cramping, and bloating. So if you start to feel those symptoms come on, reduce your intake by a few grams and then slowly work your way back up.
The average American consumes about 10 to 15 grams of fiber each day. So a good way to start is adding another gram to your diet every day or so over several weeks until you're getting what you need. And always make sure you drink more water as you increase your fiber intake as it helps the fiber move through your digestive system more easily.
What We're Reading...
- More on the differences between insoluble and soluble fiber.
- Something different: Elon Musk's Twitter takeover keeps getting messier.
Here's to our health, wealth, and a great retirement,
Dr. David Eifrig and the Health & Wealth Bulletin Research Team
October 27, 2022