Fiber: why it's not 'all that' and a bag of high-fiber cereal

On Friday afternoon, I was working at one of my favourite local cafes in Leslieville Toronto and getting ready to wrap up my week of work. Just as I was about to close my computer, I got a call from CTV News requesting an interview that evening.

The topic they wanted to me to cover was…Fiber.

Specifically, in response to this study released last week…

I’ve done a number of interviews with CTV News (and have absolutely love the opportunity to share my knowledge with their viewers).

But I’ll be honest and tell you that my nerves were sky high after Friday’s request. You see, my perspective (and research) on fiber didn’t perfectly align with the study I was supposed to be talking about.

WHAT THE MEDIA IS SAYING – Everyone, quick! Buy that high-fiber cereal.

WHAT I AM THINKING – Hold up on the fiber! Read this first.

So this news story prompted me to get on my computer and make sure you have all the latest information when it comes to feeding your family…good ol’ fiber.

How much fiber do we need?

We are told again and again, that we need to eat MORE fiber. But how much?

Well, the Institute of Medicine recommends the following:

38 grams of fiber for men
25 grams of fiber for women
19 grams for children aged 1-3 years old
25 grams for children aged 4-8 years old

As we get into the teenage years, girls need about 26 grams. While older/teen boys should get 31 grams to 38 grams per day.

But we’re not getting enough…

On average, men consume 21 grams per day (vs. 38 grams required).
And women are only getting 17 grams per day (vs. 25 grams required).
Our little humans are also falling short. For instance, the average fiber intake for children between 3 and 5 years of age is about 11 grams per day.

.TAKEAWAY – No one, regardless of gender or age group, is getting sufficient fiber according to the IOM’s standards.

Fiber 101: A closer look at what fiber actually is (and does)

Before we dive into the benefits (and challenges) associated with the “F” word, let’s back up a little and take a closer look at the types of fiber. Because not all fiber is equal!

In general, “Fiber” refers to a category of carbohydrates that humans can not digest.

There are 3 types:

INSOLUBLE FIBER (a dietary fiber found in whole food)
SOLUBLE FIBER (a dietary fiber found in whole food)
FUNCTIONAL FIBER (a manufactured fiber, or extracted and isolate from whole foods)

Insoluble fiber

Insoluble fiber doesn’t dissolve in water. Dr. Hyman describes it as “a scouring pad moving food through your intestines”. It speeds up the movement of food through the digestive system.

Two researchers go so far to say that insoluble fiber “is the ultimate junk food”, as “it is neither digestible nor absorbable and therefore devoid of nutrition.”.

Benefits of Insoluble Fiber:

Some say it acts as a laxative, preventing constipation (but keep reading!).

Examples of insoluble fiber: parts of plant cell walls, like cellulose

Soluble fiber

Soluble fiber on the other hand, attracts water like a sponge and turns into a gel-like substance. It slooooows down digestion keeping us fuller longer. Unlike insoluble fibers (which pass through the digestive system unaltered), naturally occurring soluble fibers are fermented by the bacteria found within the digestive tract.

Benefits of Soluble Fiber:

Fermentation generates essential nutrients for survival/growth of gut bacteria
Reduces appetite
Improves blood sugar sensitivity
Lowers cholesterol
Prevents cancer
Balance hormone levels
Remove excess estrogen and reduces the risk of breast cancer
Makes vitamins and minerals

Examples of Soluble fiber: inulin, pectin, gums (like guar), mucilages (such as psyllium), etc.

Functional fiber

Functional Fiber is an isolated, non-digestible (insoluble) form of carbohydrate extracted from whole foods – or manufactured – and added to prepared foods to boost its fiber nutrition.

Packaged products are using functional fibers as a way to reach 3 grams – which is the minimum amount required to have the words “good source of fiber” on the label. Yet in comparison to a whole food, it’s not..

Here’s are some of the common highest fiber whole foods.

Half an avocado (6 grams)
Medium artichoke (10 grams)
One cup of raspberries (8 grams)
One cup sweet potato or winter squash (6 grams)
Apple with peel (5 grams)

The challenge with “functional fiber” found in products like high fiber cereal bars, is that it can be more upsetting to your gastrointestinal system than naturally occurring dietary fiber (from whole foods). And as you’ll see below, fiber binds to critical nutrients (like iron), ushering them out of our bodies. So instead of taking a fiber supplement which is void of nutrients, eating whole foods is a better choice because it replaces lost minerals.

Have you heard about this gem called “resistant starch” yet?

I also want to quickly give a shout out to resistant starch…

Like fiber, some starch is resistant to digestion as well, and passes through the digestive system unchanged. This “resistant starch” (found in foods like green bananas) functions like soluble fiber in the gut which is fermented by colonic bacteria. It’s known as a “prebiotic” because it becomes food for our “probiotics”. This fermentation explains why people experience more gas and bloating.

Benefits of Resistant Starch: [source]

Improves digestive health
Enhances insulin sensitivity
Lowers blood sugar levels
Significantly reduces appetite

Yuriel Kaim calls them “super starches”. Here’s why:

To thrive, your large intestine and the bacteria within it must have proper fuel. Short-chain fatty acids—especially one called butyrate —are the preferred fuel. To make butyrate, the large intestine needs starch. But most starch is broken down in the small intestine. So resistant starch moves past the small intestine and into the large intestine…and is one of the sources of butyrate.

Examples of Resistant Starch:

Green (unripe) bananas
Plantains
Properly prepared cooked and cooled parboiled rice or legumes
Cooked and cooled potatoes

Why should we feed our families fiber?

As mentioned, CTV News had asked me to cover a recent study that touting the benefits of fiber. They looked at people who included the most fiber in their diets, then compared them with those with the lowest intake.

In the end, a fiber-rich diet was linked to:

A 15% to 30% reduced risk of death and chronic diseases
A 22% reduced risk of stroke
A 16% lower risk of Type 2 diabetes and colorectal cancer (although this is up for debate – see below)
A 30% reduced risk of death from coronary heart disease

Plus…given the microbiome benefits from soluble fiber and resistant starch, going “low-carb” may be disadvantageous. Low carb means low fiber and low starch, which starves bacteria over the long term. Yet a thriving gut is incredibly important for a healthy digestive system, and a healthy mind (there’s a ton of research on the mind-body connection and improvements in depression with a strong microbiome.)

This is all sounds AMAZING right?

But before we all run out and start loading our grocery bags with “high-fiber” products, let’s take a peek at ‘other side’ of fiber.

But wait! Fiber isn’t always the answer

Many parents worry about their child’s intake of fiber, and rightly so. However, you should know that fiber is not the perfect nutrient for everyone. In fact, it’s considered an “anti-nutrient”…

Here are some of the downsides of fiber:

Slower transit time

A high ﬁber diet has been shown to be associated with excessively long colons (apparently this is a thing!). As a result, it can take longer for food to travel out of the body. Given that our stools hold toxins, ideally we want to ’empty’ our colon sooner than later!

Limited absorption of key nutrients

Adding fiber supplements (insoluble fiber) can bind to minerals such as zinc, magnesium, calcium, and iron, which prevents the absorption of these vital nutrients.

According to a study in the Journal of Gastroenterology:

The main feature of a high-fiber diet is its poor digestibility.

No effect on colorectal cancer

Initial studies in the seventies and eighties supported the theory that fiber was associated with a decrease in colorectal cancer. However, with adjustments for the confounding factors the correlation was weakened.

Troublesome for those with chronic constipation.

Because fiber is non-digestible, increasing fiber intake simply meals that stool weight increases as well. So the more fiber you eat (or feed your child) the more poop they will have. Which can be problematic if they are already backed up.

To quote the same study above:

Although stool frequency may be increased by the mass effect of fiber packing in the colon in normal individuals, this is not so in individuals who are chronically constipated.

I know this is completely against what understand to be true. However, several studies that looked at dietary ﬁber intake by people with chronic constipation did *not* find any difference in ﬁber intake [source].

.

The Bottom Line: The best way to feed your family fiber

Focus on dietary fiber from whole food plant sources.

Ideally limit “functional fiber” intake from fiber-fortified cereals or other packaged products which are isolated from whole foods (or manufactured).

Don’t toss the peel!

Majority of the fiber is stored in the outer peel of the fruit. For example, a medium apple with the peel contains ~4.5 grams of fiber. However, take that peel away and you’re only looking at 2 grams!

Opt for smoothies over juice.

Fiber is retained and blood sugar is controlled.

Re-consider fiber intake if chronically constipated.

If you or your child already eat plenty of fiber and the constipation is caused by something else, then adding more fiber may not help and could even make the problem worse [source]. Look at stress, irritable bowel syndrome (IBS), food intolerances, liquid intake, etc.

Basically….

As long as you are feeding your family a variety of whole plant foods, fiber intake should take care of itself.

As for that CTV interview, we ended up getting pulled from the schedule due to ‘breaking news’ that night. So even if you didn’t hear it from me on TV you’ve got it all here. 🙂