Wednesday, September 20, 2023

SearchResearch Challenge (9/20/23): What IS dietary fiber?

 I realized I don't know what "fiber" really is!  

I was at a farmer's market buying a few veggies for the week ahead, and while standing in line I was browsing my news feed, and came across an article about the amount of dietary fiber in different foods.  I was impressed to read that my favorite breakfast cereal, a "high fiber" food, delivered a "whopping" 3.57 grams of fiber in each serving.  

Years of SRS have taught me to be very wary of anything I read, especially when it's surrounded by such superlative adjectives. 

So I found myself wondering my SearchResearch type of questions:  "Is that a lot of fiber?"  And "so how much fiber should I be getting?"  

When I got home I did a little searching around and found that... I really don't understand what fiber is! 

In particular, I thought that fiber was the indigestible part of your food--you know, the little threads, husks, hulls, and tiny fragments that just pass straight through without much digestion seeming to take place. 

But when I let my cereal sit for too long in the milk, I know it turns into a pure paste.  There's nothing like the kernels of corn or bits of apple skin that (as far as I can tell) are untouched by my digestive juices.  How could there be any "fiber" in that glop?  

Later, I saw a bottled drink for sale in my grocery store that promised a solid 6 grams of fiber in a single drink.  So far as I could tell, the drink looked pretty much like some kind of exotic juice--not the pulpy slurry I would have expected.  

Can you help me understand what's going on here?  Today's Challenges are: 

1. So what, really, is dietary fiber?  Is it something more than indigestible bits like wheat bran, corn kernels, and rice husks?  

2. What is the current recommendation for dietary fiber in my diet?  Is 5 grams of fiber in a serving a lot?  Or is it a little?  

These don't look like difficult questions--BUT--when I did my research, I found the story much more interesting and complicated than I'd originally thought.  

Among other things, I've started looking at the listed amount of fiber in a food product with a huge grain of salt.  (Which will then upset my sodium intake, but so be it.)  

What IS the story with fiber?   It seems there's more here than meets the eye, the tooth, and the entire alimentary canal.  

Can you find out? 

Let us know what you discovered, and what you did to find out about it.  

Keep Searching!  


  1. Good day, Dr Russell & everyone!

    I love these kind of Challenges that change what we think we know.

    Searched [Dietary fiber] on YouTube and results now show first videos with healthy sources and verified. Also in past weeks noticed that when you watch a video from a MD, video shows a box with information saying that. I think that is great.

    About fiber, I only know there's soluble and insoluble. So it will be great to find more. Specially because the recommended of dietary fiber must surely have changed through time.

    Also surprised to read about the salt. At first, thought you were meaning cautious about what were you reading. Then, knew you didn't mean that.

    1. With [Fibra requerimientos México salud]

      WHO (OMS) suggests 25 grams per day. Mexico in 2016 consumed between 16 and 28 g per day

    2. With [who dietary fiber 2023]

      WHO updates guidelines on fats and carbohydrates

      Keeping salt intake to less than 5 g per day (equivalent to sodium intake of less than 2 g per day) helps to prevent hypertension, and reduces the risk of heart disease and stroke in the adult population

      NY Times 2023

      What is fiber?
      How does fiber benefit health?
      How can you increase your fiber intake?
      12 fiber-filled foods and the amounts of fiber they supply per serving.

    3. Semi out of topic. Music medicine.

    4. “Music is auditory mathematics.”

      -P. Hunt

    5. This comment has been removed by the author.

  2. I did a search on understanding on dietary fiber with the intent of looking for medical sites and found one that answered all of the questions clearly and in in detail

  3. from:

  4. almost aids digestion as much as those German parsnips…
    result of Korean street food fiber??:::::
    this - from the NYT article you found was useful too, as a historical overview:
    cooking & reading as evolutionary tools…


  5. Linus Pauling Institute » Micronutrient Information Center

  6. searching LPI site - wealth of reliable info

  7. from your image…
    hopefully you snagged some of those good German parsnips…

  8. 1. So what, really, is dietary fiber? Is it something more than indigestible bits like wheat bran, corn kernels, and rice husks?

    Wikipedia citing many sources says: Dietary fiber consists of non-starch polysaccharides and other plant components such as cellulose, resistant starch, resistant dextrins, inulin, lignins, chitins (in fungi), pectins, beta-glucans, and oligosaccharides.[1][2][3]

    Consumer Reports online:
    The food fix: Getting adequate fiber and staying hydrated are key for preventing constipation (and the gas and bloating that can come with it). Men and women over age 50 should aim for 30 grams and 21 grams of fiber per day, respectively. Look for foods with insoluble fiber in particular, says Melissa Phillips, MS, a registered dietitian at the University of Wisconsin Health system’s Digestive Health Center in Madison. "It’s the broom that sweeps everything through the intestines," she says. Leafy greens, fruits and veggies with edible skin on, dried fruit, nuts, whole grains, beans, and popcorn are good sources of insoluble fiber. (Difficulty chewing can make it tough to eat fiber-rich foods. If you have this problem, speak to your dentist.)

    When you increase your fiber intake, increase your fluid, too. It helps bulk up and soften the stool, easing its passage through the system. Aim for a minimum of 1.5 liters a day (6.5 cups), according to the Academy of Nutrition and Dietetics.

    2. What is the current recommendation for dietary fiber in my diet? Is 5 grams of fiber in a serving a lot? Or is it a little?

    Consumer Reports online:
    Adult women should get between 21 and 25 grams of fiber while men should consume between 30 and 38 grams of fiber per day. So 5g at each meal is just right.

    Consumer Reports online commentary; ...For the most part, high-fiber foods are fruits, vegetables, legumes, and other whole foods that don’t always come with a label. But for packaged products, say, cereal and bread—“excellent source of” or “high in” fiber guarantees that you’ll get at least 20 percent of the 28-gram daily value, or 5.5 grams, in a serving of the food. Something that’s a “good source” will have 10 to 19 percent of the daily value. (These claims also mean the same thing for other nutrients, such as calcium and vitamin C.)
    Curious timing Dan; Mrs just started swallowing Fiber pills, so we had already done a bit SR on this.

    1. That information about the Mrs was not on the open internet...

  9. Thanks, remmij... I somehow missed that in the aquatic news of the week. The waters of SoCal (and Catalina in particular) are my old home waters, and while I've seen thousands of dolphins, I've never seen a Risso's. Great photography.

  10. "aquatic news of the week."… made me wonder if there was such a thing— found this, which led to more octopuses, views & bits… including Pacific white-sided dolphins (Lagenorhynchus obliquidens) above Davidson Seamount.
    has video:

  11. had to give "statue/jellyfish" a whirl - DALL-E2