Should you be fibermaxxing? Here's what the science says

The average person eats 10-15 grams of fiber per day, according to the USDA. The problem? That’s WAY under the recommended daily amount. Fiber – a type of carb that our bodies are unable to digest – is prevalent in foods like fruits, veggies, whole grains, and beans. And it’s key for everything from feelings of fullness, to gut health, to good poop. That’s why a lot of people online are “fibermaxxing”: trying to meet or exceed the daily recommendation of fiber, in hopes it’ll improve their health. But how should YOU add fiber to your diet… and are the fibermaxxers overdoing it? Gastroenterologist Berkeley Limketkai https://www.uclahealth.org/providers/berkeley-limketkai is here to help parse the science on how little fiber is too little, how much fiber is too much – and, like Goldilocks, how we can figure out the amount that’s just right. Interested in more food and dietary science? Email us your question at [email protected] mailto:[email protected]. Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave http://plus.npr.org/shortwave. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

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• 0:00Speaker 00

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• 0:19Emily Kwong?

  You're listening to Short Wave from NPR.

• 0:24Emily Kwong?

  Shortwavers, some people on our team are very online. I'm actually not one of them, but I have been alerted to this phenomenon on social media known as maxing, whether that's looks-maxing, gym-maxing, protein-maxing, or fiber-maxing.

• 0:41Speaker 02

  I'm tired of not getting enough fiber in, so welcome to day one of becoming a fiber-maxer.

• 0:46Speaker 03

  I'm fiber-maxing hard. Fiber is officially scared of me now.

• 0:50Speaker 04

  This is for anybody trying to diet. Quit protein-maxing, bro, and fiber-max.

• 0:53Emily Kwong?

  I will say, I've looked at some of these videos now, and fiber-maxers are right about one thing. Over 90% of people in the US don't get enough fiber.

• 1:01Speaker 05

  The standard American diet, or the Western diet in general, actually is very depleted of fiber.

• 1:06Emily Kwong?

  This is Berkeley Lim Kekai. He's a gastroenterologist at UCLA, and he says most Americans are fiber-deficient because, well, we're eating a lot of other stuff.

• 1:15Speaker 05

  We do like our refined carbohydrates, the sweets. We do love our fried and fatty foods. We do love our ultra-processed foods, which are intentionally created to be more attractive, tasty, and unfortunately, ever since being little children, folks don't really like eating their broccolis as much.

• 1:34Emily Kwong?

  The average person eats 10 to 15 grams of fiber per day, but the recommended daily average is more than double that number. And usually, the place that makes itself known is the porcelain throne, the lavatory, the toilet.

• 1:50Speaker 05

  When they don't consume enough fiber, they tend to have more constipation. And as such, they could actually experience more Straining when having bowel wounds, they can feel like they're not completely evacuated after each toilet session. They could feel that a feeling of having a bowel wound is more extended over time, or the interval between bowel wounds may be longer. So those are some of the initial telltale signs of not having enough fiber intake.

• 2:16Emily Kwong?

  I know what you're thinking. You're listening to this and saying, Short Wave, you already did an episode on you're pooping all wrong, and now you're telling me I'm fibering all wrong? Maybe. I'm saying you're fibering perhaps not enough. And we have answers for you.

• 2:30Speaker 05

  Especially in the United States, increasing fiber is generally a good thing. Too much of any good thing can lead to detriments to your health or your well-being. But in general, yes, fiber is your friend.

• 2:44Emily Kwong?

  Today on the show, we're tackling fiber. We speak to a gastroenterologist to parse the science of how little is too little, how much is too much, and like Goldilocks, how do you know what's just right? I'm Emily Kwong, and you're listening to Short Wave, the science podcast from NPR.

• 3:05Emily Kwong?

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• 4:08Emily Kwong?

  Okay, I'm here with Berkeley Lim Kekai, a gastroenterologist, to talk about fiber. Fiber is a carb that our bodies cannot digest. Berkeley, can you talk about some of the benefits of fiber?

• 4:21Speaker 05

  So I guess the way I look at fiber and its potential benefits are, on one hand, the mechanical aspects of its effects, which leads to changes in bowel habits. And the other way is looking at it from the functional effects. So that's where, on one hand, it's able to shape the gut microbiome and at the same time serve as nutrients or raw materials for the microbiome to generate these anti-inflammatory molecules.

• 4:49Emily Kwong?

  Wow, it does a lot, actually, fiber.

• 4:51Speaker 05

  It does.

• 4:53Emily Kwong?

  And do all forms of fiber do all the things? Because I know there's soluble fiber versus insoluble fiber, and then there's prebiotic fiber. So what are all those types? And what does what?

• 5:05Speaker 05

  There are many different forms of fiber. There are nuanced differences between them that then actually leads to a differential effect on the types of bacteria that they promote and in terms of the types of molecules that they tend to be converted into. And there are also some types of fibers that, when consumed in disease states, may actually be detrimental to the body or actually be pro-inflammatory, paradoxically.

• 5:34Emily Kwong?

  Yeah, and can you explain what is the difference between soluble and insoluble fibers?

• 5:38Speaker 05

  Yeah, so soluble fibers are the types of fibers that, as the name implies, it dissolves in liquid. And so they can actually help form a gel, the stool, or help produce a stool mass. And these are more helpful for individuals who tend to have looser stools or more diarrhea. By contrast, insoluble fibers are not as well digested as they pass through the gastrointestinal tract. They tend to draw more liquid into the intestines, thus leading to a more liquefaction of the stools. And so these are more helpful for individuals who tend to have a more constipation-like bowel habit.

• 6:16Emily Kwong?

  What a power couple. That insoluble, insoluble fiber. And then where does prebiotic fiber fit into this?

• 6:23Speaker 05

  So the term prebiotic and dietary fibers are actually almost synonymous.

• 6:28Emily Kwong?

  Oh, okay.

• 6:29Speaker 05

  One could even theoretically consider them interchangeably. There are some nuanced differences, but the predominant form of prebiotics actually come in the form of plant fibers. Interestingly, not all plant fibers are dietary because there are leaves and trees outside your building or your home that you do not necessarily.

• 6:46Emily Kwong?

  That we cannot eat.

• 6:46Speaker 05

  Exactly, exactly.

• 6:48Emily Kwong?

  Yeah, so prebiotics are just plant fibers. And some are soluble and some are insoluble?

• 6:55Speaker 05

  In general, yes.

• 6:56Emily Kwong?

  Okay, okay, cool. Complicated. Well, then, in that case, I want to know how people can increase their fiber safely. What's the best way to do that?

• 7:06Speaker 05

  Yeah, one of the best ways to increase fiber in their diet is actually to increase the proportion of fruits and vegetables that they incorporate into their meals. And the reason for this is because, on one hand, you know, there is the benefit of actually getting the fiber in these fiber-rich foods, but at the same time, these particular food types actually also have these molecules called polyphenols that have anti-inflammatory, antioxidantative, and anti-cancer effects. In addition to that, we would actually also recommend eating the colors of the rainbow. And that is, you have different colored vegetables or fruits, you know, throughout the week.

• 7:48Speaker 05

  And the reason for that is because there are also other types of micronutrients and vitamins that actually then help balance out your diet and your micronutrient intake if you do actually have this kind of diversity of foods.

• 8:00Emily Kwong?

  Awesome. So, yeah, eating lots of fruits and vegetables, eating the rainbow. What about like whole grains? Does switching entirely to whole grains help with fiber intake?

• 8:08Speaker 05

  Very much so. Whole grains are actually very rich in fiber and have a lot of beneficial monounsaturated fats. So there are also other potential benefits from whole grains themselves.

• 8:19Emily Kwong?

  Another way some people are trying to get fiber or Fiber Max is with supplements. There's also foods with fiber additives. What do you think of all that?

• 8:28Speaker 05

  Yeah, so fiber supplements are actually beneficial and a good source of fiber intake. In clinic, we oftentimes recommend fiber supplements for our patients. The supplements is an easy way of boosting daily fiber intake.

• 8:41Emily Kwong?

  Gotcha.

• 8:42Speaker 05

  The potential disadvantage of consuming a fiber supplement is that while it is a great source of fiber, it does not contain all those other nutrients or beneficial molecules that natural fiber in whole foods contains.

• 8:57Emily Kwong?

  There is a benefit to the whole foods approach. And it's interesting because fiber, at least on the business side, like food brand watchers are saying fiber is going to be the next thing. There's a booming prebiotic soda market. So what do you think of these sodas? Are they a medically sound way of getting fiber? Or is it a scam?

• 9:17Speaker 05

  It's a great question. One could use these different nutrients and add them to virtually any product and use that to increase the attractiveness of their product and maybe the health benefit profile of those products. However, if in totality, or if the other components of such product actually does the complete opposite,

• 9:38Emily Kwong?

  Yeah.

• 9:38Speaker 05

  then it's not really that beneficial to consume in the first place, even if there's something that is said to be potentially beneficial.

• 9:45Emily Kwong?

  So this kind of brings us back to Fiber Maxing, where people on social media are just trying to consume as much fiber as possible. Like, the number is the point. Seventy or eighty grams.

• 9:56Speaker 05

  Yes.

• 9:56Emily Kwong?

  At the end of the day, what do you think about people eating that much fiber? Is it ever a good thing?

• 10:02Speaker 05

  So seventy to eighty grams, or even ninety, or even beyond that, of fiber per day is not unprecedented. If you look at other cultures where they consume predominantly fruits and vegetables, or in those who are vegan, they already routinely consume a very high consumption Of fiber per day.

• 10:19Emily Kwong?

  Yeah.

• 10:19Speaker 05

  However, someone who is not really a customer adapted to consuming that high of a fiber intake and then suddenly ramps up to seventy to ninety grams per day could, along the way, experience a lot of kind of adverse effects from such high fiber intake. Alterations in their bowel habits, maybe disruption of the gut microbiome. Potentially could also cause a compromise in certain micronutrient intake such as calcium, iron and zinc. And also can lead to some degree of malnutrition.

• 10:50Emily Kwong?

  Ooh, yeah. So what is the best way to increase your fiber intake, but responsibly?

• 10:55Speaker 05

  If one actually wanted to increase their fiber intake, I would actually recommend that they meet with a dietitian or nutritionist so they can actually look at kind of the overall balance of their diet to make sure that while, yes, they're increasing dietary fiber consumption, that they're not compromising then on other nutrients. You know, start low and ramp up. Stay within the recommended guidelines initially. And if one is able to then tolerate that amount of fiber, one could theoretically increase it thereafter. While keeping in mind that along the way, you know, if one were to develop, let's say, changes in their bowel habits or increased abdominal cramping, discomfort or pain,

• 11:37Speaker 05

  or even feeling more bloating and distension, that it may be a sign to kind of down throttle kind of the increase in fiber, at least temporarily.

• 11:48Emily Kwong?

  That sounds like very good advice because I feel like everything I'm learning from you is that moderation and intention are really important in diet and especially with fiber because it is such a delicate balance. And also so much depends on the individual. What works for you might not work for your friend.

• 12:10Emily Kwong?

  Is that the overall message for you?

• 12:13Speaker 05

  Very much so. Life is a balance and too much of any good thing can actually sometimes be harmful. While one can still aim for increasing fiber intake, you also need to do that in a judicious, kind of intentional and strategic manner. So that while optimizing your health in one area, you don't actually compromise your health in other areas.

• 12:35Emily Kwong?

  Very important advice. Dr. Berkeley Lim Kekkai, thank you so much for talking to me about fiber and how to, you know, find that Goldilocks middle with it.

• 12:46Speaker 05

  Well, thank you very much for the invitation. It was a great pleasure chatting with you today.

• 12:51Emily Kwong?

  Shortwavers, we have been doing a lot of health questions lately. If you have a question, write to us. Our email is [email protected]. We'd love to look into it. And while you're at it, follow us on whatever app you're listening to. This episode was produced by Hannah Chin. It was edited by Rebecca Ramirez. Tyler Jones checked the facts. Robert Rodriguez was the audio engineer. I'm Emily Kwong. Thank you for listening to Short Wave from NPR.

• 13:20Emily Kwong?

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