Why is this a great resolution?
The benefits of getting enough fiber involve quality of life and overall health, including improved gut health and function, reduced risk of insulin resistance and type 2 diabetes, and improved control of appetite and inflammation (Ariyarathna 2025, Bai 2022, Guan 2022, Kim 2020, Omary 2025, Weickert 2018, Zheng 2025). Fiber is critical for supporting the microbes in our guts that provide energy and regulate metabolism and immune system function (e.g., Cronin 2021, Guan 2021, Yuksel 2025).
But most people in Western/“developed”/“industrialized” countries don’t get enough fiber in their diets (Quagliani 2016).
How much is enough?
Good question! U.S. dietary guidelines indicate that age and gender influence how much fiber we need (2020). They recommend 31 grams of fiber for men aged 31–50, but only 28 grams for men over 50. Similarly, women aged 31–50 are recommended to get 25 grams of fiber, but older women (over 50) only 22 grams. Why do women and older people “need” a few grams less? No idea… it isn’t made clear, and I can’t think of a reason on my own. But at the least, these numbers give us a good “ballpark” estimate of how much fiber we should be getting.
How to get enough?
For much of my life, when I heard “fiber,” I thought “roughage”—things like bran and fibrous parts of vegetables such as broccoli. What I was thinking of is called insoluble fiber, and it is made of plant parts that do not dissolve in water. But there is another type of fiber called soluble fiber that does dissolve in water (but to me doesn’t seem very “fiber-y”).
Other fibers we might encounter are not in foods but are refined from plants or manufactured for supplements. Examples are guar gum, psyllium, xanthan gum, or alginate. These are typically soluble fibers (Weigert 2018).
What kind of fiber is best?
I’ve been unclear on what kind is best because the literature on that has been confusing. Historically, most studies of fiber benefits have studied soluble fiber, but most fiber-containing foods contain both. And as it happens, we need both kinds of fiber.
Soluble fiber includes beans, lentils, chickpeas; grains—especially wheat bran, barley, and oats; most fruits, especially apples, avocados, and bananas; and green leafy vegetables, especially cabbages.
Insoluble fiber is found in green leafy vegetables, intact grains and bran, and fruit and vegetable skins.
I find all foods with fiber to be delicious, but some are my favorites: grains, greens, and beans.
Fun Facts About Grains
- Grains are underappreciated generally, and even vilified by some. But they are key sources of both soluble and insoluble fiber.
- Grains are grass seeds, from the grass family Poaceae (for plant nerds). This includes wheat, rice, maize, oats, rye, barley, triticale, sorghum, and millet.
- The seeds have three parts: bran, germ, and endosperm. Processing grains removes the bran and germ, which leaves only the starchy endosperm and some proteins. This dramatically reduces the grain’s nutritional composition (Ariyarathna 2025), and therefore flours are often “enriched” to replace some of the nutrients.
- What counts as “whole grain”? “According to the Cereals and Grains Association, whole grains consist of the intact, ground, cracked, flaked, or otherwise processed kernel, excluding inedible parts such as the hull and husk. In whole grains, all the anatomical components, including the endosperm, germ, and bran, must be present in the same relative proportions as found in the intact kernel” (Ariyarathna 2025). This description implies that foods we buy that are labeled “whole grain” may actually have been reconstructed from processed, refined grains. This is why there are recommendations for consuming “intact grains” as much as possible, such as cracked wheat.
- A paradox: even though “insoluble fiber” is supposedly not fermented (although it almost certainly is, albeit slowly), it has reliable and consistent unexplained benefits for insulin resistance and type 2 diabetes (Ariyarathna 2025, Omary 2025, Weikert 2018).
- The traditional Mediterranean diet, which many studies have shown is beneficial for a wide range of conditions, contains nearly 50% grains (Capurso 2021).
Fun Facts About Greens
- I overhear so many people talking about how they hate greens, and how they always avoid eating gasp a salad. I see memes on the internet disparaging salad, and… I’m sad, because green leafy vegetables are super important for gut and brain function.
- Greens are sources of cellulose, which has been shown to increase fecal butyrate and improve gut inflammation (Kim 2020).
- Diets high in leafy greens are associated with better cognitive function than diets low in green leafy vegetables (Morris 2018, Agarwal 2023, Liu 2025).
Fun Facts About Beans and Other Legumes
- Beans are excellent sources of fiber.
- Concern about “lectins” has inspired advice to avoid eating them, but beans and other legumes don’t have that many more lectins than other vegetables, and the lectins they do have are denatured by cooking. Who eats raw beans anyway?
- Beans, along with grains, are a staple of the Mediterranean and other traditional diets that are highly nutritious and associated with good health.
Bottom Line
A diet that is low in refined grains (white flour, especially from ultra-processed food) but rich in intact grains, beans, fruits, mushrooms, and vegetables will provide enough fiber.