Health Lifestyle Nutrients

The Importance of Fiber in Gut Health and Hormonal Balance

12 min read

Hormonal balance affects your longevity, weight, and mood. And new research is telling us that the cornerstone of balanced hormones is your gut microbiome, which — it turns out — depends on fiber. So can eating more fiber really help you to lose weight, live longer, and feel better?

The world’s first telephone exchange was set up in New Haven, Connecticut in 1878. It connected 21 customers, including the local drug store and post office, so running it wasn’t exactly a demanding job in those early days. The first switchboard operators were a couple of teenage boys, which made sense: That’s who worked in the telegraph offices that phones would eventually replace.

But as the number of telephone owners increased and the switchboard work became more challenging, managers came to the shocking conclusion that teen boys might not be the demographic best suited to the job. Apparently, they tended to lose focus easily. They engaged in frequent bouts of roughhousing. And according to Marion May Dilts, author of the 1941 book The Telephone in a Changing World, “when some other diversion held their attention, they would leave a call unanswered for any length of time, and then return the impatient subscriber’s profanity with a few original oaths.”

So by the end of WWI, the job of switchboard operator was mainly associated with women — who were relied upon to patch call after call through to the correct party, to facilitate communication and coordination in all areas of national life, and to do so in an effective and efficient manner.

Much like a switchboard operator used to facilitate communication and patch phone calls to the correct party, hormones have a similar job in your body. Your cells, tissues, organs, and various systems also frequently need to talk to each other. And it’s crucial that the right message gets sent at exactly the right time to the right destination. Hormones are the chemical messengers that relay information throughout your body, coordinating every aspect of your health and physiology.

When you’re healthy and in balance, that communication system works with exquisite orchestration, enabling all parts of your body to help each other get the job done. When something’s awry in your hormonal balance, however, you can experience unpleasant symptoms that sometimes devolve into outright disease.

One of the systems most responsible for the production and deployment of hormones is your microbiome, those 100 trillion cells that aren’t you exactly, but live in and on you and take on many of the critical functions that keep you alive.

When you nourish your microbiome on a fiber-rich diet, it manages the switchboard of your endocrine (hormone) system with care (like a competent and conscientious adult). When your microbiome is undernourished and fiber-deprived, however, it can create the wrong kinds of hormones at the wrong times — causing chaos throughout the body.

In this article, we’re going to look at the microbiome and how fiber impacts its makeup and function. We’ll also explore the link between fiber, gut health, and specific hormonal disorders and diseases.

Hormonal Imbalance

Unwell tired young woman lying on sofa at home wave with hand fan, suffer from hot weather, lack of air conditioner, exhausted overheated girl use waver, have hormonal imbalance, health problems

Hormones are essential to human health. In your body, hormones help regulate growth and development, metabolism, sexual function, reproduction, and mood. If hormone levels are too high or too low, that may represent a normal and temporary fluctuation, or it could indicate a chronic hormone disorder.

Hormones can lead to problems not just in deficiency or excess, but also if the target sites in your body don’t respond to the hormones the way they’re supposed to.

Hormonal imbalances can occur for many reasons, including life changes like puberty, pregnancy, and menopause; bouts of extreme stress; environmental factors; and certain medications. But one of the biggest factors determining the health of your hormonal system is the health of your gut — specifically your gut microbiome, which regulates the levels of many critical hormones in your body.

The Microbiome’s Role in Human Health

The microbiome is more than just a series of microorganisms taking up residence in your gut. The bacteria, viruses, and single-celled organisms that live there interact with and adapt to your bodily systems. There are many beneficial bacterial strains in the microbiome and a few harmful ones that can end up there, too. Together, these critters regulate metabolism, help you digest food and absorb the nutrients it contains, and support your immune system. All important stuff!

And nowhere are they more crucial than their role in supporting the endocrine system. Your gut microbes participate in regulating the levels of reproductive, immune, and metabolic hormones. In other words, they’re pretty darn crucial to your hormonal and overall health.

The Relationship Between Gut Health and Fiber


Factors such as age, lifestyle, and genetics all contribute to the makeup of your microbiome, but one of the biggest determinants is the food you eat. As a result, your microbiome is constantly changing based on what you feed it. And the number one nutrient that the beneficial bacteria love — which will make them stick around, reproduce like crazy, and generally have a nonstop party — is fiber.

Types of Fiber

There are two main types of fiber: soluble and insoluble. The most important difference, of course, is that insoluble fiber has two more letters and therefore will give you a better Scrabble score. Aside from that, soluble fiber also dissolves in water, while insoluble fiber does not.

Insoluble Fiber

Insoluble fiber adds bulk to your stools and acts like a broom, cleaning out your digestive tract. It also promotes healthy bowel movements and helps with insulin sensitivity, both of which have an impact on hormonal health.

Soluble Fiber

We can further divide soluble fiber into two categories: viscous and fermentable.

Viscous fiber is the kind that forms a gel when it comes in contact with water in your digestive tract. Its main claims to fame are that it helps to balance blood sugar and lowers cholesterol.

Fermentable fiber doesn’t do much for us directly. But don’t turn up your nose at it just yet. It’s food for a select group of gut bacteria: probiotics. That’s why you may know fermentable fiber by another name: prebiotics.

Without prebiotics, probiotic gut bacteria starve. And since nature abhors a vacuum, a gut without probiotic bacteria becomes a playground for harmful bacteria to colonize and wreak havoc on your health.

One specific type of prebiotic, called resistant starch, has an especially crucial role. It impacts insulin sensitivity and helps produce short-chain fatty acids (SCFAs) in the gut. These SCFAs keep your gut and immune system healthy as they circulate throughout your body, regulating inflammation and talking to your cells and tissue.

For a deeper dive on this topic, check out our article on prebiotics, probiotics, and the little-known postbiotics, here.

All of the types of fiber are essential for an optimally functioning digestive system. To the extent that your diet is deficient in fiber, your microbiome will be out of whack (that’s not medical jargon, in case you were wondering). And that can not only cause digestive problems but can lead to a cascade of problems due to your hormonal system’s reliance on the microbiome to provide a pool of well-behaved chemical messengers.

Fiber’s Impact on Insulin


Insulin is one of the most important hormones in the body. Without it, your cells can’t get the energy they need, and blood sugars become dangerously high. When your pancreas doesn’t produce enough insulin, or when your body loses the ability to use insulin properly (a condition called insulin resistance), the result is diabetes.

You need insulin to move sugar in your blood into energy that powers your body; but it does a bunch of other stuff as well, like regulating blood pressure, storing fat, and promoting cell growth. But insulin is a double-edged sword, and too much insulin can lead to obesity, cardiovascular disease, and decreased lifespan.

While fiber can’t make up for a malfunctioning pancreas, it can help your body to need less insulin by reducing insulin resistance through its support of beneficial gut microbiota. These bacteria enhance the communication between the gut and other tissues that are involved in insulin and glucose balance. Fiber signals them to increase insulin sensitivity so less of the hormone is required to shuttle glucose from the bloodstream to the cells that need it. And fiber itself lowers blood sugar directly by slowing the absorption of sugar into the bloodstream.

A 2019 study on adolescents found several interesting things. First, only two of the over 750 participants in the study met the US daily fiber intake recommendations. Second, both insoluble and soluble fiber intakes were inversely associated with fasting insulin and insulin resistance markers — meaning the less fiber the adolescents ate, the more insulin was required to turn food into usable energy. Third, lower fiber intake of all types was associated with higher insulin levels, which as we’ve seen can cause all sorts of long-term health problems.

A 2021 meta-analysis also found that dietary fiber could significantly reduce HbA1c and fasting blood glucose in patients with type 2 diabetes. And soluble fiber, in particular, such as the beta-glucan found in whole grains and some mushrooms, can do good things for glucose levels and insulin responses, especially those mediated by hormones produced by the gut.

Fiber, Sex Hormones, and Cancer Incidence

Among the hormones impacted by fiber intake are the ones related to reproductive function. Excess circulating levels of these steroidal hormones, such as estrogen and testosterone, are linked to increased cancers of the reproductive organs.

Hormones, Fiber, and Breast Cancer

Day in a life of female cancer survivor at home and outdoors

Many studies have shown that high circulating levels of insulin and its close relative insulin-like growth factor 1 (IGF-1) are risk factors for breast cancer. So how do you get high IGF-1 levels? One way is by consuming a lot of animal products, which don’t contain any fiber.

And if you consume dairy from cow’s milk, you may also be pumping up your IGF-1 levels because of a synthetic hormone called recombinant bovine growth hormone (rBGH). This drug is often given to cows to increase their milk production and make them mature more quickly.

Certain types of breast cancer are also affected by sex hormones such as estrogen. In fact, estrogen receptor-positive breast cancer is the most common subtype of breast cancer.

Diet affects both of these risk factors. There have been multiple studies showing that the more fiber you eat, the lower your risk of breast cancer. These include the giant Nurses’ Health Study II, which found an inverse relation between fiber and breast cancer in over 44,000 nurses. And a 2020 meta-analysis of 20 studies calculated an 8% reduction in breast cancer risk for those who ate the most fiber compared to those who ate the least.

A 2020 paper also identified a healthy gut microbiome, specifically including bacteria from the Firmicutes, Bacteroidetes, and Actinobacteria phyla, as the mediating mechanism between fiber consumption and the reduction in breast cancer risk.

Several biological mechanisms may explain the beneficial effects of dietary fiber on breast cancer risk. Fiber may decrease breast cancer incidence by controlling blood glucose and improving insulin sensitivity. It may also increase serum concentrations of sex hormone-binding globulin (SHBG), thereby reducing the circulating levels of estrogen in the body. Also, dietary fiber can shuttle estrogen out of the body by triggering more frequent and larger bowel movements (since excess hormones leave the body through excrement).

Fiber and Prostate Cancer

The fact that fiber increases SHBG is relevant to prostate cancer as well as breast cancer. SHBG binds the sex hormones testosterone and estradiol and decreases their biological activity, which can reduce the risk of aggressive prostate cancer.

In fact, it turns out that many diagnoses of prostate cancer are hormonally linked: sex steroids, particularly androgens such as testosterone, appear to contribute to the development and progression of prostate cancer. Again, the consumption of animal protein (which, I repeat, contains zero fiber) correlates with an increased risk of prostate cancer, and greater odds of recurrence after remission. As with breast cancer, this is likely due at least in part to increased levels of circulating IGF-1.

On the other hand, a plant-based diet can lower IGF-1 levels, putting men at a lower risk for prostate cancer. A 2012 study found that increased total, insoluble, and soluble fiber intake were all associated with a lower risk of aggressive forms of prostate cancer.

A large study that followed over 43,000 Japanese men for almost 12 years found that fiber intake may be protective against aggressive prostate cancer, and the protective association was greatest in those who consumed the most fiber.

The improved insulin sensitivity that fiber induces can also reduce that risk. Insulin may affect cancer development by influencing cell division and decreasing insulin-like growth factor (IGF) binding proteins, which increase the bioactivity of IGF-1.

Learn more about IGF-1, including how it works and how to bring IGF-1 levels down in your body.

Fiber, Satiety Hormones, and Obesity

Woman Preparing Vegetables in Kitchen On Her Own Smiling

We’ve known for a while that fiber can help fight obesity. But we’re discovering that one of the mechanisms by which it does so is via hormones produced by the gut microbiome. For example, fiber intake predicts ghrelin levels in people with obesity. Ghrelin is a gut hormone produced and released by your stomach. It’s your stomach’s way of telling the brain, “Hey, I’m empty; it’s time to eat. Create the sensation of hunger!”

Ghrelin plays an important role in promoting fat development, so it makes sense its dysregulation could influence the development of metabolic disturbances associated with diet-induced obesity.

In lean, healthy people, ghrelin levels increase before meals and drop after eating. By contrast, in people with obesity, insulin resistance, or type 2 diabetes, fasting ghrelin levels are lower, and don’t show much if any variation. In fact, ghrelin levels either drop less or not at all after eating in obese people, compared with lean ones.

One older study showed that variation in ghrelin levels was positively associated with fiber intake. In fact, fiber consumption had as much influence on ghrelin levels as total calories consumed, even though fiber doesn’t provide calories. So a high fiber intake increases the perception of satiety, reduces appetite, and lowers food intake.

This effect could be due to fiber’s ability to slow down the process of moving food through the stomach. “Decreased gastric emptying,” as this phenomenon is called (or, if you prefer, you can just think of it like “stuff stays in your tummy for longer”), allows the stomach to pull out more nutrients more effectively, and therefore downregulates hunger, since the stomach is getting what it needs and doesn’t need the brain to call for more.

Fiber may also impact levels of another hunger-related hormone, leptin. Leptin functions as a counterweight to ghrelin: It’s secreted by fat cells and signals the brain to decrease sensations of hunger. When leptin levels are high for a long time due to excess fat, the body can stop paying attention to its message of “stop eating.” 

One way to help people overcome obesity is to lower their leptin levels and stop leptin resistance, so their bodies can re-establish a balance. It’s like if someone has been shouting at you for so long that you no longer pay any attention to them, unless they stop shouting for a while, you’ll have a hard time listening to them ever again.

A small 2017 study of overweight adults found that adding resistant starch to a moderate- to high-fat diet lowered leptin levels. And a larger 2021 study of 17-year-olds also found that higher fiber intake was significantly associated with lower leptin. This may contribute to reductions in low-grade chronic inflammation and improved health outcomes, such as the prevention of obesity and type 2 diabetes.

Fiber-Rich & Hormone Balancing Recipes

Fiber is in a wide range of fruits, vegetables, legumes, and whole grains, which are all designed to supply your body with the nutrients it needs to live a happy, healthy, and balanced life. Speaking of balance — regulate your hormones with ease as you enjoy these tasty, fiber-filled recipes for breakfast, lunch, or dinner (and maybe a tasty afternoon, fiber-filled snack, too).

1. Oatmeal Banana Bites

Oatmeal Banana Bites on a baking rack

Packed with plenty of fiber from oats and bananas, these muffin-like bites are a tasty snack that does just the trick for proper hormone balance. The banana’s prebiotic fiber will feed your good gut bacteria. And the oats provide both soluble and insoluble fiber, preventing a spike in your blood sugar. Plus, these Oatmeal Banana Bites are super simple to make — and tasty, too!

2. Smoky Sweet Potato Black Bean Salad

Smoky Sweet Potato Black Bean Salad in a white bowl near a wooden spoon

Sweet potatoes and black beans are two plant-based foods that are excellent for balancing hormones, feeding a healthy gut microbiome, managing a healthy insulin response, and supplying the body with protein, carbohydrates, and phytonutrients. Plus, the combination of sweet and smoky flavors is absolutely scrumptious, making this simple, mouthwatering salad one you can enjoy anytime!

3. Moroccan Bulgur Bowl with Savory Orange Dressing

Moroccan Bulgur Bowl with Savory Orange Dressing in a white bowl on top of a table

The Moroccan Bulgur Bowl is filled with a healing blend of spices, loads of fiber-rich veggies, and nourishing healthy fats to keep your hormones in check. Plus, the flavor combinations are scrumptiously unique! And the creamy Savory Orange Dressing drizzled on top of fragrant bulgur, veggies, crunchy pistachios, and cooling mint takes this meal to the next level.

Keep Your Hormones Balanced — With Fiber!

The microbiome plays an important role in human health, including influencing hormonal balance. And one of the biggest controllable factors in the health of your microbiome is fiber. Prebiotic fiber, in particular, feeds good gut bacteria that help keep your hormones where they need to be.

Fiber also helps your digestive system stay healthy and get rid of waste, which includes spent and excess hormones. Getting enough fiber doesn’t just have a positive impact on hormone levels — it can also help prevent chronic diseases and conditions like type 2 diabetes, cancer, and obesity.

By eating foods with various types of soluble and insoluble fiber, you can keep your body’s information switchboard running smoothly and effectively, without disruption in hormonal balance.

Editor’s Note: The best way to increase your fiber intake is to eat lots of whole plant foods. And there are a few that are especially potent. Mindbodygreen has put some of the best forms of organic, low-FODMAP soluble fiber together in one place — paired with carefully selected probiotic strains for maximal promotion of satiety and regularity. The ingredients in their formula have been clinically shown to improve digestion, reduce bloating and gas, and support healthy blood sugar and cholesterol levels. Find out more about organic fiber potency + here. (Bonus: If you make a purchase from that link, you’ll save 20% at checkout, and mindbodygreen will make a contribution in support of FRN’s work. Thank you!)

Tell us in the comments:

  • What are your favorite high-fiber foods?
  • Do you notice a difference in your hunger after eating a high- vs low-fiber meal?
  • What fiber-rich recipe will you make next?

Featured Image: Creative House

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