One of the most responsible systems for producing and deploying hormones is your microbiome, those 100 trillion cells that are not exactly you, but live inside and on you and take on many of the critical functions that keep you alive.
When you feed your microbiome with a fiber-rich diet, it carefully manages the switchboard of your endocrine (hormonal) system (like a competent and conscientious adult). When your microbiome is malnourished and lacking fiber, however, it can produce the wrong types of hormones at the wrong times, causing chaos throughout the body. In this article, we will examine the microbiome and how fiber affects its composition and function. We will also explore the link between fiber, gut health, and specific hormonal disorders and diseases.
Hormonal Imbalance
Hormones are essential for 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, this can represent a normal and temporary fluctuation or could indicate a chronic hormonal disorder.
Hormones can cause problems not only in cases of deficiency or excess, but also if the target sites in your body do not respond to hormones as they should.
Hormonal imbalances can occur for many reasons, including life changes such as puberty, pregnancy, and menopause; episodes of extreme stress; environmental factors; and some medications. But one of the biggest factors determining the health of your hormonal system is the health of your gut, particularly your gut microbiome, which regulates the levels of many critical hormones in your body.
The Role of the Microbiome in Human Health
The microbiome is more than just a collection of microorganisms residing in the gut. The bacteria, viruses, and single-celled organisms that inhabit it interact and adapt to your body systems. There are many beneficial bacterial strains in the microbiome and some harmful ones that can also end up there. Together, these creatures regulate metabolism, help digest food and absorb the nutrients it contains, and support the immune system. All important things!
And nowhere are they more crucial than in their role supporting the endocrine system. Your gut microbes are involved in regulating reproductive, immune, and metabolic hormone levels. In other words, they are crucial to your hormonal and overall health.
Factors like age, lifestyle, and genetics all contribute to the composition of your microbiome, but one of the biggest determinants is the food you eat. Consequently, your microbiome constantly changes based on what you feed it. And the number one nutrient that beneficial bacteria love – that will make them stick around, reproduce like crazy, and generally throw 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 dissolves in water, whereas insoluble fiber does not.
Insoluble Fiber
Insoluble fiber adds bulk to stool and acts like a broom, cleaning the digestive tract. It also promotes healthy bowel movements and helps with insulin sensitivity, both of which impact hormonal health.
Soluble Fiber
We can further divide soluble fiber into two categories: viscous and fermentable.
Viscous fiber is the type that forms a gel when it comes into contact with water in the digestive tract. Its main claims to fame are that it helps balance blood sugar and lowers cholesterol.
Fermentable fiber does not do much for us directly. But don’t wrinkle your nose just yet. It is food for a select group of gut bacteria: probiotics. That’s why you might 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 where harmful bacteria can colonize and devastate your health.
A specific type of prebiotic, called resistant starch, has a particularly crucial role. It affects insulin sensitivity and helps produce short-chain fatty acids (SCFA) in the gut. These SCFAs keep the gut and immune system healthy while circulating throughout the body, regulating inflammation and communicating with cells and tissues.
To explore this topic further, check out our article on prebiotics, probiotics and the little known postbiotics.
All types of fiber are essential for a perfectly functioning digestive system. To the extent that your diet is low in fiber, your microbiome will be out of control (this is not medical jargon, in case you were wondering). And this can not only cause digestive problems but can lead to a cascade of issues due to your hormonal system’s dependence on the microbiome to provide a well-educated pool of chemical messengers.
The impact of fiber 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 sugar rises dangerously high. When your pancreas doesn’t produce enough insulin or when your body loses the ability to properly use insulin (a condition called insulin resistance), the result is diabetes.
You need insulin to turn blood sugar into energy that fuels your body; but it also does a lot of other things, 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 reduced lifespan.
While fiber can’t compensate for a malfunctioning pancreas, it can help your body need less insulin by reducing insulin resistance through its support of beneficial gut microbiota. These bacteria improve communication between the gut and other tissues involved in insulin and glucose balance. Fiber signals them to increase insulin sensitivity, so less hormone is needed to carry glucose from the bloodstream to the cells that need it. And fiber itself directly lowers blood sugar by slowing sugar absorption into the bloodstream.
Fiber, sex hormones, and cancer incidence
Among the hormones influenced by fiber intake are those related to reproductive function. Excess circulating levels of these steroid hormones, like estrogens and testosterone, are linked to increased tumors of reproductive organs.
Hormones, fiber, and breast cancer
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 high levels of IGF-1 occur? One way is consuming many animal products, which contain no fiber.
And if you consume dairy from cow’s milk, you might also increase your IGF-1 levels due to 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 faster.
Some types of breast cancer are also influenced by sex hormones like estrogens. In fact, estrogen receptor-positive breast carcinoma is the most common subtype of breast carcinoma.
Diet affects both of these risk factors. There have been several studies showing that the more fiber you eat, the lower the risk of breast cancer. These include the giant Nurses’ Health Study II, which found an inverse relationship between fiber and breast cancer in over 44,000 nurses. And a 2020 meta-analysis of 20 studies calculated a 8% reduction in breast cancer risk for those who ate more fiber compared to those who ate less.
A 2020 paper also identified a healthy gut microbiome, including in particular bacteria from the phyla Firmicutes, Bacteroidetes and Actinobacteria, as a mediating mechanism between fiber consumption and reduced risk of breast cancer.
Several biological mechanisms can explain the beneficial effects of dietary fiber on breast cancer risk. Fiber may reduce breast cancer incidence by controlling blood sugar and improving insulin sensitivity. It can also increase serum concentrations of sex hormone-binding globulin (SHBG), thereby reducing circulating estrogen levels in the body. Additionally, dietary fiber can help eliminate estrogens from the body by triggering more frequent and larger bowel movements (since excess hormones leave the body through the stool).
Fiber and prostate cancer
The fact that fiber increases SHBG is relevant for both prostate and breast cancer. SHBG binds the sex hormones testosterone and estradiol and decreases their biological activity, which may reduce the risk of aggressive prostate cancer.
In fact, it turns out that many prostate cancer diagnoses are hormonally linked: sex steroids, particularly androgens like testosterone, appear to contribute to the development and progression of prostate cancer. Again, consumption of animal protein (which, I repeat, contains no fiber) is associated with an increased risk of prostate cancer and higher chances of recurrence after remission. As with breast cancer, this is likely due at least in part to increased circulating IGF-1 levels.
On the other hand, a plant-based diet can lower IGF-1 levels, putting men at lower risk of prostate cancer. A 2012 study found that increased total, insoluble, and soluble fiber intake was associated with a lower risk of aggressive forms of prostate cancer.
A large study following over 43,000 Japanese men for nearly 12 years found that fiber intake may be protective against aggressive prostate cancer and the protective association was stronger in those consuming more fiber.
The improved insulin sensitivity that fiber induces may also reduce this risk. Insulin can influence cancer development by affecting cell division and decreasing insulin-like growth factor binding proteins (IGFBPs), which increase the bioactivity of IGF-1.
Fiber, satiety hormones, and obesity
We have long known that fiber can help combat obesity. But we are discovering that one of the mechanisms by which it does so is through hormones produced by the gut microbiome. For example, fiber intake predicts ghrelin levels in people with obesity. Ghrelin is an intestinal hormone produced and released by the stomach. It’s how your stomach tells your brain: “Hey, I’m empty; it’s time to eat. It creates the feeling of hunger!”
Ghrelin plays a major role in promoting fat development, so it makes sense that its dysregulation could influence the development of metabolic disorders associated with diet-induced obesity.
In lean and healthy people, ghrelin levels increase before meals and decrease after eating. By contrast, in people with obesity, insulin resistance, or type 2 diabetes, fasting ghrelin levels are lower and show little or no variation. Indeed, ghrelin is an intestinal hormone produced and released by the stomach. It’s how your stomach tells your brain: “Hey, I’m empty; it’s time to eat. It creates the sensation of hunger!”
Ghrelin plays an important role in promoting fat development, so it makes sense that its dysregulation could impact the development of metabolic disorders associated with diet-induced obesity.
In lean and healthy people, ghrelin levels rise before meals and fall after eating. Conversely, in people with obesity, insulin resistance, or type 2 diabetes, fasting ghrelin levels are lower and show little or no variation. In fact,
ghrelin levels decrease less or not at all after eating in obese people compared to lean individuals.
An earlier study showed that variation in ghrelin levels was positively associated with fiber intake. In fact, fiber consumption had the same influence on ghrelin levels as total calories consumed, even though fiber does not provide calories. So a high fiber intake increases the feeling of fullness, reduces appetite, and lowers food intake.
This effect may be due to fiber’s ability to slow down the process of moving food through the stomach. The “slowing of gastric emptying,” as this phenomenon is called (or, if you prefer, you can simply think of it as “things stay in the stomach longer”), allows the stomach to extract nutrients more effectively, and thus downregulates hunger, since the stomach gets what it needs and doesn’t need the brain to ask for more.
Fiber may also influence levels of another hunger-related hormone, leptin. Leptin acts as a counterbalance to ghrelin: it is secreted by fat cells and signals the brain to reduce hunger. When leptin levels are high for a long time due to excess fat, the body may stop paying attention to its “stop eating” message.
One way to help people overcome obesity is to lower leptin levels and stop leptin resistance, so their bodies can restore balance. It’s like someone yelling at you for so long that you stop listening unless they stop yelling for a while, you’ll struggle to ever hear them 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 study from 2021 involving teenagers also found that higher fiber intake was significantly associated with lower leptin. This may contribute to reduced chronic low-grade inflammation and improved health outcomes, such as prevention of obesity and type 2 diabetes.
Keep your hormones balanced with fiber!
The microbiome plays an important role in human health, including influencing hormonal balance. One of the biggest controllable factors in your microbiome health is fiber. Prebiotic fiber, in particular, feeds the good gut bacteria that help keep your hormones where they should be.
Fiber also helps your digestive system stay healthy and eliminate waste, which includes depleted and excess hormones. Getting enough fiber not only positively impacts hormone levels but 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 center functioning regularly and effectively, without disruptions in hormonal balance.
This article in no way replaces medical consultation, to which you should always adhere.
Source foodrevolution
