How Stress Impacts your Immune System, Digestion & Blood Sugar

In this season of higher levels of chronic, low grade stress, it is normal to feel more triggered, tired, overwhelmed, bloated, and anxious. Your diet can absolutely trigger these same symptoms but so often, you may underestimate the role that stress plays on how you feel. It’s hard to directly see or measure the effects of stress. But here’s the truth: poorly managed, low grade stress can hijack your brain, digestion, immune system, and metabolism just like eating excessive processed foods. 

In my virtual nutrition clinic, people come to me to change their diet in order to improve their health and address bloating and GI issues, high blood sugar levels, poor memory, weight gain and more. Everyone is more willing to change their diet than to learn how to manage their stress, buffer their schedule, think nicer thoughts about themselves, and rest more. The truth is, for most people it’s easier to change their diet than it is to reprogram their response to stress. This is why I run cortisol testing on every person, to better understand their resilience to the stress in their lives. It can also help them visually see that poorly managed stress can act as a neurotoxin, digestive disruptor, immune system suppressor, weight gain accelerator and blood sugar spiker. 

What is Stress? 

Stress comes in several “flavors.” They include:

• Physical stressors, such as overgrowth of harmful bacteria, surgery, pregnancy
• Psychological stressors, such as worrying about things outside of your control, jumping to worst case scenarios or having regrets
• Mental stressors, such as over-committing or taking on too much work
• Immune-impacting stressors such as eating sugary foods or drinking alcohol to relieve stress, which can adversely impact the immune system

One thing all of these stressors have in common is a disruption or disturbance in homeostasis or internal balance. 

When you lose your job, have an argument with your significant other, fear the outcomes of the pandemic while social distancing, or you don’t get enough sleep: Those can all be stressors.

A healthy body can usually adapt to these stressors. Adaptation is actually key because your perception of any given stressor largely determines the toll that stress can take on your health. In some cases, you may thrive and become more resilient when stress occurs. Think about a time when you closed a big deal at work or had to make a speech. You might have felt anxious or stressed out, but facing that challenge made you stronger to confront similar situations in the future. 

These acute stressors can be beneficial and fuel your excitement. But the key is to eventually reach a point of equilibrium or balance to prevent these stressors from becoming chronic. In this article, I will review how the stress response works, which nutrients are depleted with stress, how stress impacts the gut microbiome, how stress can dampen the immune system and how stress can increase blood sugar levels. If you are like most people and you downplay the toll that low grade, chronic stress can take on the body, you may rethink that stance by the end. 

The Stress Response and Your HPA Axis

There are two systems that are housed within your autonomic nervous system: your parasympathetic nervous system or “rest and digest state” and sympathetic nervous system or “fight or flight” system. You are either in fight or flight mode or rest and digest. Because stress initiates a cascade of events as your body shifts into a “fight or flight” mode, most people spend a lot of time in this state. This physiological response prompts the body to confront or run away from a potential threat. 

As early humans, acute stress might have helped you survive. When hurt or threatened, stress hormones like cortisol and neurotransmitters could create enhanced alertness and prepare the immune system for potential challenges. 

That stress response can benefit everyone today needing to make a potentially life-threatening decision quickly. Take for instance, our brave healthcare workers who have to quickly be prepared to save lives when patients are admitted to the emergency room.

When that happens, a part of your brain called the amygdala sends a distress signal to another part called the hypothalamus. The hypothalamus responds by activating the sympathetic nervous system, which signals the adrenal glands to distribute a hormone called epinephrine or adrenaline into the bloodstream. 

The sympathetic nervous system is your body’s “on” switch: It activates physical changes. As a result, the heart beats faster. Blood flow increases to the muscles and other vital organs to prepare you to run from a tiger. Your pulse and blood pressure become elevated, and you may breathe more quickly. More oxygen goes to your brain. 

All of these things help the body become more alert, and they happen quickly. When you experience a stressful situation, you don’t have much time to think about options.

If the brain continues to perceive something as dangerous, the hypothalamus releases corticotropin-releasing hormone (CRH), which travels to the pituitary gland and helps trigger the release of adrenocorticotropic hormone (ACTH). ACTH travels to and signals the adrenal glands to release a stress hormone called cortisol. 

This second component of the stress response system keeps the sympathetic nervous system, the body’s “on” switch, fired up. When the threat subsides, the parasympathetic nervous system kicks in. 

If the sympathetic nervous system is the gas pedal or “on” switch, the parasympathetic is the brake or “off” switch, telling the adrenals to calm down. This system is also known as your rest and digest response. As a result, your cortisol production goes down. This complex feedback loop helps prevent over-activation of this response when the stressor subsides.

At least that’s what’s supposed to happen. 

Chronic exposure to stress can keep that feedback loop in overdrive, which can take its toll on, and eventually overtax, the adrenal glands. This article explains more about how stress can contribute to adrenal dysfunction.

Chronic stress, which keeps the stress response in overdrive, can occur from a real or simulated event. Perhaps your overactive imagination of something you perceive as threatening keeps the stress response going. Having a fear-based mindset and assigning fear-based thoughts to events will keep you in this overdrive response. 

In either case, real or imagined, chronic stress keeps those stress hormones elevated when they should ideally taper down. That type of stress can manifest in a wide array of health conditions including osteoporosis, diabetes, hypertension, autoimmune disease and brain-related problems.

In other words, chronic stress prolongs the stress response long after that reaction serves you. Over time, this type of stress can deplete nutrients, weaken the immune system, suppress digestive enzyme production and disrupt your digestion, and create unhealthy blood sugar fluctuations. 

Stress Can Deplete Nutrients

Not only does chronic stress set you up to make less desirable nutrition choices like diving into half a bag of cookies or tortilla chips, it also places an increased physiological demand on the body. That can increase the need for specific nutrients, but stress can also deplete important vitamins and minerals in the process.

Vitamin B6, or pyridoxine, is one particular nutrient that chronic stress can deplete. And because vitamin B6 helps convert the amino acid, tryptophan into serotonin, low vitamin B6 can further exacerbate mood fluctuations tied to stress. Supplementing with a B complex formula, which includes B6 vitamins, may help improve your stress response. Chronic stress can also deplete vitamin C by increasing the rate at which you burn through this antioxidant. The adrenal glands are rich in this water-soluble vitamin. In animal studies, adrenocorticotropic hormone (ACTH) causes the adrenals to lose vitamin C. With humans, adrenal vitamin C secretion is an integral part of the stress response. 

We aren’t entirely sure why the body releases vitamin C during the stress response. One reason could be to support the body’s antioxidant system by quenching the increased oxidative stress that occurs with psychological stress. 

Chronic stress can also deplete minerals, such as magnesium. Researchers have associated low levels of this mineral with stressful conditions including photosensitive headache, fibromyalgia, chronic fatigue syndrome, audiogenic stress, cold stress, and physical stress. 

I write about specific nutrients that can help curb the stress response and support adrenal health in this article. 

Stress Can Impair your Digestion

During a fight-or-flight response, the digestive process slows down or even stops since you can only have one foot on the gas or brake at a time. The body diverts that energy to the brain and other organs that handle the immediate threat.  After all, when you’re in danger, digesting food isn’t exactly a top priority for the body. When you are in fight or flight, the body actually slows down production of pancreatic enzymes that are important for digesting your food and assimilating nutrients. 

When your stress levels stay high disrupted digestion can lead to abdominal pain and other gut-related problems. If you do not work on actively lowering your stress then this can happen even when you are eating the most nutritious, organic foods. Many of the clients in my virtual nutrition practice report improved bowel movements and less bloating while on vacation which is likely attributed to that “rest and digest” response. 

Underlying proper digestion -- and, by extension, a healthy gut -- require digestive enzymes, short chain fatty acids or metabolites and a healthy microbiota. 

Collectively called the microbiome, these trillions of microorganisms include thousands of different species such as bacteria, fungi, parasites, and viruses. Most of them reside in the large intestines. Everyone has a unique network of microorganisms, which are largely determined by their DNA.

Among their duties, these intestinal microbiota determine how reactive your nervous system is to stress and help regulate your immune response. A healthy gut can help you adapt to specific conditions, protecting against stress-related diseases. 

The relationship between stress and the microbiome is self-perpetuating since stress also influences the intestinal microbiota. Researchers have found that different types of stress -- maternal separation, chronic social defeat, heat stress, and so on -- can alter the composition of those microbiota. And the more stress you endure, the more imbalance that can occur between various microbial populations. 

In one study, researchers looked at military personnel -- a population prone to intense stress -- to determine how psychological, environmental, and physical stressors could impact gut microbiota both immediately and longer-term. 

They concluded that gut microbiota could be a factor contributing to adverse stress-associated health outcomes. However, these microbiota may also provide a tool for favorably modulating the stress response.

Not only does this impact digestion and can manifest in bloating, constipation, diarrhea and other GI symptoms but it can also impact your mental health and your mood. A 2016 study showed that stress induces changes in the microbiome that reduces both the richness and diversity of bacteria, key components of a healthy gut. The reduced diversity dampens the production of beneficial short chain fatty acids and neurotransmitter synthesis, directly affecting brain health and mood. 

Using probiotics can positively alter the stress response and even restore tight junction integrity (decreased leaky gut) in stressed mice. We are still understanding the roles that gut microbiota play in stress. Scientists have been able to isolate and study specific probiotics, such as Lactobacillus helveticus R0052 and Bifidobacterium longum R0175. These specific strains show the potential to improve emotional responses and support resilience in healthy individuals. 

These types of studies continue to reveal that the quality of these gut bacteria -- meaning the diversity and balance of gut flora -- can impact your emotional behavior and stress response. 

Stress Can Dampen the Immune Response

Almost 70 percent of the immune system resides in the gut, collectively called the gut-associated lymphoid tissue (GALT). The gut forms a barrier against pathogens and other threats that, left unregulated, can lead to infections. When the gut becomes compromised, so can the immune system.

In 2004, a meta-analysis of over 300 empirical studies spanning three decades found a relationship between psychological stress and immune health. 

Overall, acute stressors -- those lasting minutes, such as the stress of taking an exam -- were beneficial, helping to support and strengthen the immune system. Chronic stressors had the opposite effect: they suppressed both cellular and humoral measures. 

During acute stress, cortisol and epinephrine help move immune cells from the bloodstream and storage organs, including the spleen, to where those immune cells are needed to fight infection. 

And while acute stressors may increase resistance to infections and be beneficial, many people experience too much of a good thing, leading to chronic stress which can impair the body’s ability to mount a strong immune response.  

Chronic stress can reduce the immune system’s ability to fight off antigens, which are potentially harmful substances that create an immune response. An over-activated immune response, triggered by chronic stress, can suppress immune function and increase the risk of infections and cancer. 

More specifically, chronic stress decreases the body's lymphocytes, the white blood cells or leukocytes that help fight off infection. Lower levels of lymphocytes put you at a higher risk of viral infections. 

Other research shows that in elderly people especially, psychological stress could significantly decrease the function of neutrophils, which can make up 55 to 70 percent of your white blood cells, and lead to infectious diseases.

The key here is balance. While suppressed white blood cells can increase your risk of infection, high levels of certain white blood cells can indicate an underlying problem such as increased stress or inflammation. 

In one study, researchers looked at the levels of disease-promoting inflammatory leukocytes in 29 medical residents in the intensive care unit (ICU), which is obviously a high-stress job. Leukocytes were significantly higher for on-duty workers one week later compared to off-duty workers.

Researchers weren’t entirely certain that stress was the culprit for that increase in leukocytes, so they conducted an animal experiment that put mice in high-stress situations. 

They discovered that just as with humans, chronic stress levels elevated certain white blood cells, including inflammatory monocytes. This eventually led to plaque inflammation in their arteries.

Stress Can Keep Blood Sugar Elevated

Stress leads to an increased production of certain hormones, including cortisol and epinephrine. The stress response shuts down other hormones, such as insulin. When you’re stressed, the body wants to release rather than store glucose. The end result of these hormonal shifts is to allow more glucose into the bloodstream for energy. This happens even if you do not eat sugary foods! 

Glucocorticoids, which are synthesized in the adrenal cortex in response to adrenocorticotropic hormone (ACTH), help maintain circulating levels of glucose for your body to manage a stress response.

Glucocorticoids help regulate multiple aspects of glucose homeostasis, including gluconeogenesis or the creation of new glucose in the liver, as well as glucose uptake in muscle and fat tissues. The major goal of glucocorticoids during the stress response is to preserve glucose for the brain. 

Cortisol and other glucocorticoids bind to glucocorticoid receptors, found in almost every cell within the body. Researchers find that chronic stress can result in glucocorticoid receptor resistance, which can subsequently increase the inflammation that can contribute to a number of diseases.

Over time, elevated glucocorticoid levels can keep blood sugar levels elevated. As a result, fat cells become less sensitive to insulin. This increases the body’s inclination to store fat and contributes to insulin resistance, where the cells no longer “hear” the signal of insulin. Simply stated, chronic stress can increase blood sugar levels and body fat accumulation. 

Imagine what happens when the glucose from stress compounds with stress eating sugary foods like cookies and ice cream! This is not meant to scare you or shame you but rather to serve as knowledge that can empower you to prioritize nutrition to the best of your ability during stressful periods! 

Higher cortisol levels have also been associated with an increased risk of cognitive decline and Alzheimer’s in healthy people. That’s because elevated levels of this hormone can lead to oxidative stress, amyloid ? peptide accumulation (that can contribute to Alzheimer’s), inflammatory mediators, and other brain-related problems. Elevated blood sugar levels are also independently a risk factor for cognitive decline. So not only do your blood sugar levels impact your waistline, more importantly they impact your cognitive function and energy levels! 

Nutrition Can Only Improve your Health So Much In Stressful States

As you can see again and again from these examples, nutrition can only improve your health so much if you are not managing your stress levels. When you live in a state of chronic stress, you cannot support the body’s basic physiological needs which can lead to harming your digestive system, your immune health and your blood sugar levels. 

You will never fully eliminate stress from your life, but you can learn how to better manage your response to stress so it doesn’t create long-term health problems. There is no “right” or “wrong” way to manage your stress. How you do that depends on what works for you. Doing yoga a few times per week, practicing meditation for 10 minutes per day, deepening your breath, moving your body everyday, spending 20 minutes in nature, or even playing with your dog are all great ways to increase your stress response and resilience. 

In the current season filled with uncertainty and fear, try to refocus your attention on what it is you can control. Worrying about the unknown or what if situations are not in the best interest of you or your health.

If you are interested in learning more about tangible ways to reduce your stress response and become more mindful, checkout this article!