Stress, which is a part of human life, has proven to have various effects on the human body, including gut health. So if you ever wonder how your digestive system gets affected, you are in a stressful situation – this is for you. 

What is Stress?

Stress may be defined as a form of stimulus, which is external or internal in nature, and causes a biological response in the body, and threatens homeostasis. (1) The type of changes and effects stress can have on the body depends on several factors like the type of stress, timing of the stress, and the body's overall health. Based on these factors, stress can either have minor effects on the health of a person, or it may even lead to life-threatening consequences.

What is the Gut Microbiota?

The Gut Microbiota is composed of several different kinds of bacteria, archaea, yeasts, viruses, and fungi. The number of these organisms may range from somewhere between 1000 cells/ml of the acidic content to 10¹¹ cells/mL. (2) Amongst all these organisms, the bacteria present in the gut are most researched and are composed of two phyla known as the Bacteroides and Firmicutes. These two phyla makeup at least 90% of the gut microbiota of humans and are responsible for the majority of functions.

The importance of the gut microbiota can be evaluated by the fact that a healthy gut is one that has a healthy gut microbiota. Healthy gut microbiota is when the advantageous microorganisms in the gut are found in larger numbers as compared to those which may harm the gut. On the other hand, an unhealthy gut microbiota would mean the prevalence of harmful or dysbiotic gut microorganisms. (3)

What is the Connection Between Stress and Gut Health?

In easy words, stress has the ability to, directly and indirectly, affect gut health. While the direct changes might include changes in the normal gut physiology, changes in the gut permeability, and digestive mechanisms, the indirect effects are those which may be caused through changes in diet and its metabolism.

Changes in the Gut Microbiota

Studies have shown a change in the gut microbiota in individuals who constantly find themselves in stressful situations. This has been demonstrated by a higher number of inflammation-causing microorganisms in the gut as compared to those that benefit the gut, in turn promoting an unhealthy gut. (4)

Increased Permeability of the Gut

Another negative effect of stress in the gut is that it has the ability to increase the overall permeability of the gut lining, which leads to leaking out of content from the gut into the bloodstream without undergoing the proper filtration mechanism that has been designed to keep the harmful substances out. This type of gut is also referred to as a leaky gut and allows the transmission of unhealthy organisms into the bloodstream, which may negatively impact the individual's health. (5)

Changes in Functional Physiology of Intestine

Another proven effect of stress on the gut is that it has the ability to cause changes to the functional physiology of the gut. An example of this is the development of diseases like Crohn's disease and other conditions of the gut which cause ulcers. Studies have shown that these conditions are commonly associated with stress and are found to be more prevalent in those who find themselves in prolonged stressful conditions. (6) Studies have also shown that stress experienced during childhood can lead to the development of these diseases much later in life, which shows the extent of direct effect stress has on gut health.

Changes in Diet and Appetite

Stress may also cause negative changes in the gut indirectly by changing the way an individual eats. The effect of stress on one's appetite has been investigated in numerous studies and is shown to involve certain areas of the brain. These include the ventral tegmental area and the amygdala through certain receptors known as NMDA glutamate receptors. (7)

Moreover, the kinds of food one eat may also be impacted by stress, which in turn has the potential to negatively impact the digestive system. A stressful situation may lead to one eating unhealthy foods which may contain high levels of saturated fats and calories, continuous consumption of which may eventually lead to an upset stomach.

Changes in Metabolic Response to Diet

Other than indirectly affecting gut health via a changed diet, stress also has the ability to change how the food that is consumed is metabolized in the body and causes changes to the metabolic responses. Studies have shown those who are under stress may have lower oxidation of fats in the body, increased levels of Insulin, and a decreased energy expenditure after consumption of a fatty meal. (8)

Natural Ways to Beat Stress

Since stress has the ability to cause changes to gut function and overall health, finding ways to relieve stress naturally may not only be beneficial for one's mental health but also benefit their gut health. These ways include:

• Taking a Break: If the daily routine is getting too hectic for you and you find yourself in constant stress, it is always wise to take a break and work on your mental health. You may take a walk in the park, catch up with your friends or just listen to music.
• A Healthy Diet: Just like stress has the ability to affect gut health, and an unhealthy diet may also worsen one's stressful state and negatively impact their mental health. Hence, one should try to cut out sugary and fatty foods from their diet once in a while.
• Regular Exercise: Regular Exercise, even if it just a morning walk, may prove to be advantageous in stressful situations as exercise has the ability to cause stress relief.
• Good Night's Sleep: Getting at least seven to eight hours is mandatory for those who are already on a tight and hectic schedule. A good night's sleep has the ability to rejuvenate the individual and give them the energy to carry out their everyday activities peacefully.

Natural Ways to Improve Gut Health

Having an unhealthy gut can prove to be very troublesome for an individual and has the potential to affect their everyday activities. Besides finding ways to beat stress, there are other factors that may play a positive role in the maintenance of gut health. These include:

1. Chewing food Slowly: Being on a tight schedule does not allow most individuals to take out enough time to eat their food. This leads to them taking big bites and gulping down the food without chewing. This can put unnecessary pressure on the digestive system and eventually lead to pathosis. Hence, one should try to chew food slowly and take their time eating meals.

2. Healthy Foods: As discussed previously, regular consumption of fatty foods can take a negative toll on the gut. Hence one should try to add more fibers, grains, and other healthy nutrients to their diet to allow the maintenance of a healthy gut.

3. Water Consumption: Consumption of adequate water throughout the day has an impact on the gut lining and can help balance out the unhealthy bacteria with the healthy bacteria in the gut. 

References:

1. Schneiderman N, Ironson G, Siegel SD. Stress and health: psychological, behavioral, and biological determinants. Annu Rev Clin Psychol. 2005;1:607-628. doi:10.1146/annurev.clinpsy.1.102803.144141

2. Sender R, Fuchs S, Milo R. Revised Estimates for the Number of Human and Bacteria Cells in the Body. PLoS Biol. 2016 Aug 19;14(8):e1002533. doi: 10.1371/journal.pbio.1002533. PMID: 27541692; PMCID: PMC4991899.

3. Roberfroid M, Gibson GR, Hoyles L, McCartney AL, Rastall R, Rowland I, Wolvers D, Watzl B, Szajewska H, Stahl B, Guarner F, Respondek F, Whelan K, Coxam V, Davicco MJ, Léotoing L, Wittrant Y, Delzenne NM, Cani PD, Neyrinck AM, Meheust A. Prebiotic effects: metabolic and health benefits. Br J Nutr. 2010 Aug;104 Suppl 2:S1-63. doi: 10.1017/S0007114510003363. PMID: 20920376.

4. Jiang H, Ling Z, Zhang Y, Mao H, Ma Z, Yin Y, Wang W, Tang W, Tan Z, Shi J, Li L, Ruan B. Altered fecal microbiota composition in patients with major depressive disorder. Brain Behav Immun. 2015 Aug;48:186-94. doi: 10.1016/j.bbi.2015.03.016. Epub 2015 Apr 13. PMID: 25882912.

5. Kiecolt-Glaser JK, Derry HM, Fagundes CP. Inflammation: depression fans the flames and feasts on the heat. Am J Psychiatry. 2015 Nov 1;172(11):1075-91. doi: 10.1176/appi.ajp.2015.15020152. Epub 2015 Sep 11. PMID: 26357876; PMCID: PMC6511978.

6. Hommes D, van den Blink B, Plasse T, Bartelsman J, Xu C, Macpherson B, Tytgat G, Peppelenbosch M, Van Deventer S. Inhibition of stress-activated MAP kinases induces clinical improvement in moderate to severe Crohn's disease. Gastroenterology. 2002 Jan;122(1):7-14. doi: 10.1053/gast.2002.30770. PMID: 11781274.

7. Nasihatkon ZS, Khosravi M, Bourbour Z, Sahraei H, Ranjbaran M, Hassantash SM, Sahraei M, Baghlani K. Inhibitory effect of NMDA receptors in the ventral tegmental area on hormonal and eating behavior responses to stress in rats. Behav Neurol. 2014;2014:294149. doi: 10.1155/2014/294149. Epub 2014 Aug 7. PMID: 25177106; PMCID: PMC4143587.

Kiecolt-Glaser JK, Habash DL, Fagundes CP, Andridge R, Peng J, Malarkey WB, Belury MA. Daily stressors, past depression, and metabolic responses to high-fat meals: a novel path to obesity. Biol Psychiatry. 2015 Apr 1;77(7):653-60. doi: 10.1016/j.biopsych.2014.05.018. Epub 2014 Jul 14. PMID: 25034950; PMCID: PMC4289126.