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What Causes Intestinal Flora

Poor dietary habits, overuse of antibiotics, mental stress, environmental pollution, and chronic diseases are the major causes of intestinal flora imbalance. Balancing dietary structure, increasing fiber intake, avoiding overuse of antibiotics, maintaining regular sleep patterns, and reducing stress can help restore the balance of intestinal flora.

Poor Diet Habits

The structure of the diet has a significant impact on intestinal flora. Changes in modern dietary habits, such as a diet high in sugar, fat, and low in fiber, have become key causes of intestinal flora imbalance. In Western dietary habits, excessive intake of fats and sugars significantly reduces the amount of friendly bacteria within the intestines, especially bifidobacteria and lactobacilli. This promotes the domination of harmful bacteria such as Bacteroides and Clostridium, disturbing the balance of the intestinal flora. According to research conducted in the United States, after a test group consumed high-fat food for four days, harmful bacteria in the intestines increased by 50%, while beneficial bacteria decreased by 25%.

Insufficient fiber intake is also one of the major factors closely related to flora imbalance. Dietary fiber is considered the main nutritional source of intestinal flora, stimulating the production of short-chain fatty acids, which are important for maintaining intestinal barrier function and immune regulation. Current dietary changes toward more processed and refined foods have been associated with a sharp decline in fiber intake. Food and Agriculture Organization of the United Nations data shows that the average dietary fiber intake of most people in the world is less than 20 grams a day, far below the 25 to 30 grams recommended. This change in dietary structure exacerbates the imbalance in intestinal flora.

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Overuse of Antibiotics

Antibiotics effectively fight bacterial infections, but overusing them is a leading cause of intestinal flora imbalance. This is due to the non-selective action of antibiotics; not only do they kill pathogenic bacteria, but they also destroy a great amount of useful bacteria in the intestines. Because antibiotics can have such a devastating impact on the intestinal flora, studies have shown that intestinal flora may take weeks or even months to partially recover from a course of antibiotics, and some species never reoccupy the intestines. One study suggested that after one week of treatment with broad-spectrum antibiotics—a group that includes amoxicillin—the number of lactobacilli present in the intestinal flora decreased by 95% and had not completely recovered even after three months.

More seriously, long-term usage of antibiotics can result in the buildup of drug-resistant strains, intestinal microecological imbalance, intestinal infections, and even colitis, obesity, diabetes, and other diseases. All this has been further aggravated by the extensive use of antibiotics in recent years in the animal husbandry industry. Antibiotics are conventionally used in agriculture. A survey by the European Union showed that about 70% of total antibiotic usage is in agriculture, which could affect human intestinal health through the food chain.

Mental Stress

A hidden cause of intestinal flora imbalance is mental stress. Psychological stress acts directly on intestinal functions via the “gut-brain axis.” Long-term mental stress will change the motility and secretion of the intestines, thus influencing the diversity and stability of intestinal flora. In conditions where mental stress is heightened, the permeability of the intestines increases, leading to a so-called “leaky gut” phenomenon. It allows bacteria and their metabolic products to enter the bloodstream and initiate a systemic inflammatory response.

Research on college students showed that during the high-pressure state before final exams, intestinal flora diversity was seriously decreased while harmful bacteria such as Clostridium increased. Additionally, the quantity of beneficial bacteria, including lactobacilli and bifidobacteria, significantly decreased. This shows that mental stress not only influences mental health but, through neuroendocrine pathways, negatively affects intestinal flora.

Environmental Factors

It is also important to mention environmental pollutants, food additives, and pesticides as factors that damage the intestinal flora. Due to the acceleration of industrialization in recent years, more attention has been paid to the increase in pollution in the air, soil, and water, especially regarding the influence on human health. As the main organ of nutrient absorption and detoxification, the intestines are exposed to these external factors and are easily affected.

It has been demonstrated that PM2.5, through respiration, can enter the intestines and interfere with flora balance. Animal experiments show that exposure to high concentrations of PM2.5 reduces the number of beneficial bacteria in the intestines and increases the amount of harmful bacteria, such as Bacteroides. In addition, common chemical additives in food, such as preservatives, artificial sweeteners, and emulsifiers, are also considered likely to lead to intestinal flora imbalance. Results from one study showed that aspartame, an artificial sweetener, could cause metabolic dysfunction in the gut microbiota, hence increasing the risk of metabolic disorders such as diabetes and obesity.

Chronic Diseases

Chronic diseases are closely related to intestinal flora imbalance, and they influence each other. Compared with healthy individuals, the intestinal flora in diabetic patients differs significantly. Studies have indicated that the intestines of patients with type 2 diabetes have higher proportions of Bacteroides and Clostridium, while there is a great reduction in beneficial bacteria such as lactobacilli and bifidobacteria. This may aggravate insulin resistance and further worsen the condition.

The most typical diseases related to intestinal flora imbalance are inflammatory bowel diseases, including Crohn’s disease and ulcerative colitis. It was shown that the diversity of gut flora in patients was significantly reduced in these diseases, especially a decrease in bacteria from the Firmicutes phylum, while harmful bacteria from the Proteobacteria phylum increased. Harmful bacteria such as Clostridium difficile and Shigella in patients’ intestines can increase greatly. These bacteria further disrupt the intestinal barrier, leading to chronic inflammation. Intestinal flora imbalance is not only a result of these diseases, but it may also be one of their causes.

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Irregular Daily Routine

For modern people, one of the most important causes of intestinal flora imbalance is the fast pace of life and irregular daily routines. In fact, it has been proved that long-term staying up late, jet lag, and other disturbances to the circadian rhythm could disrupt the endocrine system and thus affect the normal function of the intestines. Research has shown that the circadian clock is closely related to the activity cycle of gut flora; these irregular routines disrupt the diurnal rhythm of the intestinal flora.

One experiment showed that in the intestinal flora of volunteers who worked night shifts, Firmicutes bacteria significantly decreased, and harmful Bacteroides bacteria greatly increased. Long-term night shift workers are more likely to experience indigestion, constipation, diarrhea, and other intestinal problems because these issues are directly related to intestinal flora imbalance. Keeping a regular routine can balance the intestinal flora, and irregular routines can cause flora imbalance, which in turn affects overall health.

Age

As age increases, immune function and metabolic function slowly decline, and so does the diversity of intestinal flora. It is known that the intestinal flora diversity in elderly people is far lower compared to that of young ones, with a significant decrease in the number of useful bacteria; thus, the intestinal flora are unbalanced. A U.S. study about the elderly showed that intestinal flora diversity in people over 80 years decreased by about 40%, especially with a significant reduction in the number of bacteria from the phylum Firmicutes and bifidobacteria.

This imbalance of intestinal flora in the elderly may be followed by a series of health problems, such as weakened immunity, increased chronic inflammation, and poor nutrient absorption. Intestinal flora imbalance is also related to neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease. In this process of reduction in diversity, the function of the intestinal barrier will gradually weaken and allow harmful bacteria and their metabolic products to enter the blood, triggering a systemic inflammatory response and influencing brain health.

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