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32 Benefits and Side Effects of Probiotics [Updated Jan/2023]

Probiotics are currently one of the most popular health foods, thanks to modern medical evidence that supports the link between gut microbiota activity and human health and disease.

Therefore, the modification of the gut microbiota has received increasing attention as a potential treatment for human and animal diseases.

In empirical medicine, what are the benefits of taking probiotics? Are there any side effects of probiotics? See discussed in the text for details.

What are probiotics?

Probiotics/lactic acid bacteria are simply a group of microorganisms that can effectively promote human health, and can resist gastric acid and bile acid, and can adhere and colonize in the intestinal tract.

According to statistics, the human gastrointestinal tract contains a rich and diverse microbial community, gathering more than 100 trillion microorganisms. These microbiomes encode more than 3 million genes (the human genome is composed of approximately 23,000 genes) and produce thousands of metabolites. And 80% of immune cells are distributed here, which has a decisive influence on metabolism and immune function. Note 1

These gut microbiota play an important role in maintaining the stability of the intestinal environment, including the metabolism of nutrients, the synthesis of vitamin K and vitamin B12, the metabolism of exogenous organisms, and the prevention of pathological biological invasion and the maintenance of barrier function.

Current evidence finds that the composition of the gut microbiota changes in many disease states, such as cardiovascular disease, cancer, malignancy, type 2 diabetes, obesity, colitis, asthma, psychiatric disorders, inflammatory diseases, and many immune diseases.

What is the difference between probiotics and lactic acid bacteria

Probiotics are the general term for all “beneficial bacteria”, and lactic acid bacteria are just one type of probiotics, which metabolize sugars to produce lactic acid. Since 90% of probiotics are lactic acid bacteria, probiotics are almost equal to lactic acid bacteria. Common lactic acid bacteria are: Lactobacillus acidophilus (also known as A bacteria), Lactobacillus paracasei 33 (also known as LP33)

What are the benefits of probiotics?

  1. Probiotics are beneficial for vaginal infections

A vaginal infection is defined as any condition with abnormal vaginal discharge, smell, irritation, itching, or burning. Common causes are bacterial vaginosis, vulvovaginal candidiasis and trichomoniasis.

Bacterial vaginal infections and vulvovaginal candidiasis are the most common, occurring in an estimated 5% to 70% of women.

If left untreated, bacterial vaginal infection is a risk factor for adverse pregnancy outcomes, including second-trimester miscarriage, spontaneous preterm birth, and endometritis after caesarean section.

A systematic literature review and integrated analysis (meta-analysis, including 30 studies related to vaginal infections in non-pregnant women) pointed out that, compared with traditional drug treatment alone, probiotics combined with drugs can reduce the recurrence rate in the short term, and Improve cure/remission rate. Note 1

*Conclusion: For the common vaginal infections of non-pregnant women, probiotics combined with traditional pharmacological treatment can improve the therapeutic effect in the short term. However, due to the heterogeneity between the studies, more high-quality trials are still needed to determine the best strain and Treatment programs

  1. Probiotics are good for psychological stress

Psychological stress refers to the physical and psychological reactions that a person has in the process of adapting to a certain lifestyle due to his lack of ability or cognitive ability, which puts the body and mind in a state of tension.

However, long-term stress can cause serious damage to a person’s physical and mental health, prone to negative emotions such as hostility, paranoia, anxiety, depression, as well as relationship sensitivity and sleep problems.

A systematic literature review and meta-analysis (7 randomised controlled trials, 1,146 healthy participants) noted that oral probiotics reduced subjective stress levels and improved stress-related anxiety or depression. Note 1

*Conclusion: For healthy people, oral probiotics may reduce the subjective stress level, but limited by the small number of samples, more studies are needed to confirm the impact of strain differences

  1. Probiotics help lose weight

Obesity, which can be attributed to an imbalance between energy expenditure and energy intake, has become a major public health problem as it is linked to type 2 diabetes, nonalcoholic fatty liver disease, high blood pressure, insulin resistance, cardiovascular disease and other metabolic diseases (worldwide, more than one-third of adults are affected by obesity).

While exogenous factors, such as excessive caloric intake and sedentary lifestyle, are major contributors to obesity, endogenous factors, such as specific genetic variants, may make some people more likely to be obese.

A systematic literature review and meta-analysis (20 randomized controlled trials, 1411 overweight or obese participants) noted that probiotic supplementation helped reduce body mass index (-0.73 kg/m2), waist circumference (-0.71 cm), hip circumference (-0.73). cm), but there was no significant decrease in body weight (-0.26 kg). Note 1

*Conclusion: Up to now, supplementation of probiotics has not significantly helped weight loss, and it needs to be further verified by more large-scale studies with precise design.

  1. Probiotics are beneficial for acute upper respiratory infections (common cold)

Acute upper respiratory infection or an acute infection of the nose, sinuses, pharynx, middle ear, larynx, epiglottis, airway and bronchus with complex symptoms caused by viruses or bacteria.

The common cold (the most common), acute sinusitis, acute pharyngitis, acute laryngotracheobronchitis, acute epiglottitis, acute sinusitis and acute otitis media are all forms of acute upper respiratory infections.

Common symptoms include cough, fever, headache, sore throat, runny nose, and sneezing. Depending on the condition, symptoms usually subside within a few days.

A Cochrane Database of Systematic Reviews (13 randomized controlled trials, 3720 participants of all ages) showed that oral probiotics reduced the number of episodes of acute upper respiratory tract infections, mean duration of attacks, antibiotic use, and cold-related absenteeism compared with placebo. Note 1

*Conclusion: Oral probiotics may be positively helpful for the prevention of acute respiratory infections, but due to the low quality of the evidence contained, more studies are needed to support it.

  1. Probiotics are good for allergies (for allergic rhinitis)

Allergic rhinitis, the most common phenomenon of allergies, is estimated to affect about 10% to 30% of the general population, and is caused by allergens caused by specific inflammation of the nasal mucosa, mainly symptoms such as runny nose, itching, sneezing and nasal congestion.

Allergic rhinitis often causes great inconvenience to patients’ lives, and even can not concentrate on school and work, and the treatment is mainly to avoid allergens, nasal corticosteroids, decongestants, antihistamines (antihistamines), but only 38.8% of patients said that symptoms were controlled and difficult to eradicate symptoms. Note 1

A systematic retrospective analysis (22 double-blind controlled studies with a total of 2242 participants) found that probiotics helped alleviate seasonal allergic rhinitis symptoms such as nasal congestion, nasal itching, and runny nose, and also had immunomodulatory effects (reducing the Th1:Th2 ratio), especially with the LP-33 strain. Note 2

  1. Probiotics are good for chronic periodontitis

Periodontal disease refers to the inflammatory reaction of the tissues around the teeth due to the accumulation of bacteria or dental plaque. It can occur from gingivitis that is easy to treat to severe and irreversible periodontitis.

Chronic periodontitis is characterized by swollen and bleeding gums, receding gums, and deep pockets between teeth and gums, causing teeth to loosen or even fall out.

In addition to poor oral hygiene habits, causative factors include: smoking, systemic diseases, steroids, antiepileptic drugs, anticancer drugs, inappropriate crowns and bridges, incomplete teeth, loose fillings, pregnancy and use of oral contraceptives.

A literature review and meta-analysis (7 randomized, double-blind, placebo-controlled trials of chronic periodontitis) suggested that the use of probiotics in addition to traditional scaling and root planning helped increase the magnitude of improvement in periodontal damage indicators, such as periodontal probing depth and clinical attachment level attachment level). Note 1

The underlying mechanism may be related to the production of antibacterial compounds by probiotics, improving the epithelial barrier, and inhibiting the adhesion and growth of harmful bacteria

*Conclusion: Adjuvant probiotic therapy can bring additional benefits to improve periodontitis, but is limited by possible bias and heterogeneity, and more high-quality randomized clinical trials are still needed for further verification.

  1. Probiotics are beneficial for blood pressure regulation

Like smoking, diabetes, and dyslipidemia, hypertension is an important risk factor for cardiovascular disease, and about 30% of deaths worldwide are caused by cardiovascular disease

In most countries, 15% to 30% of adults and more than 50% of the elderly suffer from hypertension, which is also a serious public health problem.

A meta-analysis (9 randomized controlled trials, 543 participants) showed that daily consumption of probiotics helped improve blood pressure (systolic blood pressure -3.3 mm Hg diastolic blood pressure -1.4 mm Hg), and was most pronounced in subjects with a period of use for more than 8 weeks, multiple strains, blood pressure greater than 130/85 mm Hg, and daily doses greater than 10 billion colony forming units. Note 1

The underlying mechanism may be related to the improvement of blood cholesterol, lowering blood sugar levels and insulin resistance, and regulating the renin-angiotensin system of probiotics

*Conclusion: Daily regular intake of probiotics may have a positive effect on blood pressure regulation

  1. Probiotics reduce the incidence of allergies and atopic physique in children

The term atopy refers to the phenomenon that individuals or families are prone to produce immunoglobulin E (IgE) antibodies to environmental predisposing factors (such as pollen, house dust mites and food allergens) due to genetic predisposition.

Atopic physique is often related to atopic dermatitis, asthma, allergic rhinitis, hay fever and food allergies.

A systematic literature review and meta-analysis (17 randomized controlled trials, 2947 participants) showed that continuous use of probiotics before and after natal (referring to pregnancy, lactation, and children under 1 year of age) helped reduce the risk of idiosyncratic reactions (atopy) and food allergies in young children. Note 1

*Conclusion: Continuous supplementation of probiotics before and after childbirth can help reduce the incidence of atopic physique and food allergies in young children, but more long-term studies are needed to confirm the best strains, doses, and treatment time

  1. Probiotics are beneficial for postoperative wound infections

With the rapid development of surgical skills, postoperative wound infection is still a major issue, accounting for 38% of all hospital infections.

Infection at the surgical site not only increases the number of extra days of hospitalization by 7 to 10 days, but also increases the risk of death by 2 to 11 times.

A meta-analysis (28 studies, 2511 participants) found that the use of probiotics during gastrointestinal surgery reduced the incidence of postoperative infections (including respiratory, urinary tract and wound infections) compared with placebo or control. Note 1

In addition, the hospitalization period and antibiotic treatment time of the probiotic group were also shorter than those of the control group.

Another meta-analysis (4 studies, 246 participants) pointed out that probiotics can reduce infection events (intra-abdominal and urinary tract infections) after liver replacement surgery, but also reduce intensive care unit stays and antibiotic use. Note 2

*Conclusion: Oral probiotics during surgery can reduce postoperative infection events and reduce the length of stay in hospital

  1. Probiotics are good for irritable bowel syndrome

Irritable bowel disorder is a common functional gastrointestinal disease, with a prevalence rate of 11.2% of the population, mainly characterized by abdominal distension, abdominal pain, abnormal bowel movements and changes in frequency (constipation and diarrhea), although the exact causative factors are still unknown, but may be related to chronic mucositis, changes in intestinal epithelial cells and immune function, and visceral hypersensitivity caused by changes in intestinal flora.

A meta-analysis (including 21 studies of irritable bowel disorder) suggests that probiotic supplementation is an effective therapy for patients, with significant effects in small doses of single strains and short periods of time (as measured by overall symptom response and quality of life). Note 1

*Conclusion: The use of probiotics may help to improve irritable bowel syndrome, but more studies are still needed to confirm the effective strains, dosages and required treatment period

  1. Probiotics improve high cholesterol

Hypercholesterolemia is the metabolic abnormality with the highest prevalence in adults. The causes are mainly related to poor eating habits, obesity, inactivity, and smoking. It is the main cause of atherosclerosis and cardiovascular diseases.

A literature review and integrated analysis (Meta-Analysis, including 15 randomized controlled trials with 976 participants) also pointed out that oral administration of Lactobacillus probiotics, especially L. reuteri and L. plantarm strains, has reduced Effects of total cholesterol and low-density lipoprotein cholesterol.

In addition, subgroup analysis of the same study also found that the intake of related foods containing Synbiotics (synbiotics, a mixture of probiotics and prebiotics) had the effect of improving HDL cholesterol and triglycerides. Note 1

The underlying mechanism may be related to the cholesterol assimilation effect of probiotics, the binding of cholesterol to cell membranes, the destruction of cholesterol particles and the dissociation properties of bile salts

*Conclusion: Oral probiotics have the effect of regulating cholesterol, but considering the high heterogeneity and possible deviations of the included studies, more large studies still need to confirm

  1. Probiotics are good for colorectal cancer

Colorectal cancer is the third most mortal cancer in both men and women, after prostate cancer and lung cancer, and it is estimated that about one million new cases are diagnosed worldwide every year. Note 2

Surgery is the most common basic treatment for colorectal cancer, but preoperative preparation strategies and surgical trauma often disrupt the balance of intestinal microorganisms and barrier function, resulting in immunosuppression and increased postoperative infection.

A meta-analysis (17 studies, 1242 participants) pointed out that the use of probiotics after colorectal cancer surgery has the effect of protecting the intestinal mucosa (physical and biological barriers), but the strain and duration need to be confirmed. Note 1

*Conclusion: Probiotics can protect the intestinal mucosa and biological barrier for patients with colorectal cancer after surgery

  1. Probiotics are beneficial to diabetes and blood sugar control

Diabetes is caused by the inability to produce enough insulin or poor insulin action, resulting in abnormal blood sugar levels. According to estimates by the World Health Organization, by 2030, nearly 400 million people worldwide will suffer from this disease

Diabetes is not a terminal illness, but the terrible thing is that the condition is not properly controlled, leading to long-term high blood sugar. The consequence is serious damage to the blood vessel and nervous system, nephropathy, cardiovascular disease, retinopathy, etc., which greatly reduces the quality of life.

A meta-analysis (12 studies, 770 participants) pointed out that taking probiotics has potential effects on regulating blood sugar (fasting blood glucose and insulin) and lowering blood lipids (triglycerides and total cholesterol), with multiple strains and subjects used for more than 8 weeks being the most significant. Note 1

The author believes that the underlying mechanism is related to the activation of insulin by probiotics and the inhibition of cholesterol absorption.

  1. Probiotics increase Helicobacter pylori eradication rate

Helicobacter pylori is a gram-negative bacterium that colonizes the gastric mucosa. If it is not treated for a long time, it can easily cause chronic gastritis, peptic ulcer, gastric adenocarcinoma and other gastrointestinal diseases. Note 1

The current conventional therapy to eradicate this bacteria is triple therapy, including hydrogen ion pump blocker and two antibiotics. However, due to the development of drug resistance, the eradication failure rate is often between 10% and 45%.

A meta-analysis (30 randomized controlled trials) found that the combination of probiotics and Helicobacter pylori (triple therapy) helped increase eradication rates by 13.8% and reduce a variety of treatment-related side effects (including nausea, vomiting, epigastric pain and diarrhoea).Note 2

The underlying mechanism is related to the regulation of immune response by probiotics, improvement of intestinal barrier function, stimulation of mucus secretion, and inhibition of bacterial adhesion to epithelial cells.

  1. Probiotics are good for oral hygiene

Oral hygiene is the most frequently neglected health problem in daily life. Once neglected, it often becomes an important threshold of “disease in the mouth”

Oral diseases can rarely cause bleeding gums, periodontal disease, and tooth loss, but according to research, these diseases not only affect appearance, cause bad breath, but also greatly increase the risk of cognitive impairment and dementia. Note 2

This is because periodontal disease and missing teeth will increase the bacteria in the oral cavity and induce pro-inflammatory reactions through blood circulation.

A systematic review has shown that probiotics help reduce the number of caries pathogens (CFU counts). Regarding periodontal disease, the literature also points to the effect of improving the detection of bleeding, depth of detection, and gum index. Note 1

However, the author mentioned that due to the diverse pathogenic factors of oral diseases, reducing the number of colonies does not guarantee complete control of the disease, so more accurate experiments are needed to confirm the effective strain, dosage and treatment time.

  1. Probiotics improve functional constipation/also known as habitual constipation

Functional constipation is the most common form of constipation in adults and young children. It refers to primary persistent constipation caused by non-organ diseases. It is estimated that the prevalence rate exceeds 14%.

Common treatments for constipation include fiber supplements, laxatives, and stool softeners. However, due to the many causes of constipation, about 47% of patients have doubts about the effect and safety.

A systematic review (14 studies with 1182 participants) and meta-analysis suggest that the use of probiotics helps improve overall gut transit time, stool frequency, and stool consistency in patients with functional constipation. Among them, B. Lactis strains are most effective.Note 17

However, the authors note that some results remain at risk of heterogeneity and bias, so further confirmation by more studies is needed.

  1. Probiotics improve diarrhea caused by antibiotics

Antibiotic-associated diarrhea (AAD) is defined as antibiotic-related diarrhea of unknown cause (ranging in prevalence from 5% to 49%) that occurs within two months of exposure to antibiotics, with disruption of gastrointestinal microbiota and mucosal integrity, pathogen overgrowth, and metabolic imbalance thought to be the main mechanisms of pathogenesis.

Extended-spectrum β-lactamases, glycopeptides, and fluoroquinolones antibiotics that act on anaerobic bacteria are often associated with this disease.

A systematic literature review and meta-analysis (36 randomized placebo-controlled trials with 9312 participants) noted that oral probiotics reduced the incidence of antibiotic-associated diarrhoea. Note 1

Further subgroup analyses showed that protection remained significant when grouped by reason for antibiotic treatment, duration of probiotics, amount of probiotics, and time from antibiotic to probiotic.

*Conclusion: Probiotics may provide positive help in adults with antibiotic-associated diarrhea, but due to the heterogeneity of the samples included, more studies are needed to further confirm the optimal dose, strain, and duration.

  1. Probiotics are beneficial for attention deficit hyperactivity disorder and Asperger’s disease

ADHD and Asperger’s syndrome are common physical and mental symptoms that occur in childhood.

ADHD often shows symptoms such as inability to concentrate, lack of self-control, difficulty obeying others’ instructions, and excessive activity, causing parental distress, and traditional medicine generally believes that symptoms will improve when they grow up, but in fact, nearly thirty percent of children in adulthood although the symptoms of hyperactivity improve, but there is a lack of attention, which in turn leads to interpersonal, work, and even marriage problems

Asperger’s syndrome is considered a specific type of autism, and unlike autism, Asperger patients are usually of normal intelligence, close to par language skills (some are even highly gifted in some areas, such as music and mathematics), but lack social skills and empathy.

According to a preliminary clinical control observation, pregnant women in the experimental group who took the probiotic Lactobacillus GG during pregnancy (continued until breast milk) did not have ADHD and Asperger’s syndrome

However, 17% of children in the placebo group developed ADHD and Asperger’s syndrome, so the study preliminarily concluded that probiotics in pregnant women and infants after birth can help reduce the incidence of these two physical and mental symptoms. Note 15

  1. Probiotics are beneficial for acute diarrhea in children

Acute Diarrhea in Children is the second most common disease after respiratory infections, defined as more than three loose or watery stools in 24 hours and a course of less than two weeks. It is caused by a variety of factors and multiple pathogens.

Diarrhea is characterized by increased frequency and consistency, often accompanied by fever, vomiting, and electrolyte and pH imbalances.

Viruses (mainly rotavirus) and bacteria (pathogenic Escherichia coli, salmonella, Staphylococcus aureus…) are the most common causes of acute diarrhoea, related to environmental and hygiene conditions and unsafe drinking water supply, other causative factors include: intestinal bacterial disorders due to excessive antibiotic use, allergies, improper diet, poor air quality and climatic factors.

A systematic literature review and meta-analysis (84 randomized controlled trials, 13,443 children with acute diarrhoea) noted that certain single strains (including Saccharomyces boulardii, Lactobacillus rhamnosus GG, Lactobacillus reuteri, Bifidobacterium lactis, E. coli neesonii 1917) and multiple strains of probiotics were helpful in treating acute diarrhea in children compared with placebo or no treatment. Note 1

In addition, Saccharomyces boulardii may be the most effective probiotic for the treatment of acute diarrhea in children, and Bifidobacterium lactis is also promising.

*Conclusion: Probiotics may provide positive help in children with acute diarrhoea, but further validation is needed due to possible publication bias and heterogeneity

  1. Probiotics are beneficial for COVID-19

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2, also known as novel coronavirus), has become a global health problem.

In the process of development, the new coronavirus mutates into Alpha, Beta, Gamma, Delta, Omicron, Lambda, Mu and other variants, 60% of infected people recover without hospitalization after 28 days, and some patients still have various symptoms after 3 to 12 weeks, the so-called long COVID syndrome.

A systematic literature review and meta-analysis (7 clinical trials and 2 cohort studies) noted that probiotics as adjunctive therapy significantly reduced symptoms (51% improvement) in patients with COVID-19, with cough, headache, and diarrhoea most prominently improved. Note 1

*Conclusion: For the adjuvant treatment of COVID-19, probiotic supplementation may bring positive help, but limited by the small sample size, more studies are needed to confirm the effect of probiotic strain type and dose.

  1. Probiotics are beneficial for blood lipid regulation

Dyslipidemia is a chronic metabolic disorder characterized by elevated levels of triglycerides, total cholesterol, and low-density lipoprotein cholesterol, and decreased levels of high-density lipoprotein cholesterol.

Patients with dyslipidemia have an increased risk of coronary heart disease, stroke, non-alcoholic fatty liver, diabetes and even death, and some diseases can also affect blood lipid levels, such as diabetes, hypothyroidism, Cushing’s disease….

A systematic literature review and meta-analysis (including 38 randomized controlled trials) suggested that probiotic supplementation helped reduce total cholesterol, triglycerides, and low-density lipoprotein cholesterol levels , but had no significant effect on high-density lipoprotein cholesterol levels. Note 1

*Conclusion: Probiotic supplementation may have a positive effect on lipid regulation, but due to the heterogeneity of the studies included, more high-quality studies are needed to confirm the optimal strain.

  1. Probiotics are beneficial for postoperative intestinal obstruction

Postoperative ileus/POI, defined as a transient cessation of coordinated bowel movements, is a common cause of delayed return to normal bowel function after abdominal surgery (e.g., colorectal and gynaecological surgery), occurring in 10% to 15% of cases.

Delayed bowel movements associated with POI can lead to vomiting, bloating, and food intolerance, while POI often leads to invasive interventions, such as nasogastric tube insertion, and increased length of hospital stay (LOS) and treatment-related costs.

A systematic literature review and meta-analysis (21 randomized controlled trials, 1776 patients with gastrointestinal cancer) pointed out that perioperative supplementation with probiotics or synbiotics was effective in promoting the recovery of gastrointestinal function after gastrointestinal cancer surgery compared with the control group, including shortening the time to first exhaust, time to first bowel movement, days to first solid diet, days to first liquid diet, and length of postoperative hospital stay, and reducing the incidence of postoperative abdominal distension and postoperative intestinal obstruction. Note 1

*Conclusion: Probiotics may have a positive effect on postoperative gastrointestinal recovery, but due to the small sample size and heterogeneity between studies, more high-quality, large-sample studies are still needed to confirm the optimal course and dose.

  1. Probiotics reduce the occurrence of gastroesophageal reflux (spitting up milk) in infants

Gastroesophageal reflux is generally defined as the retrograde passage of gastric contents into the esophagus with or without vomiting, rare episodes of reflux are usually physiological, especially in infants, and most episodes are transient and do not cause symptoms or complications.

Epidemiological studies have shown that gastroesophageal reflux occurs in about 50% of infants younger than 2 months, 60% to 70% of infants aged 3 to 4 months, and 5% of infants aged 12 months. The male-to-female ratio is about 2:1, and about 25% of infants regurgitate four or more times a day.

A systematic literature review and meta-analysis (6 randomised controlled trials, involving 736 infants and 67 women) noted that supplementation with probiotics (Lactobacillus reuteri DSM 17938 or the original strain Lactobacillus reuteri ATCC 55730) helped reduce reflux rates in infants compared with placebo. Note 1

*Conclusion: For infant gastroesophageal reflux, the use of probiotics may be a non-invasive, safe, cost-effective and prophylactic aggressive strategy, but due to the small sample size and heterogeneity between studies, more studies are needed to further verify the efficacy of different strains and doses.

  1. Probiotics are beneficial for early-onset caries in children

Dental caries is the most common chronic infectious disease in childhood and is caused by the interaction of bacteria (mainly Streptococcus mutans) and sugary foods on tooth enamel (prevalence is higher in children aged 3 years, from 36% to 85% in the Far East).

Early tooth loss caused by tooth decay is associated with stunted growth, language development disorders, absenteeism or inability to concentrate at school, and decreased self-esteem.

A systematic literature review and meta-analysis (9 randomized controlled trials involving 2363 preschoolers) pointed out that the preventive effect of probiotic supplementation on early childhood caries was statistically significant, although not large. Note 1

*Conclusion: Probiotics may bring positive help to the prevention of early childhood caries, but due to the bias and heterogeneity of samples, more long-term trials are needed to verify their clinical benefits.

  1. Probiotics are beneficial for immune function

Human beings live in a world where pathogenic and non-pathogenic microorganisms coexist, containing a large number of toxic or allergenic substances that threaten normal homeostasis.

They challenge the host through a very broad range of pathogenic mechanisms. Therefore, the immune system uses a complex set of protective mechanisms to control and eliminate these microorganisms and toxins.

A systematic literature review and meta-analysis (18 randomized placebo-controlled trials with 1,047 participants) showed that oral probiotics (strain: Lactobacillus plantarum/Lactobacillus plantarum) increased IL-10 (interleukin-10) levels and reduced IL-4 (interleukin-4), IFN-γ (interferon) and TNF-α (tumor necrosis factor) levels. Note 2

*Conclusion: Lactobacillus plantarum can promote host immunity by modulating pro-inflammatory and anti-inflammatory cytokines, but more studies are needed to verify due to the heterogeneity of the samples included.

  1. Probiotics are beneficial for infantile colic

Infantile colic is a common condition in infants and young children, defined as episodes of irritability, irritability, or crying lasting more than 3 hours a day, at least 3 days a week for 3 weeks or more (incidence of about 20%), often causing parents to be exhausted, nervous, anxious, and depressed.

Possible causes include allergy to cow’s milk proteins, excess gas in the gut, dysbacteriosis of the gut, maternal smoking, and gastrointestinal inflammation. Infantile colic can begin as early as 2 weeks of age, usually peaks at 6 to 8 weeks, and resolves spontaneously by 3 to 4 months of age.

A systematic literature review and meta-analysis (32 randomized controlled trials, 2242 infants with colic) noted that the use of a patented strain (L reuteri DSM 17938) probiotic appears to be the most evidence-based intervention to reduce crying time in infants with colic. Note 1

*Conclusion: For infantile colic, the use of probiotics (L reuteri DSM 17938 strain) may provide positive help.

  1. Probiotics are beneficial for inflammatory bowel disease

Inflammatory bowel disease includes a group of gastrointestinal disorders (including Crohn’s disease and ulcerative colitis) characterized by recurrent inflammation, periods of relapse and remission, and epithelial injury.

The etiology is unknown, but there is evidence that immune dysregulation, environmental factors, and genetic polymorphisms are multifactorial causes of the disease, and dysregulation of the gut flora also plays a role in the initiation or continuation of intestinal inflammation.

A systematic literature review and meta-analysis (including 38 randomized controlled trials related to inflammatory bowel disease) suggested that supplementation with probiotics, prebiotics, and synbiotics reduced the disease activity index of ulcerative colitis and contributed to disease remission. In particular, formulations based on lactic acid bacteria and bifidobacteria or multiple strains are most effective (while daily doses exceeding tens of billions of CFU can be used as a reference range for use). Note 2

*Conclusion: The use of probiotic supplementation may provide positive help in inflammatory bowel disease, particularly ulcerative colitis, but further validation is needed due to the heterogeneity of the studies included.

  1. Probiotics are beneficial for celiac disease

Celiac disease is an autoimmune disease (prevalence of 0.5% to 1% of the general population) characterized by malabsorption or indigestion triggered by gluten intake (gluten is a general term for alcohol-soluble proteins found in various grains, including wheat, rye, barley)

The main symptoms are: stomach pain, gas, bloating, diarrhea, weight loss, anemia, edema, bone or joint pain.

Celiac disease can be associated with a variety of autoimmune and idiopathic diseases, including herpetiform dermatitis, type 1 diabetes, Hashimoto’s thyroiditis, alopecia areata, Edison’s disease, Sjogren’s syndrome, chromosomal disorders, neurological disorders, and liver autoimmune disorders (primary cholangitis, autoimmune hepatitis)

A systematic literature review and meta-analysis (randomized controlled trial, 5279 people with celiac disease) noted that oral probiotics improved gastrointestinal symptoms as assessed on the GI Symptoms Rating Scale. Note 1

In addition, when using different questionnaires, there was no difference in gastrointestinal symptoms after taking probiotics.

*Conclusion: Probiotics may be beneficial and considered safe in some patients with celiac disease, but more studies are needed to validate this due to small sample sizes and risk of bias of the included studies.

  1. Probiotics are beneficial for recurrent aphthous stomatitis

Recurrent aphthous ulcers (RAS) is one of the most common painful diseases of the oral mucosa, and the word “aphthous” is derived from the Greek word “aphtha”, which means ulcer.

Mainly divided into mild, severe and herpetiform ulcers, more than 85% of RAS manifests as mild ulcers less than 1 cm in diameter, healing without scarring

Severe ulcers, also known as Sutton’s disease or recurrent necrotic perimucosa, are >1 cm in diameter, last for weeks to months, and heal with scars

Herpetiform ulcers are clinically distinct in that they manifest as multiple clusters of ulcers scattered across the oral mucosa, which, despite the name, are not related to the herpes simplex virus.

A systematic literature review and meta-analysis (7 RCTs) suggested that probiotics alone may relieve oral pain but not ulcer severity. Note 1

In addition, the combination of probiotics and steroids or anesthetic antibacterial gels is more effective than steroids or anesthetic antibacterial gels alone, significantly reducing the severity of ulcers and reducing oral pain.

*Conclusion: For recurrent aphthous stomatitis, the use of probiotics may bring positive help, but due to the small sample size and heterogeneity, more studies are needed to further validate.

  1. Probiotics are good for sleep quality

Sleep plays a vital role in brain function and system physiology of many body systems.

Sleep problems are common, including insufficient quantity and quality of sleep, and sleep problems that affect sleep continuity are collectively referred to as sleep disruption.

Short-term consequences of disrupted sleep include increased stress response, somatic pain, decreased quality of life, emotional distress and mood disorders, cognitive, memory, and performance disturbances.

A systematic literature review and meta-analysis (14 randomized controlled trials) suggested that probiotic/paraprobiotic intake improved subjective sleep quality (as measured using the Pittsburgh Sleep Quality Index), but had no significant effect on response to other subjective sleep scales, nor did it affect sleep efficiency and sleep latency. Note 2

*Conclusion: Current evidence does not support the use of probiotics to improve sleep status, and more studies are needed to further validate.

  1. Probiotics prevent diarrhea caused by radiotherapy and chemotherapy

Chemoradiotherapy-induced diarrhea is a common problem, especially in patients with advanced cancer, mainly caused by an imbalance in the absorption and secretion of the small intestine due to acute damage to the intestinal mucosa.

It occurs in 50% to 80% (CTC grade 3 to 5 accounts for more than 30%), and commonly used treatments for diarrhea include 5-fluorouracil (5-FU), capecitabine, and irinotecan (CPT-11).

This type of diarrhoea can lead to fluid and electrolyte depletion, malnutrition, dehydration, and hospitalization. In addition, diarrhea may interfere with and reduce cancer treatment by delaying or reducing doses, which may affect patient survival.

A systematic literature review, meta-analysis (23 randomized placebo-controlled studies involving 2570 patients with abdominal or pelvic cancer), noted that compared with placebo, probiotics could reduce radiochemotherapy-induced diarrhoea, especially the incidence of diarrhoea grade ≥ grade 3 and ≥ 2, but not the incidence of grade ≤ grade 2 diarrhea (as measured by the toxicity criterion of CTC treatment). Note 1

*Conclusion: The use of probiotics in patients with abdominal or pelvic cancer may prevent radiochemotherapy-induced diarrhoea, particularly severe diarrhoea, but limited by the heterogeneity of the studies included, more studies are needed to confirm optimal use.

  1. Probiotics are beneficial for Alzheimer’s disease

Alzheimer disease, the most common cause of dementia, is observed in brain tissue with deposition of fine amyloid and hyperphosphorylation of tau (a microtubule-assembled protein that accumulates inside cells and manifests as neurofibrillary tangles).

Other changes include reactive microglia proliferation and extensive loss of neurons, white matter, and synapses.

According to the age of onset, Alzheimer’s disease is divided into early-onset Alzheimer’s disease (EOAD, age of onset< 65 years) accounts for 1% to 5% of all cases, and late-onset Alzheimer’s disease (LOAD, age of onset≥65 years) accounts for 95% of the affected population, and the annual global healthcare cost is estimated to be as high as 172 billion US dollars.

A systematic literature review and meta-analysis (3 randomized controlled trials involving 161 elderly Alzheimer’s patients) noted that supplementation with probiotics (lactic acid bacteria and bifidobacteria) failed to improve cognitive function. Note 1

However, supplementation with probiotics can improve plasma triglycerides, very low-density lipoprotein cholesterol, insulin resistance, and plasma malondialdehyde.

*Conclusion: To date, there is no clear evidence to support the use of probiotics to improve Alzheimer’s disease.

Are there any side effects of probiotics?

General bacteria to be selected probiotics, must undergo rigorous testing, confirm safety, in order to become beneficial probiotics, so for most people, probiotics safety is very high, but at the beginning of taking may accelerate intestinal peristalsis, temporary exhaust or bloating, which is mostly a normal reaction. Note 1

To reduce the likelihood of side effects, start with a low dose initially and slowly increase to the full dose over a few weeks, which can help the body adapt.

If gas, bloating, or any other side effects persist for more than a few weeks, stop taking probiotics immediately and consult a professional doctor.

In addition, side effects of constipation and thirst have been reported from taking yeast-based probiotics.

Probiotic safety precautions

1. Patients with immunocompromised, intravenous catheters, recent surgery, acute pancreatitis or critical illness who want to use probiotics should discuss with their doctor first to avoid unknown side effects (such as infection)

2. Patients with Small intestine bacterial overgrowth (SIBO) should consult a doctor before use, as symptoms may worsen

3. Some probiotic-rich foods, such as yogurt, sauerkraut, and kimchi, contain biogenic amines (histamine, tyramine, tryptamine, and phenylethylamine) that may induce headaches in people who are sensitive to the substance, and if probiotic-rich foods trigger such symptoms, probiotic supplements may be a better option

4. Histamine intolerance should avoid using probiotics containing the following strains, such as: Lactobacillus buchneri, Lactobacillus helveticus, Lactobacillus hilgardii, Streptococcus thermophilus (Streptococcus lactis thermophilus), as these strains produce histamine in the digestive tract

5. Some probiotic supplements contain possible allergens (yeast, dairy, eggs, or soy), lactose, or prebiotics (lactulose, inulin, oligosaccharide), which may cause adverse reactions in people with allergies or intolerances