Probiotics — Health Benefits, Facts and Current Scientific Research

An adult human body contains approximately 2 kilograms of microbiome . Probiotic bacteria make up an important part of our microbiome. This means we carry beneficial bacteria weighing more than the brain. Probiotics are microorganisms naturally found in the digestive system that aid digestion and reduce inflammation . As probiotic use increases in Western societies, a recently published article suggests that we should examine the safety of probiotic supplements more closely.

What Is the Microbiota / Microbiome?

Every human consists of more than approximately 60 trillion cells. Around 30 trillion are human cells (3x10 to the power of 13). Around 30 trillion are microorganisms living in the human body (bacterial cells are approximately 10 times smaller than human cells, and viruses are much smaller still). Viruses, bacteria or fungi may make up these harmless microorganisms, known as the microbiome / microbiota / flora . They are found most densely in the gut, followed by the skin, mouth and vagina . The gut microbiota weighs approximately 2 kilos and is now considered an organ because of both its function and its weight. We continue to live in a mutually beneficial relationship with these microorganisms.

Probiotics for Health

Probiotics have a good safety record in generally healthy people. Side effects usually consist only of mild digestive complaints such as gas. On the other hand, their microorganisms may cause infections with adverse effects. People at high risk include surgical patients, sick infants and people with weakened immune systems.

Crohn's disease and most research on probiotics suggest that, for a group of inflammatory bowel diseases (IBD) including Crohn's disease, probiotics are a promising option . Today, however, live microorganisms are becoming a commercial product advertised as offering a wide variety of medical benefits.

Although there are several different classes and types of probiotics, the most common are:

• Bifidobacterium
• Lactobacillus
• Saccharomyces boulardii, a type of yeast

Probiotics are available as supplements in capsules, liquids and powders, and occur naturally in fermented foods with active live cultures, such as yogurt .

Foods containing probiotics include:

• Yogurt
• Traditional ayran
• Kefir
• Sauerkraut
• Brined olives
• Mozzarella cheese
• Cheddar cheese

Provided a person is not allergic to foods containing probiotics, including them in the diet to improve general health and support disease treatment is a relatively low-risk alternative to probiotic supplements.

The United States Food and Drug Administration (FDA) has not approved any probiotic to prevent or treat a health condition

Examples of fermented foods that are not probiotic:

• Beer
• Chocolate
• Bread yeast
• Soy sauce
• Wine

These and similar foods undergo additional processes that inactivate live cultures. Examples include cooking, filtering or pasteurization.

What Is a Prebiotic?

A person can also include prebiotic foods in their diet. These are food sources that feed bacteria in the digestive tract and promote their growth.

Prebiotic Foods

• Onion 
• Leek
• Asparagus

As probiotics and prebiotics become increasingly popular, a new study asks whether we know enough about their potential dangers. After reviewing the available literature, scientists discovered that adverse events associated with probiotic supplement use are often overlooked .

This comprehensive analysis of 384 randomized controlled trials found that probiotic-related side effects were not properly reported. In some cases, the studies did not even report harms. In fact, 28 percent gave no information on side effects, and only 2 percent properly recorded harm assessments. In summary, the authors believe that probiotics may not work the same way for everyone and that some types may not be safe.

Another recent study (10.04.2019) offers a critical perspective on the benefits of probiotics. Scientists from the St. Louis University School of Medicine in Washington investigated the behavior of an Escherichia coli strain in mice's intestines.

How Do Probiotics Change in the Gut?

Dantas and colleagues chose the probiotic E. coli Nissle 1917 because it is thought to have antidiarrheal properties.

They wanted to see how the bacterium behaved in mice's digestive tracts, so they used rodents with four types of gut microbiome:

• A microbiome with no preexisting bacteria
• An unhealthy microbiome
• A normal gut microbiome
• A normal gut microbiome treated with antibiotics

Dantas and colleagues fed the mice probiotics and different diets. They designed the diets as:

• A normal, high-fiber diet,
• A Western-style diet high in fat and sugar but low in fiber, and
• A Western-style diet that was also high in fiber.

After 5 weeks, the researchers analyzed the mice's microbiomes and found that the bacteria had acquired new characteristics. Under certain conditions, the bacterium could harm its host by eating the protective layer lining the intestines. Previous research has linked damage to this protective layer with irritable bowel syndrome. In this study, the probiotics appear to have evolved .

The new study's findings show that a probiotic beneficial to one person may harm another.

This is not a reason to avoid developing probiotic-based treatments. It is new information that can help us understand how they change and develop under different conditions.

The researchers therefore continued their work and designed a probiotic treatment for phenylketonuria, a metabolic disease that can cause brain damage.

In phenylketonuria, the body cannot break down a substance called phenylalanine. Its excessive accumulation causes neurological damage. Prof. Dantas and colleagues genetically modified the Nissle E. coli strain to enable phenylalanine digestion and excretion in urine.

Using a mouse model of phenylketonuria, the researchers found that phenylalanine levels fell by half the day after the genetically modified E. coli strain was given to the rodents.

Studies like these continue, and science keeps advancing. One of this article's main messages is that using probiotics with expert advice may be beneficial. Meanwhile, probiotics and prebiotics added to our diets through natural foods will help improve and develop the intestinal microflora.

Related Topic

- Probiotic Supplements May Reduce the Effectiveness of Immunotherapy