May 26, 2020

All about prebiotics and probiotics

Even though the terms "prebiotics" and "probiotics" sound similar, they are quite different things. Below, we will look at these differences in more detail and how these ingredients can promote overall health. Before beginning these considerations, it's important to know that the large intestine is home to trillions of bacteria from over 500 different species, some of which are good for your health. Bacteria such as Lactobacillus, Bifidus and Acidophilus have a wide range of functions, from improving immune function to synthesizing some vitamins.

What are prebiotics and probiotics?

Prebiotics are certain forms of fiber that cannot be digested by the gut. Instead, they are digested by bacteria that live in the large intestine. As a result, prebiotics provide a food source that promotes the growth of these good bacteria.

Probiotics are live bacteria that are consumed to increase the amount of natural bacteria already living in the digestive tract. Probiotics can be consumed in the form of fermented foods or supplements, among others (1). They promote a healthy balance of gut flora and are associated with a range of health benefits.

Where do prebiotics and probiotics come from?

As mentioned earlier, prebiotics are forms of dietary fiber found in higher amounts in foods such as garlic, leeks, onions, asparagus and whole wheat. The best known source of probiotics is fermented dairy products such as yogurt. However, live probiotics can be added to many foods and supplements.

Benefits of prebiotics and probiotics

Both prebiotics and probiotics help to increase the number of good bacteria living in the digestive tract and improve their health. This results in some potential health benefits. These health benefits include weight loss support, better digestion, improved immune system function and many more, which we will discuss in detail later (2, 3).

These health benefits are thought to be the result of probiotics' ability to restore the natural balance of gut bacteria, also known as gut flora (4). An imbalance in this case means that there are too many bad bacteria and not enough healthy bacteria in the gut, which can be the result of illness, taking medications such as antibiotics, a poor diet and other reasons.

Consequences of this can include problems with the digestive system, allergies, mental health issues, obesity and more (5).

Other benefits of probiotics are that they can prevent a whole range of diseases and even cancer. It has been theorized that increasing the number of good bacteria could reduce the number of bacteria that are a contributing factor to the development of colon cancer. A clinical study has shown that the consumption of probiotics was able to reduce the likelihood of occurrence and severity of respiratory infections such as colds and flu in children.

The main health benefits of probiotics and the scientific evidence at a glance

Probiotics can help prevent or treat diarrhea

Probiotics are known for their ability to prevent diarrhea or reduce the severity of diarrhea. Diarrhea is a common side effect of antibiotics, which is due to the fact that antibiotics can disrupt the balance of good and bad bacteria in the gut (6).

Several studies suggest that the use of probiotics results in a reduced risk of antibiotic treatment-related diarrhea (7, 8, 9). One study found that taking probiotics reduced the incidence of antibiotic-related diarrhea by 42% (10).

However, probiotics can also help with other forms of diarrhea that are not associated with antibiotic use. A large study review of 35 scientific studies found that certain strains of probiotics can reduce the duration of infectious diarrhea by an average of 25 hours (11). Probiotics were found to reduce the risk of traveler's diarrhea by 8%. They also reduced the risk of diarrhea from other causes by 57% in children and 6% in adults (12).

The effectiveness varies depending on the type and dose of probiotics used (13). Strains such as Lactobacillus Rhamnosus, Lactobacillus Casei and the yeast Saccharomyces Boulardii are most commonly associated with a reduced risk of diarrhea (9, 12).

Summary: Probiotics can reduce the risk and severity of different types of diarrhea.

Probiotic supplements can lead to improvement in some mental illnesses

An increasing number of studies link gut health to mental health (14). Both animal and human studies have concluded that probiotic supplements can improve some mental disorders (15).

A review of 15 human studies found that supplementation with Bifidobacterium and Lactobacillus strains for 1 to 2 months can relieve anxiety, depression, autism, obsessive-compulsive disorder and memory impairment (15).

One study observed chemical workers over a period of 6 weeks. Those who consumed 100 grams of probiotic yogurt per day or took a probiotic in capsule form experienced benefits in terms of general health, as well as relief from depression, anxiety and stress (16).

Benefits were also observed in a study conducted with 40 subjects suffering from depression. Taking a probiotic supplement for 8 weeks reduced the severity of depression and lowered levels of C-reactive proteins (a marker of inflammation) and hormones such as insulin (17).

Summary: Scientific research shows that taking probiotics could help alleviate symptoms of mental disorders such as depression, anxiety, stress and memory problems.

Certain probiotic strains can help keep the heart healthy

Probiotics may help keep the heart healthy by lowering levels of "bad" LDL cholesterol and blood pressure. Certain lactic acid-producing bacteria can lower cholesterol levels by breaking down bile acid in the digestive tract (18).

Bile acid - a naturally occurring fluid consisting largely of cholesterol - aids digestion. By breaking down bile acid, probiotics can prevent it from being absorbed in the digestive tract, from where it enters the bloodstream as cholesterol (19).

A review of 5 studies found that consuming probiotic yogurt for 2 to 8 weeks lowered total cholesterol levels by 4% and LDL cholesterol levels by 5% (20).

Another study of 6 months duration found no changes in total cholesterol levels or LDL cholesterol levels, but the scientists were able to observe small increases in the levels of "good" HDL cholesterol (21).

The consumption of probiotics could also lower blood pressure. A review of 9 studies concluded that probiotic supplements could lower blood pressure, albeit only slightly (22). To benefit from blood pressure benefits, supplementation had to exceed a duration of 8 weeks and a daily dose of 10 million CFUs (22).

Summary: Probiotic supplements may protect the heart by lowering levels of "bad" LDL cholesterol and modestly lowering blood pressure.

Probiotics may reduce the severity of certain allergies and eczema

Certain probiotic strains may reduce the severity of eczema in infants and children. One study found that symptoms of eczema were reduced in infants who received probiotic-enriched milk compared to infants who received regular milk (23).

Another study examined children of women who had taken probiotics during pregnancy. These children had an 83% lower risk of developing eczema during the first two years of life (24).

The link between probiotics and reduced severity of eczema is still weak and further research is needed to confirm this link (25, 26).

Some probiotics could also reduce inflammatory reactions in people who suffer from an allergy to milk or dairy products. However, here too the evidence is weak and further research is needed (27).

Summary: Probiotics can reduce the risk and severity of certain allergies such as eczema in children. However, more studies are needed to definitively confirm this.

Probiotics can reduce the symptoms of certain digestive tract conditions

Over one million people in the US suffer from inflammatory bowel diseases such as ulcerative colitis and Crohn's disease (28). Certain types of probiotics from the Bifidobacterium and Lactobacillus strains have been shown to reduce the symptoms of the disease in people with mild ulcerative colitis (29).

Surprisingly, one study found that supplementation with the probiotic E. coli Nissle was as effective as a drug used for this purpose in maintaining relief in people with ulcerative colitis (30).

However, probiotics do not appear to have a significant effect in Crohn's disease (31). However, there is evidence that probiotics may have benefits in other bowel diseases. Early research suggests that they may reduce symptoms in irritable bowel disease (32).

Probiotics have also been shown to reduce the risk of severe necrotizing enterocolitis by 50%. This is a fatal intestinal disease that can occur in premature infants (33).

Summary: Probiotics may help reduce the symptoms of various intestinal diseases such as ulcerative colitis, irritable bowel disease and necrotizing enterocolitis.

Probiotics may help improve the function of the immune system

Probiotics may help boost your immune system and inhibit the growth of harmful gut bacteria (34). Some probiotics have also been shown to promote the production of natural antibodies in the body. They may also increase the activity of immune cells such as IgA-producing cells, T lymphocytes and natural killer cells (35, 36).

A large study review concluded that taking probiotics could reduce the risk and duration of respiratory tract infections. However, the quality of the evidence was low (37).

Another study of 570 children found that taking the strain Lactobacillus GG reduced the frequency and severity of respiratory tract infections by 17% (38).

The probiotic Lactobacillus Crispatus has also been shown to reduce the risk of urinary tract infections in women by 50% (39).

Summary: Probiotics may help to strengthen the immune system and protect against infections.

Probiotics may help lose weight and belly fat

Probiotics may support weight loss through a number of different mechanisms (49). For example, some probiotics prevent the absorption of dietary fat in the gut. This fat is excreted in the stool instead of being stored as body fat (41, 42).

Probiotics can also help you feel fuller for longer, burn more calories and store less fat. This is partly related to an increase in levels of certain hormones such as GLP-1 (43, 44).

But probiotics may also support weight loss directly. In one study, dieting women who took Lactobacillus Rhamnosus over a 3-month period lost 50% more weight than women who were given a placebo alone (45). Another study conducted with 210 subjects found that even low doses of Lactobacillus Gasseri resulted in an 8.5% reduction in abdominal fat over a 12-week period (46).

However, it is important to be aware that not all probiotics support weight loss. Some studies have surprisingly found that certain probiotics such as Lactobacillus Acidophilus can even lead to weight gain (47).

All in all, more studies are needed to better understand the link between probiotics and weight (48).

Summary: Certain probiotics may promote weight and fat loss, while others have been associated with weight gain.

Disadvantages and side effects

The side effects of consuming prebiotics are the same as those of a high-fiber diet. Not everyone tolerates a rapid increase in fiber intake well. Diarrhea, flatulence and other stomach problems can be the result. For this reason, it is important to increase the intake of prebiotics slowly. Probiotics are well tolerated by most people - just look at how many people eat yogurt regularly. It is therefore very safe and harmless to consume probiotics under normal circumstances. However, there is a small group of people who suffer side effects from probiotics. People with a severely compromised immune system can develop sepsis (bacteria entering the bloodstream) as a result of consuming probiotics. However, this is extremely unlikely in healthy people.

Recommended intake

The amount of fiber consumed daily from all sources combined (which includes probiotics) should be around 30 grams. However, it is important to remember to increase your fiber intake slowly to prevent digestive problems. The recommended dosage for probiotics is a little more complicated. One study showed that 100 million Lactobacillus bacteria per day were effective in preventing infections. However, the amount of bacteria you take is not so easy to determine as manufacturers do not always state this on the label. The timing of intake is not important with prebiotics and probiotics.

Prebiotics and probiotics sources

You can take probiotics in the form of a range of different foods or in the form of supplements.

Live probiotic cultures are often found in fermented dairy products such as yogurt and certain milk drinks. Fermented foods such as pickled vegetables, tempeh, miso, kefir, kimchi, sauerkraut and fermented soy products may also contain some lactic acid bacteria.

Alternatively, you can take probiotics in the form of tablets, capsules or powder, which contain these bacteria in dried form. Many supplements contain prebiotics, but their presence is not always obvious. Very rarely do manufacturers use the term prebiotics on the label. Instead, manufacturers usually state directly the prebiotics they use (e.g. inulin, fructooligosaccharides, etc.). If you are looking for prebiotics in supplements, you should therefore make sure that the product contains soluble fiber. Quite often so-called greens supplements contain prebiotics.

Fortunately, probiotics are somewhat easier to find. Supplement manufacturers quite often advertise the presence of probiotics and the types of bacteria they contain (e.g. Lactobacillus, Bifidus, etc.). Generally, the names of bacteria end with the syllable "-us". So if you see an ingredient with "-us" at the end, there is a good chance that it is a probiotic. So-called greens products are often good sources of probiotics. However, probiotics are sometimes also found in protein powders and other supplements.

Combinations with other supplements

Prebiotics and probiotics should be part of any balanced diet, regardless of goals and training status. For this reason, they combine well with any other supplement.

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