Probiotics: The Science Behind Good Bacteria

Probiotics are often found in fermented foods, but not all fermented foods contain probiotics. Probiotics are very specific microorganisms that have been scientifically studied for their health benefits and are considered "good bacteria".

Microorganisms have been used in food since the beginning of human civilization. In one way or another, fermented foods are present in almost all cultures worldwide.¹ Probiotics are among them.

What are probiotics?

The FAO and WHO have defined probiotics as ‘live microorganisms which when administered in adequate amounts confer a health benefit on the host’.² Basically, this means that probiotics must be alive (living bacteria or yeasts) in a certain quantity at the moment of consumption.

This also implicitly means that probiotics are considered safe for consumption. As with any other food component, probiotics are assessed for consumption safety, with extra measurements taken for vulnerable groups like babies. Clinical trials must also be conducted with a probiotic strain to prove it has health benefits.³

Today, probiotics are present in various forms in the market, ranging from food supplements to foods like dairy, plant-based products, and juices.

How many probiotics do you need?

The quantities of probiotics often come in very large numbers: 1 billion, 10 billion, 20 billion, 50 billion and the list goes on.

It is generally accepted by the scientific community that at least one billion microorganisms per day will have probiotic effects—less than this amount is also possible, but only if backed by clinical results.⁴

But is a higher number really better?

Not necessarily. Probiotic strains that have been clinically proven to have health benefits could have more of an effect in the dose studied compared to higher doses of a strain that has not been clinically studied.⁵

Good bacteria vs. bad bacteria

Because probiotics offer health benefits, they are sometimes called “good bacteria”. This is, of course, a simplification of reality. Bacteria belong to a vast family of organisms and can be found almost everywhere on Earth, including in humans. It is estimated that our planet is inhabited by trillions of different species of microorganisms (i.e. one million million!), and less than 1% are human pathogens.^6,7 So, in fact, there are a lot of “good guys” if this expression is used to describe the bacteria that are not harmful to human health.

Probiotics health benefits

Probiotics are being studied in a broad variety of fields, from oral health and dermatology to gastrointestinal conditions and immune functions and even psychological features such as mood.⁸ The species generally studied belong to Bifidobacterium and Lactobacillus.⁹ However, the level of evidence for the uses of probiotics can vary significantly, with some benefits more accepted than others. Some of the more commonly agreed benefits of probiotics include the following:

1. Improving Lactose Digestion. The yoghurt symbiosis (Lactobacillus delbruekii subsp. bulgaricus and Streptococcus thermophilus) can improve lactose digestion in people with lactose maldigestion. This benefit has been recognized by the European regulatory agency.¹⁰ 
2. Gut Health. There is more and more science studying how specific probiotic strains can help to support a healthy gastrointestinal tract.⁴ Also, there is active research on how they interact with the body’s microbiota, the community of bacteria living in the gut.^11,12
3. Immune System. Similarly, studies have also explored the role of probiotics in supporting a healthy immune system, although this benefit seems to be more strain-specific than others.³
4. Mood. Although early in research, scientific findings indicate probiotics could positively impact mood through the gut-brain connection.^13,14