Probiotics have become the new health craze and many people are embracing these friendly bacteria to enhance their overall well-being.

However, have you ever wondered if the probiotics you consume are actually alive and active? One way to test their viability is through the “probiotic milk test”. It is a straightforward and convenient home test.

But here is the question: Does this test really live up to its claims?

Let’s find out.

What is the Milk Test?

The milk test is a simple, at-home test to determine the viability of a probiotic product. The test only requires cold milk, a glass, and a probiotic supplement.

How to perform the milk test

Step 1: Pour half a cup of cold milk into a glass. 

Step 2: Take two probiotic capsules and open those into the milk.

Step 3: Stir up and let it sit for 48 hrs at room temperature.

Interpreting the result

If the milk curdles after two days, the probiotic is considered viable.

How does the milk test work?

The proteins in milk are sensitive to changes. Naturally, the proteins in milk float around freely and repel each other. 

When the pH of milk is lowered(acidic), the proteins become more negatively charged and are attracted to each other, causing them to clump and form curds.

Probiotic bacteria like Lactobacillus can ferment lactose (the sugar in milk) to produce lactic acid and make the milk acidic.

Is the milk test reliable?

My patients often ask me if the milk test is really an effective way to test the quality of the bacteria in probiotic supplements at home.

The answer is no.

Though the test can be performed easily at home, it is not a reliable way to decide whether probiotics are active.

Three reasons why the milk test can be wrong

• Not all probiotic bacteria can cause milk curdling

The probiotic bacteria from the genus Lactobacillus are unique in their ability to convert lactose to lactic acid in the production of natural yogurt. Their milk fermentation occurs under normal conditions. 

On the other hand, Bifidobacterium can only do this conversion when little oxygen is present and therefore frequently fails the milk test.

• Chymosin in probiotic products can cause misleading results

Chymosin is an enzyme that can cause milk curdling. It is often added to probiotic products because it will help the product to curdle milk more quickly.

• Probiotics need to be released from the capsules and exposed to milk

The milk test is also invalid when you use micro-encapsulated or enteric-coated forms, designed for better survival of probiotics in the harsh acidic environment of the stomach.

It is unlikely that these probiotics can interact with the lactose in the milk because the milk is not acidic enough to activate the probiotics by breaking down the protective coating, resulting in a failed milk test.

Which test can reliably tell the viability of probiotics?

A reliable method to scrutinize the viability and effectiveness of a probiotic is through microbiological lab testing.

Microbiological lab testing

Microbiologists intubate probiotics on culture media and determine the number of viable organisms by the resulting growth of bacterial colonies. The test also stipulates the probiotics in the product and detects any contamination with chemicals or harmful microbes.

Bottom line

While the milk test may offer some insight into microbial activity, it is not entirely dependable as it only applies to certain probiotics. For accurate measurement of probiotic viability, laboratory testing is the recommended approach. 

Another straightforward method is to observe the signs of probiotic effectiveness. 

To ensure that you consume viable and efficacious probiotics, it is crucial to select a top-notch probiotic supplement with the guidance of your healthcare provider.