Do probiotics survive stomach acid?

Kathy Wheddon Nutritional Therapist DipION

If you are reading this, then the chances are that you have some concerns about whether or not the probiotics you are taking, or thinking of taking, survive to reach the gut alive. You may be confused as to whether spending money on probiotics is indeed an investment in your own good health, or if it is a waste of money. I'd say that this common concern about survival through stomach acidity is a very valid one, but if you read on, I hope to put your mind at rest that there are some effective, well tested and researched probiotics available on the market. Learn more about how to identify high quality probiotic supplements by reading the article: Researching probiotics online - how to identify quality content

In part, the concern over the survival of probiotics through the stomach has been perpetuated by one small study1 performed at University College London back in 2014, which tested 8 probiotic products and found that only one of the probiotics tested survived gut acidity and then flourished in the intestines. We reported on this study at the time, and for Health Professionals our write up can be found here.

So, if only certain probiotic strains are able to survive the harsh conditions of the stomach, whilst many don't, how can we tell the good from the bad, and spend our money wisely.

pH testing of strains

One way to be sure of the efficacy of probiotic supplements is to ensure that the strains of bacteria used undergo rigorous in-vitro pH testing2 whilst the product is still in its development stage.

This testing exposes the bacterial strains to different levels of acidity in a laboratory environment and shows the percentage of bacteria that survive at different pH levels. It gives a good indication as to how well the strains will fare in the acid environment of the stomach, and then on exposure to the bile acids in the upper portion of the GI tract.

Obviously the stomach is a challenging environment that exposes any probiotics taken to a low (acidic) pH; however, the exact pH changes constantly, dependent on the time of day and the presence or absence of food. It is recommended that our probiotics are taken with breakfast each day, as stomach acid is naturally at its weakest in the mornings, and this is then buffered (or diluted) still further by the presence of food in the stomach. Taking your probiotic supplements at this time of day offers you the greatest percentage survival of bacteria, and therefore the greatest health benefits from the product.

Survival rate of L. acidophilus Rosell-52 & B. Infantis Rosell-33 after 30 mins in acidic conditions

Bar chart survival rates in acidic conditions

The above bar chart shows the percentage of two different strains of probiotic bacteria (Lactobacillus acidophilus Rosell -52 and Bifidobacterium infantis Rosell-33) that survive when subjected to three different pH levels. As you can see these two strains offer 100% survivability scores at pH4, which is similar to the average stomach acid levels in the morning following a meal. These strains are naturally robust strains, that show good survivability in acid conditions.

Enteric coating and timed-release technologies

Some probiotic manufacturers use a type of technology such as Bio-tract®, which is a time-release technology thought to protect their bacteria from the low pH in the stomach. Whilst this may well be of benefit for some strains of probiotic bacteria, it is really not necessary if the strains themselves display excellent natural survivability in acid conditions, as ours do.

Enteric coating, can also help probiotics to survive transit through the harsh stomach environment. Enteric coating is a special coating for capsules, which is intended to remain intact in the stomach but to dissolve in the small intestine, and provides another option for ensuring probiotics survive to reach the gut alive. However, critics of enteric coating have pointed out that it can involve the use of synthetic chemicals, as well as highlighting some doubts over whether the capsules eventually break down in the lower GI tract to release the probiotics, or if they pass through the intestines intact with their beneficial probiotic cargo still on board.

Therefore, it may be better to simply use hardy strains of bacteria that do not require other types of 'manufactured' protection to survive transit through the stomach.

For more about this subject, you may enjoy reading a page from our information section, 'Probiotic Myths - BUSTED!' - see 'The Survival Myth'.

The ultimate proof of survival: human clinical trials

But ultimately, the most conclusive proof that any probiotic reaches the gut alive is how it makes people feel when they are taking it.

Choosing a product that has credible scientific research behind it (most importantly human clinical trials) showing that it positively impacts human health is the best way to know that you are spending your money wisely. By choosing a probiotic that has been used in studies on human subjects, and has demonstrated a positive influence on the health of the test subjects is perhaps the only reliable way to select the best probiotic for you. Learn more by reading the article: Research - is it all equal?.

Different human trials look at different areas of health, for example a study may look for benefits to gut health from taking a certain probiotic strain, or it may look for improvements in vaginal health, or even in cholesterol levels. Be sure to look for studies that are relevant to your particular set of health symptoms, so that you can select the best probiotic product for yourself. Enjoying health benefits from taking a probiotic is the ultimate confirmation that the live cultures you are taking are surviving the journey through your stomach and colonising effectively.

microscopic bacteria
Choose a probiotic proven to survive to reach the gut alive

And finally...YOU!

If you find a probiotic product that constantly receives positive independent reviews and feedback, then this is another indication that the live cultures it contains are surviving their journey through the stomach and thriving as part of their host's resident microflora.

After all, the only thing that is important is whether or not the product works and brings health benefits. So why not conduct your own mini human trials and see which product works best for you. Take a look at our Probiotic Myths for more information on this topic.


  1. Gaisford, S., & Fredua-Agyeman, M., (2014) ‘Comparative survival or commercial probiotic formulations: test in biorelevant gastric fluids and real time measurements using microcalorimetry’, Beneficial Microbes.
  2. Institut Rosell Lallemand (2016), 'Resistance to Gastric Acid', General Probiotic Training 27-29