Do probiotics survive to reach the gut alive?
If you are reading this, then the chances are that you have some concerns about whether or not probiotics 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 in fact a waste of money. I'd say that this 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 viable, well tested and researched probiotics out there.
In part, the concern over the survival of probiotics through the stomach has been perpetuated by a 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 flourished in the intestines. We reported on this study at the time, and our write up can be found here.
So, it appears that some probiotics may not survive transit through the stomach, and some DO!
But how can we tell which is which?
pH testing of strains:
Survival rate of L. acidophilus Rosell-52 & B. Infantis Rosell-33 after 30 mins in acidic conditions
Enteric coating and timed-release technologies:
Those strains of bacteria with a high survival rate do not need to use technology like Bio-tract®, a time-release technology thought to protect the bacteria from the low pH in the stomach for our product range, though this may well be of benefit for other strains of probiotic bacteria.
A Unique Delivery System (UDS™), as used by some brands, or a special enteric coating, can 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 which could well provide another good option for ensuring probiotics survive to reach the gut alive. On the other hand, 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 probiotic cargo still on board. Therefore, it may be better to use hardy strains of bacteria that do not require this level of protection to survive transit through the stomach.
Some bacteria also undergo other forms of stability testing to show how they survive at different temperatures, and which confirm that they remain viable until the date of expiry. Thanks to a sophisticated method of freeze drying known as lyophilisation, some probiotics offer 'fridge-free technology', which means that you don't need to refrigerate any of the products.
The Ultimate Proof of Survival - Human Clinical Trials
But ultimately, what is the most conclusive proof that you're buying probiotics that reach the gut alive? How do you know that your live cultures have survived transit through the stomach and are surviving and thriving in your gut?
Quite simply, it's from measurable results obtained from credible scientific research, most importantly, human clinical trials. It's best to choose a probiotic that has been used in studies on human subjects, and which have then yielded clinically significant, measurable results that suggest the live cultures are positively influencing the health of the test subjects.
Whilst in vitro trials appear to demonstrate that certain probiotics are stomach acid resistant, the real 'proof of the pudding' are the clinical trials which show notable effects on gut health, or cholesterol levels, or vaginal health. This is the ultimate confirmation that the live cultures survive stomach acid and colonise in the intestines or vagina and offer health benefits.
A finished product trial is one conducted on the exact formula and dosage used in each product, rather than on one or two of the strains they contain - the higher the better!
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.
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