Prebiotics: Lactulose – An Underutilised Prebiotic with Potential

lactulose prebiotic treat blastocystis naturally herbal medicine naturopathic treatment for gut health

Following on in the series on prebiotics, this week we will be covering a very underappreciated and utilised prebiotic known as lactulose.

The few people that may already be familiar with this substance may be confused at the moment, and understandably so. Lactulose is generally used as a laxative and is recommended to treat constipation.

Lactulose is a semi-synthetic disaccharide (two simple sugars joined together) composed of both galactose and fructose. As a prebiotic lactulose escapes digestion in the small intestine and reaches the colon intact where it can be metabolised by specific bacteria (2).

While anything synthetic seems less than ideal in my mind lactulose does have an incredibly long history of use, dating back 40 years, with no evidence of serious side effects (3).

Lactulose Uses

A very interesting review looking to summarise the scientific findings of lactulose starts with a powerful statement on the effects of lactulose

“The major principle of action is the promotion of growth and activity of lactic acid bacteria in the gut which counteract detrimental species such as clostridia or salmonellae. This shows that prebiotic action, if used accordingly, can have medically significant effects”

Another review summarised a number of findings that included

  • Reduction in urinary tract infections
  • Increase in Bifidobacteria species
  • Increase in Lactobacilli species
  • Increased production of short chain fatty acids (SCFA’s)
  • Drop in colonic pH
lactulose prebiotic

Figure taken from Medical, nutritional and technological properties of lactulose. An update.

A very nice table presented in the same review listed some past and current research that points to lactulose’s beneficial uses including:

  • Acidification of gut contents
  • Ammonia depletion
  • Increased peristalsis
  • Increased osmotic pressure
  • Softening of stool
  • Facilitated defecation
  • Selective bacterial growth
  • Stabilisation of ecosystem
  • Inhibition of toxin-producing enzymes
  • Prevention of gallstones
  • Decrease of serum lipids
  • Shorter residence time of toxins
  • Prevention of carcinoma (colorectal and maybe other organs)
  • Prevention of gastrointestinal infections (Rotavirus, Candida, etc.)
  • Prevention of urogenital infections
  • Prevention of radiation enteritis
  • Anti-endotoxic (numerous applications possible)
  • Glucose- and insulin control
  • Improved mineral absorption
  • Prevention (therapy) of inflammatory diseases (e. g. diverticulitis)

So to summarise the effects of lactulose stems from the selective feeding of both Bifidobacteria and Lactobacilli species in the colon. These beneficial bacteria have a range of beneficial effects including the production of short chain fatty acids that, among other benefits, reduce the colonic pH. This drop in pH is less favourable for the more pathogenic microbes and results in reduced numbers.

A review looking into beneficially altering the gut flora to assist in the treatment of inflammatory bowel disease had a nice summary on the two beneficial genera Bifidobacteria and Lactobacilli. 

Lactobacilli and Bifidobacteria, and producing acidic products of fermentation inhibitory to pathogens, exert antagonistic effects towards other microorganisms. They compete with other microbes for substrates and site of colonisation. The protective mechanism exerted by these bacteria have been termed colonisation resistance”  

Have you had any experiences with prebiotics? Share your thoughts in the comments below.

References and Resources

  1. Fully Functional series on Prebiotics
  2. Lactulose 
  3. Medical, nutritional and technological properties of lactulose. An update.
  4. Promotion of a favorable gut flora in inflammatory bowel disease.
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  1. hi Todd
    thanks for this thorough review on Lactulose.
    Im grazing though the literature, but cant seem to find timing of WHEN best to take lactulose to increase those healthy buggers in my colon.
    Thank you

    1. No problem at all. Timing isn’t an issue, so whenever it fits in your schedule. The best advice I’ve been given from an experienced clinician is to start on a very small dose and gradually build it up over the span of a week or two.

  2. Hi Todd
    I feel very grateful to you and all your hard years of trials and errors. Have just been diagnosed with Blastocystis Hominis and will follow your gameplan. I respect that you can’t give detailed advice but could you tell me in what form was the Lactulose that you took? Was it liquid or capsule? Also, a brand name would be helpful. I live in Canada.

    1. hey jean. Sorry to hear about your parasite infection. Well done for finding it though! The lactulose I use is called Lac-dol. It is a liquid that we can get here at most chemists over the counter and quiet cheap too. I have heard it is harder to source in the states. I’m not so sure about Canada.

      Remember to start low and slow and work up to the dosage (2-3 tsp 2x daily) over a period of a few weeks. Lactulose really helps to acidify the colon and helped with my gut symptoms. Blastocystis doesn’t grow well and their pathogenic enzymes (proteases) apparently don’t function in an acidic environment. You will still need antimicrobials to go after the bug.

  3. Hi Todd, I had a colonoscopy in early Jan, I had very mild diverticulitis,but a few days after I started getting mild cramping in colon. I did’nt worry to much at first, but it gradually got a bit worse. I went on low fibre diet and I am still on it as it has’nt got better. I was also diagnosed with Blastocystis hommis in Sept ‘19. Could it be making my bowels inflammed.Would like to know what you think,thank you,Lesley

    1. Hey Lesley. Thanks for your comment and sorry to hear about your gut symptoms. Blastocystis is a bizarre bug. I haven’t come across it causing inflammation (in fact we still don’t know how or even if it causes issues to the gut). I am starting to look broader when coming across blastocsystis (SIBO investigations if bloating, food intolerances, etc). Healing your gut would be one option, maybe before looking at treating blastocystis.

  4. Thanks Todd, I have seen a naturopath and he has put me on a gut relief powder and knows I have Blastocystis.He said we’ll see how things go with the powder first,then go from there.Here’s hoping it’s just inflamed bowels from colonoscopy.Lesley

    1. It could be. Many of the gut relief powders have demulcent herbs (aloe, slippery elm, marshmallow root, etc). They will definitely help to soothe the gut. Sounds like you are in good hands 🙂

    1. Hey Caroline, I have used lac-dol mainly (found at most chemists here in Australia). They are all very similar and are used at a much higher dose as a laxative. The therapeutic dose is 2 tablespoons per day but you have to start with only a fraction of that and slowly work your way up over the course of about a month or so. I you can’t tolerate even the smallest amount (symptoms like bloating and distention) then you may be dealing with a SIBO picture that would need to be treated before you can circle back to using lactulose as a prebiotic.

      Hope that helps! Keep us posted here on how you go.


      1. Thanks Todd, do you know what the equivalent in the US would be? So I don’t have SIBO, I was treated for a very mild form of it that went away, which is great. I’ve been treated for the blasto infection 4 times, however, which has been costly and frustrating to say the least. I’m trying to figure out something that will work but haven’t gotten traction on a protocol that really does that trick. I also have super low counts of Bifido and Lacto… Thanks for all your brilliant information!

        1. Unfortunately lactulose is prescription only in the states (at least it was last time I checked). Very bizarre as it has been used in infant formulas since at least the 60’s if not before! The next step would be to narrow in on what effects you are trying to gain from the prebiotic. Lactulose is one of the best proximal colon acidifiers (great for blastocystis infections and to quickly shift a dysbiotic large bowel). Partially hydrolysed guar gum is very effective at increasing a number of beneficial bacteria whereas GOS appears to be the best tolerated prebiotic for IBS.

  5. Hi Todd,
    I’ve been consuming about 70g/d of various fermentable fibres for about three years. Recently I’ve added lactulose to the mix. There’s 3.3 g/ 5ml in a product called ‘Actilax’ here in Australia. I’m taking 20ml of that /d. It seems to produce really comfortable twice daily bowel movements. So whatever else it’s doing to enhance my gut health is an added bonus.
    My actual question is about beet pulp as a prebiotic. It’s in a lot of petfood now for it’s prebiotic prowess. It’s considred moderately feermentable, and is often referred to as a ‘super fibre’. But what do you know about humans eating it too?

  6. Hi I have IBS since about 30yrs.. Recently diagnosed with BH parasite. Don’t want to take antibiotics. I was reading about Lactulose and thought I might try it I already take probiotic plus Kéfir and saccharose
    bulardi… I live in France have a Mediterranean diet.

  7. Hi Todd, thank you again for yesterday. I just wanted to say that I have been reading more of your articles. They are so informative! Lactulose was something I always thought was just used as laxative. So interesting!

    1. Yes indeed! Lactulose can be tricky to use but when it is tolerated it can work a treat to help balance the gut, maintain healthy gut transit and normalise bowel movements.

  8. Hey Todd, thanks for your great work.

    Was wondering what information can be inferred when lactulose leads to gas in the colon (caecum)?

    Is that normal? Which probiotic & pathogenic bacteria ferment it?


    1. Hydrogen production in the colon is healthy and normal and many bacteria are hydrogen producers. Methane production in the colon is common and only an issue with symptoms. If lactulose doesn’t cause symptoms of bloating it can be very helpful to balance a dysbiotic environment in the gut!

    1. Lactulose is fine long term. SIBO it really depends on the case. I often recommend it to patients AFTER successful methane eradication to keep the bug from growing back and patients regressing back to square one. It can be hard to work with so go slow!

      1. I just finished a round of Rifaximin and Flagyl for Methane and Hydrogen Sulfide bacteria/archaea overgrowths. I am adding in Nystatin for 5 days as well. Wondering if restarting Lactulose would end up just feeding the bad bacteria, as that’s what’s they use for SIBO breath tests, or if it’s net affect is better than not taking it at all?

  9. Wondering if lactulose would feed Candida. I’m working to reduce overgrowth and would like to support the lactobacillus but don’t want to also feed the Candida.

    Thank you!

      1. Hi Todd, Ive read your website all day, so intriguing. I have been tested for SIBO, H. Pylori, I had endoscopy and colonoscopy all came back fine – no divirculitis, no celiac or bacteria. I’ve done stool cultures and they only thing that came up is this BH parasite. I am dealing with long covid and as we know that directly impacts the gut but my symptoms are lack of appetite, weight loss and gas/belching- I first had diarrhia and then a little constipation but things are moving now. I would like to treat this parasite naturally. Before knowing I had BH I started eating garlic in the morning and I instantly noticed that helped with my gas/belching and rumbling tummy. My functional med doctor gave me a supplement with a bunch of herbs in it- I also had my primary doc give me a perscription for Flagyl- although I know the success rate isnt very high with that med. I currently am taking a digestive enzyme, probiotic (just ordered Florastor) and about to start the med from my functional med dr. I am so curious, do you know of any other stomach testing I should do to rule out anything else? Thanks in advance!

  10. Hi Todd

    Interesting article, when ever I have taken lactulose for a camera capsule or endoscopy, I have had an initial die off and around 12 hours later felt brilliant.

    I had hydrogen sibo but no diarrhoea or bloating but think the lactulose clear the bacteria in the small intestines plus the toxins but it only last a short while. I am think about doing a low dosage over serval weeks?


  11. Does lactulose feed the methane producing bacteria? But by feeding the good bacteria could it eventually over grow the bad methane bacteria in colon?

  12. Hi Todd!
    Very interesting information, also read your post about Blastocystis.
    Was wondering if lactulose could increase electrolytes loss in patients taking diuretic drugs?? or if it is safe at low doses (2-3 tsp 2x daily).
    Which dosage would be the upper limit recommended for these patients?

    Thanks in advance! Greetings from Mexico!

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