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Lactulose is a form of sugar used medically in the digestive tract as a treatment for constipation (a laxative). Lactulose selectively feeds certain bacteria and is considered a prebiotic.
Lactulose is not absorbed in the intestine like other forms of sugar, meaning it can travel through the digestive tract to the large intestine. When lactulose gets to the large bowel, it provides a food source for bacteria there, but also draws water to the intestine and stimulates the bowels as a laxative. Lactulose is an artificial FODMAP.
The full treatment instructions for using lactulose effectively are in the ultimate guide to treating bacterial vaginosis, Killing BV.
Using lactulose in the vagina
Lactulose can be used in the vagina to selectively feed lactobacilli while actively starving bacterial vaginosis-related pathogens. However, lactulose can feed some pathogens – check which bugs love lactulose.
In laboratory research, lactulose did not feed yeasts or BV-associated bacteria while broadly stimulating vaginal lactobacilli.1 That fits closely with what we see in our own clinic, where we use lactulose a great deal as a vaginal prebiotic and find it a highly effective, reliable way to help protective lactobacilli recover. The formal clinical-trial evidence is still catching up with the laboratory findings and our clinical experience, but in practice it is one of our go-to tools for rebuilding a lactobacilli-dominated vagina.
Lactulose actively limits the growth of Candida albicans and Atopobium vaginae and does not affect (as in, does not limit or promote) the growth of Gardnerella vaginalis, Prevotella bivia, or Mobiluncus curtisii.
Top vaginal warriors, Lactobacillus crispatus, L. gasseri and L. jensenii, had growth broadly and easily stimulated by lactulose. Lactulose was preferred over other sugars as a food source.
Lactulose can also lower vaginal pH toward the healthy range (around 3.5 to 4.5), likely because it boosts the lactic-acid-producing lactobacilli.
What is lactulose?
Lactulose is made from milk sugar, lactose. Raw milk does not contain lactulose but is created in milk during the heating process (pasteurisation).
The higher the heat, the more lactulose is produced. Lactulose is an isomer of lactose, created by one molecule each of fructose and galactose. Lactulose is a disaccharide, with di meaning two, and saccharide meaning sugar. Disaccharide means two sugars together.
Where to buy lactulose
How to use lactulose vaginally
We like to put the lactulose into vegetable capsules, which come with the My Vagina LactoLush Prebiotic Kit.
Lactulose safety
Lactulose may require medical advice in some countries when used orally for treating diarrhoea. Lactulose may contribute to health problems if it is used too much or used incorrectly.
When used vaginally these cautions do not apply since the liquid is not entering the digestive tract and is not absorbed into the bloodstream.
Do not continually use lactulose outside of treatments, as it may result in lactobacillus overgrowth, which can produce some uncomfortable symptoms.
How does lactulose work?
Lactulose is not broken down by enzymes in the human digestive system or vagina and therefore remains as a source of food for bacteria and microbes that can use it. Lactobacilli, the protective vaginal bacteria that you want to keep around, can utilise lactulose.
Lactulose safety and effectiveness (pregnancy, breastfeeding)
Lactulose has been used medically since the 1950s and is on the World Health Organisation’s list of essential medicines (for oral use).
There have been no reports of harm from using during pregnancy and is considered safe to use during breastfeeding.
Frequently asked questions
Does lactulose help BV?
Yes. In our clinic we use lactulose extensively and find it a very effective vaginal prebiotic — it feeds protective lactobacilli while, in laboratory studies, not feeding (and sometimes limiting) BV-associated bacteria and yeast.1 Formal vaginal trials are still limited, but both the science and our hands-on clinical experience point firmly the same way.
Is lactulose safe to use in the vagina?
Lactulose is not absorbed into the bloodstream, so the cautions around swallowing it do not really apply vaginally. Do not use it continuously outside a treatment plan, though, as it can overfeed lactobacilli and cause an overgrowth with its own uncomfortable symptoms.
This article is general information and not a substitute for personalised medical advice. If a vaginal infection is not settling, please see an experienced practitioner.
- Collins SL, McMillan A, Seney S, et al. Promising prebiotic candidate established by evaluation of lactitol, lactulose, raffinose, and oligofructose for maintenance of a Lactobacillus-dominated vaginal microbiota. Applied and Environmental Microbiology. 2018;84(5):e02200-17.
