Before we get to whether altering gut microbiota could alleviate lactose intolerance, it’s important to understand that this condition isn’t straightforward to diagnose ().
- Assessment of lactase activity from small intestine biopsy, the most direct approach for diagnosis, is fraught with both false positives and negatives as this enzyme is patchily, not evenly, distributed in the small intestine.
- of lactase variants doesn’t help much either because lactase activity and GI tract symptoms are found to correlate little.
This brings us to the fact that some people may wrongly believe they have lactose intolerance.
- Some may instead be lactose maldigesters/malabsorbers capable of digesting “normal” servings of dairy who may unwittingly exceed their lactose tolerance limit, not surprising given recent trends in increased portion sizes of frozen yogurts, shakes and milk.
- A meta-analysis of 21 masking (hidden) studies from 1996 to 2002 found similar range and severity of GI tract symptoms in self-identified lactose maldigesters given either a cup of milk or placebo under masked conditions ( ). This suggests considerable influence of nocebo effect on lactose intolerance symptoms.
- Some lactose maldigesters may instead have non-celiac gluten sensitivity who could benefit from cutting out gluten rather than dairy ( ).
- While breath tests may somewhat help in differentiating lactose versus fructose intolerance ( ), going on a diet helps more accurately identify the trigger for the GI tract symptoms but this is an undertaking both complicated and difficult. FODMAPs are fructose, lactose, fructans, galactans, and polyols such as sorbitol, mannitol, xylitol, maltitol; poorly absorbed in the small intestine, they are rapidly fermented by colonic bacteria.
If lactose intolerance has been correctly diagnosed, a few studies suggest encouraging colonization with lactase active bacteria by feeding either specific prebiotics or scientifically confirmed probiotic bacterial strains such as Lactobacillus casei Shirota and Bifidobacterium breve Yakult can alleviate lactose intolerance ().
A few studies have also reported utility of Lactobacillus bulgaricus, Streptococcus thermophiles, Bifidobacterium longum, Lactobacillus acidophilus.
One of the better-done prebiotic studies was a double-blind RCT* () where the subjects (total n = 85) got a proprietary mix of highly purified short-chain galactooligosaccharides (GOS) called “RP-G28”. A follow-up found those who got this mix had significant increase in lactose-fermenting Bifidobacterium, Faecalibacterium, Lactobacillus and Roseburia in stools days later, changes that persisted even after subjects resumed dairy intake ( ).
Preliminary studies have also found kefir could reduce lactose intolerance symptoms (8). Kefir is a lactic acid containing milk product where “kefir grains”, a mix of lactic acid bacteria and yeast, ferment milk lactose.
Caveat is studies to date had small numbers of subjects, few studies were randomized double-blind RCTs, and different studies used different protocols, strains and doses. Unsurprisingly, contradictory results are fairly common.
Key problem is lactase activity is strain-specific; some strains hydrolyse lactose much more efficiently compared to others so some probiotics or fermented dairy products may alleviate lactose intolerance better compared to others. Until this issue is nailed down, using such products to alleviate lactose intolerance will remain unpredictable.
1. Vonk, Roel J., et al. “Probiotics and lactose intolerance.” Probiotics. InTech, 2012.
2. Savaiano, Dennis A., Carol J. Boushey, and George P. McCabe. “Lactose intolerance symptoms assessed by meta-analysis: a grain of truth that leads to exaggeration.” The Journal of nutrition 136.4 (2006): 1107-1113.
3. Tavakkoli, Anna, et al. “Characteristics of patients who avoid wheat and/or gluten in the absence of celiac disease.” Digestive diseases and sciences 59.6 (2014): 1255-1261.
4. Volta, Umberto, et al. “An Italian prospective multicenter survey on patients suspected of having non-celiac gluten sensitivity.” BMC medicine 12.1 (2014): 85.
5. Almeida, Camila Casuccio, et al. “Beneficial effects of long‐term consumption of a probiotic combination of Lactobacillus casei Shirota and Bifidobacterium breve Yakult may persist after suspension of therapy in lactose‐intolerant patients.” Nutrition in Clinical Practice 27.2 (2012): 247-251.
6. Savaiano, Dennis A., et al. “Improving lactose digestion and symptoms of lactose intolerance with a novel galacto-oligosaccharide (RP-G28): a randomized, double-blind clinical trial.” Nutrition journal 12.1 (2013): 160.
7. Azcarate-Peril, M. Andrea, et al. “Impact of short-chain galactooligosaccharides on the gut microbiome of lactose-intolerant individuals.” Proceedings of the National Academy of Sciences 114.3 (2017): E367-E375.
8. Guzel-Seydim, Zeynep B., et al. “Functional properties of kefir.” Critical reviews in food science and nutrition 51.3 (2011): 261-268.