Lactobacillus: What It Is, Its New Names and Where It Is Found

Lactobacillus is not one single supplement. It is a large, varied group of bacteria, and different strains behave differently. Some live naturally in fermented foods and parts of the human body, including the gut and vagina. Others are sold in capsules or sachets. This guide explains what the name means and where you meet these bacteria; for help choosing a supplement, see Habuild's guide to probiotics: strains, uses and how to choose one.

What does the name Lactobacillus mean?

Lactobacilli are rod-shaped bacteria that turn sugars into lactic acid. That acid is what gives curd and many fermented foods their sour taste and helps preserve them.

A full probiotic name has three parts: genus, species and a strain code, for example Lacticaseibacillus rhamnosus GG. The strain code matters because closely related organisms can behave differently. Research on one strain for diarrhoea cannot be assumed to apply to another strain sold for digestion, even if both say "Lactobacillus" on the front.

Why the names on labels have changed

In 2020, scientists compared the whole genomes of more than 260 Lactobacillus species and found the group too diverse to remain one genus. They split it into 25 genera. A few species kept the Lactobacillus name, such as L. acidophilus, while many others were renamed:

• •L. rhamnosus and L. casei became Lacticaseibacillus.
• •L. plantarum became Lactiplantibacillus.
• •L. reuteri and L. fermentum became Limosilactobacillus.

A new name does not mean the organism has become stronger or safer. When comparing a product with a study, check the species and strain code rather than the genus alone.

Where you find lactobacilli in food

Plain curd, chaas, kefir, idli and dosa batter, kanji and traditionally fermented vegetables can all contain lactic acid bacteria, sometimes including lactobacilli. These foods add flavour and variety, but their microbes are rarely identified or present in a measured amount. Cooking, baking and heat-treated packaging can also kill live cultures.

That is why fermented food and a probiotic supplement are not interchangeable. Food can be a pleasant everyday habit; a supplement is a targeted product for a defined reason. For an Indian food list, see our guide to probiotic foods.

Probiotics are also different from prebiotics, the fibres in onions, garlic, oats, dal and fruit that feed gut microbes. Our article on prebiotics and probiotics explains how the two work together.

Reading a Lactobacillus product label

• •Look for the full species and strain code, not just "Lactobacillus" or "probiotic blend".
• •Check whether the CFU count (colony-forming units, the number of live organisms) is guaranteed until expiry, not only at manufacture.
• •A larger CFU number is not automatically better; the effective amount belongs to the strain and use studied.
• •Follow storage instructions. Heat and moisture reduce live counts, so keep products away from the stove and hot cars.
• •Check for added inulin, fructo-oligosaccharides or sugar alcohols, which can cause gas in sensitive people.

Keeping homemade curd safe

Use clean utensils, refrigerate curd once set and do not leave fermented foods warm indefinitely. If milk causes symptoms, do not force curd as a treatment; a fortified dairy alternative can provide variety, but check its protein and calcium.

Who should be careful

Most healthy adults tolerate lactobacilli, although temporary gas or bloating can occur. Stop and seek advice if symptoms are severe or persistent, or come with fever, blood in the stool, dehydration or weight loss.

Premature babies, people who are critically ill, those with central venous lines and people with severely weakened immunity should not start a live-microbe product without medical advice, because rare serious infections have occurred. Never shorten an antibiotic course or replace prescribed treatment with curd or a capsule; a pharmacist can advise on timing if a probiotic has been recommended alongside antibiotics.

Editorial sources

• •Zheng J et al. A taxonomic note on the genus Lactobacillus (PubMed, 2020)
• •NIH Office of Dietary Supplements: Probiotics fact sheet
• •NCCIH: Probiotics, what you need to know
• •NHS: Probiotics