What Is VSL3?

VSL3 (also written VSL#3, VSL 3) is a high-potency probiotic supplement. Indeed it is one of the strongest probiotic supplements on the market with 450 billion live bacteria (colony forming units) per dose. It is available in lemon flavored and unflavored powder form as well as in convenient capsules.

VSL3 is classified as a medical food, which is intended for use especially in the dietary management of disease under the supervision of a physician.

It contains three a blend of three genera (Streptococcus, Lactobacillus, Bifidobacteria) and eight strains of beneficial probiotic bacteria: Strains:

  • Streptococcus thermophilus

  • Bifidobacteria breve

  • Bifidobacteria longum

  • Bifidobacteria infantis

  • Lactobacillus acidophilus

  • Lactobacillus plantarum

  • Lactobacillus paracasei

  • Lactobacillus delbreuckii subspecies bulgaricus

These bacteria are freeze-dried or lyophilized – dried and frozen within a vacuum. This is the best way of extending the life of the bacteria. It ensures that the bacteria, when stored correctly, are live at the point of consumption.

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Product Ingredients

All VSL3 products contain the same mixture and number of bacteria per serving. The specific bacterial blend in these probiotics contains:

  • 450 billion bacteria containing Streptococcus thermophilus, Bifidobacteria (B. breve, B. longum, B. infantis), Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus paracasei, Lactobacillus delbrueckii (sub-species bulgaricus).

A few additional ingredients are also included in each of the products. Have a look at the table below to see the specific ingredients for each VSL3 product.

VSL3 ProductIngredients
Unflavored powderBacterial blend
Flavored powderBacterial blend
Silicon dioxide
Natural lemon flavor
CapsulesBacterial blend
Stearic acid
Silicon dioxide
Microcrystalline cellulose
The unflavored powder is intended to be taken as a beverage and needs to be mixed with water for consumption.

The flavored powder can be mixed with yogurt, apple sauce, ice cream or any other cold food for use.

All products need to be refrigerated (39ºF to 46ºF or 4ºC to 8ºC). Provided the items are stored correctly, the shelf life of VSL3 is an impressive two years!


We think this probiotic is a high quality product. We believe it offers the following advantages:

  • Very high number of viable bacteria per serving. With 450 billion bacteria per serving, this probiotic supplement offers way more bacteria than most other products on the market.
  • The products do NOT contain inulin, FOS (fructo-oligosaccharides) or other prebiotics. This makes them suitable for all types of people, including those with bowel complaints such as Irritable Bowel Syndrome (IBS) and food intolerances.
  • Excellent value for money. The cost of a 10 billion bacteria unit of VSL3 is much less than many of the less potent probiotics on the market.

  • Choice of powder or capsules. Powder is a good starter form for introducing probiotic supplements into your system for those with serious digestive disease. It allows the user to measure out small doses, allowing them to begin by consuming tiny amounts of probiotics only. Capsules on the other hand are a convenient and easy way to take probiotics, especially when you are out and about.

  • VSL3 probiotic products can be stored for up to a week at room temperature without losing potency, meaning they are suitable to take on short breaks away where access to refrigeration may be difficult (camping, hostels, hotels).

  • Contains a good mix of bacterial strains including those from both the Lactobacillus and Bifidobacteria genera (clans). All of the bacterial strains in these products have a safe history of use as food ingredients.

  • VSL3 is one of very few probiotic supplements that are supported by double-blind placebo controlled scientific studies. Some of these studies have shown that this product provides bacteria that help the gastrointestinal tract and that it can help in the dietary management of ulcerative colitis,1,2,3 Irritable Bowel Syndrome (IBS)4,5 and pouchitis6,7,8.

  • Disadvantages

    As far as the disadvantages of these products are concerned, the key issue is that all VSL3 probiotics contain traces of soy, dairy and gluten and therefore they may not be suitable for people with celiac disease or severe allergies to these foodstuffs.

    Our Evaluation

    VSL3 is a high strength probiotic

    We believe VSL3 probiotic supplements to be good products that offer excellent value for money – see our cost comparison page for information on selecting the best value probotics. They meet the good quality criteria set out in our buyer’s guidelines and contain a good mixture of beneficial bacteria in very high quantities. VSL3 can be purchased in both powder and capsule form, making the products suitable for all kinds of people. Additionally their high potency makes them particularly suitable for those suffering from digestive disease.

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    1.Tursi A et al; Low-Dose Balsalazide Plus a High-Potency Probiotic Preparation is More Effective than Balsalazide Alone or Mesalazine in the Treatment of Acute Mild-to-Moderate Ulcerative Colitis; Med Sci; 2004 Nov;10(11):PI126-31.

    2.Bibiloni R et al; VSL#3 Probiotic-Mixture Induces Remission in Patients with Active Ulcerative Colitis; Am J Gastroenterol; 2005 Jul;100(7):1539-46

    3.Venturi, A. et al; VSL#3® - The Probiotic Medical Food for the Dietary Management of Patients with Ulcerative Colitis; Aliment Pharmacol Ther; 1999 (67); 13(8):1103-1108

    4. Brigidi P. et al; Effects of Probiotic Administration upon the Composition and Enzymatic Activity of Human Fecal Microbiota in Patients with Irritable Bowel Syndrome or Functional Diarrhea; Research in Microbiology; 2001; Volume 152, Issue 8, Pages 735-741

    5. Kim H.J et al; A Randomized Controlled Trial of a Probiotic, VSL#3, on Gut Transit and Symptoms in Diarrhoea-Predominant Irritable Bowel Syndrome; Aliment Pharmacol Ther; 2003; 17:895-904

    6.Mimura T et al; VSL#3® in the Dietary Management of an Ileal Pouch; Gut; 2004; 7; 53:108-114

    7. Gionchetti P et al: ;Prophylaxis of Pouchitis Onset with Probiotic Therapy: a Double-Blind, Placebo-Controlled Trial; Gastroenterology; 2003;124:1202-1209

    8.Gionchetti P. et al; Oral Bacteriotherapy as Maintaining Treatment in Patients with Chronic Pouchitis: a Double-Blind, Placebo-Controlled Trial; Gastroenterology; 2000; 119:305-309

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