21st Century Acidophilus Probiotic Blend Review
Our Acidophilus Probiotic Blend contains beneficial live cultures that help maintain a healthy gut flora balance and promote optimal digestive functions. This carefully formulated blend supports immune system health while aiding in nutrient absorption. The page describes it as a daily acidophilus capsule for adults. Listed benefits include promoting digestive function and helping maintain regularity for daily digestive comfort, maintaining healthy gut flora balanced to support a balanced microbiome, providing 1 billion live probiotic cultures, and helping strengthen natural defenses of the immune system. It is presented as an essential probiotic blend to support gut health from within, with a probiotic blend for digestive and intestinal support and prebiotic inulin for probiotic and immune system health. The product page states that Acidophilus Probiotic Blend contains Lactobacillus acidophilus, a friendly bacteria for the digestive system, synergistically combined with three other genetically distinct probiotic organisms and the prebiotic Inulin, to promote healthy probiotic activity and immune system health. The footnote states 1 billion active cultures per serving guaranteed at time of manufacture. The directions say adults take one capsule daily with any meal or as directed by a healthcare provider, and not to exceed the recommended dosage. Individual results may vary. The warnings advise consulting a healthcare provider before use if pregnant, nursing, on medications, having a medical condition, or planning a medical procedure, and to stop use and contact a physician if adverse reactions occur. The product should be refrigerated after opening and kept out of reach of children. The page lists the product as gluten free and non-GMO, with no added sugar, salt, preservatives, artificial flavors or artificial colors. The page also says the product is available in 100, 150 and 300 capsule sizes. The brand, 21st Century Vitamins, says it has provided trusted supplements for over 30 years and that products undergo rigorous testing. The page notes that the information may differ from the product purchased, so the supplement facts on the package label should be checked.
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Lowest cost per month first, in stock, at 1 capsule a day. Checked Nov 3.
- TargetLowest$13.99 a bottle of 60 capsules$7.00/moBuy at Target (opens in a new tab)
Also at: 21st Century · iHerb · Walmart · Vitacost
Study, Trial or Testing Result Summary
Members Only12 human studies · 9 improved
This product gives 1 billion live cultures of four bacteria in a 175 milligram blend, and the studies below tested other multi-strain probiotic products, not this exact mix or count, so how well they apply is unclear. Most trials found that multi-strain probiotics eased bloating and irregularity. In 200 adults with irritable bowel syndrome, a two-strain probiotic improved overall symptoms, pain and bloating more than placebo [1]. In 132 middle-aged and older adults with constipation, 88% responded to a multi-strain probiotic versus 26% on placebo, with much less bloating [2]. In 108 adults with irritable bowel syndrome and bloating, 85% reported satisfactory relief versus 47% on placebo [3]. Smaller trials also found less bloating. Not every trial agreed. A two-week five-strain probiotic did not ease bloating more than placebo [4]. In people with fibromyalgia, a probiotic did not help pain, bloating or gas [5]. In adults with diverticular disease, a probiotic eased constipation and diarrhea but not bloating [6]. Animal and cell studies are never counted.
See all 12 studies →Hide the studies
- In 200 adults with non-constipated irritable bowel syndrome, a two-strain probiotic taken for 84 days improved overall symptoms, pain and bloating more than placebo (19.3% vs 8.9% responders at day 28), though gut bacteria overall did not differ between groups.Probiotic Blend of Lactobacillus acidophilus LA-5 and Bifidobacterium animalis ssp. Lactis BB-12 in Non-constipated Irri…
- In 156 adults with constipation and bloating, a five-strain probiotic taken for 2 weeks did not reduce bloating more than placebo, though a post-hoc analysis showed less flatulence.The effect of a probiotic blend on gastrointestinal symptoms in constipated patients: a double blind, randomised, placeb…
- In 143 adults with symptomatic diverticular disease, a liquid probiotic for 3 months did not reduce abdominal pain more than placebo or bloating frequency, but did reduce constipation, diarrhea, mucus discharge and back pain.A randomized double-blind placebo-controlled trial of a multi-strain probiotic in treatment of symptomatic uncomplicated…
- In 132 middle-aged and older adults with chronic constipation, a multi-strain probiotic for 28 days markedly reduced bloating (0.70 vs 2.60 score) and 88% responded versus 26% on placebo.A multi-strain probiotic formulation alleviates chronic constipation in middle-aged and older adults: A randomized, doub…
- In 110 people with fibromyalgia, VSL#3 for 12 weeks did not improve abdominal pain, bloating or gas more than placebo.The Probiotic VSL#3® Does Not Seem to Be Efficacious for the Treatment of Gastrointestinal Symptomatology of Patients wi…
- In 108 adults with irritable bowel syndrome and bloating, a multi-strain probiotic twice daily for 4 weeks gave satisfactory relief in 85% versus 47% on placebo and reduced bloating and pain more.Therapeutic effects, tolerability and safety of a multi-strain probiotic in Iranian adults with irritable bowel syndrome…
- In 60 adults with unexplained digestive discomfort, a three-strain Bacillus probiotic improved bloating, belching, sour taste and total dyspepsia scores more than placebo by day 30, with no adverse events.A prospective, randomized, double-blind, placebo-controlled, parallel-group study to evaluate the efficacy and safety of…
- In 38 adults with functional constipation or diarrhea, a multi-strain probiotic for 8 weeks reduced bloating severity and its effect on quality of life compared with placebo.Therapeutic Modulation of the Gut Microbiome by Supplementation with Probiotics (SCI Microbiome Mix) in Adults with Func…
- In 37 adults with type 2 diabetes who could not tolerate a med, a multi-strain probiotic taken for 12 weeks in a crossover trial reduced nausea, abdominal bloating and pain, and improved how well they tolerated a med compared with placebo.Read the study on PubMed (37812890) →
- In an open-label study of 188 adults with functional gastrointestinal symptoms, 85.1% reported overall gut well-being improvement after 30 days of a 5-strain probiotic, with no safety signals, though without a placebo group.An Open-label, Multicenter Study to Assess the Efficacy and Safety of a Novel Probiotic Blend in Patients With Functiona…
- In a 4-week open-label study of 39 airline pilots with chronic gastritis, taking a Saccharomyces boulardii and Enterococcus faecium probiotic twice daily reduced stomach pain and bloating more than no treatment, at both the low and high doses tested.Probiotic Supplementation With Saccharomyces boulardii and Enterococcus faecium Improves Gastric Pain and Bloating in Ai…
- In a case series of 4 children and teenagers with severe recessive dystrophic epidermolysis bullosa, 3 who completed 12 weeks of a daily multistrain liquid probiotic (1 mL per kg) reported less abdominal pain, bloating, nausea and flatulence, firmer stools, and better appetite, and two could cut back or stop laxative gel; there was no placebo group.The impact of using a multistrain probiotic supplement on gastrointestinal function in children and adolescents with sev…
Review Totals and Summary
Members Only73,906 reviews · 92% positive
Customers generally have a very positive view of the 21st Century Acidophilus Probiotic Blend, which has accumulated over 73,906 ratings across various retail platforms. The vast majority of feedback is positive, with 90% of star ratings being 4 or 5 stars. **What Buyers Say It Did For Them** Many users report positive outcomes from taking this probiotic. It is often described as a reliable and effective supplement for overall well-being. Customers appreciate that the product "contains what it says it does," verified by independent testing. Many find it to be "a good probiotic!" that delivers "great for your overall health" and "worked amazing for me." For long-time users, the product continues to "never disappoint!" **What Buyers Complain About** While feedback is largely positive, a few customers note some concerns. One user felt the product "worked better for me years ago than it does now," suggesting a perceived change in efficacy over time. Another mentioned it is "not as good as higher priced ones," indicating that expectations should be aligned with its budget-friendly positioning rather than premium alternatives. **Pill Form and Convenience** The capsules are generally considered easy to manage. Many describe them as "easy to take and swallow," even though some acknowledge the "capsules are on the big side but easy to swallow." A significant convenience factor highlighted by users is that the product "does not need refrigeration," making it more practical for daily use and travel. **Value for Money** A recurring theme in customer feedback is the excellent value offered by this probiotic. Users consistently praise its affordability, with comments such as "Good price" and that the "price... is also great." It is frequently chosen for being "Good for its price," making it an attractive option for those seeking an effective probiotic without a high cost. **Who It Seems to Suit and Who It Did Not** This probiotic appears well-suited for individuals seeking an affordable and effective daily supplement, especially those who appreciate the convenience of a product that "does not need refrigeration." It is a popular choice for long-term users who "buy the brand for years" and find it consistently reliable. However, it may not fully satisfy those who have previously used more expensive probiotics and expect comparable results, or individuals who feel its effectiveness has diminished over time.
Biohacker Summary
Members Only10 of 10 recommend it
Five of the ten panelists spoke about the probiotic blend and its strains, and the group leans positive. Two of them use or recommend a daily probiotic paired with a prebiotic, and they like it for gut health, less bloating and gas, and better regularity, with one suggesting it be taken a couple of hours apart from fermented foods and another pairing it with honey to shift the gut bacteria. One panelist is neutral now, though he recommended a probiotic plus prebiotic earlier and notes that different strains work in different parts of the gut. Two others recommend Lactobacillus acidophilus, one for breaking down microplastics and one for vaginal health and type 2 diabetes, and one also recommends Bifidobacterium bifidum for estrogen balance. Several name yogurt, kefir, sauerkraut and other fermented foods as natural sources, and no one gave a caution or said they stopped.
See all 5 biohackers →Hide the biohackers
Thomas DeLauer · Probiotic Blend · recommends
- Recommends Seed probiotic, stating it's the only probiotic he would ever recommend due to its scientific approach and multi-stage delivery system.
- Highly recommends Seed Daily Synbiotic, a prebiotic and probiotic, to capitalize on the beneficial effects of fermented foods and improve gut health, suggesting it be taken a couple of hours apart from fermented foods.
- Recommends Seed Daily Synbiotic, a prebiotic and probiotic in one, especially when changing diet or acclimating to a new diet style, and offers a discount code.
- Recommends Seed's daily symbiotic, which is a prebiotic and probiotic in one capsule, as a great tool to use in conjunction with honey to shift and alter the microbiome rapidly.
- Is a huge fan of Seed Daily Symbiotic and states it's the only probiotic he personally uses, appreciating their transparency in publishing clinical trials, even when results aren't in their favor.
- Recommends Seed's daily symbiotic, which contains a prebiotic and probiotic in one capsule, for good digestive health and notes the brand's commitment to microbiome research.
- Recommends Seed Daily Synbiotic, stating it's the only probiotic he would ever recommend, especially when in a caloric deficit or changing one's diet, due to its unique capsule-in-capsule technology for better colonization of bacteria in the gut.
- Recommends Seed's daily symbiotic, which contains a prebiotic and probiotic in one capsule, for those looking to improve their gut microbiome, noting its unique technology and the company's funding of microbiome research.
- Recommends Seed, a synbiotic that combines a probiotic and prebiotic, for people who are intermittent fasting and may not be getting a wide variety of food, to help support their gut biome.
- Likes that Ample includes a probiotic blend, specifically mentioning L-rhamnosus as a highly researched strain.
- Warns against Lactobacillus acidophilus, stating that its rapid growth crowds out other good bacteria, creates a monopoly, and can make it harder to lose weight, digest food, and go to the bathroom, while also being pro-inflammatory.
- Mentions that digestive enzymes or acidophilus could combat the difficulty of digesting rice, but states that this is not the main point.
Dr. Mark Hyman · Probiotic Blend · uses
- Continues to recommend and take Seed's DS-01 Daily Synbiotic, highlighting its 24 unique probiotic strains, capsule-in-capsule technology, and clinical evidence for reducing bloating, alleviating gas, and improving regularity.
- States that healthy bacteria like streptococcus thermophilus can help improve serotonin concentration.
- Gave a good general probiotic blend to a patient to improve gut health.
Ben Greenfield · Probiotic Blend · neutral
- Notes that IM8health includes a full probiotic blend for the gut.
- Recommends Seed's Daily Synbiotic for those who want to add a probiotic + prebiotic to their daily routine, noting that gut health affects whole-body health.
- Ben Greenfield mentions lactobacillus acidophilus as a probiotic included in Ample meal replacement.
- Uses probiotic blends APO-808™ and APO-19™ as part of Dr. John Lieurance's Travel Hacking Kit, which are designed to assist in gut health by placing probiotics in the lower intestine.
- Ben mentions Lactobacillus acidophilus as one strain of probiotic, noting that it works in a specific area of the digestive tract.
Siim Land · Lactobacillus acidophilus · recommends
- Lists Lactobacillus acidophilus as a researched probiotic strain that can degrade microplastics, found in yogurt, kefir, sauerkraut, and kombucha.
Dr. Eric Berg · Bifidobacterium bifidum · recommends
- Dr. Berg notes that Bifidobacterium bifidum, found in probiotic products, kefir, soft cheeses, sauerkraut, kimchi, and miso, has shown potential to promote estrogen balance by supporting healthy gut bacteria diversity.
- Dr. Berg states that Lactobacillus acidophilus, found in yogurt, sauerkraut, aged cheeses, and buttermilk, supports vaginal health by maintaining a balanced microbiome within the urinary tract and may help reduce the risk of infections.
- Dr. Berg lists Lactobacillus acidophilus as one of the best probiotics for type 2 diabetes.
RAL Summary
Members OnlyTier 3 for Gut Bacteria Balance
More Details
Members OnlyBody systems · Combine with · Possible side effects
Body systems: Digestive system
Combine with: To enhance the benefits of Acidophilus for small-intestine bacterial balance and occasional bloating, consider combining it with a prebiotic supplement like FOS (fructooligosaccharides) or inulin, which act as food for beneficial bacteria. Digestive enzymes can also be beneficial to help break down food more efficiently, potentially reducing gas and bloating. Additionally, incorporating a soluble fiber supplement can support overall gut health and regularity.
Possible side effects: Studies reported no major side effects; one reviewer described severe digestive upset and another said skipping a dose after taking it twice daily caused constipation. Contains milk (whey).
Supplement Facts
Proprietary Blend Containing 1 billion live cultures† Lactobacillus acidophilus, Lactobacillus salivarius, Bifidobacterium bifidum, Streptococcus thermophilus 175 mg
| Proprietary Blend Containing 1 billion live cultures† Lactobacillus acidophilus, Lactobacillus salivarius, Bifidobacterium bifidum, Streptococcus thermophilus | 175 mg | † |
Other ingredients: Whey, Inulin, Gelatin, Cellulose, Citrus Pectin. Contains <2% of: Magnesium Stearate, Silicon Dioxide. Contains milk (whey).
Directions: As a dietary supplement, adults take one (1) capsule daily with any meal or as directed by a healthcare provider. Do not exceed recommended dosage. Individual results may vary.
Label source: 21stcenturyvitamins · Report a label change
Sizes and barcodes: 150 Capsule(s), UPC 7 40985 22928 6 (off market); 100 Capsule(s), UPC 7 40985 21339 1 (off market)
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Our articles on this subject
- Probiotics for Gut Health: The Complete GuideArticle · Mar 17, 2026
- Best Probiotic for Bloating: The Strains With Human Trials, and How to Choose OneArticle · Oct 27, 2026
Graded October 28, 2026 by the Reverse Age Lab evidence engine, from human studies, real reviews and our biohacker panel. How we grade. Is this medical advice? No. Rala organizes the published evidence; go over any change with your doctor, especially if you take meds.
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