HOWARU Shape B420 Probiotic: What the Research Shows and Doesn't

HOWARU Shape B420 is a trademarked name for one probiotic strain, Bifidobacterium animalis subsp. lactis B420. Its key human evidence is a six-month, placebo-controlled trial in 225 adults, fully funded by DuPont Nutrition & Health (Stenman et al., 2016).

In that trial's prespecified comparisons, B420 on its own showed no significant body-fat difference from placebo, whether researchers looked at everyone with follow-up data or only those who stuck to the protocol. One group did show a significant difference. It was B420 taken with a polydextrose fiber, and only in the smaller per-protocol analysis.

What is HOWARU Shape?

HOWARU Shape is the trade name; the science name is Bifidobacterium animalis subsp. lactis B420. Read it left to right. Bifidobacterium is the genus, animalis the species, lactis the subspecies, and B420 the strain. Bifidobacterium is one of the two most common groups of bacteria in probiotics, alongside Lactobacillus, according to the NIH National Center for Complementary and Integrative Health.

Older papers call it Bifidobacterium lactis 420 (Putaala et al., 2008), because B. lactis was reclassified in 2004 as a subspecies of Bifidobacterium animalis (Masco et al., 2004). Same organism, newer name.

The strain code is the part that matters. NIH notes that different types of probiotics may have different effects. A label that stops at the species name tells you very little about what research, if any, stands behind it, and a blend that lists only a total CFU count doesn't tell you how much of any one strain you get. Even scientists at a probiotic maker call quality control of single strains inside a multi-strain formulation very challenging (Fenster et al., 2019).

What does the B420 research show?

A 2024 systematic review of 60 studies found that gut bacteria profiles correlate with fat mass and lean mass (Komodromou et al., 2024), but correlation isn't cause. When current and former scientists at B420's manufacturer reviewed its research in 2020, the human evidence they cited on weight was a single randomized, placebo-controlled study (Uusitupa et al., 2020). Here it is, read straight.

Who was studied, and at what dose?

The double-blind trial enrolled 225 adults aged 18 to 65 with a BMI of 28 to 34.9 at four research centers in Finland (Stenman et al., 2016). They were randomized in equal proportions to placebo, a polydextrose fiber, B420, or B420 plus the fiber, daily for six months. B420 was dosed at 10 billion CFU (colony-forming units) a day, as a powder from a sachet mixed into a fruit smoothie. Subjects were not required to modify their existing dietary or exercise habits during the study period. Body composition was monitored with dual-energy X-ray absorptiometry (DEXA). The prespecified primary outcome was the relative change in body fat mass compared with placebo.

DuPont Nutrition & Health fully funded the trial and supplied the study products, and the lead author was a DuPont employee.

What did the trial find?

The same trial produced two sets of results, and they reach different conclusions. The paper analyzed everyone with follow-up data, 209 of the 225 people randomized, and separately a per-protocol group, the 134 who completed the trial with more than 80% compliance and no antibiotic use. In the larger analysis, the trial's primary outcome, change in body fat mass, did not differ significantly between groups (Stenman et al., 2016). In the per-protocol analysis, B420 plus fiber showed a 4.5% body-fat difference from placebo, about 1.4 kg. B420 alone showed a 3.0% difference (P = 0.28), which is not statistically significant, in a group of just 24 people.

Group (daily, six months)	What they took	Body fat vs placebo: everyone with follow-up	Body fat vs placebo: per-protocol
Placebo	12 g microcrystalline cellulose	Comparison group	Comparison group
Fiber alone	12 g polydextrose	No significant difference	+0.3%, not significant
B420 alone	10 billion CFU B420 in 12 g microcrystalline cellulose	No significant difference	-3.0%, not significant
B420 plus fiber	10 billion CFU B420 in 12 g polydextrose	No significant difference	-4.5% (about 1.4 kg), significant

After unblinding, and because the B420-alone group had ended up smaller than the others, the authors added a factorial analysis estimating B420's effect across both groups that received it. That post-hoc analysis did find a 4.0% body-fat difference for B420 (P = 0.002). The authors noted that the smaller per-protocol population weakens the statistical power and that further studies are needed (Stenman et al., 2016).

In the per-protocol group-by-group comparisons, body weight did not differ significantly from placebo, with B420 alone showing only a trend (P = 0.15). Five-day food diaries recorded lower calorie intake in both B420 groups than in the placebo group (Stenman et al., 2016).

What did the gut bacteria follow-up find?

A follow-up analysis of stool samples from the 134 per-protocol participants found more Lactobacillus and Akkermansia with B420 at the end of the six months (Hibberd et al., 2019). The authors, all at DuPont, classed the microbiota results as exploratory outcomes. A shift in gut bacteria is a measurement, not a health outcome.

Does B420 affect the gut barrier?

The gut-barrier idea comes mostly from the lab. In a cell-culture study, a cell-free liquid from B420 cultures increased tight junction integrity in Caco-2 cells (Putaala et al., 2008). In people, the trial measured serum zonulin, which the authors describe as a potential marker of intestinal permeability. Zonulin seemed to stay lower with B420, but the factorial analysis showed only a trend (P = 0.063) (Stenman et al., 2016). That is a hint, not a demonstrated effect.

B420 alone or B420 with fiber: what is the difference?

A probiotic paired with a prebiotic is a synbiotic. Prebiotics are nondigestible food components that selectively stimulate the growth or activity of desirable microorganisms, according to the NIH National Center for Complementary and Integrative Health. In the B420 trial, the prebiotic was 12 g a day of polydextrose.

That pairing is where the trial's headline numbers live. In the per-protocol analysis, only B420 plus fiber showed a significant body-fat difference from placebo, and only the combination increased lean body mass compared with placebo; neither B420 nor the fiber alone had an effect on lean mass (Stenman et al., 2016). So when you see this trial quoted, check which group the number came from. For how the two categories differ, see our breakdown of prebiotics vs probiotics.

What are DRcaps?

DRcaps are a capsule shell, not a probiotic. They are made from hypromellose (HPMC) with gellan gum as a gelling agent, and they are designed to slow capsule opening after swallowing and to help protect acid-sensitive ingredients (Rump et al., 2021).

In a small MRI study, six healthy volunteers swallowed single DRcaps capsules filled with tracers after fasting. The capsules opened in the small intestine in four people, in the stomach in one and in the esophagus in one, at an average of about 37 minutes (Rump et al., 2021). The capsule's manufacturer funded the study, and five of its 13 authors worked for that company. It tested the shell with tracers, not a probiotic, and it measured where the capsule opened, not any health outcome.

One more gap is that the B420 trial delivered B420 as a powder in a smoothie, so DRcaps were never part of it (Stenman et al., 2016).

Packaging is the other half of delivery. A review by DuPont scientists, whose employer makes probiotics, lists water activity, oxygen and temperature among the basic challenges to keeping probiotics viable (Fenster et al., 2019). Even the B420 trial packed its sachets above its 10 billion CFU target to allow for losses (Stenman et al., 2016).

How much B420 was studied, and when do you take it?

The main trial used 10 billion CFU of B420 once a day for six months, in a smoothie (Stenman et al., 2016), and its authors describe earlier human studies of B420 as using quite low doses. The trial didn't compare doses or times of day, so it can't tell you whether morning, evening or with a meal matters. With any B420 product, follow the directions on its label.

Is B420 safe, and what are the side effects?

In the six-month trial, there were no differences between groups in the incidence of adverse events. Across all four groups, placebo included, 199 of 224 participants reported at least one adverse event over the seven months, digestive symptoms were generally mild, and there were no changes in blood pressure, heart rate or liver enzymes (Stenman et al., 2016).

The NIH National Center for Complementary and Integrative Health says probiotics have an extensive history of apparently safe use, particularly in healthy people, but few studies have looked at their safety in detail, and the risk of harmful effects is greater in people with severe illnesses or compromised immune systems. The B420 trial excluded people who were pregnant, planning a pregnancy or breastfeeding, so it offers no data on those groups (Stenman et al., 2016).

The FitProbio+ label cautions: "Consult your healthcare professional prior to use. Individuals taking medication should discuss potential interactions with their healthcare professional. Do not use if tamper seal is damaged." If you are pregnant or nursing, take medication, or have a health condition, talk to your healthcare provider before starting any probiotic.

How does FitProbio+ use B420?

FitProbio+ is a single-strain formula. Each capsule provides 25 mg of Bifidobacterium animalis subsp. lactis B420, listed on the label as 10 billion CFU, and the directions are to take one capsule with water daily, or as directed by your healthcare professional. It contains B420 on its own, with no polydextrose.

The capsule is a DRcaps acid-resistant vegetarian capsule, listed on the label as hypromellose, gellan gum and water, and each capsule is sealed in a nitrogen-purged blister pack. The other ingredients are microcrystalline cellulose, ascorbyl palmitate and silica. FitProbio+ is formulated to exclude wheat, gluten, soy, animal and dairy products, fish, shellfish, peanuts, tree nuts, egg, ingredients derived from genetically modified organisms (GMOs), artificial colors, artificial sweeteners, and artificial preservatives.

The trial described above tested B420 powder mixed into a smoothie, not FitProbio+.

Where should you go from here?

For how probiotics work in general, and how to choose and store one, read our ultimate guide to probiotics, or browse all Fitties ingredient spotlights. No probiotic stands in for a balanced, nutrient-dense diet and consistent physical activity.