Level 2 · Historic RCT

First Double-Blind Trial of Ionized Water for Diarrhea (1998)

Let's travel back in time. Year 1999. Research on molecular hydrogen as medicine practically did not exist. The concept of "ionized water" was considered by many to be pseudoscience.

In Japan, a team of researchers — led by Tashiro — decided to do something bold: design a placebo-controlled double-blind clinical trial to investigate whether alkaline ionized water (water that has been electrolyzed, generating dissolved molecular H₂) helped patients with chronic diarrhea.

The question was simple: does it really work, or is it just marketing?

The result was historic. Not because it was a "dramatic breakthrough," but because it was the first rigorous human RCT to show that water containing H₂ had measurable biological effects.

That study opened the door. What followed was a decade and a half of exponential research. TODAY, there are hundreds of articles on H₂ in top scientific journals.

It all started in 1999, with chronic diarrhea.

Molecular hydrogen water and First Double-Blind Trial of Ionized Water for Diarrhea (1998)

What Chronic Diarrhea Is and Why Ionized Water Changes the Equation

Chronic diarrhea means persistent loose bowel movements for more than 4 weeks. It can have multiple causes: residual bacterial infection, irritable bowel syndrome (IBS), dysbiosis (imbalanced gut flora), chronic inflammation, increased intestinal permeability.

01Oxidative stress in the intestinal epithelium (the cells lining your gut)
02Exaggerated inflammatory response
03Altered tight junctions (the connections between intestinal cells)
04Increased permeability ("leaky gut")
05Result: water and electrolytes pass through too fast, loose stools

Standard treatment: antidiarrheals (loperamide), dietary modification, antibiotics if infectious.

Now, alkaline ionized water contains dissolved H₂. H₂ reduces oxidative stress in the intestinal epithelium. It reduces inflammation. It restores the integrity of tight junctions. And in theory, it allows normalization of stool consistency.

But in 1999, this was speculative theory. No one had tested it.

The Study: What They Measured and What They Found

A simple but elegant study, published in Digestion & Absorption (a journal specialized in GI research):

n=32 patients with chronic diarrhea. Duration: 8 weeks. Experimental group: alkaline ionized water generated by an ionizer, intake of 1–2 liters daily (typically with meals). Control group: normal filtered water (no ionization, no H₂). Both groups: instructed not to change diet or other factors.

Measurements: • Frequency of bowel movements per week • Stool consistency (Bristol stool scale) • Subjective symptoms: urgency, abdominal discomfort, flatulence • Reported gastrointestinal tolerance (discomfort, complications)

Results (ionized water group vs control): Bowel movement frequency: decreased from 4–5 loose movements daily to 1–2 normal movements within 4 weeks. Control showed no significant change. Stool consistency: significantly improved (less "type 6–7" on the Bristol scale, more "type 4–5" = normal). Subjective symptoms: 60–70% reduction in urgency, abdominal discomfort, and flatulence in the ionized water group. Tolerance: no adverse effects reported. Ionized water was well tolerated even at 2 liters per day of intake.

Important: changes were not immediate. It took 2–3 weeks before noticeable changes. By week 8, most participants in the ionized water group had normalized GI function.

Translation: H₂-rich ionized water had a consistent, measurable, reproducible effect in chronic diarrhea.

The Historical Significance of This Study

Here is the context I want you to grasp: in 1999, no one took ionized water research seriously. It was fringe. It was considered pseudoscience.

But Tashiro et al. said: "fine, let's design a rigorous RCT and simply see what happens."

The study was published in a legitimate research journal. The design was robust (double-blind, placebo-controlled, randomized). The results were clear.

That changed the conversation. Suddenly, ionized water was seen as "legitimate enough for a clinical trial." And that opened the door in Japan (where the study was conducted) and other countries to investigate H₂ more seriously.

The direct result: research on molecular H₂ exploded. Between 2000–2010, hundreds of animal studies. Between 2010–2020, the first major wave of human RCTs. Between 2020–2025, consolidation of H₂ as a serious medical intervention with robust evidence.

It ALL started here, in 1999, with chronic diarrhea.

How to Incorporate It: Practical Steps

If you have chronic diarrhea, here is the approach:

Step 1: Consult a doctor to rule out treatable causes (infections, celiac disease, inflammatory bowel disease, documented IBS). Don't assume it is "chronic and incurable."

Step 2: If there is no specific cause (i.e., it is IBS or functional diarrhea), consider ionized water as a complementary option. The protocol in the study was simple: 1–2 liters daily.

Step 3: Get a quality H₂ water ionizer. You need an H₂ concentration of at least 0.5 ppm. Ionizers typically generate 1–1.6 ppm.

Step 4: Allow 4–8 weeks before evaluating. GI changes don't occur in days; they occur gradually.

Step 5: Combine with smart nutrition: avoid inflammatory foods (processed, high in sugar), include soluble fiber (oats, apples, carrots), make sure you consume probiotics (yogurt, kimchi, sauerkraut).

What You Can Expect

Based on the 1999 study:

Weeks 1–2: possibly no change, or mild worsening (sometimes GI systems respond with transient changes).

Weeks 2–4: gradual normalization of frequency. If you had 4–5 loose movements daily, expect a reduction to 2–3 normal movements.

Weeks 4–8: full stabilization. Most participants in the study were fully normalized by week 8.

After that: keep ionized water as part of the routine. Once normalized, you can reduce to 500 mL daily for maintenance.

Frequently asked questions

Why ionized water specifically, and not simply inhaled H₂?

The study used ionized water. Both forms contain molecular H₂. Ionized water is more practical for gastrointestinal use because it delivers H₂ directly to the gut.

Does it work for all types of diarrhea?

The study was in chronic diarrhea without a specific cause. Acute infectious diarrhea may require antibiotics first. Chemotherapy-induced or other specifically caused diarrhea may need different interventions.

Does it interfere with antidiarrheal medications?

Theoretically no, but if you take loperamide or other medications, consult a pharmacist.

Is it safe for an already inflamed gut?

In the study, participants with chronic diarrhea (who typically have some inflammation) tolerated ionized water well without adverse effects.

How long have we known that ionizers generate H₂?

Since the 1980s in Japan. The first scientific report of the benefits of ionized water was in the 1990s. This study (1999) was one of the first rigorous RCTs.

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