Supplement analysis backed by scientific evidence · PT

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PABA

Para-aminobenzoic acid was once marketed as "vitamin Bx" — it is not a vitamin for humans, and the grey-hair and vitiligo claims that sell it come from uncontrolled 1940s reports. Its one real use, high-dose potassium para-aminobenzoate for Peyronie's disease, is a prescription drug in parts of Europe.

What the science says

  • Restores grey hair to its natural color Limited evidence

    This claim traces to uncontrolled case series from the 1940s in which large PABA doses were said to darken grey hair in some subjects. No controlled trial has ever confirmed it, and the effect — where reported at all — reversed on stopping. Human hair greying is driven by melanocyte stem-cell depletion, which PABA has no established mechanism to reverse.

  • Slows plaque progression in Peyronie's disease Moderate evidence

    A prospective, placebo-controlled randomized trial of potassium para-aminobenzoate (POTABA) 12 g/day for 12 months in 103 men found significantly less plaque-size progression and a lower rate of penile-curvature deterioration versus placebo, though it did not reduce curvature that was already established. This is a drug-level dose under medical supervision, not a supplement use, and POTABA is prescription-only in Germany and several other countries.

  • A required vitamin humans need to supplement Limited evidence

    PABA is a substrate bacteria use to synthesize folate; humans absorb folate directly and have no PABA requirement, no deficiency syndrome and no established RDA. Because of this role it directly antagonizes sulfonamide antibiotics, which work by blocking bacterial PABA utilization.

Dosage & safety

Studied doseSupplements typically supply 100-500 mg/day, a dose with no demonstrated benefit for any condition. The Peyronie's protocol is potassium para-aminobenzoate 12 g/day in four divided doses for 12 months — 24 to 120 times the typical supplement dose, taken under urological supervision, and poorly tolerated by many patients.
SafetyDoses above roughly 8-12 g/day cause nausea, anorexia, rash and fever, and are the main reason patients drop out of Peyronie's protocols; hepatotoxicity and symptomatic hypoglycemia have been reported at high intakes. PABA antagonizes sulfonamide antibiotics and should not be combined with them; it may also interact with dapsone and methotrexate. Do not use in pregnancy or in children. Topical PABA was one of the classic sunscreen contact and photocontact allergens and was withdrawn from sunscreens — the FDA does not consider it generally recognized as safe and effective for that use — so people with a known PABA sunscreen allergy should avoid the oral form. Avoid in kidney or liver disease.

Scientific references

Where to buy

Swanson Vitamins, PABA, 500 mg, 120 Capsules

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