A fragrant citrus-peel oil sold cheaply as a supplement. Its most reliable human use is easing heartburn and acid reflux, with most people improving within about two weeks. It also appears to calm inflammation and oxidative wear, with early hints for metabolic, liver, and breast-cancer-prevention effects. Well tolerated; longevity-relevant benefits remain unproven. (Full Review)

Protocol

Standard Dose

500–1,000 mg daily

d-limonene (typically orange-peel-derived), once daily for digestive and general-wellness use

Reflux Approach

1,000 mg every other day

Over about 20 days, derived from the citrus-peel pilot studies

Timing & Dosing

With a meal

Single daily dose at ≤1,000 mg; split into two doses if GI tolerance is an issue

Time to effect

Reflux Relief

Several days to 2 weeks

On the every-other-day or daily regimen

Anti-Inflammatory & Metabolic

Over weeks

Slower, where present

Benefits

Medium: Relief of acid reflux and heartburn; reduction of systemic inflammation

Low: Antioxidant activity; metabolic and liver-fat support; breast-cancer chemoprevention signal

Speculative: Anxiety and mood modulation; neuroprotection

Contraindications

Citrus allergy

Pregnant or breastfeeding individuals

Active, undiagnosed GI symptoms warranting medical evaluation

Key Interactions

Prescription drugs metabolized by CYP2C9/CYP2C19 (warfarin, antiseizure agents, clopidogrel, proton-pump inhibitors)

OTC antacids and reflux products (calcium carbonate, famotidine)

Fat-soluble supplements (e.g., CoQ10)

Additive anti-reflux or anti-inflammatory botanicals (deglycyrrhizinated licorice, slippery elm, ginger, peppermint oil)

Cancer therapy (only under oncology supervision)

Risk & Side Effects

Medium: Gastrointestinal upset; skin sensitization and contact allergy

Low: Citrus allergy and idiosyncratic reactions; theoretical renal concern

Speculative: Drug-metabolism interference at high doses; pregnancy and lactation uncertainty

Monitoring

Marker	Target	Why
High-sensitivity CRP (hs-CRP)	< 1.0 mg/L	Tracks systemic inflammation, a primary target
Interleukin-6 (IL-6)	< 1.8 pg/mL	The inflammatory messenger reduced in the human citrus-peel study
ALT / AST (liver enzymes)	ALT < 25 U/L (men), < 22 U/L (women); AST ~ similar	Monitors liver-fat/metabolic goals and general tolerance
Fasting glucose	70–90 mg/dL	Relevant to metabolic and fatty-liver use
Liver-fat measure (CAP / ultrasound)	No significant steatosis	Primary endpoint in fatty-liver research with limonene

Cadence: For reflux, reassess symptoms at the end of a ~20-day course; for inflammatory or metabolic goals, recheck relevant labs at roughly 8–12 weeks, then every 6–12 months if continued.

Qualitative Assessment

Frequency and severity of heartburn or acid-reflux episodes
Post-meal digestive comfort and reduction in regurgitation
General energy levels and sense of well-being
Absence of side effects such as nausea or citrus-flavored belching (eructation)

Limonene for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment