Fisetin vs Spermidine

Mechanism

Fisetin is a naturally occurring flavonol (3,7,3',4'-tetrahydroxyflavone) found in strawberries, apples, and persimmons that acts as a senolytic by inhibiting the PI3K/Akt/mTOR survival pathway and BCL-2 family anti-apoptotic proteins in senescent cells. It also activates sirtuin-mediated pathways (SIRT1), reduces NF-kB-driven inflammation, and scavenges free radicals as a direct antioxidant. Fisetin demonstrated the most potent senolytic activity among 10 flavonoids screened in a 2018 study, reducing senescent cell burden in aged mice and extending both healthspan and lifespan markers.

Standard Dosing

Research indicates 20 mg/kg/day for 2 consecutive days as an intermittent senolytic protocol (approximately 1400-2000 mg for a 70-100 kg individual).

Timing

Take with fat-containing meal for improved bioavailability (fisetin is lipophilic with poor water solubility). Liposomal or lipophilic formulations preferred.

Cycle Duration

Intermittent senolytic courses ongoing. Daily low-dose use for antioxidant/anti-inflammatory effects can be continuous.

Side Effects

• GI discomfort at high senolytic doses
• Diarrhea
• Headache
• Generally well-tolerated — no serious adverse events reported in clinical trials to date

Contraindications

• Known hypersensitivity to fisetin or flavonoids
• Pregnancy and breastfeeding (insufficient safety data)
• Active chemotherapy without oncologist coordination

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Mechanism

Spermidine is an endogenous polyamine that induces autophagy primarily through inhibition of the acetyltransferase EP300 (p300), leading to hypoacetylation of multiple autophagy-related proteins and subsequent activation of the core autophagy machinery (Atg5, Atg7, Beclin-1). It promotes mitophagy (selective clearance of damaged mitochondria) and is essential for the hypusination of eukaryotic translation initiation factor 5A (eIF5A), a post-translational modification critical for TFEB-mediated lysosomal biogenesis. Spermidine also reduces age-related inflammation by suppressing NF-kB signaling and promotes cardiovascular health through improved endothelial nitric oxide bioavailability.

Standard Dosing

Research indicates 1-6 mg/day orally for longevity and autophagy support. Epidemiological data associates >80 micromol/day dietary spermidine intake with reduced cardiovascular mortality.

Timing

Morning with or without food. Some protocols suggest taking before a fasting period to potentiate autophagy (fasting naturally increases endogenous spermidine synthesis).

Cycle Duration

Ongoing. Endogenous spermidine levels decline with aging, suggesting lifelong supplementation may be beneficial.

Side Effects

• Generally very well-tolerated
• Mild GI discomfort at higher doses
• Headache (rare)

Contraindications

• Known hypersensitivity to polyamines
• Pregnancy and breastfeeding (insufficient safety data at supplemental doses)
• Active malignancy (polyamines promote cell proliferation in rapidly dividing cells — debated)
• Wheat allergy (if from wheat germ source)

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