Assessment of the Effects and Safety of Spermidine Supplementation on Blood Lipids and Body Weight in Overweight or Obese Individuals With Hyperlipidemia: A Randomized, Double-Blind, Placebo-Controlled Trial

This is a single-center, randomized, double-blind, placebo-controlled, parallel-group trial designed to evaluate the efficacy and safety of spermidine supplementation in overweight or obese adults with hyperlipidemia.

A total of 50 eligible participants will be randomly assigned in a 1:1 ratio to either the experimental group (spermidine capsule 10 mg/day) or the control group (placebo capsule, identical in appearance, packaging, and taste). Randomization will be performed by a third-party statistician using a computer-generated random number table with variable block sizes. Allocation concealment will be ensured through sequentially numbered, opaque, sealed envelopes. All outcome assessors, investigators, and participants will be blinded to group assignment throughout the study.

The intervention period lasts 1 month. Participants in the experimental group will take 2 capsules (10 mg total) of spermidine (extracted from North American high-selenium wheat germ, 100:1 concentration process) orally per day after breakfast. The placebo group will receive an identical regimen of microcrystalline cellulose capsules. During the trial, all participants will receive standardized dietary advice designed to avoid high-polyamine foods (e.g., natto, fermented soy products, mushroom, germ products) and maintain stable total energy intake without overeating. They will also be advised to avoid new nutritional supplements and any other weight-loss interventions. Weekly telephone follow-ups will monitor compliance and dietary/exercise logs. Compliance will be assessed by pill counts of returned capsules, with <80% adherence defined as protocol deviation.

Assessments are scheduled at baseline (Day 0) and at study end (Month 1). Baseline evaluations include anthropometric measurements, blood biochemistry, stool sample collection, and questionnaire assessments. At Month 1, all baseline measurements will be repeated, and adverse events will be recorded and assessed for causality using the Naranjo scale. Safety monitoring includes liver and kidney function tests and documentation of gastrointestinal or other adverse reactions throughout the trial.

Primary outcome is the change in triglycerides (TG) from baseline to 1 month. Secondary outcomes include changes in LDL, total cholesterol, weight, BMI, body fat percentage, waist-to-hip ratio, fasting glucose, liver/kidney function parameters, and adverse event rates. Statistical analyses will follow the intention-to-treat principle using SAS 9.4. Primary analysis will employ two independent sample t-tests or Mann-Whitney U tests for between-group comparisons.