The Effect of Astaxanthin After Varicocele Surgery on Antioxidant Status and Semen Quality in Infertile Men: A Triple-Blind Randomized Clinical Trial

Written by Keely Puchalski, ND. Results from this small triple-blind RCT suggest 90 days of astaxanthin (6 mg/day) after varicocelectomy improved sperm motility, increased seminal antioxidant capacity, upregulated NRF2-pathway gene expression, and reduced pro-inflammatory cytokines in infertile men with varicocele, though the study is limited by small sample size, retrospective trial registration, and lack of baseline data and protein-level validation.

man smilingVaricocele (VC) — abnormal dilation of spermatic veins — is the most common correctable cause of male infertility, accounting for 35–50% of primary and up to 81% of secondary cases1. Oxidative stress (OS) from reactive oxygen species (ROS) drives testicular injury in VC, damaging sperm DNA, lipids, and proteins2. VC also sustains chronic seminal inflammation, with elevated TNF-α, IL-1β, and IL-6 further impairing motility and spermatogenesis2.

Varicocelectomy (VCT) is the gold-standard treatment but often fails to normalize semen parameters due to persistent OS3. A 2019 meta-analysis by Wang, et al. supports adjuvant antioxidant therapy post-VCT to improve sperm concentration, motility, and DNA integrity4.

Astaxanthin (ASX), a xanthophyll carotenoid in algae, plants, and some red-orange animals (e.g., crabs & flamingoes), exerts antioxidant effects via NRF2 signaling5, which, when released from Keap1, induces cytoprotective enzymes like SOD, activates anti-apoptotic BCL2, and suppresses pro-apoptotic BAX6. Prior studies demonstrated ASX-mediated NRF2 activation in granulosa cells and women with PCOS7,8, supporting its plausibility in male reproductive tissue. No previous trial examined ASX in infertile men with VC; this study assessed its effects on NRF2-pathway genes, semen parameters, and seminal oxidative/inflammatory markers post-VCT.

This parallel, 1:1, triple-blind RCT at the Royan Institute (Tehran, Iran; Dec 2021–May 2023) retrospectively registered in the Iranian registry, randomized 44 men (41 completed; ASX n=21, placebo n=20). Eligible participants were infertile men aged 18-40 with grade II/III sub-inguinal VC confirmed by Doppler, abnormal sperm, BMI 18.5-30, and infertility ≥12 months. Exclusion criteria were comprehensive and baseline characteristics were well matched.

All underwent sub-inguinal VCT by the same surgeon, then received randomized ASX 6 mg/day (Astareal, Tokyo, Japan) or placebo for 90 days. Outcomes — semen parameters, seminal TAC/TOS, cytokines (TNF-α, IL-1β, IL-6), and sperm mRNA of NRF2, Keap1, SOD2, SOD3, BCL2, BAX — were measured at baseline and 3 months post-surgery via WHO-standardized semen analysis, ELISA, and RT-PCR (2−ΔΔCT). Paired/unpaired t-tests were used; p<0.05.

Key Findings

Gene Expression & Oxidative Stress

  • NRF2, SOD2, and BCL2 mRNA: significantly upregulated in ASX group (p=0.007, 0.008, 0.016) compared to placebo.
  • Keap1 mRNA: also significantly upregulated compared to placebo (p=0.004) — counterintuitive, addressed below
  • BAX mRNA: significantly downregulated compared to placebo (p=0.044)
  • TAC — seminal plasma and sperm lysates: significantly higher in ASX group compared to placebo (p=0.016, p=0.001)

Note: Baseline mRNA levels were not reported, so within-group changes over 30-day treatment cannot be confirmed.

Pro-Inflammatory Cytokines (SF)

  • Post-treatment levels of IL‑1β, IL‑6, and TNF‑α were significantly lower in the ASX group compared to placebo (all p ≤ 0.002).

Note: Baseline cytokine levels were not reported, so within-group changes over 30-day treatment cannot be confirmed.

Semen Parameters (SF)

  • Total motility: significantly improved vs placebo (change: +9.55% vs. +4.55%; p=0.048)
  • Progressive motility: significantly improved vs placebo (+10.50% vs. +3.80%; p=0.006)
  • Sperm count improved significantly within the ASX group from baseline, but between-group differences were not significant.

No adverse events were reported, and adherence was strong. Overall, the study provides encouraging evidence that astaxanthin may improve sperm motility, enhance seminal antioxidant capacity, and modulate NRF2-pathway gene expression in infertile men post-varicocelectomy. These results support the potential of astaxanthin as a safe, adjunctive therapy.

However, several methodological limitations temper these conclusions. The trial involved retrospective registration, preventing verification of pre-specified endpoints and increasing the risk of outcome reporting bias. It was powered only for TNF-α, leaving it underpowered for semen parameters, TOS, and gene expression outcomes. While two semen analyses were reportedly used at screening, only a single sample appears to have been collected at each study timepoint, not accounting for intra-individual variability. The 3-4 day abstinence period also introduced further variability in sperm measures amongst individual participants. Baseline TOS and cytokine levels were not reported, making it impossible to confirm claims of reduced oxidative stress or inflammation. Mechanistic conclusions rely solely on mRNA data without protein-level validation, leaving NRF2 activation and anti-apoptotic effects unverified. The simultaneous upregulation of Keap1 and NRF2 in the treatment group is mechanistically counterintuitive and untested. Finally, these findings should be interpreted alongside mixed prior evidence: one RCT reported improved ROS and pregnancy rates with astaxanthin9, another found no benefit in men with oligoasthenoteratozoospermia10, and a meta-analysis concluded human antioxidant evidence remains inconclusive11.

Next steps could include larger, prospectively registered trials with multiple semen samples per timepoint, standardized abstinence windows, baseline data sets, protein-level verification of NRF2 activation, and fertility outcomes.

Source: Ayub Mohammed Salih S, Jabarpour M, Sedighi Gilani MA, Sajadi H, Saedi Marghmaleki M, Shabani Nashtaei M, Salem M, Amidi F. The effect of astaxanthin after varicocele surgery on antioxidant status and semen quality in infertile men: A triple-blind randomized clinical trial. Food Sci Nutr. 2024;12(10):7977–7988. doi:10.1002/fsn3.4365

Click here to read the full text study.

Posted March 19, 2026.

© 2024 The Author(s). Food Science & Nutrition published by Wiley Periodicals LLC.

Keely Puchalski, ND, is a licensed naturopathic physician and natural products expert with a clinical focus on mental health. She earned her ND from Sonoran University of Health Sciences (formerly Southwest College of Naturopathic Medicine) in 2020. Dr. Puchalski has conducted original research in botanical medicine, with discoveries leading to multiple patents and high-impact journal publications. She has authored eight peer-reviewed papers and presented her work at national conferences, webinars, and educational events.

She is the co-founder of Restored Counseling & Wellness Center in Gilbert, AZ, where she leads a collaborative team of therapists and naturopathic doctors dedicated to integrative mental health care:  https://restoredcw.com.

References:

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  2. Hamada A, Esteves SC, Agarwal A. Insight into oxidative stress in varicocele-associated male infertility: part 2. Nat Rev Urol. Jan 2013;10(1):26–37. doi:10.1038/nrurol.2012.198
  3. Finelli R, Leisegang K, Kandil H, Agarwal A. Oxidative Stress: A Comprehensive Review of Biochemical, Molecular, and Genetic Aspects in the Pathogenesis and Management of Varicocele. World J Mens Health. Jan 2022;40(1):87–103. doi:10.5534/wjmh.210153
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  9. Comhaire FH, El Garem Y, Mahmoud A, Eertmans F, Schoonjans F. Combined conventional/antioxidant “Astaxanthin” treatment for male infertility: a double blind, randomized trial. Asian J Androl. Sep 2005;7(3):257–62. doi:10.1111/j.1745-7262.2005.00047.x
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