22/10/2025
🔬 精子の質の低下とその背景
過去50年間で精子の質は着実に低下しており、1973年から2011年の間に世界的な精子濃度と総精子数が大幅に減少しました。特に欧米諸国では総精子数が約60％も減ったと報告されています。
この傾向の要因として、アデレード大学ロビンソン研究所のHannah Lyons氏らは以下を挙げています：
• 糖尿病やメタボリックシンドロームなどの慢性疾患
• フタル酸、ビスフェノールA、カドミウム、ダイオキシン、鉛などの内分泌かく乱物質への曝露
• 高温環境
• 不健康な生活習慣（薬物・アルコール・喫煙・栄養バランスの悪い食事・運動不足）
これらはホルモンバランスの乱れや精巣細胞の損傷、酸化ストレス（活性酸素種〈ROS〉の増加）によるDNA損傷を通して精子の質を悪化させると考えられています。
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💊 サプリメントと生活習慣改善による回復効果
近年の研究では、精子の質は比較的短期間で改善できることが示されています。
不妊の男性132人を対象とした研究では、3か月間のマイクロ栄養素摂取により以下の改善が見られました：
摂取した栄養素：
L-カルニチン、L-アルギニン、亜鉛、ビタミンE、グルタチオン、セレン、コエンザイムQ10、葉酸
改善率：
• 精液量：＋33%
• 精子濃度：＋215%
• 運動率：＋93%
• 総運動率：＋36%
• 形態正常率：＋23%
また、6か月以内の妊娠率もサプリメント群で25.8%と、健康群の15%を上回りました。
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🏃♂️ サプリ＋生活改善の併用効果
同大学のMarkus Lipovac氏ら（2021年）は、サプリメントと生活改善（食事・運動・喫煙と飲酒の減少）を組み合わせた339人の男性を追跡。
結果として、DNA断片化指数（DFI）が有意に減少し、特にDFIが高い男性では妊娠率が41%と大幅に上昇しました。
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⚠️ 精子の質は全身の健康の指標
精液検査は生殖能力だけでなく、男性の全身的健康状態の指標にもなります。
不妊や精子異常を持つ男性は、入院や早死のリスクが高い傾向にあります。
• 不妊男性の死亡リスク：＋26%
• 乏精子症・無精子症男性の死亡リスク：＋67%
また、前立腺がんや精巣がんのリスク上昇とも関連しています。
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📚 参考文献
• Marina Urbanietz, What Your S***m Says About You, Medscape, 2025年8月
• PubMed: 40481278, 34184957
S***m quality has steadily declined over the past 50 years. Between 1973 and 2011, the global s***m concentration and total s***m count decreased significantly. This decline was most pronounced in Western countries, with a reduction in the total s***m count of almost 60%.
Marina Urbanietz’s August 2025 Medscape article, What Your S***m Says About You, offers a concise review of selected studies on how supplements and lifestyle can influence s***m parameters, drawing on a recent paper in a Nature journal.
Semen analysis not only provides information on fertility but also offers insights into the overall health. The cited paper reported that s***m quality can significantly improve with basic lifestyle and dietary changes.
The study, led by Hannah Lyons, a researcher at the Robinson Research Institute and School of Biomedicine at the University of Adelaide attributed the s***m count decline to multiple factors.
These include chronic conditions such as diabetes and metabolic syndrome, exposure to endocrine-disrupting chemicals such as phthalates, bisphenol A, cadmium, dioxins, and lead, and heat exposure.
Lifestyle factors, including certain medications, substance use, poor diet, and physical inactivity, can impair s***m production by disrupting hormonal regulation, damaging testicular cells, and increasing oxidative stress due to elevated levels of reactive oxygen species (ROS).
High ROS levels can damage s***m DNA, compromise the membrane integrity, and reduce s***m motility. Established risk factors include smoking, heavy alcohol consumption, drug abuse and excessive exercise.
S***m quality can recover more rapidly than previously believed. In a study of 132 men with fertility issues, a 3-month micronutrient regimen, including L-carnitine (440 mg), L-arginine (250 mg), zinc (40 mg), vitamin E (120 mg), glutathione (80 mg), selenium (60 µg), coenzyme Q10 (15 mg), and folic acid (800 µg), significantly improved semen parameters. Volume, s***m concentration, progressive motility, total motility, and morphology increased by 33.3%, 215.5%, 93.1%, 36.4%, and 23.0%, respectively (all P < 0.001). No improvements were observed in healthy individuals (n = 73).
In the 6 months following the intervention, the pregnancy rate among the partners of the participating men was also recorded. More pregnancies occurred in the intervention group (25.8%) than in the healthy group (15%). Although this study had some limitations, including age differences and limited risk factor data, two additional trials supported these findings. The researchers concluded that micronutrients may restore s***m production within 3 months.
A 2021 study by Markus Lipovac, PhD, also at the Robinson Research Institute at the University of Adelaide, and colleagues, evaluated 339 men who received the same micronutrient supplements along with lifestyle changes. These include a healthy diet, regular exercise, and reduced smoking and alcohol consumption.
Of these, 162 men received supplements and lifestyle guidance, whereas 177 followed lifestyle and dietary modifications. After 6 months, s***m DNA fragmentation index (DFI) and pregnancy rates were assessed. In the supplement group, DFI decreased from 10.48 to 6.51 overall and from 20.39 to 9.93 in men with DFI > 15% (P < .001). Pregnancy rates were higher with supplements: 27.78% vs 15.25% overall and 41.30% vs 22.86% in men with DFI > 15%.
The limitations of this study include missing demographic data, lack of randomisation, and lack of information on the extent of lifestyle changes.
Semen analysis may reflect the overall health of men, not just their fertility. Men with infertility or abnormal semen are at a higher risk for hospitalisation and early death. For example, men with infertility had a 26% higher risk for death (95% CI, 1.01-1.59), and men with oligo- or azoos***mia had a 67% higher risk (risk ratio, 1.67; 95% CI, 1.26-2.21) than those with normal s***m counts.
Abnormal s***m parameters often reflect poor health or disease and are linked to a higher risk for cancer. Studies have shown that men with infertility have an increased risk for prostate and testicular cancer.
For more information see: https://www.medscape.com/viewarticle/what-your-s***m-says-about-you-2025a1000kve?ecd=wnl_tp10_daily_250807_MSCPEDIT_etid7624212&uac=48709HJ&impID=7624212
and
https://pubmed.ncbi.nlm.nih.gov/40481278/
and
https://pubmed.ncbi.nlm.nih.gov/34184957/
