What doses and durations of zinc, L-carnitine, and maca improve semen volume in older men?
Executive summary
Randomized and observational studies suggest L‑carnitine, zinc and maca can improve some semen parameters, and several trials report increased seminal volume after supplementation—however doses and durations vary across studies, benefits are modest and direct evidence specifically in "older men" is limited [1] [2] [3]. Clinical trials typically use L‑carnitine in the 1,000–3,000 mg/day range for 3–6 months, maca at 1,500–3,000 mg/day for about four months, and zinc as part of multi‑nutrient formulas in amounts from ~10 mg up to commonly used supplemental levels, but single‑agent zinc trials show mixed results [4] [5] [3] [6].
1. L‑carnitine: a consistent signal at 500–3,000 mg/day for 3 months
A body of interventional work finds L‑carnitine (often as L‑carnitine and L‑acetylcarnitine) improves motility and sometimes semen volume when given over months; mono‑therapy doses in trials include 500 mg twice daily (1,000 mg/day) and higher regimens up to 3,000 mg/day, with positive effects typically observed after about three months [2] [5]. One prospective study of an antioxidant product containing 1,500 mg L‑carnitine reported improved semen quality after treatment [4], while a case report and other reports used 3,000 mg/day for three months with improved motility and reported volume changes—these amounts and timeframes are the most frequently tested in the literature [5] [1]. Meta‑analytic work also attributes gains in progressive motility and total motility to carnitine supplements, supporting the biological plausibility for downstream increases in ejaculate metrics [7].
2. Zinc: useful in combination, uncertain as a lone agent for volume
Zinc is biologically important for testes and seminal biochemistry and appears in many effective multi‑nutrient formulas, where typical zinc content ranges from about 10 mg in commercial combinations to higher supplemental levels reported in fertility guides [4] [8]. Systematic reviews and meta‑analyses report zinc supplementation increases some semen parameters such as total motility, but randomized trials assessing zinc (or zinc plus folic acid) have returned mixed results for semen volume specifically, with at least one clinical trial showing no significant effect on volume or overall semen quality versus placebo [7] [6]. Some individual studies find biochemical improvements in zinc‑bound seminal proteins after zinc therapy, but the evidence does not uniformly support zinc alone as a reliable volume‑increaser [1].
3. Maca (Lepidium meyenii): limited but positive trials at 1,500–3,000 mg/day for ~4 months
A small controlled study showed maca improved seminal volume, sperm count per ejaculate and motility after four months of oral tablets at 1,500–3,000 mg/day in healthy adult men (ages reported 24–44), and reported no change in serum hormones—this suggests maca can increase ejaculate volume but the trial was small, in younger men, and not targeted to older men [3]. Commercial and lay publications promote maca at similar daily doses as part of multi‑ingredient “volume” blends, but independent, large randomized trials in older cohorts are lacking [9] [10].
4. Practical synthesis, limitations and safety caveats
Taken together, the best‑documented regimens in peer‑reviewed reports are L‑carnitine 1,000–3,000 mg/day for about three months and maca 1,500–3,000 mg/day for roughly four months, often producing modest increases in semen volume and other parameters; zinc is commonly included (≈10 mg in combination products) but has inconsistent single‑agent evidence for volume gains [2] [5] [3] [4]. Important limitations: most trials enroll mixed‑age or younger men (maca study 24–44), many studies use combination supplements so isolating one ingredient’s effect is difficult, sample sizes are often small, and at least one randomized trial found no benefit from zinc+folic acid [3] [6] [1]. Safety and interactions are not fully addressed in these reports; clinical guidance is recommended before high‑dose, multi‑month supplementation, particularly in older men with comorbidities or on medications [4] [9].
Bottom line
For men seeking evidence‑based regimens most trials support L‑carnitine at roughly 1–3 g/day for 3 months and maca at 1.5–3 g/day for ~4 months as the best‑studied approaches tied to increased seminal volume, while zinc is better supported as part of combination therapies than as a lone proven volume booster; direct, high‑quality data focused solely on older men remain sparse and results should be interpreted within those limits [2] [5] [3] [7].