foundation
Vitamin D is a fat-soluble vitamin your skin produces from sunlight, but it functions more like a hormone than a traditional vitamin. It influences over 1,000 genes and plays roles in immune function, bone health, mood regulation, and hormone production — with vitamin D receptors found throughout the body, including in testicular tissue. Deficiency is remarkably common among men who work indoors, live in northern latitudes, or simply spend most of their time out of direct sun.
We include vitamin D3 (cholecalciferol) — the same form your body naturally produces from sun exposure and the most effective form for raising blood levels. At 75mcg (3,000 IU), we provide a meaningful daily dose for men who don't get regular sun exposure.
The statements on this page have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Modern life keeps you indoors, and the deficit shows up everywhere — hormones, mood, immunity. Vitamin D helps close the gap most men don’t realize they have.
+15 ng/mL vs placebo
Blood 25(OH)D, ng/mL · sufficient, 30+
200 men aged 18–69 starting below 30 ng/mL, 2,857 IU a day (close to our 3,000 IU) for 12 weeks. Testosterone did not change.
View study →−19% odds of infection
Individual data from 10,933 people aged 0–95 in 25 randomized trials. Very deficient means below 10 ng/mL at the start.
View study →1,000+ genes
The receptor is also found in the testes, where testosterone is made.
View study →The daily value for vitamin D is 20mcg (800 IU), but this represents a minimum to prevent severe deficiency, not an optimal intake.
Note on individual variation: Some people may need more or less depending on their baseline levels, sun exposure, skin pigmentation, body composition, and other factors. If you're concerned about your vitamin D status, blood testing can provide clarity.
Clinical studies use 25–125mcg (1,000–5,000 IU) daily. Our 75mcg (3,000 IU) provides a meaningful dose for those without adequate sun exposure.
A vitamin that functions like a hormone, influencing over a thousand genes — with receptors all the way down to testicular tissue.
Martineau AR, et al. (2019). Health Technology Assessment. Source
A major meta-analysis of individual participant data (n=10,933 across 25 RCTs) found that vitamin D supplementation reduces acute respiratory infection risk by 12% overall, and by 70% in severely deficient individuals. Regular daily/weekly dosing was more effective than large, infrequent doses.
Pilz S, et al. (2011). Hormone and Metabolic Research. · Paez-Allendes L, et al. (2026). Nutrients. Source
In a year-long trial of 54 overweight men in a weight-loss program, whose vitamin D averaged below 20 ng/mL at the start, total testosterone rose from 10.7 to 13.4 nmol/L in the 31 taking 3,332 IU of vitamin D a day and from 11.8 to 12.7 nmol/L in the 23 on placebo. Only the vitamin D group’s rise was significant, but the study did not compare the two groups, and testosterone was not a planned outcome. Later, larger trials designed to test testosterone did not repeat this: at 2,857 IU a day for 12 weeks, testosterone did not change in men with normal or low testosterone, including those starting below 20 ng/mL of vitamin D. A 2026 meta-analysis of 11 randomized comparisons found no clear effect of vitamin D supplementation on total testosterone.
Lerchbaum E, et al. (2019). Nutrients. Source
In a 12-week double-blind, placebo-controlled trial of 200 men aged 18–69 whose vitamin D was below 30 ng/mL, 20,000 IU of vitamin D3 once a week (2,857 IU a day, close to our 3,000 IU) raised median blood 25(OH)D from 21 to 39 ng/mL, while placebo went from 21 to 26 ng/mL (192 analysed). The difference between groups, adjusted for baseline, was 15.0 ng/mL (95% CI 12.5–17.5, p<0.001). The same trial found no effect on total testosterone, free testosterone or SHBG, either in men with normal testosterone or in men with low testosterone. Funded by the Austrian National Bank; the manufacturer supplied the drops and placebo.
Mielgo-Ayuso J, et al. (2018). Nutrients. Source
Elite male rowers supplementing with vitamin D3 (3,000 IU/day for 8 weeks) preserved hematological markers associated with recovery — hemoglobin, hematocrit, and transferrin all improved vs controls who declined. Serum vitamin D levels correlated with testosterone and cortisol levels, though supplementation did not significantly change hormone levels directly.
Pike JW, Meyer MB. (2010). Endocrinology and Metabolism Clinics of North America. Source
Vitamin D exerts effects by binding to and activating the vitamin D receptor (VDR), which regulates the activity of over 1,000 different genes. This explains its wide-ranging effects throughout the body.
Chen C, et al. (2019). Causal Link Between Vitamin D and Total Testosterone in Men: A Mendelian Randomization Analysis. J Clin Endocrinol Metab. Source
A Mendelian-randomization study - a genetic design built to test causation rather than correlation - found that vitamin D has a causal effect on total testosterone in men (Chen et al., 2019). Supplementation trials have not yet shown that raising vitamin D raises testosterone.
Vitamin D protects against depression: umbrella meta-analysis (2023). Source
An umbrella meta-analysis pooling ten separate RCT meta-analyses found vitamin D supplementation significantly reduced depressive symptoms versus placebo (pooled SMD -0.40), with the clearest effects when correcting a deficiency.
Every claim we make is grounded in peer-reviewed research. Tap any study to read the abstract.
One of the most studied nutrients in existence. Deficiency is common and correcting it improves immune function, bone health, and testosterone in deficient men. Effects are most meaningful when you're actually low.
No ingredient works alone. Vitamin D3 was chosen because it amplifies — and is amplified by — specific formula partners.
Vitamin D receptors exist in testicular tissue, and deficiency is associated with lower testosterone levels. Tongkat ali and fenugreek support testosterone through separate pathways. Addressing vitamin D status alongside these herbs means covering more of the factors that influence testosterone levels.
Both vitamin D and zinc are common deficiencies that affect testosterone production. Addressing both simultaneously covers two potential bottlenecks — zinc supports testosterone synthesis directly, while vitamin D supports the broader hormonal environment.
Vitamin D and boron both support the hormonal environment through different pathways — vitamin D through receptor-level signaling, boron through its effects on free testosterone and estradiol. Both also influence mineral metabolism, making them complementary in a formula focused on men's health foundations.
Always consult with a healthcare professional before starting any new dietary supplement, especially if you have an existing medical condition or take prescription medications.
