Essential for men’s virility and testosterone production, Vitamin D is widely deficient and declines with age.
- Vitamin D Receptors (VDRs) are present in the testes, prostate and sperm. Some believe this reflects Vitamin D’s key roles in reproductive health.
- Vitamin D-metabolizing enzymes are present in the “T-factory” Leydig Cells, suggesting D may be involved in testosterone synthesis.
- D boosts calcium absorption. Some research shows men experience a bigger jump in T levels when they combine strength training with calcium.1
- It might keep SHGB in check. SHGB hormone binds, neutralizes and diminishes active free testosterone. Vitamin D might boost T by subtracting SHGB.
Other Benefits for Men
- Beyond testosterone support, Vitamin D is good for bone strength, immune health, sperm motility, muscle metabolism and physical performance.
- Side Effects
- Available Vitamin D Forms
- Supplements In Review Recommendation
- Inside Scoop: Don’t Step in D2
Most known for helping immunity and bone density, Vitamin D recently went from relative obscurity to red-hot sales as an “overall health” vitamin. The new scoop, however, is that Vitamin D boosts T–and it appears to do this very well. Vitamin D, especially in the superior D3 form, has now become a popular men’s supplement for testosterone and more.
What we know: Plenty of strong evidence correlates good Vitamin D status to high T-levels. One large population study found the inverse to be true, as well. In this study, Vitamin D deficiency was tied to hypogonadism: Teste shrinkage and man-boob growth caused by exceedingly low T-levels.2
Science doesn’t know how Vitamin D boosts T, at least not yet. But its location may be a hint: Vitamin D, Vitamin D Receptor sites (VDRs), and Vitamin D-metabolizing enzymes are all highly concentrated in the male reproductive system… including within testosterone pathways.
- The male reproductive tract has been identified as “a target tissue for vitamin D.”3 This suggests Vitamin D may be involved in masculine health and androgen (male sex hormone) production.
The big problem with D? We’re just not getting it.
When exposed to sunlight, our skin can synthesize Vitamin D… But many simply aren’t getting enough sun. Those who bask in sunshine and (wisely) use sunblock may not be getting D benefits: Even using a weak SPF 8 sunblock will reduce skin Vitamin D synthesis by 95%.4
In our daily diets, Vitamin D can be a little challenging, but doable: It is found in milk (via fortification), and in some fatty fish. Despite dietary sources and the ABSOLUTELY FREE Vitamin D that can be obtained by standing out in the sun for a few minutes, most men fail to get enough Vitamin D. This nutritional shortfall is a lot worse than you might think:
The Most Widespread Nutritional Disorder in the World…
… is Vitamin D deficiency. In America, some research suggests nearly 75% of adults are insufficient in Vitamin D. Globally, 1 BILLION people are believed to be insufficient!5 Falling short on D could cause big problems for men’s testosterone levels, especially as we get older.
Part of the problem is, Vitamin D is like a nutritional puzzle. As we age, we need more Vitamin D. But as we age, we also lose the ability to absorb and use Vitamin D. Getting Vitamin D is so challenging, researchers have acknowledged that “supplement use is an important contributor to achieve minimum target levels.”6
Since it appears to have a role in healthy testosterone and is apparently difficult for men to get enough of, the best T-booster supplements will usually have a good amount of Vitamin D. Let’s look at some of the research, and see why Vitamin D’s place in T-booster supplements seems to be backed by science.
In one study on male rams, Vitamin D (as D3) was shown to activate and energize the testes’ Leydig Cells (“T-factories”). Then, when combined with Luteinizing Hormone (LH), D3 appeared to significantly boost testosterone (ram study).7 This ram study is intriguing because it suggests a “mechanism of action” that’s consistent with its presence in the male reproductive tract.
- To us, this admittedly early animal research suggests that Vitamin D might first signal the testes to make testosterone… and then might be used in the process of forming T, releasing T, or both.
Human studies are where Vitamin D holds the most weight for boosting T. Check out these three clinical trials, and note their similarities:
652 Korean men over the age of 40 were tracked and tested for fasting blood levels of Vitamin D, total testosterone and free testosterone. At study’s end, researchers reported that higher D levels were tied to higher total and free testosterone levels in the men. Because of its apparent T-boosting activity, researchers suggested Vitamin D might be a safe, cheap way to “treat hypogonadism” in men.
- This study also had two surprising side-discoveries: When the study began, 49% of the 652 participants were found to be deficient in vitamin D–which instantly validated their course of study. Researchers also found that subjects who consumed the most alcohol had the highest T levels, an anomaly that creates more questions than answers.8
In a study of 165 healthy-but-overweight men who were dieting, researchers administered either 3,332 IU Vitamin D or placebo daily for 1 year. At the study’s conclusion, researchers reported that the supplement group experienced a significant across-the-board T-boost:
- Total testosterone levels went from 10.7 ± 3.9 nmol/l to 13.4 ± 4.7 nmol/l; p < 0.001
- Bioactive testosterone levels went from 5.21 ± 1.87 nmol/l to 6.25 ± 2.01 nmol/l; p = 0.001
- Free testosterone levels went from 0.222 ± 0.080 nmol/l to 0.267 ± 0.087 nmol/l; p = 0.001
Researchers in this study concluded D supplementation “may increase testosterone levels.”9
A team of German researchers investigated how Vitamin D levels might affect the hormone levels of a fairly large pool of participants: 2,299 men. Researchers discovered that men with sufficient Vitamin D had significantly higher levels of testosterone and a better Free Androgen Index (FAI) ratio of T to SHBG (female sex hormone).10
- Higher D levels link to lower SHBG levels. Since SHGB binds to testosterone and neutralizes it, this “blocking” bio-activity of D could be helpful for T-levels.11
Our take: Vitamin D seems to be an effective T-Booster by strong association.
We have reviewed some fairly large studies on Vitamin D and testosterone that seem to reach the same conclusions:
- When Vitamin D levels are high, testosterone levels are high.
- When Vitamin D levels are low, testosterone levels are low.
Abundant evidence suggests Vitamin D is strongly correlated to healthy T-levels. Where evidence seems to be lacking, however, is in a definitive explanation of D’s exact T-boosting mechanisms of action. Scientists don’t know how Vitamin D does it, but many seem to agree: It works for boosting T.
Could Vitamin D be a natural aromatase inhibitor?
Petri dish-grade research seems to say so, finding Vitamin D as the active Calcitrol “hormonal” form was able to produce significant reductions in aromatase.12 A similar study found Vitamin D3 achieved a significant decrease in aromatase activity by modulating key inflammatory responses. This research seems to suggest Vitamin D’s T-boosting activities may include aromatase inhibition.13
What does the “IU” in Vitamin D dosage mean? It stands for “International Units,” a numeric measure of Vitamin D’s bio-activity, rather than its weight (like mg). An approximate conversion to weight: 1 microgram (mcg) of Vitamin D = 40 IU. Some Vitamin D dosage notes:
- Recommended daily allowance for men up to age 70: 600 IU
- Recommended daily allowance for men up to age 70+: 800 IU
- Tolerable upper intake level for men: 4,000 IU (100 mcg)
- Retail dosage range: 400 IU – 10,000 IU
- One glass of fortified milk supplies 100 IU of Vitamin D
- T-benefits have been documented at 3,000+ IU daily
The IU thing is kind of annoying, since we’re all conditioned to evaluate supplement dosages as a measure of weight. But, now you know how IU works in Vitamin D supplements.
Vitamin D is very well tolerated and rarely causes problems. Very mild adverse events like sleepiness, dry mouth, upset stomach and weakness have been reported.
The National Institute of Health (NIH) says taking 4,000 IU of Vitamin D daily might be risky because of its potential to dramatically raise blood calcium to unsafe levels. But right away they also acknowledge that higher Vitamin D doses are required in cases of deficiency. It’s a mixed message, but one NIH tip is clear: Only take mega-dose Vitamin D under a doctor’s direction.
Available Vitamin D Forms
Vitamin D2 (ergocalciferol): This form, invented in the 1920s to fight rickets, produces D2 by exposing foods to UV radiation. Despite some marketing claims, D2 may be absorbed just as well as D3. D2 spikes blood levels, but crashes fast.
Vitamin D3 (cholecalciferol): D3 spikes and sustains blood levels, making it 3X as potent as D2, Vitamin D3 is the natural form that your skin makes when exposed to sunlight.14 The body seems to prefer D3, and uses it with far greater efficiency than it does D2.
Supplements In Review Recommendation
- Vitamin D as D3, 5,000 IU daily
Ties between Vitamin D and T levels are simply too strong to ignore. Testosterone benefits, whole body health and excellent tolerability make Vitamin D a great fit for any T-booster program. The D3 form is an easy call: It’s stronger and easier to utilize than D2, especially for older men.
5,000 IU is a higher dosage, but we think it’s justified given today’s apparent low-D epidemic. 5,000 IU is also the doctor-recommended dose from the Vitamin D Council. If you buy a T-booster with Vitamin D, look for magnesium too: It may have synergy with D that enhances T-boosting activity.15
Inside Scoop: Don’t Step in D2
The supplement industry has almost completely phased out D2 at this point. D3 is so much better, and everybody knows it. If you buy a straight-D supplement, most will be D3. But be warned: Sketchy brands will still try to pawn off D2… because it’s a cheap ingredient that improves their profit margins.
- The dirty trick: They hide cheap, inferior D2 in big complexes with lots of ingredients… so no one will notice.
If you’re buying any kind of complex with Vitamin D–multivitamins, bone health formulas, T-boosters–check to see what kind of Vitamin D they are using. If it’s D2, ditch that brand altogether.
- Cinar V, et al. Testosterone Levels in Athletes at Rest and Exhaustion: Effects of Calcium Supplementation. Biological Trace Element Research. June 2009, Volume 129, Issue 1, pp 65-69. ↩
- Lee DM, et al. Association of hypogonadism with vitamin D status: the European Male Ageing Study. Eur J Endocrinol. 2012 Jan;166(1):77-85. doi: 10.1530/EJE-11-0743. Epub 2011 Nov 2. ↩
- Pilz S et al. Effect of vitamin D supplementation on testosterone levels in men. Horm Metab Res. 2011 Mar;43(3):223-5. doi: 10.1055/s-0030-1269854. Epub 2010 Dec 10. ↩
- Holick MF. (2004) Sunlight and Vitamin D for bone health and prevention of autoimmune disease, cancers, and cardiovascular disease. Am J Clin Nutr 2004;80(suppl):1678S-1688S. ↩
- Ginde AA, et al. Demographic Differences and Trends of Vitamin D Insufficiency in the US Population, 1988–2004. Arch Intern Med. 2009 Mar 23; 169(6): 626–632. ↩
- Baraké R, et al. Vitamin D Supplement Consumption Is Required to Achieve a Minimal Target 25-Hydroxyvitamin D Concentration of ≥75 nmol/L in Older People. J. Nutr. March 2010 vol. 140 no. 3 551-556 ↩
- Huang Y, et al. Effect of Vitamin D on basal and Luteinizing Hormone (LH) induced testosterone production and mitochondrial dehydrogenase activity in cultured Leydig cells from immature and mature rams. Anim Reprod Sci. 2015 Jul;158:109-14. ↩
- Tak YJ, et al. Serum 25-hydroxyvitamin D levels and testosterone deficiency in middle-aged Korean men: a cross-sectional study. 2015 vol.17 324-328 ↩
- Pilz S, et al. Effect of vitamin D supplementation on testosterone levels in men. Horm Metab Res. 2011 Mar;43(3):223-5 ↩
- Wehr E, et al. Association of vitamin D status with serum androgen levels in men. Clin Endocrinol (Oxf). 2010 Aug;73(2):243-8. ↩
- Knochenhauer ES, et al. Differential binding of estradiol and testosterone to SHBG. Relation to circulating estradiol levels. J Reprod Med. 1998 Aug;43(8):665-70. ↩
- Krishnan AV, et al. Tissue-Selective Regulation of Aromatase Expression by Calcitriol: Implications for Breast Cancer Therapy. Endocrinology. 2010 Jan; 151(1): 32–42. ↩
- Villaggio B, et al. 1,25-dihydroxyvitamin D3 downregulates aromatase expression and inflammatory cytokines in human macrophages. Clin Exp Rheumatol. 2012 Nov-Dec;30(6):934-8. ↩
- Houghton LA, Vieth R. The case against ergocalciferol (vitamin D2) as a vitamin supplement. Am J Clin Nutr October 2006 vol. 84 no. 4 694-697 ↩
- Xinqing Deng, et al. Magnesium, vitamin D status and mortality: results from US National Health and Nutrition Examination Survey (NHANES) 2001 to 2006 and NHANES III. BMC Med. 2013; 11: 187. ↩