Modern health folklore and bioscience state that testosterone makes you manly and Vitamin D makes your bones strong. However, recent research indicates that these two famous biomarkers have a wide variety of functions in the body and may, in fact, impact each other’s levels. Below we document some of the key reasons why you need to stay optimized in Vitamin D and testosterone, and look at the nitty-gritty research examining the fascinating relationship between them.
Some background on vitamin D
- Vitamin D is an important fat-soluble nutrient naturally found in very few foods, such as mushrooms and fatty fish (i.e. sardines, salmon, mackerel). Other foods, such as milk, are fortified with vitamin D. The body does produce high amounts of vitamin D when skin is directly exposed to sun (i.e. not through a window), so it’s sometimes referred to as the “sunshine vitamin.” However, excess sun exposure may increase the risk of skin cancer. Because vitamin D is difficult to find in foods and prolonged sun exposure carries health risks, dietitians and doctors often prescribe supplements of varying doses.
The liver first converts vitamin D to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol, before it is used in the body. Blood levels of this compound are the best indicator of one’s Vitamin D status.1 The kidneys then convert this substance to 1,25-dihydroxyVitamin D [1,25(OH)2D], also known as calcitriol, the active form of vitamin D. Calcitriol is the form of vitamin D that is considered to be a hormone.
Vitamin D in the body
- Vitamin D is typically associated with maintaining bone health and helping the body absorb minerals such as calcium and magnesium. 2,3 However, recent research has revealed that this biomarker also regulates cell growth and the immune system while maintaining neuromuscular and cardiovascular health.4,5,6 Optimal levels of this overlooked vitamin are also crucial for athletes, as vitamin D stimulates muscle growth, increases power, and cuts unnecessary body fat.7,8
Despite its ever-expanding catalogue of beneficial physiological functions, vitamin D deficiency is still very prevalent. In 2011, it was estimated that 25% and 8% of Americans were at risk for vitamin D inadequacy and deficiency, respectively (serum 25(OH)D 30-49 and <30 nmol/L, respectively). 9
On the other side of the coin, excess vitamin D caused from sunlight exposure and high-dose vitamin D supplements can lead to kidney problems and nausea.10 Some InsideTracker users, such as Laura Ingalls, experience joint pain as a result of excess vitamin D intake. Only about 14% of InsideTracker users have optimal levels of vitamin D, making it one of our least optimized biomarkers.
Testosterone: Critical for performance and health
- Testosterone is a crucial steroid hormone produced by both men and women. In men, testosterone levels elevate during puberty and stimulate the production of sperm and the formation of secondary sexual characteristics such as body hair and a deeper voice. In both men and women, testosterone helps increase bone strength, stimulates the development of muscle mass and strength, and improves libido and mood. Testosterone is also crucial for athletes of both genders; it helps speed tissue recovery and stimulate red blood cell blood production.
Testosterone is found in the bloodstream in one of two forms. It can be bound to the proteins albumin or sex hormone-binding globulin (SHBG), where it is known as “bound testosterone.” These proteins transport testosterone throughout the body. However, it remains biologically inactive, meaning that it does not exert its typical effects upon body cells. About 97-98% of testosterone is bound to one of these proteins.11
The other 2-3% circulates in the blood where it can freely exert its biological effects. This portion is known as “free testosterone” (FT). While relatively small in proportion, FT is critical to maintaining optimal performance and health. The sum of bound and free testosterone is referred to as “total testosterone” (TT). All four of these testosterone biomarkers—SHBG, free testosterone, albumin, and total testosterone—are crucial indicators of health and fitness and measured in InsideTracker’s Ultimate Panel.
Testosterone in the body
- Knowing your testosterone levels is crucial for many reasons. Low testosterone in men is linked to infertility, irritability, and erectile dysfunction. In both men and women, low testosterone can lead to a variety of cardiovascular diseases and mental health concerns such as depression.12,13 Testosterone is critical for performance because it facilitates anabolic (recovery) processes, and low levels of free testosterone may lead to poor recovery, poorer fitness gains, and increased chance of injury.14 Elevated testosterone in women can also lead to sexual dysfunction.
If your testosterone levels are too low, consider increasing your recovery time if you’re overtraining, or lifting weights if you aren’t already exercising. Also, check for possible magnesium and zinc deficiencies and increase your intake of animal proteins.
Is there a relationship? Evidence of a possible connection
- A reasonable amount of research suggests an association between adequate levels of vitamin D in the body, as measured by 25(OH)D, and TT.
Results from a 2012 study showed a positive, independent association between concentrations of 25(OH)D and levels of TT and FT.15 Most importantly, the researchers noted this association was linear at lower levels and plateaued at higher ones.15 This suggests that the positive association between vitamin D and levels of free and total testosterone stops when vitamin D levels are optimal in the body.
Relationship between Total Testosterone and Concentration of Serum 25(OH)D
Nimptsch, et al. Clinical Endocrinology, 2012
Another study of middle-aged men displayed a positive correlation between TT, FT, and 25(OH)D.16 It also found that subjects with optimized levels of testosterone (>26.51 ng/mL) had, on average, 15% more vitamin D than those with suboptimal levels of testosterone.16
Because vitamin D plays a key role in optimal athletic performance, scientists have also investigated the relationship between serum 25(OH)D levels and testosterone in young, active men. A 2015 study found serum vitamin D concentrations to be a significant, positive predictor of total testosterone.17 This result suggests that highly active people—such as military personnel and athletes—may remedy low testosterone by optimizing their vitamin D levels.
Vitamin D and testosterone: Not just for men
- Scientists have also observed a direct correlation between vitamin D and testosterone in women. In a recent cross-sectional study of women, researchers observed a positive, significant correlation between serum 25(OH)D concentrations and total testosterone levels.18 This suggests that increasing levels of vitamin D may restore healthy levels of testosterone, though more research investigating the mechanism through which this happens needs to be done.
Does supplementation with vitamin D boost testosterone?
- In a 2011 randomized controlled study, researchers found men who were given a daily high-dose vitamin D supplement significantly increased their total testosterone from 10.7 nmol/L to 13.4 nmol/L, whereas there were hardly any changes in testosterone concentrations in the group given a placebo.19 These findings suggest that men deficient in vitamin D who take a proper vitamin D supplement may fix low levels of low testosterone.
Some conflicting research on supplementation
- Not all research indicates that vitamin D supplementation optimizes testosterone levels, though. In a 2015 study, Dutch researchers completed a meta-analysis of three intervention studies investigating the effects of vitamin D supplementation on serum testosterone concentrations in vitamin D-deficient subjects.
As expected, the concentrations of serum 25(OH)D increased substantially. However, there was no increase in mean testosterone concentrations at the end of any of the three studies. As a result, the researchers concluded that vitamin D supplementation was not associated with an increase in testosterone levels.20 Thus, short-term, low-dose supplementation in vitamin D-deficient men may not increase testosterone in men with suboptimal levels.
Analysis: Can vitamin D treat low T?Let’s recap the evidence for the relationship between Vitamin D and testosterone:
Several studies in men show an independent association between Vitamin D intake and testosterone.
- A cross-sectional study observed a correlation between Vitamin D and testosterone in women.
- One study shows an increase in levels of testosterone after providing high-dose, long-term vitamin D supplements to Vitamin D-deficient men.
- Another study observed no increase in testosterone after providing Vitamin D-deficient men with short-term Vitamin D supplementation.
Provided with this inconsistent evidence, what do we recommend? We encourage you to conduct your own experiment. First, use InsideTracker to monitor your Vitamin D and testosterone levels and use science-based recommendations to optimize them. If you are low in vitamin D and testosterone, see if regularly taking the proper vitamin D supplement increases your testosterone. Remember the research: If you are already optimal in Vitamin D, supplementation is unlikely to affect your testosterone and may lead to too much Vitamin D in your body!
Putting it into perspectiveBecause vitamin D and testosterone influence the body’s health and performance, it is crucial that you consistently monitor levels of these biomarkers to make sure that they are optimized. Research suggests that there is a correlation between adequate levels of vitamin D and adequate levels of testosterone. However, supplementation may only help you boost testosterone if you are already proven to be deficient in both testosterone and vitamin D.
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1. Ross, A. Catherine, et. al. (editors) Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academies Press, 2011.
2. Horsley, Tanya, et al. Effectiveness and safety of Vitamin D in relation to bone health. US Department of Health and Human Services, Public Health Service, Agency for Healthcare Research and Quality, 2007.
3. Ross, A. Catharine, et al. "The 2011 report on dietary reference intakes for calcium and Vitamin D from the Institute of Medicine: What clinicians need to know." The Journal of Clinical Endocrinology & Metabolism 96.1 (2011): 53-58.
4. Shils, Maurice Edward, and Moshe Shike, eds. Modern Nutrition in Health and Disease. Philadelphia: Lippincott Williams & Wilkins, 2006.
5. Wang, Lu, et al. "Systematic review: Vitamin D and calcium supplementation in prevention of cardiovascular events." Annals of Internal Medicine 152.5 (2010): 315-323.
6. Hossein-Nezhad, Arash, Avrum Spira, and Michael F. Holick. "Influence of Vitamin D status and Vitamin D3 supplementation on genome wide expression of white blood cells: A randomized double-blind clinical trial." PLoS One 8.3 (2013): e58725.
7. Wyon, Matthew A., et al. "The influence of winter Vitamin D supplementation on muscle function and injury occurrence in elite ballet dancers: A controlled study." Journal of Science and Medicine in Sport 17.1 (2014): 8-12.
8.Forney, Laura A., et al. "Vitamin D Status, Body Composition, and Fitness Measures in College-Aged Students." The Journal of Strength & Conditioning Research 28.3 (2014): 814-824.
9. Looker A.C., C.L. Johnson, D.A. Lacher, et al. Vitamin D status: United States 2001–2006. NCHS data brief, no 59. Hyattsville, MD: National Center for Health Statistics, 2011.
10. Jones, Glenville. "Pharmacokinetics of Vitamin D toxicity." The American Journal of Clinical Nutrition 88.2 (2008): 582S-586S.
11. Emadi-Konjin, Pasha, Jerald Bain, and Irvin L. Bromberg. "Evaluation of an algorithm for calculation of serum 'bioavailable' testosterone (BAT)." Clinical Biochemistry 36.8 (2003): 591-596.
12. Westley, Christopher J., Richard L. Amdur, and Michael S. Irwig. "High Rates of Depression and Depressive Symptoms among Men Referred for Borderline Testosterone Levels." The Journal of Sexual Medicine (2015).
13. Wickramatilake, Chandima Madhu, Mohamed R. Mohideen, and Chitra Pathirana. "Association of metabolic syndrome with testosterone and inflammation in men." Annales d'Endocrinologie. Elsevier Masson, 2015.
14. Chung, Kyung-Jin and Khae-Hawn Kim. "Forbidden fruit for athletes, but possible divine blessing for rehabilitation: testosterone." Journal of Exercise Rehabilitation 11.1 (2015): 2.
15. Nimptsch, Katharina, et al. "Association between plasma 25‐OH Vitamin D and testosterone levels in men." Clinical Endocrinology 77.1 (2012): 106-112.
16.Tak, Young Jin, et al. "Serum 25-hydroxyVitamin D levels and testosterone deficiency in middle-aged Korean men: a cross-sectional study." Asian Journal of Andrology 17.2 (2015): 324.
17. Wentz, Laurel, et al. "Vitamin D Correlation with Testosterone Concentration in US Army Special Operations Personnel." The FASEB Journal 29.1 Supplement (2015): 733-5.
18. Chang, Eun Mi, et al. "Association between sex steroids, ovarian reserve, and Vitamin D levels in healthy non-obese women." The Journal of Clinical Endocrinology & Metabolism 99.7 (2014): 2526-2532.
19. Pilz, S., et al. "Effect of Vitamin D supplementation on testosterone levels in men." Hormone and Metabolic Research 43.3 (2011): 223.
20. Heijboer, Annemieke C., et al. "Vitamin D supplementation and testosterone concentrations in male human subjects." Clinical endocrinology (2015).