Often called the “sunshine vitamin”, vitamin D is well-known for supporting bone health, but its role in male reproductive health is equally significant (Yahyavi et al., 2024). Emerging research suggests that vitamin D can enhance sperm quality, regulate hormones, and combat factors that impair fertility. This article dives into the science behind vitamin D and its impact on male fertility, with actionable advice for improving vitamin D levels.
What is Vitamin D, and how does it work?
Vitamin D is a fat-soluble vitamin primarily obtained through sunlight exposure, but it is also found in certain foods such as fatty fish, fish liver oil, egg yolk or mushrooms. Once absorbed, the body converts vitamin D into its active form, calcitriol, which interacts with vitamin D receptors (VDR) in various tissues, including the testes and sperm cells. These receptors allow vitamin D to influence crucial reproductive functions, highlighting its direct role in male fertility.
Vitamin D’s role in male fertility
Vitamin D impacts male fertility in several important ways:
- Enhances sperm quality
Studies consistently link adequate vitamin D levels to improved sperm parameters:- Motility: Vitamin D improves the calcium uptake in sperm, which is critical for their movement and ability to fertilise an egg. For example, one study found that men with optimal vitamin D levels had 30% higher sperm motility than those who were deficient (Blomberg Jensen et al., 2011).
- Morphology: Better vitamin D levels are associated with healthier sperm shape and structure, which is key for effective fertilisation (Blomberg Jensen et al., 2011).
- Count: Vitamin D may support spermatogenesis (sperm production), helping to maintain a healthy sperm count (Adamczewska et a., 2023).
- Boosts Testosterone levels
Testosterone, a hormone vital for sperm production and male libido, is positively correlated with vitamin D. Research indicates that men with adequate vitamin D levels tend to have significantly higher testosterone levels compared to those deficient (Pilz et al., 2011). - Protects against oxidative stress and inflammation
Sperm cells are highly vulnerable to oxidative stress, which can damage DNA and impair fertility. Vitamin D acts as an antioxidant and anti-inflammatory agent, reducing oxidative damage and promoting healthy sperm function (Kaltsas, 2023). - Regulates reproductive hormones
Vitamin D supports the hypothalamic-pituitary-gonadal (HPG) axis, which controls reproductive hormone production. Balanced levels of hormones like luteinising hormone (LH) and follicle-stimulating hormone (FSH) are essential for proper sperm production (Blomberg Jensen et al., 2012).
Vitamin D from sunlight: The UK winter challenge
While sunlight is the best natural source of vitamin D, its availability varies significantly depending on geographic location, season, and weather. In the UK, this variation poses a unique challenge.
During the winter months (approximately October to March), the angle of the sun is too low for sufficient ultraviolet B (UVB) rays to reach the earth's surface. As a result, even on sunny days, the skin cannot produce adequate vitamin D. Studies suggest that during this period, most people in the UK rely heavily on dietary sources or supplements to meet their vitamin D needs (National Institute for Health and Care Excellence [NICE], 2016).
This seasonal limitation contributes to widespread vitamin D deficiency in the UK population, with nearly 1 in 5 adults showing low levels. For men aiming to optimise fertility, addressing this deficiency through diet or supplementation is important, particularly during the winter months.
Practical steps to optimize Vitamin D levels
- Sunlight exposure: Aim for 10–30 minutes of direct sunlight exposure on bare skin (depending on skin tone and location) several times a week during spring and summer. In winter months, consider alternative strategies. However, note that exposure to a daylight lamp to boost mood and alleviate winter depression does not significantly increase the vitamin D levels as daylight lamps do not emit enough UVB rays.
- Incorporate dietary sources: Add vitamin D-rich foods to your diet, such as salmon, mackerel, sardines, egg yolks, and fortified products like milk and cereals.
- Supplementation: If sun exposure and diet aren’t enough, consider vitamin D supplements. Most adults need 600–800 IU per day, but higher doses may be prescribed in cases of deficiency. Consult a doctor or nutritionist for personalised recommendations.
- Monitor levels: Regular blood tests can check vitamin D levels, with 30 ng/mL (nanograms per millilitre) considered sufficient. Levels below 20 ng/mL indicate deficiency.
What are the risks of over-supplementation?
While vitamin D is essential, excessive supplementation can lead to toxicity, causing high calcium levels (hypercalcemia), kidney problems, and other health issues which is why testing, and the appropriate medical advice is always essential.
Frequently Asked Questions
Q: Can vitamin D supplements alone improve fertility?
A: Vitamin D is one piece of the fertility puzzle but a general healthy diet, regular exercise, and managing underlying health conditions are also critical.
Q: How quickly can vitamin D levels improve sperm quality?
A: Positive effects may take a few weeks to months of consistent sunlight exposure or supplementation.
Conclusion
Vitamin D plays a pivotal role in male fertility, supporting sperm health, hormone balance, and overall reproductive function. For men facing fertility challenges, ensuring adequate vitamin D levels through sun exposure, diet, or supplements is a simple yet impactful strategy. If you’re trying to conceive or want to optimise your reproductive health, consider talking to your doctor or a nutritionist about checking and improving your vitamin D levels.
References
- Yahyavi SK, Boisen IM, Cui Z, Jorsal MJ, Kooij I, Holt R, Juul A, Blomberg Jensen M (2024); Calcium and vitamin D homoeostasis in male fertility. Proceedings of the Nutrition Society 83(2), 95-108.
- Blomberg Jensen M, Bjerrum PJ, Jessen TE, Nielsen JE, Joensen UN, Olesen IA, Petersen JH, Juul A, Dissing S, Jørgensen N (2011). Vitamin D is positively associated with sperm motility and increases intracellular calcium in human spermatozoa. Human Reproduction 26(6), 1307–1317.
- Pilz S, Frisch S, Koertke H, Kuhn J, Dreier J Obermeyer-Pietsch B, Wehr E, Zittermann A (2011). Vitamin D and testosterone in men. Clinical Endocrinology 75(5), 575–581.
- Adamczewska D, Słowikowska-Hilczer J, Walczak-Jędrzejowska R (2023); The Association between Vitamin D and the Components of Male Fertility: A Systematic Review. Biomedicines 11(1), 90.
- Kaltsas A (2023); Oxidative stress and male infertility: The protective role of antioxidants. Medicina (Kaunas) 59, 1769.
- National Institute for Health and Care Excellence (NICE). (2016). Vitamin D: increasing supplement use in at-risk groups. NICE Public Health Guideline (PH56).