Vitamin D and the prostate: How a deficiency can affect growth

Healthy vitamin D metabolism is not only important for bones and the immune system – the prostate also relies on active vitamin D signals. Recent studies show that a deficiency in active vitamin D can promote prostate growth and contribute to prostatic hyperplasia (BPH).

The prostate produces vitamin D itself – but not always sufficiently

Few people know that the prostate can locally activate vitamin D. This means that the cells in the prostate have enzymes that can convert vitamin D into its active form – 1,25-dihydroxyvitamin D (calcitriol). This active form acts as an internal protective mechanism: It slows cell growth, reduces inflammation, and supports the healthy function of the prostate.

However, if there is a vitamin D deficiency or a disruption in local activation, this system becomes unbalanced. The consequences are:

• increased inflammatory messengers (e.g., IL-6, IL-8),

• increased cell division in the glandular tissue,

• and gradual growth of the prostate.

Which form of vitamin D is crucial?

In the blood, we typically measure the storage form, 25-hydroxyvitamin D (25(OH)D). However, the active form, 1,25-dihydroxyvitamin D (calcitriol), which is produced directly in the prostate cells, is crucial for cell regulation.

If this final activation step is disrupted—for example, due to altered enzyme activity (CYP27B1 ↓, CYP24A1 ↑)—too little calcitriol remains in the tissue. This can weaken the prostate's protective mechanism and thus promote growth.

What do current studies say?

Several clinical studies show that men with low vitamin D levels are more likely to have a larger prostate and more severe urinary symptoms. In laboratory studies, active vitamin D (calcitriol) was able to slow cell division, reduce inflammatory factors, and even modulate the effects of dihydrotestosterone (DHT).

• Elocalcitol study: A vitamin D receptor agonist was able to slow prostate growth in early stages of BPH.

• Cholecalciferol supplementation: Men with vitamin D deficiency benefited through slower prostate growth and lower inflammation levels.

• Observational studies: Low 25-OH-D levels consistently correlate with larger prostate volume and increased urinary urgency.

Why is 25(OH)D deficiency so common?

In my daily practice, I observe a significant 25(OH)D deficiency in many men with BPH. The causes are usually lack of sun exposure, an unbalanced diet, and an age-related reduction in the ability of the skin and liver to convert vitamin D. Inflammation or certain medications can also inhibit vitamin D activation.

How can you support the body's own activation of vitamin D?

A normal intake of vitamin D is essential – but for the prostate, it is crucial that the cell can also activate the vitamin. This can be helped by:

• Sufficient 25(OH)D levels in the blood (ideally 40–60 ng/ml).

• Calcifediol (25-OH-D) as a direct, more effective storage form when liver conversion is limited.

• A low-inflammatory diet (e.g., omega-3-rich, antioxidant-rich) to promote enzyme activity.

• Regular monitoring of vitamin D and calcium levels to avoid overdoses.

  
  

Theoretically, intracellular activation could also be influenced pharmacologically – for example, with substances that directly activate the vitamin D receptor (e.g., elocalcitol). However, these approaches are currently being investigated primarily in research.

Can the prostate shrink again?

Studies suggest that incipient BPH can partially regress if inflammatory stimuli and hormonal overactivity are reduced. Vitamin D plays a supportive role in this process by inhibiting inflammation and slowing cell division. However, a complete "regression" as seen after surgery is not to be expected – the effect is more modulating and stabilizing.

Conclusion by Prof. Dr. Ralf Herwig

Research clearly shows: Vitamin D is far more than a bone vitamin. In the prostate, it acts as a biological regulator, balancing growth, inflammation, and hormonal activity. A deficiency can weaken this protective mechanism – and should therefore be specifically identified and corrected.

This article is intended to provide information. It is not a substitute for a medical examination or treatment recommendation. Men with prostate problems should always undergo a urological examination.