How Vitamin D Affects Testosterone Levels

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Most people know about some of the health benefits of vitamin D, but few people realize its role in testosterone levels.

Even though I’d read numerous research articles and written multiple blog posts about vitamin D, it wasn’t until a couple of years ago that I connected vitamin D levels and testosterone levels.

I was reviewing my lab work from the previous several years. I get a complete lab panel done about every six months and noticed a consistent trend between my vitamin D levels and testosterone.

My testosterone was consistently higher in the fall than in the spring, as was my vitamin D. That led me to search for research explicitly looking at the impact vitamin D has on testosterone. This is what I found.

Vitamin D isn’t a “Vitamin.”

Though it’s characterized as a “vitamin,” vitamin D is a hormone precursor.

Humans convert vitamin D3, or cholecalciferol, to the biologically active form, 1,25-dihydroxyvitamin D. You get vitamin D3 from sun exposure, a small amount from some foods, or through supplementation.

Another available form called D2, or ergocalciferol, comes from plants. While some animals convert D2 to D3 easily, humans do not. So it’s an ineffective source for humans.

Vitamin D regulates the expression of more than 900 genes, so it affects most systems and functions in the body.

In this blog post, I’m focusing on vitamin D and testosterone, but I’ve touched on other health benefits of vitamin D in Vitamin D: Deficiency Symptoms And Benefits Of Supplementation.

The Vitamin D–Testosterone Connection

Being a hormone precursor, it’s no surprise that vitamin D plays a role in sex hormone balance.

A cross-sectional study of 2299 men showed a similar seasonal change in vitamin D and testosterone like I experienced. It showed a low point for both in March and a peak in August, as you would expect for those living in the Northern Hemisphere.

In another study involving 2854 men, those with low vitamin D were more likely to have hypogonadism (low testosterone).

One more cross-sectional survey of 3369 men from Europe found that those with low vitamin D also tended to have low testosterone.

In a study from Amsterdam, the testosterone-vitamin D correlation was strongest for men with vitamin D below 25 nmol/L compared to the men above 75 nmol/L.

The vitamin D Council generally recommends maintaining levels between 50-80 nmol/L.

In a 12-month, double-blind, placebo-controlled study of 54 overweight men with low vitamin D, the group who took just 3332 IU per day of vitamin D experienced a significantly higher vitamin D level, total testosterone, bioactive, and free testosterone. The placebo group experienced no change in these measures.

To be fair, not all studies show that D3 improves testosterone.

A few small studies showed that vitamin D supplementation did not affect testosterone, but the highest daily dose was only 1200 IU, which isn’t enough to raise levels to be optimal in most people.

In another study, 98 men took 20,000 IU of D3 per week or took a placebo. After 12 weeks, there wasn’t a significant difference in total testosterone between the groups.

Interestingly, in women with Polycystic Ovary Syndrome (PCOS), higher daily doses of D3 helped normalize testosterone, sex hormone binding globulin, and free androgen index. 

VDR (Vitamin D receptors) and vitamin D metabolizing enzymes have been located in human and rat testis and have been shown to enhance the affinity of androgen binding receptors. This effect increases the rate at which androgens can bind to testosterone-producing glands resulting in higher concentrations of steroid hormones, leading to an increase in skeletal muscle hypertrophy, strength and power output.

Dahlquist DT, et al.

How Vitamin D Affects Testosterone

The way vitamin D improves testosterone levels isn’t fully understood. Researchers currently believe in two possible mechanisms:

1. Inhibition of testosterone aromatization. When testosterone “aromatizes,” it gets converted to estrogens. Vitamin D may reduce aromatization.
2. Increased rate of androgen binding, which increases hormone secretion and leads to increased muscle hypertrophy, strength, and power.

Will Vitamin D fix low testosterone?

With vitamin D affecting so many factors for your health, it would be foolish not to supplement with it. Higher-dose, quality vitamin D supplements cost pennies per day.

That said, it won’t work in isolation. You need to consume adequate levels of all micronutrients, especially zinc.

You also need to follow a consistent strength training regimen, get adequate sleep, eat a high-protein diet, and get rid of excess body fat.

Of course, each of those choices is necessary to experience optimal health anyway.

Photo by Karsten Winegeart on Unsplash