Sven Wombwell
Article by: Sven Wombwell
Estimated 9 minutes read

Vitamin D and testosterone are closely linked. Low vitamin D levels in men can lead to loss of muscle mass, osteoporosis (weak bones) and significantly affect sexual health. Since vitamin D deficiency reduces testosterone production, the two are more closely related than previously thought.

But precisely, what does this have to do with testosterone? Bioactive vitamin D3, or calcitriol, is a steroid hormone essential for male sexual function. Research shows that having lower vitamin D levels is linked to decreased testosterone levels in men.

Low testosterone symptoms can be very similar to a vitamin D deficiency: for example, erectile dysfunction and decreased sex drive seen in men with testosterone deficiency can also be a result  of depression caused by low vitamin D.1

Vitamin D and Testosterone Deficiency are linked.

Common symptoms of a lack of vitamin D and low testosterone include:

  • Erectile dysfunction
  • Low libido
  • Depression
  • Osteoporosis
  • muscle weakness

Vitamin D deficiency is now more prevalent than ever, and everybody over 40 or with symptoms should get their levels checked. Some studies suggest an association between insufficient vitamin D levels and cancer, cardiovascular disease, diabetes, autoimmune diseases, and depression.

Low vitamin D levels can negatively affect sexual health 3. Vitamin D and TRT administration improve erectile dysfunction in men.

What Does Vitamin D Do?

Vitamin D is usually associated with healthy bones, but it also regulates the amount of calcium, magnesium, and phosphates absorbed into your body.

These nutrients help you build bone, increase bone strength, grow teeth, and build muscle. If you are deficient in vitamin D, you are at risk of developing deformities such as rickets 4 and a softening of the bones called osteomalacia.

Vitamin D regulates many cellular functions in your body, having many benefits, such as:

  • It has anti-inflammatory, antioxidant, and neuroprotective properties
  • Supports immunity
  • It helps muscle function and growth
  • Supports Brain cell activity
  • Maintains sexual health
  • Increases insulin sensitivity

Vitamin D is crucial at optimum levels because it stimulates muscle growth, increases strength, and helps burn fat.

Vitamin D Supplementation Increases Insulin Sensitivity

Type 2 diabetes is a worldwide epidemic. Due to poor diet, too much sugar and a lack of activity, more and more people are becoming pre-diabetic and then moving on to developing Type 2 diabetes. Type 2 diabetes develops because your body becomes insulin resistant, and too much sugar is in the blood. Over 95% of people with diabetes have type 2.

The leading cause of this type of diabetes is excess body weight and physical inactivity. Insulin is a hormone that controls how much glucose is in your blood. When you become insulin resistant, the body's cells stop responding normally to insulin. Glucose can't enter the cells, so it builds up in the blood. After time this can lead to type 2 diabetes.

You can take many simple lifestyle measures to prevent or delay the onset of type 2 diabetes.

  • Keep to a healthy weight.
  • Keep physically active - Have 30 minutes of moderate activity on most days.
  • Eat a clean, healthy diet, avoiding sugar and saturated fats.
  • Don't smoke - smoking drastically increases the risk of diabetes, cancer and cardiovascular disease.

As men age, testosterone levels gradually tumble, which makes it harder to burn fat and maintain lean muscle. Commonly, men with low T are overweight and have or are developing type 2 diabetes. Through lifestyle changes, taking D supplements, eating healthy, exercising, and replacing hormones like testosterone, you can increase insulin sensitivity and even stop type 2 diabetes. One study on 5,677 people with insulin resistance showed that taking vitamin D increased insulin sensitivity by an impressive 54%.

How Does Vitamin D Deficiency Affect The Body?

Vitamin D deficiency was common in the 19th century. In the 20th century, it became less common in the western world due to fortified cereals, supplements, and dairy products. Low vitamin D levels, particularly in children, cause rickets, slow growth, soft, weak bones, and even bone deformities. Osteomalacia causes a softening of your bones, most often caused by severely reduced vitamin D. In children and young adults, soft bones often cause bowing in weight-bearing bones, especially the legs.

Vitamin D Deficiency can play a role in the following conditions:

  • Heart disease and high blood pressure.
  • Diabetes and insulin sensitivity
  • Infections and immune system disorders.
  • Falls and broken bones in older people.
  • Some types of cancer, such as colon, prostate, and breast cancers.
  • Multiple sclerosis.
  • Covid-19 (prevention of severe disease).

Vitamin D2 and D3: What's the Difference?

Two primary forms of vitamin D readily available are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). It is essential to understand their differences when choosing.

Vitamin D (D2) usually comes from plant sources, such as wild mushrooms, and is often added to fortified foods such as milk or cereal. D3 usually comes from animal sources such as fish oil, fatty fish, liver, and egg yolks. Vegetarian versions are now available and produced from lichen. D3 is also what your body produces with sunlight exposure.

Vitamin D supplement potency is measured in international units, abbreviated as "IU" on labeling. 50,000 IU capsules are prescription only, while lower strengths are available over the counter. Usually, if you are clinically deficient in vitamin D, it is best to take D3 once or twice a week at a potency of 20,00IU.

Vitamin D3 is More Beneficial Than D2

When exposed to sunlight, your skin produces vitamin D, which is instantly available for the body to use. In contrast, D2 must go through complex processes within the body before you can use it. For this reason, many doctors agree that D3 is more effective than D2.

In short, Vitamin D3 offers the most benefits.

Vitamin D and Sunlight

Your skin is responsible for producing vitamin D. When exposed to direct sunlight, ultraviolet radiation penetrates the epidermis and converts chemicals in your skin into vitamin D3. This is then carried to your liver and kidneys to transform it into an active form of vitamin D3. If you live in a country with little sunshine or get very little sun exposure, you will need to get vitamin D in supplement form.

Interestingly, vitamin D deficiency, rickets, and osteomalacia are more common in dark-skinned and migrant populations. These conditions weaken the bones, and they become soft and often deformed. In countries such as India and the Middle East, many people cover their bodies from head to toe due to religious beliefs, and vitamin D deficiency is common.

A study of 316 young adults aged 30-50 from the Middle East showed that 72.8% had vitamin D values of less than 15 ng/dL (severely deficient). Vitamin deficiency was significantly more common in women than men (83.9% vs. 48.5%, respectively). This highlights how limited skin exposure to sunlight affects vitamin D levels, particularly in women.

Where you live and the time of year also affects your exposure to sunlight. People living in the USA above 37 degrees north or 37 degrees south will make little, if any, vitamin D from the sun, especially during winter. People living in these areas are at greater risk of developing a vitamin D deficiency and should undoubtedly take vitamin D supplements.

How Can I Get More Vitamin D?

There are only two ways you can get vitamin D:

  1. Exposure to sunlight
  2. Through what you eat, either from food or supplements.

You can slightly increase vitamin D levels through diet. But most of it comes from exposure to the sun. One study highlighted how the seasons impact vitamin D even in healthy young men in the UK. The study showed that 8.4% of white people aged 19-64 had a vitamin D deficiency in the summer months, rising to nearly 40% during the winter. 

The highly publicized dangers of exposed skin and skin cancer mean that many people rightly use sunscreen to minimize risk. Yet, studies have shown that sunscreen with an SPF of 15 or more can reduce vitamin D production by up to 99%.5 The fact is that you don't need to be a sun worshipper to get enough vitamin D. Around half an hour in the sun twice a week should be enough.6 The recommended daily vitamin D intake is 400-800 IU/day or 10-20 micrograms. However, some studies suggest a higher daily intake of 1,000-4,000 IU (25-100 micrograms) is needed to maintain optimal blood levels. 

Diet and Vitamin D

When it comes to vitamin D from food, there are not many options. You will find it nearly impossible to fulfill your requirements solely from what you eat and drink. Some good sources include:

  • Oily fish such as mackerel, tuna, and salmon (avoid farmed fish)
  • Foods fortified with vitamin D, such as some dairy products, orange juice, soy milk, and cereals
  • Wild Mushrooms
  • Beef liver
  • Cheese
  • Egg yolks

Exercise and Vitamin D

Exercising does not increase vitamin D, but studies suggest7 it does support them. Vitamin D influences energy levels, muscles, and bone strength, benefiting your physical performance. Exercise strengthens bones, builds muscle, and reduces the likelihood of falls and fractures, even for those with osteoporosis. Avoid high-impact training and opt for lighter options like walking or swimming if you're at risk.

Vitamin D and Testosterone

Most guys in their 40s don't get enough vitamin D. The biggest issue here is not that they are deficient but that many have been deficient for a long time. The latest danish research shows that these two factors are more closely related than previously understood.

A lack of Vitamin D may reduce testosterone7 production and affect the estradiol and testosterone ratio (balance between testosterone and estradiol). Not getting enough vitamin D coupled with low T can affect fertility and lead to osteoporosis and loss of muscle mass, in a kind of double whammy. Additionally, low vitamin D combined with low testosterone reduces estradiol, impacting your bones, libido, brain health, muscles, energy levels and much more.

The most effective way to correct testosterone and vitamin D levels is by combining TRT with vitamin D3 and optimizing your thyroid hormones, supplementing DHEA, eating well, and getting plenty of exercise. As men age, many start to notice signs of low T, thyroid, and even vitamin D levels. The best solution is to replenish missing hormones and vitamins to the same optimal levels of youth. It could be your hormones to blame if you feel a shadow of your former self. The Male Excel bloodspot test kit is an easy at-home test that could give you the solution for a healthy future. 


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Giacomo Tirabassi, Maurizio Sudano, Gianmaria Salvio, Melissa Cutini, Giovanna Muscogiuri, Giovanni Corona, Giancarlo Balercia, "Vitamin D and Male Sexual Function: A Transversal and Longitudinal Study", International Journal of Endocrinology, vol. 2018, Article ID 3720813, 8 pages, 2018.
American Osteopathic Association. (2017, May 1). Widespread vitamin D deficiency likely due to sunscreen use, increase of chronic diseases, review finds. ScienceDaily. Retrieved February 24, 2022 from
Holt R, Juel Mortensen L, Harpelunde Poulsen K, Nielsen JE, Frederiksen H, Jørgensen N, Jørgensen A, Juul A, Blomberg Jensen M. Vitamin D and sex steroid production in men with normal or impaired Leydig cell function. J Steroid Biochem Mol Biol. 2020 May;199:105589. doi: 10.1016/j.jsbmb.2020.105589. Epub 2020 Jan 15. PMID: 31953167.
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