Role of Vitamin D and how it is produced
The subject of Vitamin D is rather confusing. Not because of the health benefits it can offer – these are pretty straight forward. The confusion comes from ‘how it is defined’.
You see, quite often it gets referred to as a ‘hormone’ instead of a vitamin, but this simply isn’t true. According to Dr Ronald Vieth it is ‘structural raw material from which hormones and pre-hormones are made’. In other words, it helps to make the hormones we all know and love, meaning it IS a vitamin as it ticks all the right boxes. However, many researchers continue to disagree.
For this article, we’re going to stick with Vieth’s view, because no matter how it is defined – what matters most is how it can help your biological functions, namely testosterone production.
Where does Vitamin D come from?
You’ve got two options when it comes to boosting your Vitamin D levels – your diet and sun exposure:Food
Vitamin D may be an important fat-soluble nutrient; however, it only occurs naturally in a few foods. The best sources are mushrooms, fatty fish e.g. sardines, salmon and mackerel, and milk (although this has usually been fortified with Vitamin D). For more tips on t-boosting foods, have a look at this list of testosterone boosting foods!
When it is ingested this way, your liver first converts it into 25-hydroxyvitamin D (calcidiol) before your kidneys convert it into 1,25-dihydroxyVitamin D (calcitriol). In these forms it can be used by your body.
Natural sunlight is your best source for this vitamin, as your body will start producing it (naturally) when you’re out in the sun for long enough. Now, figuring out how long you need to be outside in order to achieve this isn’t an exact science, as it can be affected in a number of ways:
1) How much of your body is being exposed to the sun e.g. how much skin you have got on show.
2) How dark your skin is – the darker your skin tone, the more sunlight you will need.
3) The time of day – rays are weaker first thing in the morning or late afternoon so you will need to be out for longer.
4) Where you live – the closer you live to the equator, the less sunlight you will need (the further away you are, the more you will need).
5) The season – unsurprisingly, you will require more sunlight during fall and winter compared to spring and summer.
Not as simple as it looks, right? Especially when you add into the equation having to go to work, school, travel and family commitments. Trying to get plenty of sun exposure is hard.
Maybe that is why Vitamin D deficiency is on the rise? According a recent study, only 14% of the US population receive optimal levels of Vitamin D. The rest are suspected of either being deficient or not far off it.
And this is bad, as deficiency in Vitamin D can lead to a whole host of problems, including the aromatization of testosterone into estrogen. Not only can this cause the dreaded ‘man boobs’, but general drops in testosterone can also impact on other areas of your health.
What does Vitamin D do?
Vitamin D performs several roles in the body, so keeping your levels up is important.
- Vitamin D is essential for absorbing minerals such as magnesium – which is vital given that magnesium repays the favor by helping your body to make Vitamin D more bioactive.
- Vitamin D helps your body to absorb calcium to ensure your bone strength and health are maintained.
- Vitamin D helps regulate cell growth and your immune system.
- Vitamin D helps maintain your neuromuscular and cardiovascular health.
- Vitamin D stimulates muscle growth, increased power and cuts unnecessary body fat (by raising your testosterone levels and metabolic rate).
Why is testosterone critical for your health?
Would you believe that 95% of testosterone is made in your testicles – 3mg-10mg per day to be exact? The rest is produced by your adrenal glands.
Now, most of your testosterone (97-98%) binds to two proteins: SHBG and albumin and remains inactive/unable to exert it biological effects as it floats through your bloodstream.
It is the ‘free’ testosterone (the remaining 2-3% which hasn’t been bound to these proteins) that can be used by your tissues to build up muscle mass; improve bone strength, and encourage protein synthesis, all whilst helping you to remain physically fit and performance ready.
And it is this type of testosterone that YOU are most interested in.
Testosterone can help:
What is a link between Vitamin D and testosterone?
- Muscle mass – testosterone is used to create proteins to build new muscle tissue.
- Reduce body fat – increased lean muscle mass (achieved with the help of testosterone and weight training) can help to increase your metabolism whilst ensuring your fat stores are used for fuel for your body. This can arguably help to lower body fat and encourage weight loss. In fact, studies (https://www.research.va.gov/currents/0815-5.cfm) have shown that testosterone can decrease fat mass and increase muscle size and strength.
- Physical/body development – testosterone stimulates the development of sperm and excess body hair (facial and pubic), whilst lowering your voice.
- Sex drive/libido – testosterone levels rise naturally in response to sexual arousal and activity. When we hit 30, our levels can drop leading to issues with libido and erectile dysfunction.
- Mood/quality of life – low testosterone levels have been linked to poor quality of life including symptoms of fatigue, depression and irritability. Now we need to point out here that these symptoms are more common in men with hypogonadism. If your testosterone has fallen naturally i.e. with age, then you don’t have to worry about depression developing.
- Verbal memory, concentration and focus – research has revealed that higher ratios of total testosterone can reduce the risk of Alzheimer’s disease. It has also been linked to verbal memory and your ability to process things faster.
- Healthy heart – the healthier your heart, the more blood/oxygen/nutrients can be supplied to your muscles and organs, ensuring peak performance. For instance, a study during the early 2000s saw a 33% increase in walking distance in participants undertaking testosterone therapy. This means, the more free testosterone you’ve got, the more stamina and energy you’ll have. Similarly, a study of 83,000 men found those whose testosterone levels were returned to normal, were 24% less likely to have a heart attack.
- Increase red blood cell production (through bone marrow).
- Stronger bones – testosterone plays a big part in assisting bone mineral density. As with all things, it can decrease with age (more so when testosterone levels drop), leading to weak bones and osteoporosis. By maintaining healthy testosterone levels, it can improve your bone strength, providing support for your muscles and internal organs.
- Speed up muscle tissue recovery – by facilitating anabolic processes in your body, testosterone can help to hasten muscle recovery after a workout (by using fat stores for fuel and creating protein to build new muscle cells).
- Fertility – low testosterone levels have been linked to infertility problems and low sperm counts/quality sperm.
Given that Vitamin D is essential for muscle growth, fat burn and energy, it is easy to see the link between Vitamin D and testosterone.
But how closely are they related? Can Vitamin D really raise testosterone levels? Are low testosterone and low Vitamin D connected?
Let’s look at the facts (or in this case the studies): Study One
– Testosterone and Vitamin D: participants given Vitamin D saw small but significant increases in testosterone compared to those given the placebo. They saw a rise in total testosterone of 3nmol/litre to 13.4nmol/litre after 12 months. A similar trend was seen in bioavailable testosterone and free testosterone.
NOTE: Given that the intention of this study was to originally look at weight loss, these results can only be viewed as ‘suggestive’ as the researchers did not assess other factors which are commonly influenced by testosterone, such as sex, drive, mood or muscle strength.Study Two:
During a study on mice, those that did not have receptors for Vitamin D suffered from lower levels of testosterone.
Now you could argue here, that the anatomy of mice is vastly different to humans, but these results do make you wonder. Study Three:
In a 2012 cross-sectional study published in Clinical Endocrinology, scientists measured levels of free testosterone, total testosterone and Vitamin D in 1,362 males aged over 40 years old. They found a positive correlation between Vitamin D and levels of free and total testosterone, when Vitamin D was at optimal levels in the body. Study Four:
A separate Vitamin D for testosterone cross-sectional study – done on 652 Korean men – found similar results. They measured concentrations of total testosterone, free testosterone and Vitamin D, and noted that those who had optimized levels of testosterone (>26.51ng/mL) had on average 15% more Vitamin D than those with low levels of testosterone. Study Five:
A 2015 study into serum levels of Vitamin D (25 (OH)D) and testosterone in 312 military service men (North Carolina), found that highly active people – such as military personnel or athletes – can remedy low testosterone (caused by strenuous activity) by raising their Vitamin D levels. Study Six:
During a study on men with low testosterone levels, when they were supplemented with Vitamin D, it helped to increase their free testosterone levels by 20%. It also helped to raise their total and bioactive testosterone.
One thing all these studies commented on was the fact that once optimal Vitamin D levels are achieved, testosterone production plateaued. This is probably because the participants’ testosterone levels were within the normal range too.Does Vitamin D increase testosterone?
The above studies do suggest that there is a definite link. And it is not surprising when you consider its influence on other areas of your body.
Take the following study on men with Vitamin D deficiency. Researchers noted that alongside having low testosterone and higher estrogen levels; participants also had a high percentage of body fat, less lean muscle mass, higher rates of cardiovascular disease, more instances of depression, and were less fertile than those who had adequate levels of Vitamin D.
True, more focused studies are needed to give a more definitive answer. But all evidence does appear to point in the direction that there is a Vitamin D/testosterone link.