7 Reasons To Supplement With Vitamin D3 If You Want A Stronger, Fitter Body

7 Reasons To Supplement With Vitamin D3 If You Want A Stronger, Fitter Body

If you don’t live near the equator, you’re probably not getting enough Vitamin D.

And that’s a big problem for your strength and health goals…

Author: Nicola Joyce is an accomplished athlete with competition wins in power lifting, endurance and amateur body building.

LAST UPDATED: April 2019 by Ben.

This review of vitamin D3 has supporting referenced studies.

Vitamin D Increases Testosterone

Is Vitamin D in your supplement stack? If not, you could be missing out on a whole host of the health and strength benefits of this essential nutrient.

Vitamin D is an essential vitamin (deemed crucial for human survival) that your bodies synthesises when your skin gets enough sun exposure.

You can get a little Vitamin D from foods, but it’s pretty difficult (and the doses are pretty poor!).

If you’re reading this from anywhere other than the equator, chances are your Vitamin D levels are sub-optimal.

And that’s a big problem for your health, your hormones, and your body composition goals.

You might be surprised to discover how “the sunshine vitamin” can help you get bigger, stronger, and leaner.

female fitness model in the sun

What’s The Deal With Vitamin D?

There are only 24 micronutrients deemed critical for human survival… and the Vitamin D is one of them.

Exposure to sunlight is the main natural source of this vital nutrient.

So if you spend most of the daylight hours indoors (or travelling), and don’t enjoy long sunny days 12 months of the year, alarm bells should be ringing for you right now!

Luckily, there’s an easy way to avoid Vitamin D deficiency: smart, precise dietary intake or (easier still) a cost-effective daily Vitamin D supplement.

Vitamin D supplements are natural, cheap, and widely available.

If you’re on this site, you’re already pretty clued up about supplements. Add Vitamin D to you must-have supplements and cover your bases.

Are You Deficient In Vitamin D?

It’s simple: most of us don’t spend enough time outside in bright sunlight.

The body produces Vitamin D when the UV index is 3 or higher – and this is only available year round near the equator.

How many hours do you spend outside with your skin exposed to the sun every day?

You wake up, get in the car or on the train, spend all day in the office, go to the gym (more time inside!), travel home, then go to bed, right?

On a good day, you maybe get 30 minutes of outdoor time. And it’s not guaranteed to be bright and sunny!

The outlook is even worse over winter months, when most of us don’t even get outside during daylight hours. It’s dark when we get up, and already dusk by the time we leave work.

Our main natural source of Vitamin D is sunlight.

So if you’re not getting daily exposure to bright, direct sunshine on bare skin, you are at high risk of Vitamin D deficiency.

Those at risk

Some populations are at even higher risk…

The elderly, new parents, any anyone who is ill or injured (these people simply don’t get outside much!).

People with dark skin are at higher risk of Vitamin D deficiency, because their skin pigment creates a natural barrier to sunlight.

Useful if you live on the equator, but not so helpful in the Northern hemisphere!

Vegans can also be at risk of Vitamin D deficiency, simply because the best dietary sources of the nutrient come from animal sources.

The bottom line is: unless you get at least 30 minutes strong, direct sunlight on bare skin every single day – 365 days of the year – you are at risk of Vitamin D deficiency.

The Risks Of Vitamin D Deficiency

Vitamin D deficiency can lead to:

  • – trouble absorbing calcium and maintaining skeletal tissue density
  • – low mood or even depression
  • – down-regulated insulin resistance
  • – muscle weakness and fatigue
  • – an impaired immune system and compromised recovery

How Can Vitamin D Help Build A Better Body

Your body turns Vitamin D from sunlight or supplements into a hormone called calcitroil (or activated Vitamin D).

First, your body produces cholecalciferol, which is turned into calcidiol, and then calcitroil by the liver and kidneys.

Calcitriol is the active form of Vitamin D, and is what’s measured to assess deficiency.

Optimal Vitamin D has a host of physical and mental health benefits.

We’ll focus on the ones which are likely to impact your goals of getting stronger, bigger, or leaner (that’s what you’re here for, right?).

Get In The Mood For Training

If you don’t feel motivated to train, you’ll probably have a crappy session (if you even make it to the gym that day!).

Optimal Vitamin D is linked to good brain function and mood.

Keep yourself one step ahead of low mood and lethargy by making sure your essential nutrients are in check. [1]

Absorb More Nutrients From Food

You spend time and effort getting your diet right, so make sure your gut is actually able to absorb what you give it.

Vitamin D levels are linked to a healthy gut – don’t forget that it’s a fat soluble vitamin. [2]

Avoid Aches & Pains

Vitamin D deficiency impacts bone health, so keep your levels topped up if you want to keep training hard and heavy!

Rheumatoid arthritis, achy knees and a sore back have stopped many a lifter in his tracks. Look after your essential nutrient intake to stay ahead of the ageing process. [3]

Increase Testosterone

Studies have shown that guys deficient in Vitamin D see an increase in testosterone levels once they get their Vitamin D intake sorted out through supplementation.

Additional, studies have noted that a daily dose of 3332iu over the course of a year increased testosterone levels.

Products such as TestoFuel contain 5000iu Vitamin D3 to help your natural levels of testosterone stay higher. [4] [5]

Build Stronger Bones

Vitamin D helps your skeletal tissue absorb and store calcium, and it helps to regulate the cells which build new bone tissue and maintains the stuff you’ve already got.

Training ins’t just about muscle mass. It’s also about bone density and skeletal health, especially as you get older. Help your body stay strong. [6]

Boost Cardiovascular Health

You want to be fit and healthy as well as strong, don’t you?

Vitamin D has a host of benefits for your heart.

Optimal levels of the vitamin can help avoid heart disease, lower your risk of strokes, and may reduce your chance of inflammation in the arteries (leading to arterial stiffness).

Vitamin D also plays a part in helping your cardiovascular system functioning, particularly the vasodilation and vasoconstriction of blood vessels.

If your cardiovascular system is healthy, you will be able to train harder, recover better, shuttle nutrients around your body, and ultimately build and maintain a better body. [7]

Avoid Illness

There’s nothing more annoying than having to skip a few days of training because you picked up some cough or cold (probably from some selfish guy who trained whilst he was sick!).

Supplementing with Vitamin D is associated with improved immune health, so you stand a better chance of avoiding the annual wave of illness that sweeps the gym.

Fewer days off = more seasons in the log book = better results over the year. Makes sense! [8]

Improves Insulin Sensitivity

Poor insulin sensitivity can lead to type 2 diabetes and exacerbate other health issues.

This is because when the hormone insulin is released the cells are not responding effectively which leads to high blood sugar levels.

When men were involved in a trail whereby they were supplementing 2,857iu of D3 per day over a period of 3 months it was discovered that it decreased the quantitative insulin sensitivity check index (QUICKI). [9]

Vitamin D In Foods

Taking a simple daily Vitamin D supplement is the easiest way to make sure you get your RDA.

However, there’s no harm in eating Vitamin D-rich foods, too. (Just don’t rely on them for the precise dose you need!) These foods contain decent levels of Vitamin D:

All fish and seafood, including canned tuna and canned oily fish.

A good quality cod liver oil supplement will help you get the Vitamin D benefits of oily fish.

If you’re feeling fancy, choose oysters (100g has 320 IU of Vitamin D!).

Wild mushrooms or mushrooms that were grown under UV light (they synthesise Vitamin D like we do!) Tofu, soya milk, almond milk, fortified orange juice, and fortified breakfast cereals.

athletes on the beach

How Much Is Optimal?

There’s a difference between being deficient in Vitamin D, and not getting optimal amounts.

If you eat a varied diet and get outside in daylight hours, you are probably not technically deficient.

Yet your levels could be sub-optimal.


Nutrition experts recommend 400-800 IU a day to maintain good health.

Public Health England guidelines published in 2016 stated that adults should take 10 micrograms (mug) Vitamin D daily (that’s 400 IU). [10]

This was the first time the official guidelines have been updated sine 2007, after the Scientific Advisory Committee on Nutrition (SACN) felt there was sufficient new research.

The important thing to note is that these guidelines are for everyone, not just housebound elderly folk or night time shift workers. The official guidelines include you. [11]

Not sure how much you’re getting?

The easiest method is supplementing with one Vitamin D tablet/capsule a day or use a supplement that contains Vitamin D3.

Take it, tick that box, move on with your day knowing you’re getting enough Vitamin D. Simple!

Do You Need Vitamin D2, Vitamin D3, Or Both?

Be a Vitamin D ninja and know the difference between Vitamin D2 and Vitamin D3.

They’re both important, but Vitamin D3 is the one to focus on.

  • Vitamin D3 is the form produced by your skin when you get enough sun exposure.
  • Vitamin D2 is the form which is made by plants (like those wild mushrooms, or mushrooms grown under UV light).
  • D3 from sunlight or supplements is biologically inactive, and it takes hydroxylation (enzymatic conversion) in your liver and kidney to metabolise it into the bioactive form of Vitamin D.

This same process takes longer with Vitamin D2.

Our bodies absorb supplemental Vitamin D3 faster and better, and it gives us better health benefits.

Vitamin D3 is the form that helps us maintain Vitamin D levels when we don’t get enough sunlight.

This is important stuff when you’re choosing a Vitamin D supplement. Get one that has just Vitamin D3, or both. Vitamin D2 alone won’t be enough.

Take Home

So now you know that a daily Vitamin D supplement is crucial for maintaining optimal levels of this essential nutrient.

You also know that Vitamin D3 is more important than Vitamin D2.

So you can go ahead and choose a quality, well-dosed Vitamin D3 (or combined Vitamin D2 and D3 supplement) that will be easy to take once a day, such as this.


Article by:

Nicola Joyce (aka “the fit writer”) is a fitness industry copywriter who has been writing for and about sport and fitness since 2004. Nicola is a competitive drug-free bodybuilder (with two World titles at amateur level) and has also competed in powerlifting and a couple of strongman comps. Prior to her strength training days, Nicola was an endurance athlete and has even swum the English Channel twice. She can be found on all social media at: thefitwriter.



[1] Vitamin D and depression: A case series. Nadkarni PS, Odejayi G. SAGE Open Med Case Rep. 2014 Dec 4;2:2050313X14561570. doi: 10.1177/2050313X14561570. eCollection 2014. PMID: 27489667

[2] Vitamin D deficiency changes the intestinal microbiome reducing B vitamin production in the gut. The resulting lack of pantothenic acid adversely affects the immune system, producing a “pro-inflammatory” state associated with atherosclerosis and autoimmunity. Gominak SC. Med Hypotheses. 2016 Sep;94:103-7. doi: 10.1016/j.mehy.2016.07.007. Epub 2016 Jul 14. PMID: 27515213

[3] Vitamin D and bone health. Turner AG, Anderson PH, Morris HA. Scand J Clin Lab Invest Suppl. 2012;243:65-72. doi: 10.3109/00365513.2012.681963. Review. PMID: 22536765

[4] Vitamin D supplementation and testosterone concentrations in male human subjects. Heijboer AC, Oosterwerff M, Schroten NF, Eekhoff EM, Chel VG, de Boer RA, Blankenstein MA, Lips P. Clin Endocrinol (Oxf). 2015 Jul;83(1):105-10. doi: 10.1111/cen.12711. Epub 2015 Feb 10. PMID: 25557316

[5] Effect of vitamin D supplementation on testosterone levels in men. Pilz S, Frisch S, Koertke H, Kuhn J, Dreier J, Obermayer-Pietsch B, Wehr E, Zittermann A. Horm Metab Res. 2011 Mar;43(3):223-5. doi: 10.1055/s-0030-1269854. Epub 2010 Dec 10.

[6] Vitamin D and intestinal calcium absorption. Christakos S, Dhawan P, Porta A, Mady LJ, Seth T. Mol Cell Endocrinol. 2011 Dec 5;347(1-2):25-9. doi: 10.1016/j.mce.2011.05.038. Epub 2011 Jun 1. Review. PMID: 21664413 

[7] Cardiology Patient Page: Vitamin D and Your Heart. Romero DC, Manson J. Circulation. 2015 Dec 22;132(25):e391-2. doi: 10.1161/CIRCULATIONAHA.115.019080. Review. No abstract available. PMID: 26700012

[8] Vitamin D and immune function. Prietl B, Treiber G, Pieber TR, Amrein K. Nutrients. 2013 Jul 5;5(7):2502-21. doi: 10.3390/nu5072502. Review. PMID: 23857223

[9] Vitamin D and Testosterone in Healthy Men: A Randomized Controlled Trial. Lerchbaum E, Pilz S, Trummer C, Schwetz V, Pachernegg O, Heijboer AC, Obermayer-Pietsch B. J Clin Endocrinol Metab. 2017 Nov 1;102(11):4292-4302. doi: 10.1210/jc.2017-01428. PMID: 28938446

[10] https://www.gov.uk/government/news/phe-publishes-new-advice-on-vitamin-d

[10] https://www.gov.uk/government/publications/sacn-vitamin-d-and-health-report

Vitamin D3 and testosterone
Article Name
Vitamin D3 and testosterone
We look at the importance that vitamin d3 has on testosterone production and why it is important to use a supplement.

Ben BA(Hons), PGCert

Ben established this site to be a free resource in 2015. Since then it has gained over half a million visits. He has always been interested in sport and he started playing rugby at the age of 6 represented his town, county and school. Ben also enjoys cycling, has started skiing and is in the Army Reserve representing his Regiment as part of the 150 Regimental Shooting Team. He holds a bachelor's and postgraduate degree in sport exercise & nutrition.

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