Unlike most other vitamins, vitamin D is actually a hormone that is involved in the activity (expression) of almost 1,000 different genes in the body… in layman’s terms this means that vitamin D is involved in over 1000 different bodily functions! (1)
Majority of the vitamins that we need are usually obtained in the diet, however only small amounts of vitamin D are found in foods (5-10%), with most of our vitamin D being produced inside the body by the skin from the sun through UVB exposure. Hence why vitamin D is sometimes referred to as “the sunshine vitamin”.
The Australian Bureau of Statistics estimates that just under one in four Australian adults (23%) are vitamin D deficient, this is extremely concerning considering vitamin D’s numerous roles in the body (2).
In this blog you’ll learn everything you need to know about vitamin D including what Vitamin D is and why it’s important, complications of vitamin D deficiency, how to get enough Vitamin D and whether you should supplement with vitamin D!
What is vitamin D?
Vitamin D is a fat-soluble vitamin and hormone (messenger in the body) that is primarily absorbed from UVB rays from the sun with only small amounts of vitamin D being found in foods.
After sun exposure on your skin, vitamin D is then converted into its active form calcitriol in the body, this process also involves your liver, and kidneys. Calcitriol (active vitamin D) binds with vitamin D receptors (VDR) that are found in almost every single cell in your body! (3, 4)
When the calcitriol binds to this receptor it can turn genes on or off that can result in changes in cell activity (this is how hormones typically work) that affect many different functions in the body – hence why vitamin D is so important! (5, 6)
Small amounts of vitamin D can also be consumed in the diet through 2 main forms:
- Vitamin D3 (cholecalciferol): Found in high amounts in fatty fish and eggs.
- Vitamin D2 (ergocalciferol): Found in high amounts in mushrooms, and yeasts.
Vitamin D3 (cholecalciferol) is twice as effective at increasing levels of vitamin D in the blood compared to vitamin D2 (ergocalciferol), hence why it’s better to supplement with vitamin D3 and why vegans and vegetarians have an increased risk of vitamin D deficiency (7, 8, 9).
Why is Vitamin D important in the body?
One of Vitamin D’s primary roles in the body is regulating calcium that is essential for strong bones and muscles.
However, vitamin D also has other roles in the body that include nerve function, muscle function, immune function, mood regulation, anti-inflammation and even anti-ageing!
- Bone health: Vitamin D is essential for calcium absorption and healthy bone growth. Low vitamin D is linked to osteoporosis and other bone complications (10).
- Cell growth: Vitamin D has an important role in modulating proteins for healthy cell growth, and cell death (apoptosis) that is associated with good health (11).
- Ageing: Increased ageing can occur with vitamin D deficiency because of DNA damage (telomere shortening); therefore, vitamin D may help to slow down the ageing process (12).
- Immune function: Vitamin D has an important role in modulating the cells of the immune system. Deficiency of vitamin D is linked to poor immune function and autoimmune conditions (13).
- Muscle health: Vitamin D has a role in muscle health through regulating calcium that’s involved in muscle contraction. Vitamin D deficiency is associated with poor muscle health, cramps, and spasms (14).
- Mood changes/Depression: Vitamin D is involved in the production of serotonin known as our ‘happy neurotransmitter’. Studies indicate that depression is increased in people with vitamin D deficiency (15).
- Brain health: Reduced nerve growth and brain cell growth can occur with vitamin D deficiency. This could help explain how vitamin D deficiency contributes to Alzheimer's disease and dementia (16, 17).
- Chronic Inflammation: Vitamin D regulates the immune system, and a deficiency of vitamin D can cause increased inflammatory chemicals that can result in chronic inflammatory conditions such as heart disease, inflammatory bowel disease, and asthma (18).
What happens if I don’t get enough vitamin D?
Vitamin D deficiency is associated with many conditions that include:
- Heart disease
- Cognitive impairment (decreased brain function)
- Autoimmune conditions
What are the symptoms of Vitamin D deficiency?
Vitamin D deficiency is commonly associated with poor bone health; however, vitamin D can also manifest as many other physical symptoms that include:- Regular sickness or infection
- Bone and back pain
- Low mood
- Impaired wound healing
- Hair loss
- Muscle pain (24)
Who is at risk of vitamin D deficiency?
There are many reasons why someone may be at risk of vitamin D deficiency that include:- Darker skin: melanin (pigment) is a natural sunscreen, but it also blocks the body’s ability to make vitamin D.
- Wearing too much sunscreen: sunscreen is great to protect you from skin cancer caused by the sun, however it also blocks UVB rays needed for vitamin D production.
- People who stay mostly indoors: some people may avoid the sun for medical reasons (eg. previous skin cancers, immune suppression, sensitive skin), work nights or other reasons that result in limited sun exposure.
- Being overweight: Vitamin D is fat soluble (absorbed in fat). Having increased body fat makes vitamin D less available in your blood stream.
- Living in poor latitude: People who live in areas of poor latitude have reduced sun exposure.
- Older adults: as we age our bodies aren’t able to produce vitamin D as effectively. A 70 year-old makes 4 times less vitamin D from the sun than a 20 year-old.
- Medical conditions: some people have disabilities or conditions that affect vitamin D metabolism, such as end stage liver disease, renal disease, and fat malabsorption syndromes (eg. cystic fibrosis), coeliac disease, and inflammatory bowel disorders.
- Medications: some medications affect vitamin D metabolism, if you are taking medication your doctor most likely will have notified you.
- Breast-fed babies of vitamin D deficient mothers: formula milk is fortified with vitamin D.
- People who wear covering or concealing clothing: people may cover their bodies for personal, religious or cultural reasons that reduces their exposure to the sun.
How much vitamin D do I need?
Vitamin D levels change naturally with the seasons. How much UV exposure you need to produce vitamin D in the body varies based on many factors such as season, time of day, length of day, cloud cover, latitude, skin pigment, age, and sunscreen use.
Recommended sun exposure based on location. Photo: Osteoporosis Australia
Head to https://www.cancer.org.au/assets/pdf/how-much-sun-is-enough-brochure to find more information on how much sun exposure you need based on your location.
Should I supplement with vitamin D?
Vitamin D supplements can be used to help restore vitamin D in the body with up to 4000 IU/day of vitamin D3 is considered safe by the Institute of Medicine (USA).
However, it’s best to first ascertain your vitamin D levels in the blood. Speak your doctor or healthcare professional who will be able to support you further (25).
Can I have too much vitamin D?
Yes, you can also have too much vitamin D that can also have complications that include:
- Nausea, vomiting, and poor appetite
- Stomach pain, constipation, or diarrhoea
- Bone loss
- Kidney failure (26)
That’s why it’s important to speak your doctor or healthcare professional who will be able to guide your decision on whether to supplement or not.
So, what's the bottom line?
Vitamin D is an extremely important mineral that has many important roles in the body. Vitamin D supplementation may be required as only small amounts of vitamin D are found in foods and many factors can affect UVB exposure from the sun required for vitamin D production.
It can be difficult to know whether you are vitamin D deficient. The easiest way to be sure is to get a blood test and where your healthcare professional will be able to assist you further.
If you have any questions or need support with your health, feel free to email our head nutritionist Ben at firstname.lastname@example.org
This article does not constitute as medical advice and does not take into consideration your personal circumstances. Please see your medical professional before implementing the above.