Vitamin D, not just for bone health.

The start of Autumn for the most part has been actually much warmer than I remember in previous years, which has been great while we have been in lockdown huh! But it is starting to get quite dark and gloomy now and signs are here that yes we are about to approach winter. It’s amazing how much of an impact the sun can have on our mood huh! And these overcast days make me feel less motivated and more inclined to hibernate. And it’s no wonder! The science and nutrition behind the sun and our mood is pretty amazing.

Sunlight and serotonin

Did you know that sunshine helps to stimulate the part of the brain that regulates melatonin allowing for an increase in serotonin the neurotransmitter that helps you feel happy?

As humans we are designed to be programmed to be outdoors working in the sun. So during the night when there is low or no light, the lack of light detected by our eyes should send a message to the brain to produce melatonin which is a sleep hormone. At the same time less serotonin is produced which allows the natural sleep cycle to kick in.

When our eyes detect sunlight, our brain receives this message to wake the body up. Melatonin production slows down and serotonin increases enough to send messages to other neurotransmitters to help the body wake up for the day.

So, how does lack of sunshine affect all of this? Although there is enough light to help us wake if it is constantly cloudy, appropriate levels of each these important neurotransmitters don’t quite reach their peak which could be why many people during these cloudy days report a feeling of “flatness”. That is they can cope with the day….but only just. Sound familiar?

Seasonal Affective Disorder (SAD)

This is a mood disorder that affects some people generally within the Autumn and Winter months due to the lack of sunshine. It is a condition that results in low mood or depression but with the key difference being that significant improvement is seen once spring and summer return. Some of the key symptoms of SAD include:

• Feeling depressed

• Low energy

• Poor sleep or insomnia

• Difficulty concentrating

• Losing interest in everyday activities

Lack of sunshine is the not the only factor that impacts our mood. You see a lack of Vitamin D also known as the “sunshine vitamin” is another key reason why we often feel gloomy in winter.

What is the sunshine vitamin?

Vitamin D is a fat soluble vitamin and is essential for our health. It is sometimes referred to as a hormone vitamin because it plays such a vital role within communication. (The main role of hormones is communication – and it is this communication that regulates different organs/systems within the body).

Vitamin D is a such a vital nutrient, but we actually only get about 10% of it from our food. It is found in mushrooms, oily fish like salmon and sardines and liver, foods that we don’t tend to consume a lot of.

The rest of our vitamin D comes from being exposed to sunlight – specifically ultraviolet B (UVB) rays. A biochemical process occurs when UVB penetrates our skin and this biochemical process activates stores of vitamin D we have in our body. The biochemical process converts stored vitamin D which is referred to as “pre” vitamin D (D2) and converts into “pro”vitamin D (D3).

Pre vitamin D is stored in our adipose (fat) tissue or in the liver. And when UVB from sunshine hits our skin, the activation of D3 occurs so that vitamin D can be utilised by the many processes in the body including:

• Neurotransmitter (brain) function

• Cardiovascular health

• Immune function

• Bone health

• Muscle health

• Digestive health

Research now shows that a deficiency in the essential Sunshine Vitamin may be linked with any of the following:

• Autoimmune conditions

• Poor immune function

• Arthritis and other inflammatory conditions

• Depression, anxiety, schizophrenia and other brain mood disorders

• Heart disease

• Asthma

• Osteoporosis

• Autism

• Rickets

• Diabetes

• Chronic fatigue

Why we need this sunshine vitamin for optimal health

For a long time Vitamin D was mostly associated with bone health. It is well established the role vitamin D plays for helping with calcium absorption for good bone health helping reduce the risk of osteoporosis and rickets. (Did you know research from as recent as this year shows babies in the south of the South Island are at higher risk of rickets due to low vitamin D?)

But in the last decade there has been some great leaps forward into understanding this hormonal role vitamin D has in the body in particular when it comes to the immune system, cardiovascular and brain/mood function.

Researchers have found vitamin D receptor sites located at different parts of the brain involved with cognition (process and thought) and mental illness (fear, mood, behaviour). There is a lot of growing evidence to support the need to supplement with vitamin D for not only depression but other mood and brain disorder such as dementia, Alzheimer’s disease, Parkinson’s, Bipolar and Schizophrenia and post-traumatic stress disorder (PTSD).

So… why do we need to supplement vitamin D in winter?

No UVB = No Vitamin D

You see the New Zealand Winter sun only provides us with about 10% UVB light that we need compared to that of summer. And generally these can only be achieved when the sun is at its highest between the hours of 11 and 2.

Between these hours we should be outside (in the cold) with our kit off (mostly not all!) exposing our skin for 20 minutes to get our Vitamin D. Are you kidding me? I’m in merino rugged up inside sitting in the sun if I can doing my work!

As you can see, it is actually very hard to get our natural dose of sunshine vitamin D in winter, and the further down south you go, the worse it is as there are less sunshine hours compared to the north island.

The VDR Gene and Vitamin D Absorption: Why Your DNA Matters

Optimal vitamin D status is not just about sun exposure or supplementation—it is also influenced by your genetics, particularly the VDR gene.

What Is the VDR Gene?

The VDR gene provides instructions for making the vitamin D receptor, a protein found in many tissues throughout the body, including the gut, bones, immune cells, and brain.

As well as laying out instructions for vitamin D activity, the receptor also activates genes and instructions involved in calcium absorption, immune defence, and cellular repair.

Potential variants may impact upon Vitamin D function affecting how efficiently vitamin D binds to receptor sites, how strongly vitamin D genes can “turn on or off”, or how well it can be absorbed.

Even if blood levels of vitamin D appear normal, VDR variants may reduce how effectively vitamin D works at a cellular level. This helps explain why some individuals experience symptoms of deficiency despite adequate intake.

This may impact upon:

• Reduced bone mineral density

• Increased immune dysregulation

• Higher inflammation and autoimmunity risk

• Metabolic dysfunction (thyroid, diabetes, cardiovascular)

Nutrigenomics testing, the functional test to give VDR clues:

From a functional medicine perspective, understanding VDR genetics allows for personalised vitamin D strategies. Some individuals may benefit from:

• Higher or more consistent vitamin D dosing

• Optimising cofactors such as magnesium, vitamin K2, and zinc

• Supporting gut health to improve absorption and receptor signalling

Vitamin D absorption and utilisation are not one-size-fits-all. The VDR gene plays a pivotal role in determining how effectively vitamin D supports your health. Genetic insight can help tailor nutrition and supplementation strategies for better outcomes, moving beyond standard reference ranges to truly personalised care.

The best place to start on this whole Vitamin D journey, is to get your blood markers checked. Making sure you at the optimal range of above 100nmol/L.

And if not, consider supplementation. Or if you have already been doing that, reach out and I can help you work out if further testing could help you out.