The Link Between Vitamin D, the Cold and Winter Blues
When the weather turns cold, many of us expect the usual winter health challenges like more colds and flus, less energy, motivation dropping and feeling generally more… flat.
Some people feel distinctly more depressed, or low in mood as the cooler weather wears on.
But the winter blues are not just about the cold weather.
This is the time of year we spend more time indoors, get less incidental sunlight and may have fewer opportunities for incidental exercise or movement outdoors. This can affect several systems in the body, including our circadian rhythm, mood regulation, immune function and the body’s vitamin D status - which is both impacted by the lack of sunshine, and can also contribute to these issues!
Vitamin D is often thought of as a bone health nutrient, but research also links vitamin D with immune regulation, inflammation, brain health, mood and overall wellbeing. The relationship is not always simple, but it is significant enough to be worth paying attention to, especially in winter.
Why vitamin D can drop in winter
Vitamin D is sometimes called the “sunshine vitamin” because the body produces it when skin is exposed to UVB light from the sun.
In the colder months, sun exposure often decreases. Many people leave home in the dark, spend the middle of the day indoors, rug up for the cold, covering more skin with clothing and overall, simply spend less time outside. In Australia, it is still important to balance vitamin D needs with sun safety, but winter is a common time for vitamin D levels to become lower, particularly for people with risk factors.
Low vitamin D may be more likely in people who:
spend most of the day indoors,
cover most of their skin,
have darker skin, are older,
have certain medical conditions,
take particular medications or
have reduced absorption due to gut or liver issues.
What are the winter blues?
The “winter blues” is a common way of describing a seasonal drop in mood, motivation or energy. If this is resonating for you, in winter you might notice:
Feeling flat or low
Sleeping more but still feeling tired
Reduced motivation
Craving carbohydrates or comfort foods
Feeling more withdrawn
Finding it harder to exercise or stay socially connected
Feeling slower to recover from stress or illness
For some people, seasonal mood changes can be more significant and may meet the criteria for Seasonal Affective Disorder, or SAD. SAD is a type of depression with a seasonal pattern, most commonly appearing in autumn or winter and improving in spring or summer.
If your mood symptoms are intense, persistent, affecting your ability to function, or you are having thoughts of self-harm, it is important to seek medical and mental health support promptly.
Vitamin D, mood and seasonal affective disorder
There is growing research interest in the relationship between vitamin D and mood, including winter-pattern low mood and Seasonal Affective Disorder.
The National Institute of Mental Health notes that reduced sunlight may affect molecules involved in maintaining normal serotonin levels, and that vitamin D deficiency may worsen these problems in people with winter-pattern Seasonal Affective Disorder (SAD) because vitamin D is believed to promote serotonin activity.
Research has also found that serotonin turnover in the brain may vary with sunlight and season, with one study finding lower serotonin turnover in winter. This supports the broader idea that seasonal changes in light exposure can influence mood biology.
Several PubMed-indexed studies and reviews have explored the relationship between vitamin D and depression. A systematic review and meta-analysis published in the British Journal of Psychiatry found that lower vitamin D levels were associated with depression, while also noting that further randomised controlled trials were needed to better understand whether the relationship is causal.
There are also specific studies exploring vitamin D in seasonal mood changes. One winter study found vitamin D3 enhanced positive affect in healthy participants during winter, while an early small study comparing vitamin D with broad-spectrum phototherapy in SAD reported improvement in the vitamin D group.
All this is to say there is a lot of evidence to indicate that Vitamin D levels are important - and not just for bone health. Not all studies have arrived at the same conclusion. A systematic review on nutrition interventions for SAD noted that the available randomised controlled trials on vitamin D and SAD did not consistently show clear benefit.
This means vitamin D should not be considered a standalone “treatment” for the winter blues or SAD, but it can be an important and clinically relevant piece of the puzzle, especially when someone is low, depleted or not recovering well through winter.
Vitamin D and winter immunity
Vitamin D is also involved in immune function. Rather than thinking of vitamin D as simply “boosting” immunity, it’s more accurate to think of it as supporting immune regulation, and in this way it is considered an important piece of the puzzle for those dealing with auto-immune conditions.
A healthy immune system needs to respond appropriately when exposed to viruses and infections, while also knowing when to calm down. This balance matters for inflammation, recovery and resilience. F
In winter, the immune system may already be under more pressure due to increased exposure to respiratory infections, less movement, disrupted sleep, stress, indoor environments and lower sunlight. If vitamin D is also low, this may be one more factor affecting how well the body responds.
Why testing matters
Symptoms of low vitamin D can be vague. Some people may feel tired, achy, low in mood or generally run down, while others may have no obvious symptoms at all.
The symptoms of low Vitamin D can also overlap with many other issues, including low iron, B12 deficiency, thyroid changes, chronic stress, poor sleep, hormonal changes, gut issues and inflammation.
That is why it is better to test than guess.
A vitamin D blood test can help identify whether low vitamin D is part of your winter health picture. It can also help guide whether supplementation is appropriate, and what level of support may be needed.
Should everyone supplement with vitamin D in winter?
Its tmepting to supplement and in a way, ‘cover all bases’. But that’s not the best approach.
Vitamin D supplementation can be very helpful when levels are low, but more is not always better. The right approach depends on your current levels, health history, sun exposure, medications, diet, absorption and individual risk factors.
For some people, vitamin D may be only one part of a broader nutrient picture. Iron, B12, zinc, magnesium, omega-3 fatty acids, protein intake, gut health and inflammatory load may all influence mood, energy and immune resilience through winter.
So when you come to see the Nurse Practitioner or one of our Naturopaths here at PNMC, you’ll notice the focus is on individualised support rather than generic one-fits-all approaches.
Getting your vitamin D checked at PNMC
At Perth Natural Medical Clinic, Lucia Ferguson, our Nurse Practitioner, can order pathology where clinically appropriate, including vitamin D testing.
Many pathology tests are eligible for Medicare rebates, depending on your individual situation and Medicare criteria. Medicare-rebated vitamin D testing applies under specific clinical circumstances, including certain symptoms, risk factors and health conditions.
You can also book with one of our naturopaths to discuss nutrient support, immune resilience, energy, mood and winter wellbeing more broadly.
If you have been feeling flat, tired, run down, frequently unwell or slow to bounce back this winter, vitamin D may be worth checking as part of a bigger picture.
Book a winter nutrient and mood support appointment
Book with Lucia to discuss pathology testing, or make an appointment with one of our naturopaths for individualised winter immune and nutrient support.
Call PNMC on 08 9328 9233 to book your appointment.
