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Seasonal Affective Disorder (SAD) What are we really missing? (2021 update)

Is there more than a Vitamin D deficiency involved when experiencing the winter SADs? The biological mechanisms that link Vitamin D to depressive symptoms are evident in multiple pathways where the vitamin plays a role in emotional balance, serotonin synthesis and stress response.

This all makes perfect sense when it is often linked to low mood during winter. Low Vitamin D levels are common in people with depression, yet supplementation in some cases has not been shown to improve symptoms (1). Other studies however have shown positive results, particularly when the cohort has a stronger link through medical history, pregnancy or mental health diagnosis (2, 3, 4). If Vitamin D treatment does not assist individuals experiencing SAD symptoms (where a deficiency has been confirmed), it does not mean that this Vitamin isn't playing a role in their mental health. We know for a fact it does. In likelihood, it just means that it isn’t the only cause, with other strong influences playing a part. Those who have experienced depression or the winter blues would know that this is probably the case.

It’s important to remember the cooperation of many different factors that play a part in our health. Synergistic components are essential to balancing the body’s systems. I’ll give you an example - Total health cannot be achieved by a perfect diet but no exercise. And vice versa. But then again total health cannot be achieved by just a perfect diet and a well-designed exercise routine either. We need so much more than that - restful sleep, emotional support, family, friends, job satisfaction, hobbies, creativity, long walks on the beach and candle-lit dinners... or whatever floats your boat to keep you happy. It also is well documented how a person's nutritional status can also modulate the presence of depressive symptoms (5). We do get Vitamin D from some food sources, but other nutrients such as protein, fatty acids, macronutrients and other micronutrients play a role here as well.

A lack of Vitamin D may just be that last factor involved in exposing an array of areas in your health (both physical and mental) that need some improvement. If you have any concerns about experiencing SAD this Winter and know that the weather adversely affects your mood, speak to your GP about getting Vitamin D tested. Supplementation is inexpensive and easy to take, but sunshine is often the best way to improve Vitamin D status and in turn, assist with mood balance.

Stay tuned for the next chapter of my Winter blog where I focus on Vitamin D in greater detail.


For more targeted advice suited to you, including assistance with Nutrition, Immunity and Vitamin Deficiencies, please get in touch via my website, via phone or email at

Purple Tree Therapies is located in New Farm but I can also do video consultations via Zoom.


1 Kerr, Zava, Piper, Saturn Frei & Gombart, (2015) Associations between vitamin levels and depressive symptoms in healthy young adult women. Psychiatry Research, 227(46-51)

2 Jorde, R., et al. (2008). Effects of vitamin D supplementation on symptoms of depression in overweight and obese subjects: randomized double blind trial.J Intern Med, 264(6): p. 599-609

3 Khoraminya, N., et al. (2013). Therapeutic effects of vitamin D as adjunctive therapy to fluoxetine in patients with major depressive disorder.Aust N Z J Psychiatry, 47(3): p. 271-5

4 Vaziri, F., et al. (2016) A randomized controlled trial of vitamin D supplementation on perinatal depression: in Iranian pregnant mothers. BMC Pregnancy and Childbirth. 16(1): p. 239

5 Francis, H. M., et al. (2019). A brief diet intervention can reduce symptoms of depression in young adults – A randomised controlled trial. Plos One. doi:

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