Winter Blues and Syncing Your Internal Clock: seasonal affective disorder part 2

Seasonal affective disroder funnyConfused by vitamin claims?

  • Vitamin A for skin
  • B for metabolism
  • C for immunity…the list goes on and on
  • Declaring, that they are all vitally important requirements for health and wellbeing.

Scientists are divided in their theories of how necessary these vitamins really are. Some studies announce that certain vitamins are imperative for the prevention and treatment of illnesses; while others seem to revoke them stating that they are irrelevant and have no more effect than placebo(1). In this blog, I will write about the science of vitamin D and melatonin as it relates to the treatment and prevention of Seasonal Affective Disorder (SAD).

In order to understand the function of vitamin D and melatonin as it relates to SAD, there needs to be an understanding of what’s going on in the body as we change seasons. Our bodies operate on a cyclical pattern governed by what’s known as the circadian rhythm. This biological pattern allows for cycles of sleep vs. awake, body temperature and the release of hormones. The proper timing and functioning of this internal clock is dependent largely on environmental cues, like light. Our body registers environmental cues through the receptors found in our eyes, then communicates to the brain to synchronizes bodily functions in accordance to the time of day. For example, at night when there is no light out, our body may send sleep signals.

Brain chemicals known as norepinephrine, dopamine and serotonin are all involved in mood regulation, such as being happy or sad. These levels fluctuate throughout the day, in accordance to where a person is in their circadian rhythm. These cycles can become disrupted through various means, such as being indoors and exposed artificial light, causing an increased chance of developing SAD(2).

So how does vitamin D play into all this?

First of all, vitamin D has been mislabeled. All this time, we’ve given it the title of a ‘vitamin’, when in reality it is a hormone(3). Hormones in the body carry the role of being chemical messengers for important biological and physiological functioning. This particular hormone is involved in a host of activities from bone functioning to aiding the thyroid gland and in SAD. Traditionally, severely low levels of vitamin D have been seen in developing countries as the bone deforming condition, rickets.

Typically vitamin D is naturally found in many non-plant based sources, such as:

  • Fish liver oil
  • Fatty fish
  • Egg yolk

Vitamin D production is governed by circadian rhythm and external cues. We produce vitamin D naturally by exposing our skin to the sun. This causes a series of transformation both in the skin and blood to create vitamin D. However, a by living indoors, being sedentary, increasing health risks of sun exposure, and residing in northern climates (such as Canada), delivers a higher chance of lacking this hormone(3).

Studies have shown that people who have deficiencies of vitamin D, also have higher rates of Seasonal Affective Disorder. So, either exposing your skin to the sun for 10 min per day and/or adding a vitamin D supplement can help with SAD(4,5).

Why do you turn off the light to go to sleep?

Another hormone involved in the biological patterns of sleep vs. wake is melatonin. Our brain produces the highest amount of melatonin before bed-time when it is night outside. In daylight there is no release of melatonin, which is why we are alert and awake during the day. This clock can be thrown off by light exposure at the wrong time. For example, if a person is exposed to bright light earlier than they were supposed to the circadian rhythm starts early and advances. If there is bright light exposure in the evening it may result in a delay. SAD is often known to have a delay in its rhythm (Figure 1).

The exposure to bright light at appropriate times to synchronize your internal clock can be done through light therapy. This involves the use of specialized UV exposure light boxes at certain times throughout the day, to force your biological rhythm to reset allowing for chemical messengers to be released at the appropriate time.

Appropriate light exposure combined with vitamin D and melatonin are effective ways to begin treating SAD. However, any changes to your health care must be consulted by a health professional, such as your Naturopathic Doctor or Family Physician. Treatment should also involve psychotherapy and exercise to create an overall wellness based approach to treatment and prevention.

Figure 1: Circadian rhythm and life patterns:

circadian rhythm



  1. Eliseo Guallar, Saverio Stranges, Cynthia Mulrow, Lawrence J. Appel, Edgar R. Miller, III; Enough Is Enough: Stop Wasting Money on Vitamin and Mineral Supplements. Annals of Internal Medicine. 2013 Dec;159(12):850-851.
  2. Hewitt S, Seasonal affective disorder and circadian rythms.  Peason Ed.  Biology on the Cutting Edge.  212-215.
  3. Khamba BK, Aucion M, Tsirgielis D, Copeland A, et al.  Effectiveness of vitamin D in the treatment of mood disorders: A literature review.  Journal of Orthomolecular Medicine.  2011 Nov; 26(3): 127-135.
  4. Hoogendijk WG, Lips P, Dik MG, Deeg DH, Beekman AF, Penninx BH. Depression Is Associated With Decreased 25-Hydroxyvitamin D and Increased Parathyroid Hormone Levels in Older Adults. Arch Gen Psychiatry. 2008;65(5):508-512. doi:10.1001/archpsyc.65.5.508
  5. Shipowick CD, Moore CB, Corbett C, et al. Vitamin D and depressive symptoms in women during the winter: a pilot study. Appl Nurs Res. 2009 Aug;22(3):221-5.

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