Shining a light on winter health: vitamin D supplementation

As the days become shorter and the temperature drops, the winter season brings about a delightful change in scenery. However, it also brings with it a reduction in our exposure to sunlight, which can have a significant impact on our vitamin D levels. In this article, I want to shed light on the importance of vitamin D supplementation during the winter months and provide guidance on the recommended dosage.

Why Vitamin D in winter?

Vitamin D is often referred to as the « sunshine vitamin » because our skin can produce it when exposed to sunlight. However, during the winter, many people experience a decrease in outdoor activities and sunlight exposure due to colder weather and reduced daylight hours. This reduction in sun exposure can lead to a decline in our natural vitamin D synthesis, making supplementation a valuable option. Here are the reasons why you should consider taking a vitamin D supplement during this time:

  1. Maintaining immune health: Vitamin D plays a crucial role in supporting a robust immune system. Adequate levels of vitamin D are associated with reduced risk of infections and a more efficient immune response. This becomes especially important during the winter months when colds and flu are more prevalent.
  2. Bone health: Vitamin D is essential for the absorption of calcium, which is vital for strong bones and teeth. Inadequate vitamin D levels can lead to a higher risk of bone-related issues such as osteoporosis and fractures, which may be exacerbated in the winter when outdoor physical activity decreases.
  3. Mood and mental health: Some research suggests that vitamin D may play a role in mood regulation. Seasonal affective disorder (SAD) is a type of depression that typically occurs in the winter months, and vitamin D supplementation has been explored as a potential way to alleviate its symptoms.
  4. Vitamin D is also involved in other physiological mechanisms such as blood clotting, hormone signalling, nerve transmission and muscle contraction.

Recommended dosage

I refer here to the recommendations of the NHS, they candiffer in other countries (in France, there is no public health recommendation for supplementation for example):

  • « Babies up to the age of 1 year need 8.5 to 10 micrograms of vitamin D a day.
  • Children from the age of 1 year and adults need 10 micrograms of vitamin D a day. This includes pregnant and breastfeeding women, and people at risk of vitamin D deficiency. »

Vitamin D supplements should be used as a complement to a healthy diet, not as a replacement. You can also increase your vitamin D intake through dietary sources: oily fish (salmon, sardines, herring and mackerel), mushrooms, liver, egg yolks, and fortified foods – such as some milks and fat spreads, and breakfast cereals.

But as the winter season limits our natural sunlight exposure, considering a vitamin D supplement can help ensure you maintain optimal vitamin D levels and overall well-being during the colder months.


Vitamin D and your brain

In the UK, vitamin D deficiency affects 23% of adults (21% in those over 65yo), in winter the prevalence even rises to 40% (29% in those over 65yo). Vitamin D is mainly known for its role in the regulation of calcium homeostasis and in bone integrity, but it also plays an important role in the brain and is even considered neuroprotective.

Vitamin D promotes amyloid metabolism and clearance, neuronal and synaptic growth and neurotransmission. Many studies show the association between low vitamin D status and cognitive impairment associated with ageing (dementia). More recently, a study looked at vitamin D in 4 areas of the brain, 2 associated with Alzheimer, 1 with dementia and 1 with no association to cognitive decline. They found that high concentration of vitamin D in the 4 areas were correlated with better cognitive function. In another study, MR analyses suggested a causal effect of vitamin D deficiency on dementia.

The exact mechanisms by which vitamin D acts on cerebral health are not yet elucidated, but one thing is certain: whether it is for your bones or brain, take your daily 10 microgram vitamin D supplement between October and March.