Vitamin D
Vitamin D is often called the “sunshine vitamin” because our bodies can produce it when skin is exposed to sunlight. In the UK, sunlight isn’t strong enough for much of the year, and many people struggle to maintain optimal levels through diet alone.
Vitamin D supports bone health, immune function, mood and overall wellbeing — but the right amount varies between individuals. Supplementation can be helpful, especially in winter, though it works best alongside a food-first, lifestyle-focused approach.
What It Is
Vitamin D is a fat-soluble vitamin that plays a crucial role in:
calcium absorption
bone and teeth health
immune function
muscle function
mood regulation
There are two main forms:
Vitamin D2 (ergocalciferol) — found in some plant sources
Vitamin D3 (cholecalciferol) — the form our skin produces from sunlight, and typically the one used in supplements
Vitamin D3 is generally considered more effective at raising and maintaining levels in the body.
What It’s Used For
Vitamin D is commonly used to support:
immune system resilience
mood and energy
bone strength
muscle function
overall wellbeing during winter months
low levels identified through blood testing
Because vitamin D affects many systems in the body, low levels can contribute to feeling run-down, low in mood or more susceptible to winter illnesses.
What the Evidence Says
Evidence consistently shows that vitamin D:
supports normal immune function
is essential for bone integrity
contributes to muscle function
plays a role in mood regulation
Studies also suggest that:
people living in northern climates often have low levels
deficiency is more common in individuals with darker skin tones
low levels are particularly common during autumn and winter
Supplementation is well researched, but it works best when tailored to individual needs — and ideally guided by blood testing where appropriate.
When It Can Be Helpful
Vitamin D may be useful to consider if you:
spend most of your time indoors
feel low in energy or mood during winter
live in the UK or another northern country
have limited dietary sources of vitamin D
follow a vegan or plant-based diet
cover your skin for cultural or personal reasons
have darker skin, which naturally reduces vitamin D synthesis
have low vitamin D on a blood test
People often notice improvements in energy, mood and overall wellbeing once levels are restored.
When Caution Is Needed
Although vitamin D is generally safe, caution is needed if:
you are taking medications that affect calcium levels
you have kidney disease
you have disorders of calcium metabolism
you are already using high-strength vitamin D supplements
you take multiple multivitamins or fortified products
Very high doses can cause issues — more is not better.
A balanced approach is safest.
Why It’s Not Always the First Step
Vitamin D can make a meaningful difference for many people, especially in winter. But it’s not always the first step in supporting energy, mood or immunity.
Before focusing on supplementation, it’s helpful to explore:
overall diet quality
consistent meal patterns
time outdoors and daylight exposure
sleep routines
stress management
physical activity
These foundations form the landscape in which vitamin D works most effectively.
Nutrition Support
Food sources of vitamin D include:
oily fish (salmon, mackerel, sardines)
egg yolks
fortified milk alternatives
fortified cereals
mushrooms exposed to UV light
Lifestyle factors also help support vitamin D status:
regular daylight exposure
balanced meals with healthy fats (vitamin D is fat-soluble)
gentle movement outdoors
supporting gut health, which plays a role in nutrient absorption
Vitamin D supplements can complement these foundations, particularly in autumn and winter.
If You’re Unsure Whether Vitamin D Is Right for You
If you’re uncertain about vitamin D supplementation, or you’d like support interpreting a recent blood test, we can explore this together. Sometimes a few lifestyle adjustments or dietary changes can be just as supportive.
Prefer to read at your own pace?
I share occasional, practical updates like this, and let people know when something new is published. You’re welcome to leave your email below