The Sunshine Vitamin: How Vitamin D Supports Health Year-Round
Funmi Akinola (Msc, Anutr) When the sun shines—no matter the season—doesn’t everything feel a little bit better? There’s a warmth that brightens our mood, and the sunlight brings out the beauty in the world around us. Those sunny days have a way of making everyone feel their best, and that’s something I really love. Summer has to be my favourite season; there’s just something about it that makes life feel a bit more joyful
Beyond these emotional boosts, sunlight has a profound impact on our biology. When ultraviolet B rays from the sun reach our skin, they trigger a series of processes that produce vitamin D, often called the “sunshine vitamin.” Interestingly, did you know that despite its name, vitamin D is actually a hormone? A chemical messenger that plays a crucial role in numerous bodily functions. However, with factors like sunscreen use, less time spent outdoors, and limited sunlight during the UK’s colder months, it’s often difficult to rely on natural exposure alone. This is where vitamin D supplements come into play, helping bridge the gap during the darker times of year and supporting our body’s needs year-round - basically, sunshine in a bottle.
Why Vitamin D Matters: The Benefits and Roles
Vitamin D is truly remarkable in its wide-ranging effects on the body. Here’s a closer look at the crucial functions it performs:
Bone, Teeth, and Muscle Health
Vitamin D is essential for regulating calcium and phosphate levels in the body which are critical minerals for strong bones, healthy teeth, and proper muscle function. Without adequate vitamin D, our body struggles to absorb calcium effectively. This can lead to a condition in children known as rickets, where bones become soft and prone to deformities. In adults, vitamin D deficiency can cause osteomalacia (softening of the bones) and increase the risk of osteoporosis, a condition that leads to weak bones, increasing the risk of fractures. Vitamin D plays a central role in keeping our skeletal system strong, resilient, and healthy across all life stages so you can see why keeping your levels topped up at every life stage is key right?
Immune System and Glucose Metabolism
Also, did you know that vitamin D benefits extend far beyond bone health? It plays a crucial role in supporting our immune response by activating immune cells and enhancing their ability to fend off pesky infections. Low levels of vitamin D have been linked to an increased risk of respiratory infections, including the flu and COVID-19, as well as autoimmune conditions like Multiple Sclerosis (MS). Interestingly, recent research has begun to uncover vitamin D’s potential role in glucose metabolism, hinting that it may be beneficial for blood sugar regulation. Though studies are ongoing, there’s promise that vitamin D could become an important part of preventative health strategies for metabolic conditions like type 2 diabetes and heart disease.
Cell Growth and Differentiation
Vitamin D also helps guide how cells grow and take on specific roles in the body through a process of 'cell differentiation’. This is where cells develop specific and specialised functions such as maintaining skin health or supporting tissue repair - amazing right? By guiding cells to mature properly, vitamin D helps keep tissues healthy and has even been linked to a reduced risk of certain types of cellular abnormalities which contribute to the development of diseases. Its involvement in cell differentiation also explains why it’s considered beneficial for supporting wound healing and potentially reducing the risk of some cancers.
Mood and Mental Health
Back to the joy of Summer, many of us intuitively sense that we feel better during the summer months, and there’s a scientific basis for this. Low levels of vitamin D have been associated with an increased risk of mood disorders, including depression and anxiety. This is especially relevant in the winter months, when lack of sunlight can lead to Seasonal Affective Disorder (SAD) - a type of depression that occurs during Autumn and Winter. Vitamin D receptors are present in areas of the brain involved in mood regulation, suggesting the intersection between the hormone and emotional well-being. Supplementing vitamin D can make a significant difference for some individuals who experience mood changes in the darker months.
Getting Vitamin D: Sun, Scran, and Supplements
While sunlight is the most natural way to obtain vitamin D, there are multiple ways to support your levels:
Sunlight Exposure
In the UK, 15–20 minutes of direct sunlight exposure on bare skin (without SPF) is typically enough for most people to meet their vitamin D needs. This is possible only from April to September when sunlight is strong enough to trigger production. Factors like cloud cover, time of day, and geographic location can all influence how much vitamin D we make from sunlight. However, given our love and need of SPF for skin protection, it can be challenging to balance safe sun exposure with vitamin D production. Since SPF blocks UVB rays, it also blocks vitamin D synthesis so be sure to practise sun safety whilst meeting your sun exposure needs.
Dietary Sources
While it’s challenging to meet vitamin D needs from food alone, certain foods offer a natural boost:
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Oily Fish: Salmon, mackerel, and sardines are among the richest dietary sources of vitamin D.
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Egg Yolks and Liver: Though in smaller amounts, egg yolks and liver contain some vitamin D, making them useful additions to your diet.
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Fortified Foods: Certain drinks, cereals, and spreads are fortified with vitamin D to help increase intake in populations with limited sun exposure.
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UV-Exposed Mushrooms: Did you know that some mushrooms are grown under UV light, allowing them to produce vitamin D themselves? Making them a unique plant-based option - fascinating!
While these foods can support vitamin D levels, most experts agree that dietary sources alone are unlikely to meet daily requirements for most people. That’s why supplements are recommended, especially in regions with limited sunlight.
Vitamin D Supplements
Supplements are often the most reliable way to ensure you’re meeting daily vitamin D needs. Vitamin D3 (cholecalciferol) is typically preferred over D2 (ergocalciferol) because it’s more efficiently absorbed and utilised by the body. For optimal absorption, take your vitamin D supplement with a meal containing healthy fats (like olive oil, nuts, seeds, or cheese), since vitamin D is fat-soluble. This allows your body to make the most of each dose.
How Much Vitamin D Do We Need?
For adults, a daily intake of 10 micrograms (mcg) is generally recommended, which equates to 400 IU (International Units). In the UK, government health guidelines recommend that everyone over the age of four take a 10 mcg vitamin D supplement from autumn through winter. This advice also applies year-round if you don’t get enough sun exposure or if your body has a higher demand for vitamin D.
Consider the following:
- Do you have darker skin? Higher melanin levels can reduce your body’s ability to produce vitamin D.
- Do you cover your skin for religious or work reasons when outdoors?
- Do you spend most of your time indoors during the summer months?
- Are you postmenopausal? Hormonal shifts can increase the body’s need for vitamin D
- Over 65? Ageing causes the skin to become less efficient at synthesising vitamin D from sunlight.
- Do you have a health condition that increases your risk of vitamin D deficiency?
If any of these apply to you, maintaining adequate vitamin D levels through supplements may be especially important.
While 10 mcg is considered the baseline for most people, specific needs can vary, and some may require a higher dose based on individual health assessments such as a vitamin D blood test. This is where personalising your supplement routine to meet your unique needs is key.
Too much of a good thing can sometimes be harmful, and excessive vitamin D from high-dose supplementation can lead to a toxic buildup known as hypervitaminosis D—though this is extremely rare.
Signs of Vitamin D Deficiency
Vitamin D deficiency is often referred to as the “silent deficiency” because its symptoms can be subtle. Some common signs include:
- Fatigue and muscle weakness
- Bone pain or a general sense of discomfort in muscles and joints
- Mood changes, particularly feelings of low mood or irritability
In severe cases, long-term deficiency can weaken bones, increase fracture risk, impair immune function, and exacerbate mood disorders. Recognising these symptoms and getting tested can help prevent deficiency from progressing.
Simple Steps to Ensure Adequate Vitamin D Levels
Maintaining optimal vitamin D levels is manageable with a few lifestyle adjustments:
- Embrace the Sun: When possible, enjoy a few minutes of sun exposure each day. During the peak months from April to September, brief time outdoors can go a long way in supporting vitamin D production.
- Boost Your Diet: Include foods naturally rich in vitamin D, such as oily fish, fortified drinks and spreads, egg yolks, and UV-exposed mushrooms.
- Consider a Daily Supplement: A daily 10 mcg vitamin D supplement is an easy, reliable way to meet your needs, especially in autumn and winter. Taking it with a meal containing some fat, like nuts or a drizzle of olive oil, can support maximum absorption.
The Power Duo: Vitamin D3 and K2
While Vitamin D shines for its role in calcium absorption and bone health, combining it with Vitamin K2 elevates its benefits. Together, they ensure calcium is efficiently absorbed and directed to your bones while reducing the risk of arterial calcification - a condition where calcium builds up in the arteries, increasing the risk of cardiovascular disease. This powerful synergy supports both bone density and cardiovascular health.
Why Combine D3 and K2?
- Optimising Calcium Use: D3 boosts calcium absorption, while K2 directs it to bones and away from arteries, reducing cardiovascular risks.
- Bone and Heart Health: The duo strengthens bones and supports arterial flexibility, critical during rapid growth in youth, those at risk of cardiovascular disease, or after age 50.
- Separate but Synergistic: D3 regulates calcium and supports immunity, while K2 activates proteins for calcium placement and aids healthy blood clotting.
A Note on Blood Thinners
If you’re on anticoagulants, such as warfarin, consult your doctor before taking K2 supplements, as it may interfere with blood-clotting medications.
The Bottom Line
Vitamin D is much more than a nutrient; it’s a vital hormone that supports everything from bone health and immune function to mood and cellular wellness. Living in northern climates, it can be challenging to get enough from sunlight alone, but with a combination of sunshine, diet, and a thoughtful supplement routine, you can maintain healthy levels year-round. Embrace those sunny days when you can, enjoy vitamin D-rich foods, and add a supplement to your routine as needed. By prioritising this essential nutrient, you’re investing in a healthier, happier you - whatever the season.
