Vitamin D: Why It Matters for Your Health, Mood and Wellbeing

Often called the sunshine vitamin, vitamin D plays an essential role in keeping our bones, teeth and muscles healthy. But how much do we really need, can spending time outdoors provide enough, and should we be taking a supplement during the darker months?

As the days become shorter and temperatures begin to fall, it is not unusual to feel less energetic or motivated. Dark mornings, reduced daylight and more time spent indoors can all influence our daily routines, making it tempting to retreat to the comfort of home rather than venture outside.

One nutrient that receives particular attention at this time of year is vitamin D. Commonly known as the sunshine vitamin, it has an important role in maintaining healthy bones and muscles, and scientists continue to investigate its relationship with immune function, brain health and emotional wellbeing.

Unlike many other essential nutrients, vitamin D can be produced naturally by the body when our skin is exposed to sufficient ultraviolet B (UVB) radiation from sunlight. However, in countries such as the UK, the amount we can produce changes considerably throughout the year.

Understanding how vitamin D works, where to find it and when supplementation may be beneficial can help us make more informed decisions about our health.

What is vitamin D and why do we need it?

Vitamin D is a fat-soluble vitamin that helps the body absorb and regulate calcium and phosphate, two minerals essential for maintaining healthy bones, teeth and muscles.

Without sufficient vitamin D, the body struggles to absorb calcium effectively. Over time, severe deficiency can contribute to conditions such as osteomalacia in adults, which causes softening of the bones and may result in bone pain and muscle weakness. In children, prolonged deficiency can cause rickets, a condition that affects normal bone development.

Vitamin D is also involved in normal muscle and immune function, although its best-established health benefits relate to the musculoskeletal system.

Research continues to explore whether vitamin D has wider roles in supporting cardiovascular health, cognitive function and other aspects of wellbeing. However, evidence does not currently justify using high-dose vitamin D supplements to prevent or treat these conditions in otherwise healthy individuals.

Vitamin D and mental health: Can the sunshine vitamin improve your mood?

The relationship between vitamin D and emotional wellbeing has attracted growing scientific interest, particularly because low vitamin D levels and depressive symptoms are sometimes observed together.

Vitamin D receptors are found in areas of the brain involved in mood regulation, leading researchers to investigate whether vitamin D contributes to neurological processes associated with mental health.

Several observational studies have identified an association between low vitamin D levels and depression. However, an association does not necessarily mean that vitamin D deficiency causes depression, and clinical trials have produced mixed results when investigating whether supplementation improves depressive symptoms.

The US National Institutes of Health notes that, despite observational associations, clinical trials have not established vitamin D supplementation as an effective treatment for depression.

This distinction is important. Maintaining adequate vitamin D levels supports general health, but taking additional supplements is not a proven solution for low mood, seasonal affective disorder or other mental health conditions.

Nevertheless, spending time outdoors during daylight hours can offer other psychological benefits. Natural light helps regulate our circadian rhythm, the internal biological clock that influences sleep and wakefulness. Walking, exercising and connecting with nature may also support mental wellbeing independently of vitamin D production.

Can you get enough vitamin D from sunlight in the UK?

Sunlight is an important natural source of vitamin D, but the amount our bodies can produce depends on several factors, including the season, time of day, geographical location, skin pigmentation and how much skin is exposed.

In the UK, from approximately late March or early April until the end of September, most people can produce adequate vitamin D through regular, sensible exposure to sunlight.

During autumn and winter, the situation changes significantly.

Between October and early March, the sun is generally too low in the sky for sufficient UVB radiation to reach us, meaning our bodies cannot produce enough vitamin D from sunlight, even when the weather appears bright and sunny.

This is why the NHS recommends that everyone should consider taking a daily vitamin D supplement during the autumn and winter months.

Although cloudy conditions can reduce UVB exposure at other times of year, it is important to understand that simply spending longer outdoors during a British winter will not provide enough vitamin D.

However, this doesn't mean we should abandon outdoor activities. Fresh air, natural daylight, movement and time spent in green spaces can still contribute positively to physical and emotional wellbeing throughout the year.

How much vitamin D do you need each day?

The NHS recommends that adults and children over the age of four consider taking 10 micrograms (400 International Units, or IU) of vitamin D daily during autumn and winter.

UK RECOMMENDED DAILY SUPPLEMENT DURING AUTUMN AND WINTER

10 µg

= 400 IU

For adults and children over four, including pregnant and breastfeeding women. People at higher risk of deficiency may need supplements throughout the year.

Source: NHS vitamin D guidance

Some people are at increased risk of vitamin D deficiency and are advised to consider taking supplements throughout the year. These include people who rarely spend time outdoors, individuals who cover most of their skin when outside and those with darker skin, particularly people of African, African-Caribbean or South Asian backgrounds.

Babies and younger children have separate supplementation recommendations. Parents and carers should refer to NHS guidance or speak to a healthcare professional for advice appropriate to their child's age and feeding arrangements.

It is also important to remember that more is not necessarily better. Taking excessive amounts of vitamin D over time can cause calcium to build up in the body, potentially damaging the kidneys and other organs. Adults should not exceed 100 micrograms (4,000 IU) daily unless specifically directed by a healthcare professional.

The best foods for vitamin D

Although sunlight is an important source of vitamin D during the warmer months, certain foods can also contribute to our daily intake. However, relatively few foods naturally contain substantial amounts, making it difficult to meet requirements through diet alone.

Oily fish

Salmon, sardines, mackerel, trout and herring are among the most useful natural dietary sources of vitamin D. They also provide omega-3 fatty acids, which contribute to a balanced diet.

Egg yolks

Eggs provide smaller amounts of vitamin D alongside protein and several other nutrients. The amount varies depending on factors such as the hens' feed and rearing conditions.

Fortified foods

Some breakfast cereals, fat spreads and plant-based milk alternatives contain added vitamin D. Check the nutritional label, as not all products are fortified.

UV-exposed mushrooms

Certain mushrooms exposed to ultraviolet light can provide vitamin D2, making them a useful option for vegetarian and vegan diets. Ordinary mushrooms may contain very little vitamin D unless they have been UV-treated.

A balanced diet that includes adequate calcium, protein, vegetables, fruit and other essential nutrients also helps maintain healthy bones and muscles. Green leafy vegetables can provide valuable nutrients, but most are not significant sources of vitamin D themselves.

Why getting outside still matters, even in winter

Although vitamin D production is limited during the colder months, spending time outdoors remains one of the simplest ways to support everyday wellbeing.

Regular physical activity can help maintain cardiovascular fitness, muscle strength, flexibility and mobility. Natural daylight can support healthy sleep patterns, while contact with green spaces may help reduce feelings of stress and encourage relaxation.

The key is choosing activities that suit your interests, ability and lifestyle rather than feeling pressured to follow an intensive exercise programme.

Walking is one of the most accessible ways to begin. A gentle stroll around the neighbourhood, a lunchtime walk through a local park or a weekend ramble in the countryside can provide opportunities for movement and time away from screens.

Cycling offers another enjoyable form of cardiovascular activity, particularly along traffic-free routes and designated cycle paths. For those who prefer being on the water, kayaking and paddleboarding can develop balance, coordination and upper-body strength, provided appropriate safety precautions are followed.

Hiking can combine physical exercise with the restorative experience of spending time in nature, while climbing, whether indoors or at a supervised outdoor location, offers opportunities to develop strength and confidence.

Activities need not be strenuous to be worthwhile. Gardening, walking a friend's dog or simply making time to explore a nearby green space can help establish a more active routine.

Importantly, there is no single ideal time of day to exercise. Morning activity may suit those who enjoy beginning the day outdoors, while an afternoon walk can provide a welcome break from work. The most beneficial routine is generally one that can be maintained consistently.

Signs you may not be getting enough vitamin D

Mild vitamin D deficiency does not always produce obvious symptoms, and some people may be unaware that their levels are low.

When deficiency becomes more significant, symptoms can include bone pain, muscle weakness and difficulty with certain physical activities. Severe or prolonged deficiency may affect bone health and increase the risk of fractures.

Tiredness and general aches are sometimes reported by people with low vitamin D levels, but these symptoms are common to many conditions and are not reliable indicators of deficiency on their own.

If you experience persistent symptoms or have risk factors for deficiency, speak to your GP. A blood test may be appropriate in certain circumstances, although routine vitamin D testing is not necessary for everyone.

Making vitamin D part of a healthy lifestyle

Supporting healthy vitamin D levels does not require complicated wellness routines or expensive products. For most people, it involves understanding when sunlight is sufficient, eating a varied diet and following appropriate supplementation guidance during the months when natural vitamin D production is limited.

During spring and summer, sensible sunlight exposure can help the body produce vitamin D, but sunburn should always be avoided. Extended or unprotected exposure is not necessary, and sun safety remains important even on cooler or cloudy days.

During autumn and winter, a daily supplement containing 10 micrograms of vitamin D is a straightforward option for most UK adults, while people at greater risk of deficiency may benefit from supplementation throughout the year.

Perhaps most importantly, vitamin D is only one part of the bigger picture. Good nutrition, regular movement, adequate sleep, meaningful social connections and time spent outdoors all contribute to physical and emotional wellbeing.

The colder months may encourage us to slow down, but they can also provide an opportunity to develop small, sustainable habits that support our health long after the seasons change.

Scientific research and further reading

For Wellbeing Magazine readers who would like to explore the evidence further:

• NHS – Vitamin D. UK recommendations on daily intake, sources, supplements and deficiency.

• National Institutes of Health – Vitamin D Fact Sheet. Scientific evidence on vitamin D, including bone health, deficiency and research into depression.

• NICE – Sunlight Exposure: Risks and Benefits. Evidence-based guidance on sunlight, vitamin D and protecting skin health.

• UK Government – Vitamin D Supplementation During Winter. Official explanation of seasonal supplementation recommendations.

Medical disclaimer: This article is intended for educational purposes and should not replace personalised medical advice. Speak to a GP or pharmacist before taking supplements if you have a medical condition, take regular medication or are unsure about the appropriate dose. Suspected vitamin D deficiency should be assessed by a qualified healthcare professional.