How much sunshine do we really need?
5 hours ago
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Some people just need a few minutes per day in the summer – while others require much longer
Photographs of Coco Chanel returning bronzed after a Mediterranean cruise in 1923 popularised the idea of tanning and sunbathing. Her tan became a status symbol and transformed Western attitudes to sunshine
From the early to the mid-1900s, heliotherapy – the therapeutic use of sunlight – was used to treat rickets and tuberculosis in sanatoriums, and a “healthy tan” was actively encouraged
A century later, our relationship with the sun has become much more complicated. In the past 50 years, increased skin cancer rates have led to a medical rethink, and public health campaigns have shifted towards avoidance and heavily promoted the use of sunscreen. The evidence linking excessive sun exposure with skin cancer risk still holds up today
But in recent years, so-called “moderate” sun exposure – time-limited bursts of exposure, in the middle of the day – has been found to be beneficial for our mental health, vitamin D levels and immune system.Studies also show it reduces the risk of certain cancers, boosts cardiovascular health, and improves cognition and sleep. So, how can we reap the benefits while avoiding the dangers? And how much sunshine do we really need?
Why do we need sunshine?
Moderate sun exposure helps the body produce vitamin D, which is essential for bone health and muscle function. Some studies show that high vitamin D levels are linked to lower cancer incidence and mortality, as well as a reduced risk of developing type 2 diabetes
Sunshine also lowers blood pressure. When UVA rays hit our skin, they trigger the release of nitric oxide, which causes our blood vessels to dilate. This reduces the risk of heart attacks and strokes
A landmark study of 29,518 Swedish women over 20 years found that sunshine avoiders had double the mortality rate (from all causes) compared with the highest sun exposure group. Conversely, sunbed use correlated with an increased overall mortality and cancer mortality rate. Another Swedish study conducted in 2011 found that women who used a sunbed once a month or more for at least a decade had a 90% increase in all-cause mortality
Rebecca Mason, a professor of physiology at the University of Sydney in Australia, says that getting adequate vitamin D levels helps to “dampen inflammation, respond to invading pathogens, and manage your immune system so it doesn’t attack your own cells”
Sunshine has been shown to improve sleep and boost cognitive health. Morning sunlight contains blue light wavelengths that trigger your brain into thinking it’s daytime, increasing cortisol and suppressing the sleepy hormone melatonin. This leaves us feeling more alert and energised. Higher exposure to daytime light can improve cognitive performance, reaction times and memory. In one study involving over 360,000 participants, daytime sunlight exposure (specifically around 1.5 hours) was linked to a reduced risk of developing dementia.
Sunlight exposure also increases the level of the chemical messenger serotonin in the brain, which help us to feel calmer and more focused. Patients treated for severe depression in sunny rooms have been shown to recover more quickly. Meanwhile, insufficient exposure to daylight can increase the risk of depressive symptoms, low mood and insomnia
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How much sunshine do we need?
While guidance varies according to age, geography and skin type, experts typically recommend short, frequent bursts of sunshine
Mason says that, in terms of vitamin D synthesis, exposure is most effective in the “middle of the day, little and often”, when UVB levels are at their highest
For people with light skin, Mason recommends regular, short bursts of sunshine on most days of the week, with the hands, arms or legs uncovered for a few minutes at a time. In very high UV areas, this exposure should be taken in the mid-morning or mid-afternoon instead
Those with dark skin may need significantly more sun exposure, because the higher levels of melanin also mean that vitamin D production from the sun takes longer. One study found that in the spring and summer in UK, those with dark brown skin need around 25 minutes of sun exposure at midday to produce adequate vitamin D
The UV Index rates the total amount of UV radiation (including both UVA and UVB) which reaches the ground, measuring it on a scale of 0 (no light) to 11+ (extremely high radiation).
Those with very pale skin, a personal or family history of melanoma, or who have lots of moles, are at high risk of developing skin cancers and need to take more precautions, says Mason. This also applies to people who are taking immunosuppressants
“They can still get a few minutes of exposure – [but it’s] best to have more skin exposed for a shorter time, and do so more often, than for a longer time less frequently,” she says. This is most effective nearer midday, where there is more UVB relative to the amount of UVA, compared to at other times of day. While UVB is the primary cause of skin cancer, it is essential for making vitamin D. Earlier or later in the day, you won’t get as much UVB, and you’ll be exposed to relatively more damaging UVA, which is linked to skin ageing and also plays a role in the development of skin cancer.
However, after that, Mason stresses, “they need to cover up carefully”
In rare cases, such as those with the condition albinism, it might not be suitable to have unprotected sun exposure at all
In winter, people need to spend a longer duration of time outdoors to generate enough vitamin D, depending on how much skin is exposed, and where you are. In certain parts of the world, such as Melbourne and Hobart, Mason says there isn’t enough UVB to make a significant amount of vitamin D during the winter
“We only need small to moderate amounts to have good health,” says JoAnn Manson, a professor of medicine at Harvard Medical School and Brigham and Women’s Hospital in Boston. Manson stresses that prolonged unprotected exposure should be avoided, particularly between the hours of 10:00 and 16:00, adding that incidental sun exposure is effective, be it through exercising or running errands outdoors
“The benefit and risk balance of sun exposure differs according to people’s skin type and colour,” says Lesley Rhodes, a professor of dermatology and photobiology at the University of Manchester in the UK
Studies show that darker skin provides better protection against UV-induced DNA damage, whereas lighter skin is vulnerable even at very low UV levels, emphasising the need for personalised sunshine exposure guidance. People with darker skin have higher levels of melanin, which acts as a natural filter against harmful UV rays
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But while how much sun protection you need from the Sun varies depending on your skin type and how much UV there is around, everyone, including people with dark skin, should wear sunglasses in the Sun, says Mason
In a world-first, Australia and New Zealand adopted a more personalised approach when they updated their sunshine exposure guidelines in 2024 and split their populations into three groups, according to skin type and risk of skin cancer
What are the risks of too much sun?
Spending excessive time in the Sun does not increase vitamin D production, but does increase the risk of sunburn, pigmentation and premature ageing, and is the leading cause of skin cancer.
In the UK, the number of new melanoma cases (the riskiest type of skin cancer) diagnosed in a year has reached a record high, rising above 20,000 for the first time. The non-profit Cancer Research says too much UV light exposure or sunbed use was part of the cause, with an estimated nine in every 10 cases thought to be avoidable. Skin cancer is also the most common form of cancer in the US, and 112,000 people are expected to be diagnosed with invasive melanoma in the US this year
How climate change is increasing sun risks
Climate change increases the risk of skin cancer, as warmer atmospheric conditions allow more solar radiation to reach the Earth’s surface. Over the past two decades, there has been a <4% annual increase in melanoma incidences in Scandina longer summers in the region. People living in previously cooler regions are also not used to taking protective measures, such as wearing a hat, sun-shielding clothing and sunscreen
Limiting sun exposure during childhood and adolescence is critical as research shows that the amount of sun exposure a person has in the first 20 years of their life determines, to a substantial degree, the likelihood of developing skin cancer. (Read more about why sunscreen is not enough to prevent sunburns)
Too much sun exposure can also cause cataracts. These cloudy patches on the lens of the eye are usually easily treatable with surgery, but can ultimately lead to blindness if left untended. Doctors recommend that people wear sunglasses with UV 400 lenses to protect their eyes from harmful rays
What if you don’t get enough sun?
If you live in a place with little sunlight, you are likely to develop low vitamin D levels, especially during the winter, says Rhodes. People with darker skin, limited outdoor access, photosensitivity issues or who cover up their skin are at risk of vitamin D deficiency
Sustained deficiency can lead to bone deformities, such as rickets or osteomalacia. Rickets first emerged as an urban epidemic in 17th-Century Britain, when heavy coal usage left cities like London smoke-laden and blocked UV from reaching skin
However, vitamin D deficiencies can be easily corrected with supplements. The debate around whether all adults need to take vitamin D supplements remains more contentious. The supplementation guidance varies according to age, and country-specific guidelines. (Read more: Should everyone be taking vitamin D?)
In some countries with limited winter sun, such as the US and Canada, it is common practice to fortify foods like mushrooms, cereals, and dairy products with vitamin D
It is important to not take too much vitamin D, experts warn. Consuming more than 4,000 IU (100 micrograms) daily is widely considered harmful as it can lead to hypercalcemia, which can weaken bones, and damage the kidneys and the heart
More like this:
• Mineral v chemical sunscreen: Which one should you be using?
• Sunscreen: Are you using it correctly?
• Should everyone be taking vitamin D?
A century on from the Coco Chanel tanning effect, our understanding of the risks, as well as the rewards of sun devotion, has been shaped by evolving health advice and sun safety campaigns
As Mason stresses, little and often is best. By prioritising short, frequent bursts of sunshine at midday, taking protective measures, and avoiding prolonged exposure – particularly in the peak hours of the day – we can reap the benefits of sunshine while minimising the risk of sunburn and skin cancer.
* Disclaimer:All content within this column is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. The BBC is not responsible or liable for any diagnosis made by a user based on the content of this site. The BBC is not liable for the contents of any external internet sites listed, nor does it endorse any commercial product or service mentioned or advised on any of the sites. Always consult your own GP if you’re in any way concerned about your health.
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