Sun exposure – how much sun do we need?

Most public health messages about sun exposure focus on its dangers, but there are concerns mounting that sun avoidance could also be putting our health at risk.

Whether to prevent skin cancer or accelerated ageing, we’re urged to shun the sun and apply sunscreen every day. As a result, we have become sun-phobic—but how is this behaviour affecting us?

The dangers of too much sun

It’s true that excessive exposure presents some risks. Ultraviolet radiation (UVR) given out by the sun, including UVA and UVB rays, has been found to have several harmful effects, including:

• Damaging collagen fibres
• Destroying vitamin A in skin
• Accelerating skin ageing
• Increasing the risk of skin cancers

Excessive exposure to the sun may also cause cataracts and diseases aggravated by UVR-induced immunosuppression.

The dangers of too little sun

While these adverse effects of excessive sun exposure can be serious, there are also very real dangers associated with sun avoidance. Examples of these include:

• Vitamin D deficiency
• Toxin exposure due to chemical sunscreens
• Cancer

Little sun exposure also leads to conditions associated with more sedentary and indoors-focused lifestyles, such as:

• Weight gain
• Circadian rhythm disruption
• An increase in chronic diseases

Let’s look at a few of these factors in more detail.

Sunlight and vitamin D

One of the most documented benefits of sun exposure is its ability to stimulate the production of vitamin D. This occurs when ultraviolet-B interacts with 7-dehydrocholesterol in the skin.

This process varies in efficiency depending on the intensity of the sunshine, skin type, body fat, melanin levels, plus any clothing or sunscreen worn. Fair-skinned individuals can produce up to 50,000 IU of vitamin D in around 30 minutes of exposure, tanned individuals can make 20,000–30,000 IU, and those with dark skin tend to make around 8,000–10,000 IU.

Vitamin D is critical for good health, with deficiencies being linked to increased risk of cancer, Alzheimer’s disease, autoimmune disease, stroke, high blood pressure, structural abnormalities and difficulty fighting infection.

Sunlight and chronic disease

Aside from assisting in the production of vitamin D, sunlight also appears to benefit health in other ways.

Ultraviolet light lowers blood pressure and reduces risk of cardiovascular disease through the increase of nitric oxide in the skin, which helps to relax and expand blood vessels.

Research suggests that exposure to sunlight may also keep the immune system in check. This reduces risk of autoimmune conditions, which are characterised by over-activity of the immune system.

Sunlight and lifespan

One fascinating study suggests that exposure to sunlight may increase lifespan.

30,000 Swedish women were monitored for 20 years. The results found that women who strictly avoided the sun were twice as likely to die prematurely than women with normal sun exposure.

What’s more, the women with normal sun exposure were not at significantly increased risk of malignant melanoma or melanoma-related death.

Does sunscreen block vitamin D?

Most people love the sunshine and feel better when they spend time outdoors. This makes sense when you consider that we’ve evolved over hundreds of thousands of generations to be outside much of the time, reaping the benefits of sunlight.

But were our ancestors putting themselves in danger by not wearing sunscreen? Not necessarily.

Not only does sunscreen block production of vitamin D, but research has failed to find evidence that sunscreens protects against skin cancer. One paper categorically states: ‘…no melanoma study has shown convincingly that sunscreen use reduces the risk of melanoma’.

In fact, sunscreens can entice us to stay in the sun for longer periods, which research suggests could even increase risk of both carcinoma and melanoma skin cancers.

Additionally, harmful chemicals found in many sunscreens may be able to cross the skin barrier and absorb into other tissues where they can disrupt hormones. Look for sunscreens without oxybenzone, avobenzone, octisalate, octocrylene, homosalate and octinoxate. The EWG website contains plenty of information about sunscreen safety.

How to benefit safely from the sun

• Two or three days a week, expose large areas of your skin to the sun without sunscreen or clothing.
• Only do this long enough to begin to turn pink, not burn, which could be ten minutes for very fair-skinned individuals, or up to two hours for those with darker skin.
• If you’re going to be exposed for longer periods, then cover up with loose clothing, sunglasses, wear a hat and use chemical-free sunscreen if necessary.
• Eat antioxidant-rich, colourful fruits and vegetables to offer some internal protection against sunburn.
• Get outside in the earlier and later parts of the day to benefit from sunlight when burning is less likely.