Why a sunscreen can put your health in the shade

Sunscreens help to prevent burning and skin cancer, but they also block our main source of vitamin D, which protects us from a range of diseases, says Helen O’Callaghan.

IT’S summer and when the days are hot parents will slather sun screen on their children — head to toe — terrified of delicate skin burning.

Applied correctly, an SPF of 20 blocks 98% of the sun’s rays, but it also blocks the skin’s production of vitamin D. Exposing skin to UVB rays is the natural source of vitamin D, which is essential for healthy bones and teeth and a strong immune system. 

Yet, wearing any sun screen with an SPF higher than eight inhibits vitamin D absorption by 90% to 95%.

So, we’re caught between a rock and a hard place — by protecting our skin from sun damage, we’re barring vitamin D from our bodies.

And research is increasingly linking low levels of the vitamin with a host of illnesses — cancer, cardiovascular disease, diabetes, inflammatory diseases, adverse pregnancy outcomes, allergies, and so on.

We need vitamin D for the development of strong bones in children and for the maintenance of healthy bones in adults. 

“Adults lose calcium every day, through wear and tear. To replace it, we need calcium in the diet and we need vitamin D to absorb the calcium,” says Aveen Bannon, dietician with Dublin Nutrition Centre.

Why a sunscreen can put your health in the shade

If calcium intake is low, vitamin D plays a role. In this case, says Kevin Cashman, professor of food and health at UCC, “vitamin D prompts the intestine to take up available calcium more efficiently”.

But studies are showing that vitamin D may be a powerful force across a range of body systems. A recent Danish study, which followed 96,000 people for 40 years, found those with the lowest vitamin D levels were 40% more likely to have cancer and 30% more likely to have died than those with adequate levels.

In the US, endocrinologist Dr Michael Holick, who specialises in vitamin D, concluded after a review of studies that the “unrecognised epidemic of vitamin D deficiency is a contributing factor to many chronic, debilitating diseases — vitamin D deficiency is insidious and has both short- and long-term consequences. 

Infants and young children who are vitamin D deficient may be imprinted for the rest of their lives with increased risks of type 1 diabetes, multiple sclerosis, rheumatoid arthritis and many common cancers”.

A number of studies link low sunlight exposure — and consequent low vitamin D production — to a higher risk of developing MS. A study of 79 pairs of identical twins found that the twin who had MS had significantly lower exposure to the sun during childhood.

The US recommended daily allowance (RDA) of vitamin D is 15mcg for those aged one to 70 and 20mcg for the over-70s. This assumes minimal sun exposure and that we’re sourcing the vitamin from supplements and fortified foods.

But most foods only have small amounts of vitamin D, making it impossible to get from diet alone what our bodies need. 

Best sources are oily fish (mackerel, fresh salmon, fresh tuna), fresh meat, liver and eggs, fortified milk and fortified breakfast cereals. But — apart from the fortified milk or cereals — these are foods that many children will resist.

“Most Irish people who are getting some dietary vitamin D are getting it in fortified foods. It definitely merits a supplement,” says Bannon, who prescribes vitamin D supplements for “pretty much most people who walk through my door”.

Professor Cashman says only 17% of the Irish population is taking a vitamin D supplement. “Over 80% of us are relying on food for vitamin D and it’s in foods that often don’t factor in people’s diets.”

Not surprisingly, then, 90% of us fall below the recommended, 15mcg daily intake.

In the 2010 Children’s and Teen’s National Nutrition Survey, the average vitamin D intake was 1.9mcg per day for five- to eight-year-olds, 2.1mcg for nine- to 12-year-olds and 2.4mcg for 13- to 17-year-olds. The 2010 National Adult Nutrition Survey found the average daily intake for adults was 3.5mcg — only one-fifth of the recommended level.

In 2013, UCC researchers — reviewing a national survey — found when Irish adults’ blood levels of vitamin D were measured, 20% were clinically deficient in the vitamin in winter, and 6% in summer.

“We’re talking about clinical deficiency, where there are adverse effects on bone, for sure, and maybe other adverse health effects, too,” says Dr Mairéad Kiely, who, along with Professor Cashman, is a joint director of the vitamin D research group at UCC (www.ucc.ie/en/vitamind/).

Today’s indoor, screen-obsessed culture doesn’t help vitamin D levels. A recent Dutch study found that one-third of six-year-olds were vitamin D deficient. Children who watched TV for two or more hours daily were 32% more likely to be vitamin D deficient than children who watched less.

Playing outside for at least an hour a day decreased children’s risk for vitamin D deficiency by 29%, compared to those who played outside for less than one hour.

Is there a safe level of sun exposure that allows for vitamin D production but does not damage skin? Or do we have to stick to zero tolerance?

“We still don’t have reliable evidence,” says Professor Cashman. Australia is looking to relax some of their sun exposure guidelines — they recommend people go out for 10 or 15 minutes before applying sun screen. Other countries, such as the US and Britain, are “looking quietly” at the issue.

Rosemary Scott, Irish Cancer Society health promotion officer, says the message isn’t about keeping people out of the sun, but about being in it safely. “People need sun exposure for vitamin D. They also need to be out and physically active — that’s really important for avoiding many cancers.” 

She points to a message on the Irish Cancer Society’s website (www.cancer.ie/sunsmart), which — to meet vitamin D needs — follows the WHO recommendation: ‘Get five to 15 minutes of casual sun exposure to hands, face and arms two to three times a week during summer months. But a little sun goes a long way — never let your skin redden or burn to get vitamin D and never use a sun-bed to increase vitamin D levels’.

Casual sun exposure is driving up vitamin D levels in summertime, says Kiely, citing the five-minute walk with the children for ice-cream or the few minutes spent outside hanging clothes on the line.

And, says Scott, most people don’t use sun screen as advised by manufacturers. “They don’t put it on all over. They don’t apply it to dry skin 20 minutes before going out. They don’t re-apply it every two hours, or more often, if they’ve been sweating or playing sport.”

A spokesperson at the Department of Dermatology in Cork’s South Infirmary agrees: “The majority of people don’t wear sun-block all the time. Even if they get 15 minutes of sun on a cloudy day — [when they most likely wouldn’t wear sun-screen] — they’re probably getting enough vitamin D.”

So, they’re snatching vitamin D in the gaps.

Apart from the sun screen issue, there are other challenges to getting vitamin D from the sun. The Vitamin D Council in the US advises that when the sun’s rays enter the atmosphere at too much of an angle, UVB rays are blocked and skin can’t produce vitamin D. This happens during early and later parts of the day and during most days of winter.

“We have a very short vitamin D summer in Ireland — May to mid-October. There’s a lot of cloud cover. So we get a very small opportunity to produce vitamin D, compared to Spain or Portugal — where people have from February to mid-November,” says Kiely, who points to studies showing better vitamin D production/status among white-skinned people in south England than among whites in Scotland.

A good way to see if the sun’s high enough in the sky to make vitamin D is to look at your shadow. If it’s longer than you are tall, you’re not making much vitamin D; if it’s much shorter, you are.

According to the Vitamin D Council, moderate but frequent sun exposure is healthy — but over-exposure and intense exposure can increase the risk of skin cancer.

To get your vitamin D, they advise getting half the amount of exposure that it takes for your skin to turn pink. Skin colour also determines how quickly you’ll produce vitamin D — pale skin makes it faster than darker skin. 

In Ireland, in the early 2000s, there were 30 cases of rickets — a disease caused by calcium and vitamin D deficiency. Only two of the cases were in the non-immigrant population.

“People of colour are at higher risk of vitamin D deficiency if they’re living in latitudes far from the Equator. Immigrants, from places like Africa or South Asia, are most at risk — their women have even higher risk, because of the cultural dress code and so do their babies,” says Kiely.

Because it’s fat-soluble, the body can store vitamin D. But it’s a myth that the amount we get in summer lasts us through winter.

“Our vitamin D stores will decrease by half each month once winter sets in,” says Professor Cashman.

At UCC, Professor Cashman and Dr Kiely are leading ODIN, a major EU-funded project to address vitamin D deficiency in Europe by using food-based solutions.

“We’re looking at foods with a healthy profile being naturally enhanced or bio-fortified. What if you could buy fortified eggs, or other products naturally enhanced through animal food? It’s about safely introducing more vitamin D, without necessarily asking people to take supplements,” says Kiely.

When the sun shines, it’s essential to get things in balance — sunshine can damage but, once respected, it can also be fabulously health-promoting.

ODIN is currently recruiting women in the first half of pregnancy, for a study into how much vitamin D a pregnant woman needs. Contact m.kiely@ucc.ie.


Why a sunscreen can put your health in the shade

Oliver Gillie, an award-winning, British-based health journalist — and a campaigner for vitamin D and sunshine for over 10 years — questions those who say that many vitamin D health benefits advanced by studies are a myth. 

He refers to papers published by two teams (Philippe Autier of the International Prevention Research Institute, Lyon, and Mark Bolland of the Department of Medicine, University of Auckland) in late 2013/early 2014 in The Lancet. 

These argued clinical trials of vitamin D failed to show clear benefit, but Gillie says the vitamin D doses used were too low.

Speaking to Feelgood, he said: “With quite a lot of diseases, it seems insufficient vitamin D in earlier stages of life may make the person vulnerable to the disease. Giving vitamin D in adulthood can’t be expected to repair damage done in early life. It might help but not cure.”

Gillie has leukaemia — chronic lymphocytic leukaemia (CLL). He’s convinced he got it because of low vitamin D levels. 

“For years, I heeded the advice of cancer charities and the government to cover up and avoid strong sunshine.” CLL, he explains, has been investigated by 40 scientists collaborating in a major European study of cancers — they discovered CLL was consistently associated with low vitamin D.

Melanoma is a cancer in the cells that make melanin. In Ireland, incidence has risen dramatically in recent years – around 880 cases are diagnosed annually here. Gillie acknowledges the link between excessive sun exposure and melanoma. But he says the link isn’t always clear cut.

“At least 10% of melanoma is in areas not exposed to sun — soles of feet, arm pits, inside of mouth, parts of genitalia.”

And he cites research published in the European Journal of Cancer that found people with regular weekend exposure to the sun in Britain get less melanoma than those without such exposure. 

He knows he’s flying in the face of conventional medical wisdom but he’s adamant that for optimum health in countries as far north as Great Britain — and Ireland — “we need to get as much sun exposure as possible, while taking care not to burn”.


How to stay safe in the sun (from the Irish Cancer Society):

Seek shade — good shade can give up to 75% protection from UV rays.

Slip on some clothes. Choose clothes that cover as much skin as possible – three-quarter length sleeves, three-quarter length trousers. Linen and cotton, as well as dark clothes, block more UV rays.

Slap on a hat — make sure it gives shade to face, neck, head and ears. Choose child’s hat that’s comfortable and that they like, so they’re more likely to wear it.

Wear sunglasses — UV rays can damage eyes. Wear sunglasses that give UV protection and get children to wear them once they’re old enough. Choose wrap-around sunglasses. Check tags for adequate protection: look out for European Standard EN1836; British Standard BS 27241987

Use sunscreen with SPF 15 or higher (SPF 30 or higher for children) and UVA protection. Apply to dry skin 20 minutes before going outside. Reapply every two hours.

Check the UV index — when it’s three or more you’re at greater risk of skin damage that can lead to skin cancer. Find the UV index on www.irishcancer.ie 


Is there a safe level of exposure that leads to minimal skin damage but allows for vitamin D production? Professor Kevin Cashman, a director of UCC’s vitamin D Research Group, says there’s no such thing as safe sun exposure. 

“A dermatologist won’t be able to identify what level or duration of sun is safe for an individual. The recommendation at the moment is zero tolerance – the message is quite stark.”

Is this likely to change? Australia is looking to relax some of its sun exposure guidelines – recommending going out for 10 or 15 minutes before applying sun screen. 

 The Irish Cancer Society’s website (www.cancer.ie/sunsmart), carries the WHO recommendation on how to meet vitamin D needs: ‘Get five to 15 minutes of casual sun exposure to hands, face and arms two to three times a week during summer months. 

But ... never let your skin redden or burn to get vitamin D and never use a sun-bed to increase vitamin D levels’. The Vitamin D Council advises meeting vitamin D needs by getting half the amount of exposure that it takes for your skin to turn pink.

Food sources of vitamin D Oily fish (mackerel, fresh salmon, fresh tuna), meat, liver and eggs, fortified milk and fortified breakfast cereals. A mackerel fillet will have 16mcg whereas an egg just 1mcg.

Should I take a vitamin D-containing supplement? Only 17% of us take a vitamin D supplement. Dietician Aveen Bannon says vitamin D “definitely merits a supplement”. She prescribes one for most of her clients.


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