The LIGHT fantastic?

It wakes you up better than coffee, boosts testosterone and helps you fight back from illness. But there’s also a dark side...

From checking our smartphones the moment we wake to watching TV hours into the evening, most of us spend our lives bathed in artificial light.

And, as we are increasingly told, this constant exposure can be harmful for our health, disrupting our body clocks — bright light is thought to suppress the body’s production of the hormone melatonin, which triggers feelings of sleepiness.

The risks are serious, with research suggesting prolonged exposure to artificial light may increase the risk of obesity, diabetes, heart problems, high blood pressure and depression.

And the worst culprit is too much blue light at night — this is the light emitted by smartphones and other electronic devices. Light looks white to us, but actually consists of a spectrum of colours, and some artificial light has a large amount of blue light.

But artificial light isn’t all bad and can even provide health benefits.

‘The key is how lighting is used, what it’s used for and when it is used,’ says George Brainard, a professor at Jefferson medical College in the U.S. and leading researcher on light’s effect on the body.

Here, we look at some of the ways light affects our health . . .

Forget a reviving cuppa — try blue light instead

Worried about blue light disrupting your body clock? There are apps that strip this light out of devices. For instance, Apple recently added a ‘night setting’ to its software so iPhone and iPad users can avoid blue light at night.

The setting, Night Shift, changes the colour of the screen to a warmer, yellow-and-reddish hue at night, to apparently make it easier to sleep after using the device.

F.lux is another piece of software that alters screen light colour.

But dr Neil Stanley, an independent sleep expert, says blue light is only part of the story.

‘The bottom line is you shouldn’t be using your phone or iPad before bed. Yes, the blue light can be stripped away, but this just means you have to turn up the screen brightness to see what you’re doing, which will make you more alert.

‘As we age, the cornea — the transparent film at the front of the eye — becomes yellower, so older people will have to adjust the brightness even more.’

dr Stanley says that before bed we should be exposed to nothing brighter than ‘a normal bulb — as dim as possible — and a paper book’.

However, at the right time of day, the waking up effect of blue light can actually be to your advantage, with research suggesting it could make you more alert than coffee.

Scientists at mid Sweden University compared the effects of caffeine and blue light on the brain and found that both boosted alertness.

However, people exposed to blue light for an hour performed better on reaction tests than those who had drunk three coffees, the researchers reported in the journal PLOS one, in 2013.

‘ideally, we need to be exposed to bright blue light in the morning — of which daylight is the best source — and yellow or red light in the evening,’ says Professor richard Stevens of Connecticut Health Centre, who is on the board of the American medical Association.

‘The best thing is to open the curtains and get daylight in. if that’s not possible, a smartphone’s glow will make you more alert.’

Another option is to use technology such as the Philips Hue portable go LITE BLU energy light, which emits a blast of blue light and is stronger than a smartphone light.

What’s the effect of low-energy bulbs?

THEY may be better for the environment, but energy-saving light bulbs emit more blue light than old-fashioned incandescent bulbs (which have been phased out since 2009 because of european regulations).

There are suggestions that, besides disrupting our sleep, these modern bulbs might have a more direct effect on health.

in 2012, researchers at Stony Brook University in the U.S. found that rays emitted from compact fluorescent light bulbs (energysaving bulbs that are tubular and come in various shapes) can damage the skin, just as sunbathing would.

‘it is best to avoid using [these bulbs] at close distances, and they are safest when they are placed behind an additional glass cover,’ says lead researcher Professor miriam rafailovich. The risk is greatest if the bulb is a metre or less from your body, as it would be in a reading lamp.

Some experts also fear that the large amount of blue light emitted by some energy-saving bulbs may damage eyes, affecting the retina, the light-sensitive area at the back of the eye.

Yet opinion is divided on the effect on eye health, with a study published in January finding that energy-saving bulbs and electronic devices may emit less blue light than the blue sky on a clear day. it also suggested that they don’t emit enough to damage eyes.

‘None of the low-energy light bulbs, computers, tablets and mobile phones we assessed suggested cause for concern for public health,’ says lead author John o’Hagan, head of the Laser and optical radiation dosimetry Group of Public Health england.

Should we worry about street lights?

IT’S not just blue light at home that worries some experts. in an effort to save energy, street lamps in the UK are being replaced with Led (light emitting diode) lights.

Led bulbs use much less energy than other lighting and last much longer. The problem is glare, which can make it harder to see. A 2014 report in the journal optics express concluded: ‘Leds are designed to emit the same amount of light as conventional bulbs from a smaller area, which could increase the discomfort glare.

‘in addition, Leds typically have more energy in the blue part of the spectrum, which can also cause more glare because blue light is perceived as brighter by the human eye under the same light levels.’

over time, the blue light emitted by Led street lights can also attack the cells in the retina, damaging sight, says Professor Stevens. ‘i advise getting blackout blinds.’

The American medical Association says the impact of Led lamps may be five times that of conventional street lamps.

‘The need for energy efficiency is serious, but so too is minimising human risk from bad lighting,’ says Professor Stevens.

Bright light ‘affects fertility’

Too much artificial lighting, whatever the type, could be making us frail by causing muscle loss and fragile bones, according to new research. A recent study in the Netherlands found that mice exposed constantly to bright light for 24 weeks suffered signs of premature ageing including early-stage osteoporosis, muscle weakness and inflammation. After two weeks of a regular pattern of light and darkness, their health problems were reversed.

‘our study showed that the environmental light-dark cycle is important for health,’ says lead researcher Johanna meijer.

She added that while her findings were in mice, people living in cities flooded with artificial light may face similar health risks.

meanwhile, bright bedrooms may prevent women getting pregnant, U.S. and Japanese researchers warned last year. middle-aged women may be especially at risk.

in a study, around 70 per cent of older mice with normal body clocks got pregnant, compared with just 10 per cent of those whose circadian rhythm had been disturbed by bright light, according to the journal Cell reports.

Women struggling to conceive could try dimming lights in the evening and having meals at regular times to ensure a good night’s sleep, say researchers.

. . . but it can raise testosterone levels

IF IT is used correctly, light can give men a boost in the bedroom, according to an italian study published last month.

researchers asked 38 men with a low libido to stand in front of a light box — the sort typically used to treat seasonal affective disorder (SAD) — for 30 minutes each morning for two weeks.

Half were exposed to 10,000 lux of light, the equivalent of bright daylight; the other half to 100 lux, similar to an overcast day.

The bright light group had boosted testosterone levels and reported sexual satisfaction levels three times higher.

The study was inspired by previous research showing that male sexual desire fluctuates with the seasons, decreasing in darker winter months.

‘Bright light may inhibit the pineal gland in the centre of the brain and this may allow the production of more testosterone,’ says Andrea Fagiolini, an associate professor of psychiatry, who conducted the study.

Can light boxes help with dementia?

THE use of light boxes for SAD — seasonal affective disorder — is well known. But research is increasingly showing that light therapy can help treat those who have depression all year round.

in a study at the University of British Columbia, 122 depressed patients were exposed to 30 minutes of bright light soon after waking every day for eight weeks. The treatment was found to boost their overall wellbeing.

one theory is that, like antidepressant drugs, light affects important brain chemicals such as serotonin and dopamine, says psychiatrist and study leader Professor raymond Lam.

meanwhile, dutch scientists have found that bright light therapy can help reduce night-time agitation in Alzheimer’s patients, a common side-effect of the condition.

The treatment appears to help ‘re-set’ a disturbed body clock, so patients sleep less in the day and more at night.

And several studies have shown that light boxes can help reduce symptoms in Parkinson’s patients, including depression, sleeping problems and, for some, tremor.

Good lighting can speed recovery

THE more time patients spend in daylight, or in artificial light that mimics the brightness of daylight, the better their comfort, mood, sleeping patterns, concentration, alertness and recovery, according to research into the health effects of hospital lighting by Philips in a dedicated 2010 report.

A separate study found day-like lighting can reduce the length of time a patient stays, the amount of medication they need, and whether they suffer from depression or mental decline.

However, many patients find hospital lighting far too bright.

‘This is a really big issue,’ says Professor Stevens. ‘many hospital patients spend far too long exposed to bright light each day. it would be a lot better for their health if the lights were dimmed as the day wore on.’

Invest in bulbs with less blue light

IT IS becoming easier to buy energy-saving lightbulbs that emit less blue light.

The temperature of light is measured in kelvins (K) and is often stated on the packaging. ‘Warmer’ light, such as deep orange light, has fewer kelvins — for instance, a candle is about 1,500K.

daylight, which has more blue, is often above 5,000K.

if you want to replicate the warm, slightly yellow glow of an old incandescent bulb, choose an energy-saving bulb in so-called ‘warm white’ (2,700K).

in a kitchen or bathroom you might want brighter white, known as ‘natural white’ (3,000K).