What is light nutrition?

You may be wondering, what do we mean by light nutrition? It’s not a type of salad or way of eating, but you’re on the right track – just think about light instead of food. Just like how the food and drink that we put into our bodies affects our health, so too does the amount and type of light that we expose our bodies to each day and at what times.

It’s similar to how we check food and drink product labels to ensure we know what we’re putting in our bodies and its nutritional value, to give our bodies a balanced diet. We can use the same idea with light. Light nutrition is making sure that we get the right kind of light, in the right amounts, at the right time of day for us.

There are some basic principles that we can all follow to ensure optimal light nutrition. These are:

• Get outside into morning daylight as often as you can – daily is best if possible
• If you can’t get outside in the morning, try to sit/stand near a window
• If getting outside or being near a window in daylight in the morning isn’t possible for you at all, try using a specialist SAD light in the morning
• Limit your exposure to blue and intense light in the evenings for at least the hour before you go to bed and instead choose dimmer and warmer (more red) light to help cue your body to wind down to sleep
• In the UK, take a Vitamin D supplement in autumn and winter months and if you have darker skin or don’t get outside into sunlight much, you may need to supplement all year round

Factors that influence our light nutrition needs

Your chronotype

Whether you’re an early bird or a night owl, or somewhere in-between

Your environment

The natural and artificial light you’re exposed to where you spend your time

Your geography

Where in the world you are and its weather patterns

Your seasonality

How sensitive you are to changing seasons

Your demographics

Your gender, age and race

Beyond the basic principles above, you’ll find that your own individual light nutrition needs might be different to someone else’s. These are influenced by a number of factors such as demographics (age, gender, race), your chronotype, geography, seasonality and environment. Let’s look at each of these in turn:

Age

The lens of your eye gets more cloudy and yellows as you get older, letting in less light overall and particularly less blue light, meaning you will need brighter lighting to safely carry out tasks than someone younger. You will also need more blue light in the mornings to prevent Seasonal Affective Disorder (SAD) and Winter Blues and to keep your circadian rhythm entrained. In teenage years, our chronotype shifts later temporarily before returning to our normal type (see more on chronotype below). Teenagers will benefit from activities starting later in the day where possible.

Gender

80% of people that experience SAD are female. Women are four times more likely to experience SAD in your reproductive years. In childhood and post-menopause, the ratio is the same for males and females. Pregnant and breastfeeding women may also be more likely to become Vitamin D deficient and so may need to get out into sunlight a little more or supplement in spring and summer in addition to autumn and winter. Males and females often have different colour temperature preferences, with males preferring cooler (more blue) light and females preferring warmer (more red) light.

Race

People with darker skins are at greater risk of developing Vitamin D deficiency as your skin doesn’t absorb as much Vitamin D from the sun as people with lighter skins. In the UK, where the sun isn’t strong enough to make Vitamin D in our bodies all year round, you may need to supplement in spring and summer in addition to autumn and winter.

Chronotype

This is your body’s preference for when it sleeps and wakes. It is genetically determined and cannot be changed. If you have a late chronotype, research has shown you may be more at risk of developing SAD. If you are following social norms that need you to be up and working before it suits your body, you might experience a daily ‘social jetlag’ affecting your mental functioning and levels of tiredness.

Geography

People living in countries at higher latitudes (further away from the equator) are more likely to experience Seasonal Affective Disorder. This is thought to be because of the greater shifts in the length of day, which causes the circadian rhythm to have to entrain to changing patterns of light and dark. In areas that experience higher levels of heavy cloud cover you’ll find levels of Winter SAD higher than areas that have less cloud cover. Areas where winter sports are popular may experience lower levels despite their higher latitude, as snow is a good reflector of light and active outdoor lifestyles are more common. Moving to a higher latitude from an area closer to the equator can also trigger SAD.

Vitamin D deficiency is also more common at higher latitudes because the sun isn’t strong enough during the autumn and winter months to make it in our bodies and our body doesn’t store it for long. If you live in an area that changes clocks each year for daylight savings time you may also experience some discomfort while your body adjusts to the time shift.

Seasonality

How sensitive you are to the changing seasons may be caused by a number of factors, such as having a family history of mental health conditions or if other close relatives have SAD. If you have other mental health conditions yourself, you may find they get worse at certain times of the year in a consistent pattern. Some 10-20% of conditions show a seasonal pattern.

Although Seasonal Affective Disorder is most common in the winter, you can experience Winter SAD-type symptoms at other times of the year if you work or live in a poorly-lit environment or if there is a lot of cloud cover over an extended period and you’re not getting outside much. Summer SAD, Spring and Autumn SAD and Hesperian depression – often known as Sundowner Syndrome are less common forms of Seasonal Affective Disorder.

Environment

How much of your time you spend indoors and how you light that space at different times of the day can affect your physical and mental health. In industrialised countries, it is estimated we spend 90% of our time indoors – a huge difference compared to our ancestors, who were hunter-gatherers, then largely agricultural workers. They lived their lives by sunlight and firelight. It was only in the 1880s that electric lighting was introduced to UK and US homes. Our physiology hasn’t adapted as quickly as our lifestyles.

Indoors, lights may feel bright but typically an office will be lit to around 500 lux (a measure of light intensity) and homes tend to be around 200-300 lux. Sunrise on a spring morning delivers 10,000 lux. Even on a cloudy or rainy day, in daylight, it will be many times brighter outdoors than indoors. When we don’t get enough high-intensity light over a period of time, we can experience Seasonal Affective Disorder or its milder form, sub-syndromal SAD, also known as Winter Blues. This can happen if we move into a poorly-lit environment that we spend most of our daytime in.

With the introduction of LED lighting we have a greater choice than ever before how to light our homes and businesses. But with choice comes confusion and often we don’t realise how those choices may affect us and those around us at different times of the day and because of some of the different light nutrition needs we have.

For some people, LED and certain types of fluorescent light can cause mild to severe discomfort with symptoms including migraine, nausea and burning skin. This can be enough for you to need to avoid a certain place or to not be able to go outside at all under certain kinds of light, for example, LED streetlights.

Technology has introduced more blue light into our homes than ever before too, with TVs, computers, mobile tablets and phones emitting high-intensity blue light that can stimulate us and confuse our circadian rhythm, causing us sleep problems.

Now you have a better idea of what factors can influence your individual light nutrition needs, you can start to consider how you can make some environmental and behavioural changes to live your light ideal.