Are We Spending Too Much Time Indoors?

The honest answer is yes — almost certainly. The statistics on indoor time in modern industrialised countries are striking enough that even the most committed apartment-dweller usually gets a small jolt when they see them. The bigger question is what that indoor time is actually doing to people, and whether the symptoms a lot of us have learned to live with through winter are downstream of something genuinely fixable.

A brief tour of the numbers, the biology, and what to do about it.

If winter has been feeling heavier than it should, you are not imagining it. Take our two-minute quiz to see if your routine is missing a key input, or read about Daily Sunshine, our daily formula for British indoor lives.

The headline numbers

The most cited figure comes from a 2018 report by VELUX across 14 European countries: the average adult spends about 90% of life indoors. The US Environmental Protection Agency's National Human Activity Pattern Survey — the most comprehensive of its kind — produced similar results: 87% indoors plus another 6% in vehicles. That is 93% of waking life outside daylight.

Put differently, the average adult gets roughly 90 minutes a day in actual outdoor light. For people who work remotely or in deep-plan offices without windows, the figure is often lower. For older adults, lower still. For people whose evenings are spent watching screens at home, lower again. The structural ceiling on outdoor time has fallen so quietly that almost nobody is consciously aware of it.

What that does to mood

Light exposure is one of the most consistent inputs to human mood regulation. Reduced bright-light exposure is the established mechanism behind Seasonal Affective Disorder. The Royal College of Psychiatrists reports that around 2 in every 100 UK adults meet diagnostic criteria for SAD — depression that follows a seasonal pattern, typically starting in autumn and lifting in spring. Critically, the same source notes that many more people experience milder versions: lower mood, reduced motivation, less social interest, more carbohydrate cravings, more sleep. These do not reach the clinical threshold but they are real, and the indoor lifestyle pattern of modern Britain is the perfect setup for them.

The NHS lists the most common SAD symptoms as a persistent low mood, loss of pleasure or interest in normal activities, irritability, feelings of despair or guilt, feeling lethargic and sleepy during the day, sleeping for longer than normal and finding it hard to get up in the morning, craving carbohydrates and gaining weight, and difficulty concentrating. Some of those are recognisable to almost anyone who has been through a British winter. Most people, given those symptoms, do not connect them to anything as banal as the amount of daylight they are getting. Often, that is exactly the connection.

And what it does to vitamin D

The vitamin D piece is the cleanest single biological consequence of indoor life. The body manufactures vitamin D primarily from sunlight on skin. If you are not outside, you are not making it — full stop. The UK's Scientific Advisory Committee on Nutrition concluded in 2016 that diet alone supplies only a fraction of most people's needs. Most people are short on this nutrient without realising it.

Low vitamin D symptoms overlap meaningfully with SAD symptoms, which is part of why the picture can be hard to read. The most commonly reported include:

• Persistent fatigue that does not improve with sleep
• Low mood or general flatness
• Aches in bones or muscle weakness, particularly in legs and back
• More frequent colds or longer recoveries from minor illness
• Poor concentration or a sense of brain fog
• Hair shedding (with some emerging research on the link)

None of these symptoms is diagnostic on its own. All of them are common. All of them are easy to misattribute. The UK's National Diet and Nutrition Survey finds about one in five UK adults runs deficient in winter — below the 25 nmol/L threshold the NHS classifies as a clinical concern.

The compound effect

The reason indoor life produces such a recognisable pattern of winter symptoms is that the two mechanisms above — reduced light exposure and reduced vitamin D synthesis — reinforce each other. People with low vitamin D are more likely to feel low energy, which makes them less likely to go outside, which keeps the vitamin D level low and the light input reduced. The system does not self-correct. It self-deteriorates across a winter.

This is the actual mechanism behind the slightly-off feeling so many adults describe through January and February, and it is the reason the simple interventions — outdoor morning light, daily vitamin D supplementation — have a disproportionate effect on how the season feels.

What to do

Get outside in the morning, even briefly. Ten minutes of outdoor daylight, even on a grey day, is many times the light input of any indoor setting. This is the single biggest intervention available.

Supplement vitamin D from October to March. The NHS recommends 10 micrograms (400 IU) daily through autumn and winter. For people who are mostly indoor year-round, supplementation through summer often makes sense too.

Take winter mood seriously. If symptoms are significant — persistent low mood, withdrawal from normal activities, real difficulty functioning — speak to your GP. SAD is treatable, and light therapy and other interventions are well-evidenced.

For the vitamin D piece specifically, Daily Sunshine includes D3 plus K2, magnesium, B vitamins, zinc and selenium — the nutrients that work alongside it. Take our quiz for a personalised view.

The point

Yes, we are spending too much time indoors. The number is roughly 90%, it has crept up over a generation, and the body is quietly registering the change in ways most people are interpreting as personal failings rather than predictable biological responses to a structurally light-poor lifestyle.

The good news is that none of the corrections require you to overhaul anything. They require ten minutes in the morning and two capsules with breakfast. That is most of what is on offer, and most of what is needed.

Shop Daily Sunshine 10 nutrients. Two capsules a day. Free UK delivery.