Why Morning light Is So Crucial to Your Health

Steve Jones: Sunlight is powerful stuff, perhaps more powerful than most people realise. The perils of living without sunlight are really quite real. In some ways, modern life has driven us back to the Stone Age, okay, when we lived in caves.

In the 60s, there were several experiments by French people who went into caves and stayed there. They all began to sleep either for extraordinarily long periods of time or extraordinarily short periods of time, and they couldn't tell the difference. They all said they had severe mood disturbances and depression, so much so that some of them had to leave long before they really had planned to.

In winter, we often feel somewhat out of sorts at this time of the year. A lack of sunlight means that your immune system doesn't work as well, your defence mechanisms don't work as well.

Arti Jagannath: An effect on mood, increased depression, more metabolic disorders, and all of these things are offshoots of a disrupted circadian clock. It times all of our physiology and all of our behaviour. All of the active sorts of processes are compartmentalised to the day, and all of the restorative processes are kept to the night.

The wavelengths that have the most powerful impact are the bluish-coloured ones. Within our eyes, there are these cells that have a pigment that's sensitive to this blue light, that then signals to the body clock to tell it what time of day it is.

Steve: Many people don't realise what an artificial life we live. That's because artificial life depends on artificial light.

Arti: So by seeking out artificial light, what that is doing is giving your body a time cue that is incorrect. Then you might end up feeling far more alert at night, or a lot more depressed during the day. Your systems within your body tend to desynchronise and so you tend to have a higher incidence of diabetes, obesity, cardiovascular disease.

Steve: The World Health Organization sees shift work as a threat to health, and it is. Many British people spend less than half an hour a day in the open air. So it's no good staying inside and looking at the Sun and saying this is doing me good, because it isn't.

Arti: So it's probably, on a day like today, about four or five times less light simply being on this side of the glass. A good dose of bright sunshine at any time during the day has a huge impact on elevating mood and general feelings of wellbeing.

There was a study at the Broadmoor institute where they looked at the effects of the equivalent of 20 minutes of bright sunshine in the morning on mood. What they found was the bright light had a much greater effect on elevating mood than even some anti-depressants.

So our skin's not just a barrier, it's a living organ. When our skin sees sunlight, that is when it starts making vitamin D, which is an essential component of many different signalling pathways in our body.

Steve: You can get vitamin D in several ways. You can do what I do, and take a vitamin D pill. A diet of wild salmon and mushrooms and you won't get rickets. But overwhelmingly the best way is through the Sun.

Arti: Have meals at the right time, go to bed at the right time, and get out, even if it's freezing, for that daily 20-minute walk and some light exposure. Simply being outside and exposing yourself to light, so that you strengthen your circadian clock is going to have a hugely beneficial impact on health and wellbeing.

Steve: Don't retreat into your cave. In other words, when the sun comes out, go out and have a good time.

词汇表
peril [ˈperəl] 危险，危害，风险
Stone Age [ˈstəʊn eɪdʒ] 石器时代（以石器为主要工具的早期阶段）
cave [keɪv] 洞穴，山洞
mood disturbance [muːd dɪˈstɜːbəns] 情绪障碍，情绪紊乱
out of sorts [aʊt əv sɔːts] 身体不适，心情不佳
immune system [ɪˈmjuːn ˈsɪstəm] 免疫系统（人体抵御病原体的防御机制）
metabolic disorder [ˌmetəˈbɒlɪk dɪsˈɔːdə(r)] 代谢紊乱，代谢异常
offshoot [ˈɒfʃuːt] 衍生物；分支，支流
disrupted circadian clock [dɪsˈrʌptɪd sɜːˈkeɪdiən klɒk] 生物钟紊乱（调节昼夜节律的生理机制失调）
physiology [ˌfɪziˈɒlədʒi] 生理学，生理机能
compartmentalise [ˌkɒmpɑːtˈmentəlaɪz] 划分，区分，隔开
restorative [rɪˈstɒrətɪv] 复原的，恢复精力的
wavelength [ˈweɪvleŋθ] （光波、音波等的）波长；（广播的）波段，频道
bluish-coloured [ˈbluːɪʃ ˈkʌləd] 带蓝色的，有点蓝的
pigment [ˈpɪɡmənt] 色素；颜料
desynchronise [ˌdiːˈsɪŋkrənaɪz] 使不同步，失调
diabetes [ˌdaɪəˈbiːtiːz] 糖尿病
obesity [əʊˈbiːsəti] 肥胖症
cardiovascular disease [ˌkɑːdiəʊˈvæskjələ(r) dɪˈziːz] 心血管疾病
shift work [ʃɪft wɜːk] 轮班工作，倒班
elevate mood [ˈelɪveɪt muːd] 改善情绪，提升心情
equivalent [ɪˈkwɪvələnt] 等同物，相等物
anti-depressant [ˌænti dɪˈpresnt] 抗抑郁药
vitamin D [ˈvɪtəmɪn diː] 维生素D（促进钙吸收、维持骨骼健康的营养素）
signalling pathway [ˈsɪɡnəlɪŋ ˈpɑːθweɪ] 信号通路（细胞内传递信号的一系列生化反应）
salmon [ˈsæmən] 三文鱼
ricket [ˈrɪkɪt] 佝偻病，软骨症（缺乏维生素D导致的儿童骨骼发育异常）
retreat [rɪˈtriːt]  躲避，撤退，退却

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