Midnight Feasts Could Cause Melasma 夜宵也会导致黄褐斑

Overnight, keratinocytes (kind of skin epidermis cell) proliferate rapidly, preparing and protecting our outer barrier for the sunlight and scratches of the coming day. During the day, these cells then selectively switch on genes involved with protection against the sun’s ultraviolet (UV) rays. A 2017 study [1,2] found that midnight feasts could actually cause sunburn. If we eat late at night, our skin’s clock assumes that it must be dinner time and consequently pushes back the activation of the morning-UV-protection genes, leaving us more exposed the next day. So while studies are increasingly showing that a lack of sleep is detrimental to our overall physical and mental health, it now seems that our skin also benefits from additional sleep. The epidermis may be built to face the outside world, but it’s increasingly clear that it also looks inwards, even at when we choose to eat.

melasma

Melasma is a common skin problem caused by brown to gray-brown patches on the face. Most people get it on their cheeks, chin, nose bridge, forehead, and above the upper lip. 90% of patients are women. Although the exact pathogenesis of melasma is unknown, it is hypothesized that following exposure to UV irradiation or another inducer, hyperfunctional melanocytes within involved skin produce increased amounts of melanin [3,4].

Utraviolet (UV), A form of electromagnetic radiation that has a shorter wavelength (and higher energy) than visible light but a longer wavelength than X-rays. Roughly 10 per cent of the radiation produced by the sun is ultraviolet.

角质形成细胞（一种皮肤表皮细胞）在夜间迅速增殖，为第二天的紫外线和物理刮擦做好了准备并保护了我们的外部屏障。到了白天，这些细胞会选择性地打开与太阳紫外线相关的基因。 2017年的一项研究[1,2]发现午夜盛宴实际上可能会导致晒伤。如果我们在深夜进食，我们的皮肤时钟会以为那是晚餐时间，因此会推迟早上保护紫外线的基因的激活，从而使我们第二天接受到的紫外线更多。尽管越来越多的研究表明，睡眠不足对我们的整体身心健康有害，但现在看来，我们的皮肤也可以从额外的睡眠中受益。人类表皮是面向外界的屏障，但是，即使在我们选择吃饭时，它也同时在向内看。

circadian

黄褐斑是常见的皮肤问题，在脸上呈现出棕色至灰棕色斑块。大多数人会在脸颊，下巴，鼻梁，前额和上唇上方得到它。 90％的患者是女性。尽管尚不清楚黄褐斑的确切发病机理，但据推测，暴露于紫外线或其他诱导剂后，受累皮肤内功能亢进的黑素细胞会产生大量的黑色素[3,4]。紫外线（UV），一种短波电磁辐射，其能量强度高，UV波长比可见光短，但比X射线长。太阳产生的辐射大约有10％是紫外线。

 

Reference:

  1. Wang, H., van Spyk, E., Liu, 4., Geyfman, M., Salmans, M. L., Kumar, V., Ihler, A., Li, N., Takahashi, J. S. and Andersen, B., ‘Time-restricted feeding shifts the skin circadian clock and alters UVB-induced DNA damage’, Cell Reports, 20(5), 2017, pp.1061–72
  2. Regmi P, Heilbronn LK. Time-Restricted Eating: Benefits, Mechanisms, and Challenges in Translation. Iscience. 2020 Jun;23(6):101161.
  3. NP Sanchez, MA Pathak, S Sato, et al.: Melasma: a clinical, light microscopic, ultrastructural, and immunofluorescence study. J Am Acad Dermatol. 4:698–710 1981
  4. PE Grimes, N Yamada, J Bhawan: Light microscopic, immunohistochemical and ultrastructural alterations in patients with melasma. Am J Dermatopathol. 27:96–1012005