First, there must be enough vitamin D in the body, either from food, or created in the skin in response to sunlight exposure.

首先，机体内需要有足量的维生素D，可以来源于食物，也可以由皮肤受日光照射后合成。

If you need some vitamin D, call me up, I'll email you some in the post.

如果您需要一些维生素 D，请给我打电话，我会在邮件中给您发送一些。

And there's lots of health benefits to this; the sunlight gives you vitamin D which a lot of people are deficient in.

这对健康有很多好处；阳光为您提供许多人都缺乏的维生素 D。

When days get longer, our bodies have to adapt to the exact opposite: Synthesize more vitamin D and serotonin and less melatonin, which is very energy-consuming and can take days or weeks for our bodies to readjust.

当白天变长时，我们的身体必须适应完全相反的情况：合成更多的维生素 D 和血清素，减少褪黑激素，这非常消耗能量，我们的身体可能需要几天或几周才能重新适应。