It could be, according the BMJ blog:
"You are vitamin D deficient, very probably, and this is making your muscles ache, slowing you brain, thinning your bones and making you more likely to get cancer and heart disease. The secret of the Mediterranean is not its food but its sunshine. Or both. Go on, take your clothes off, get outside, and eat lots of oily fish, cheese, wild fungi and eggs. Abandon your miserable existence in the dark North and start living before it is too late. Alternatively, get a sunbed and take large daily supplements of vitamin D. It’s the elixir of life, according to this very thorough and plausible review."
Vitamin D is a steroid hormone and a component of a complex endocrine pathway sometimes called 'vitamin D endocrine system' (Medscape, 2012).
Relative vitamin D deficiency may also explain why anaphylaxis seems to be more prevalent in the Northern parts of the U.S.
Vitamin D Deficiency. Michael F. Holick, M.D., Ph.D. NEJM, 2007.
Where are EpiPens prescribed the most in the U.S.? Allergy Notes, 2007.
Image source: Wikipedia, public domain.