Vitamin D

Dietary Source

• fatty fish
• egg
• mushrooms
• dairy products
• sun 15-30 min a day for daily dosage, produced in skin
  

Is good for

• against osteoporosis
• against tooth cavity
• against muscle fatigue
• hormone balance (increases testosterone production. Increases the effects of dopamine and norepinephrine)
• antibacterial
• immune system
• fatigue
• depression
• T-cells
• against cold and flu
• reumatism
• acne
• eczema
• psoriasis
• against inflammation, cancer, multiple sclerosis, parkinsson, alzheimers, etc...
• better results in the gym
• lever problems, constipation, nearsightedness, increased insulin sensitivity, and decreases the chances to get diabetes type 2
  

Vitamin D deficiency

• fatigue; aches in hands, arms, and back
• colds, flu, depression, osteoporosis, psychosis, skin disease, rickets, dementia, IBS, Crohns disease, autism, schizophrenia, fibromyalgia, and over weight
  

During the autum and winter period it's good to supplement with vitamin D, because of the shorter hours of day light.

References:

http://articles.mercola.com/sites/articles/archive/2013/12/22/dr-holick-vitamin-d-benefits.aspx

http://www.healthline.com/health/food-nutrition/benefits-vitamin-d#Overview1

http://www.bodybuilding.com/fun/top-5-benefits-of-vitamin-d.html 

http://www.m.webmd.com/food-recipes/features/vitamin-d-vital-role-in-your-health