D-Vitamin sources

Optimal immune function require optimal d-vitamin levels. In winter time, d-vitamin levels can easily drop below ideal levels. Supplement d-vitamin intake can therefore be helpful. Typical recommended daily intake is 400-800 international units (IU). Here are some nutrition sources of d-vitamin.

Source	Concentration	IU (40 IU = 1 $\mu$g)
Fish
Cod liver oil	10 $\mu$g per 5 ml	400 IU per 5 ml
Salmon	11 $\mu$g per 100g	441 IU per 100g
Canned sardines	4.8 $\mu$g per 100g	193 IU per 100g
Milk and egg products
Almond milk	2.5-3.6$\mu$g per 250 ml	100 – 140 IU per 250 ml
Egg	1.7 $\mu$g per egg	68 IU per egg
Cheddar	0.6 $\mu$g per 100g	24 IU per 100g
Mushrooms
Dried Shiitake	240 $\mu$g per 100 g	9680 IU per 100g
Chanterelles	20 $\mu$g per 100 g	800 IU per 100g