It’s a marvel of human evolution; our skin can harness the power of the sun and make vitamin D.

Sun Exposure

Our skin is a vitamin manufacturing machine.

In general, exposing the hands, face, and arms to sunlight for 20 minutes/day 3x per week should provide adequate of Vit D in white skin.

Pigmented skin requires longer exposure to produce the same amount of D.

Aging reduces the manufacture of D from the sun.

Body Processes Involved

Healthy liver, digestion and kidney function are all required for Vitamin D distribution around the body to where it’s needed.

Food Sources

Food doesn’t contain significant amounts of Vit D.

Animal foods contain D3 (cholecalciferol – the same kind our skin makes), vegetarian sources contain D2 – this is less potent than D3.

Oily fish are a good source of D3 (salmon, herring, mackerel, cod liver oil)

Animal meat, eggs, milk  contain D3.

Mushrooms contain D2.

To give you an idea:

70g salmon = 570 IU of D3

150g of sun-dried mushrooms = 400 IU of D2

Deficiency Signs

An estimated 30% of adults are deficient.

Bone issues: osteoporosis, rickets, increased fracture risk

Other signs: muscle weakness, psoriasis, seasonal affective disorder (SAD), chronic kidney disease, autoimmune, and some cancers.

Dosing

It’s practically impossible to get too much D via food or the sun. However, ingestion via supplements can be toxic. While ‘Vitamin D’ refers to a range of related fat-soluble sterols, it’s generally recognised that D3 is the most appropriate supplemental form, more bioavailable than D2.

In the absence of sun exposure 1500-2000 IU/day (D3) is required to raise blood levels to optimal (in adults).

Look for D3 aka cholecalciferol. A non-prescription dose would be up to 1000 IU per day (adults). Children require less.

Caution: if you’re on Digoxin or other heart, BP or cardiovascular you need to check with your Dr before taking Vit D supplements

For more detailed information check out the information available from the Linus Pauling Institute

References:

Hechtman, L. (2018). Clinical Naturopathic Medicine. Elsevier.

PMID: 35684328