Several: First and foremost, sunlight. However, if you live where it's cold enough to have a winter, sunlight won't be strong enough to give you what you need. Food sources include salmon, herring, mackerel, whale blubber (for real!) and there is a small amount in some mushrooms. Easier to get it from a supplement.
Answered 2/20/2016
6.1k views
Mr. Sun: Like dr. L says. Get outside in the sun 5-30 minutes twice a week without sunblock.
Answered 12/9/2013
6.1k views
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