Vitamin D3 is vital for keeping the immune system strong and for the prevention of colds and flus. This is the main reason the flu season is in the winter when the sun is weaker, the sky often covered by clouds, and skin exposure to the sun is minimal. Vitamin D3 is involved in over a thousand functions within the body, and sunshine helps our skin synthesize it.
People who have 60 ng/ml levels of Vitamin D3 (60 nanograms of vitamin D3 per milliliter of blood) rarely get sick or do not die from the virus. Most who succumbed had about 20 ng/ml in their body.
Vitamin D3 is used up in the body within 48 hours of production. It is important to sunbathe. For fair skin, the recommended sunbathing time is around 20-30 minutes per day, depending on how much of the skin is exposed to the sun. For darker-skinned people, around an hour a day.
People who are low in Vitamin D3 from either low sun exposure or not taking enough supplementation should take higher dosages of 20,000 IU to 30,000 IU to make up for the deficit in their body and build up to maintain a minimum level of 50 ng/ml.