Vitamin D play an important role our immune system through prevention of osteoporosis, cancer, autoimmune and mental health through the anti-inflammatory mechanism and modulation of cell growth. Sun is our source of our vitamin D, health and happiness.
In the USA the fear of skin cancer due to sun exposure has grown regardless the protective benefits of sun for vitamin D synthesis. This Vitamin D worldwide deficiency was found even in the most sunny area of the world.  The deficiency can occur when oral low intake of vitamin D , limited exposure to sunlight  or the kidneys cannot convert 25(OH)D to its active form. Also, the absorption of vitamin D in the digestive tract is inadequate in gut dysbiosis, IBS, milk allergy, lactose intolerance. Who else could be at risk of deficiency? Darker skin absorb less vit D from the sun, vegans and people taking certain medications.
Older adults are at increased risk of developing vitamin D insufficiency because as they age their skin cannot synthesize vitamin D as efficiently. Using sun protection blocks the vitamin D absorption. I do not use commercially sun blocks!
The blood work normal range is from low 30 nmol/L to 60 but some people are potentially at risk at levels ranging 30-50nmol/L. In my world vitamin D optimization levels are around 60-80 nmol/L.
Best sources of vit D are: cod liver oil, swordfish, salmon, tuna but unfortunately these fish are also the most heavy metal contaminated. That is why a lot of people prefer to take the supplements form that has been tested as free from heavy metal.
Keep in mind vitamin D is also a hormone and essential in the synthesis of the testosterone levels. What is the best time to take vitamin D3? Evening.

* The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. It is intended as a sharing of knowledge and information from the research and experience of Dr. Wright and his community. Dr. Wright encourages you to make your own health care decisions based upon your research and in partnership with a qualified health care professional. If you are pregnant, nursing, taking medication, or have a medical condition, consult your health care professional before using products based on this content.information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. It is intended as a sharing of knowledge and information from the research and experience of Dr. Wright and his community. Dr. Wright encourages you to make your own health care decisions based upon your research and in partnership with a qualified health care professional. If you are pregnant, nursing, taking medication, or have a medical condition, consult your health care professional before using products based on this content.