Unless you live in Florida your vitamin D levels will begin to fall now that the weather is getting colder and we are not out in the sun as much. You may want to consider supplementation.

Vitamin D affects several body processes. The most well-known process is calcium regulation. Vitamin D also behaves like a hormone by binding to nuclear vitamin D receptors (VDRs). Nuclear VDRs have been found in over 30 organs! It also appears to exert its effects through interaction with messenger RNA to enhance or inhibit translation. Over 50 genes appear to be regulated by calcitriol! Calcitriol affects phosphorus homeostasis and is thought to help maintain normal cell growth, differentiation, proliferation, and prevent malignancy by down-regulating cancer cell growth and inducing apoptosis. Muscle dysfunction (myopathy) is well documented in individuals with vitamin D deficiency. Vitamin D also has roles in regulating blood pressure and diminishing risk of heart disease. Rheumatoid arthritis, Crohn’s disease, multiple sclerosis, and type 1 diabetes mellitus have been linked with inadequate vitamin D status.

Vitamin D is synthesized when 7-dehydrocholesterol in your skin is exposed to UVB light radiation from the sun producing cholecalciferol (Vitamin D3). Calciferol is converted by the liver to calcidiol, which is then converted by the kidneys to calcitriol. The blood is the largest storage site for calcidiol. This is the amount that is checked in a blood test for vitamin D status. The half-life of calcidiol is 15 days to approximately 3 weeks. When your body needs vitamin D for its many processes it will convert its storage form of calcidiol to the active form of calcitriol in the kidney. The half-life of calcitriol is 2 to 6 hours.

Dietary sources of vitamin D are found in animal sources in the form of vitamin D3 (cholecalciferol) or plant sources in the form of vitamin D2 (ergocalciferol). Liver, eggs, fatty fish including herring, salmon, tuna, and sardines, and shitake mushrooms are good sources. About 50% of dietary vitamin D is absorbed. Toxicity is rare. It is seen with intakes of 10,000 IU or more taken daily for several months.

Vitamin D is so important. If we are slathering sunscreen on in the summer months our skin is unable to synthesize the vitamin. In the winter it’s too cold to expose ourselves to the sun. This leaves most of the population with a vitamin D deficiency. Symptoms include bone pain, muscle weakness, fatigue, and depression. Most people will benefit from supplementing with 2,000 IU of vitamin D and some will see benefit from 5,000 IU per day. The best form is a combination of vitamin D3 and vitamin K2 since they work synergistically. Make sure to take with fat or in a gelcap lipid suspension as they are fat soluble and need fat to be absorbed by the body. If you are on a blood thinner, then vitamin K is not for you as vitamin K helps to coagulate blood and would counteract your meds. As always, best to seek out the advice of a health care professional, even when thinking about supplements.