Vitamin D
Vitamin D (cholecalciferol) has been described as a vitamin, but it actually has more characteristics of a hormone than a vitamin. For instance, you make your own Vitamin D in your skin when exposed to ultraviolet light as from the sun. Vitamin D is made from cholesterol just like your sex hormones and stress hormones. There are receptors for vitamin D on almost every cell of the body, which is why it affects almost every cell of the body.
There are several forms of vitamin D in the body causing much confusion.
There are at least 3 natural forms in the human body. First, cholecalciferol is made from cholesterol in the skin after exposure to ultraviolet light type B. Cholecalciferol has little action in the body until the liver changes it to calcidiol (25-hydroxycholecalciferol) and then the kidney fully activates it to calcitriol (1,25-hydroxycholecalciferol). All of these are forms of vitamin D3 which is available as a supplement. Ergocalciferol, or vitamin D2, is a form of vitamin D extracted from some mushrooms and often used as a supplement.
There is a lot of argument among vitamin D experts regarding the best form to take as a supplement. Vitamin D2 has been the dominant form taken, but some research is showing that vitamin D3 is a more useful form. I am not the research expert, but I feel giving the body its natural form of D3 makes the most sense. Also, people have historically consumed vitamin D in large amounts especially in areas with little direct sunlight such as the arctic. This vitamin D was the D3 form found mostly in the fats of marine animals.
Functions of Vitamin D:
Vitamin D is well-known to increase calcium absorption in the intestines and helps maintain the correct levels of calcium in the blood. Vitamin D is also a very strong antioxidant (possibly stronger than vitamin E). It protects against insulin resistance and diabetes and prevents cataracts. Many hormonal issues are corrected when vitamin D is supplemented. Vitamin D is essential for the proper functioning of the immune system. Many autoimmune conditions are related to vitamin D deficiency. Some cancers, infertility, chronic fatigue, depression, dementia, neurological diseases, and learning and attention disorders are all associated with vitamin D deficiency. This is why you have been hearing a lot about vitamin D in the media; people are really excited about this!
Vitamin D and Influenza:
I recently heard a lecture about how severe vitamin D deficiency may have been the reason the 1918 flu epidemic killed so many people especially in the urban areas. At that time, people in cities worked 12-hour shifts in factories rarely seeing sunlight. The diet was (and still is) deficient in vitamin D. One study from that same time period tracked a group of babies in New Orleans. All of the babies in the study developed rickets.
Cultures who have routinely consumed a lot of vitamin D in their diet usually get it with vitamin A and vitamin K2 (and other quinones) along with the omega 3 and saturated fats in which they are found. We find that these three vitamins work together to increase calcium absorption and utilization preventing osteoporosis, osteoarthritis, heart disease, and weight gain.
Cod Liver Oil:
I recommend getting vitamin D3 from marine animal fats as in cod liver oil. Unfortunately, most of these oils are extracted using heat which destroys much of the vitamin D. Recently, I have discovered Green Pastures who makes cod liver oil that has not been heat-processed and is now the one I recommend. You may read about it further on their web site by clicking on their name above. They also have a wonderful product that combines cod liver oil with high-vitamin butter oil (a good source of vitamin K2) providing all 3 of these vitamins in the correct ratios along with the saturated fats and omega-3 fats necessary for proper absorption. This combination is a superfood shown to us by traditional cultures all over the world.
I would highly recommend reading Nutrition and Physical Degeneration by Weston Price, DDS for much more detailed information about traditional diets and these fat-soluble vitamins.
