What is vitamin D?     

       Vitamin D is a fat soluble vitamin that appears in two forms.  It is available from plants as vitamin D2 (ergocalciferol) and from animal sources as vitamin D3 (cholecalciferol). Both these forms obtained from dietary sources are converted by the liver into calciferol. Vitamin D3 is the more biologically active form of this nutrient and has been shown to be twice as effective in producing calciferol as is true of D2. Our body makes D3 in the skin when the cholesterol compound 7-dehydrocholesterol reacts with ultraviolet light from the sun. Once made in the skin it is transported to the liver where it is made into calcidiol (25-hydroxy-vitamin D).

Why do we need vitamin D?

       The most active form of the vitamin is calcitriol (1, 25 dihydroxy vitamin D3), which is synthesized from calcidiol in the kidneys where it functions as a hormone by sending messages to the intestines to increase the absorption of calcium and phosphorus. A major biologic function of vitamin D is to maintain normal blood levels of these two minerals.  By promoting calcium absorption, vitamin D helps to form and maintain strong bones and teeth. Insufficient vitamin D can lead to thin, brittle bone tissue and dental problems.  Measuring the blood level of calcidiol is the only way to determine vitamin D levels.

       Research shows vitamin D is involved in helping to maintain a healthy immune system, improve muscle strength, regulate cell growth and differentiation, and facilitate normal cardiovascular function.  Studies suggest that higher levels of vitamin D correlates with lower incidence of certain cancers. Researchers have observed that greater exposure to sun is associated with lower death rates from colon and colorectal cancers.  Vitamin D emerged as a protective factor in a study of over 3,000 adults (96% of whom were men) who underwent a colonoscopy between 1994 and 1997 to look for polyps or lesions in the colon. About 10% of the group was found to have at least one advanced cancerous lesion in the colon. There was a significantly lower risk of advanced cancerous lesions among those with the highest vitamin D levels. Others studies have shown vitamin D to be a protective factor against breast cancer. Clinical studies show vitamin D deficiency to be associated with four of the most common cancers; breast, prostate, colon and skin cancers. 

       Vitamin D deficiency has been shown to possibly be linked to diseases such as various cancers, chronic pain, weakness, chronic fatigue, autoimmune diseases like multiple sclerosis, type 1 diabetes, high blood pressure, mental illnesses (depression, seasonal affective disorder and possibly schizophrenia), heart disease, rheumatoid arthritis, psoriasis, tuberculosis, periodontal disease and inflammatory bowel disease.  On the other hand, some research indicates that in some chronic diseases where vitamin D levels (25-hydroxy-vitamin D) appear to be low, they are low because the disease causes too much production of vitamin D’s active hormonal form (1, 25 dihydroxy vitamin D3) which can be harmful in amounts beyond normal range. 

Vitamin D and the sun:

       Human skin exposed to sunlight can, under the right conditions, produce quantities as large as 20,000 IU in just a few minutes without any apparent toxicity. This is easily enough to avoid deficiency and the vitamin does build up in the body tissue.  Exposure to sunlight also destroys vitamin D so long term exposure to sunlight cannot cause toxicity, as levels are self-adjusting.

       On the other hand, merely being exposed to sunlight does not automatically mean that vitamin D is produced as only the UV rays in sunlight trigger vitamin D production.    UV rays mainly reach ground level when the sun is high in the sky. This occurs a few hours around solar midday (1 pm summertime).  At higher latitudes, the sun is only high enough in the sky in summer. For example, in the United States those living north of a line from San Francisco to Philadelphia (about 40 degrees of latitude) will not be able to produce vitamin D in significant quantities for 3 to 6 months a year.

       Those living in the higher latitudes from the end of summertime to the following spring must rely on stores of this vitamin which gradually deplete. By some estimates 10 to 20% of the population becomes at least mildly deficient by the end of winter.  Sunscreens over 8 SPF significantly interfere with production of Vitamin D3.   Melanin, the dark pigment found in skin, screens UV light so dark skin is much less efficient at generating vitamin D. People with darker skin experience greater vitamin D deficiencies, especially if they live at higher latitudes or have an urban lifestyle, as research shows. Vitamin D deficiency is known to be endemic in dark-skinned populations in the UK.

Vitamin D from food:

       Vitamin D3 (cholecalciferol) is found in egg yolk, animal fat and various fish and cod liver oils. Vitamin D2 (ergocalciferol) is found in plants and is a less biologically active form of this vitamin. The vitamin D that is added to milk and some other foods is D2.   Multi-vitamin/mineral supplements will often use Vitamin D2 in their formula.  When buying a multiple or a vitamin D supplement, look for vitamin D3   (cholecalciferol) on the label as this is the more biologically active form. 

Vitamin D from Cod Liver Oil:

       Vitamin D3   can be obtained from cod liver oil.  Taking one teaspoon for every 50 pounds of body weight will provide the average 150 pound adult, with 2-3,000 units of vitamin D. Vitamin K is also present in cod liver oil and is an essential co-factor in building strong bones. Natural vitamin A (retinol) is also present in cod liver oil.  Vitamin A is essential to immune function, healthy skin and numerous other areas of our physiology.  Additionally, vitamin A provides a protective benefit in limiting to high of a calcium level in the body from the action of vitamin D. Vitamin A antagonizes calcium response to vitamin D in humans. Cod liver oil is also a great source for the very beneficial omega three fatty acids EPA and DHA which most Americans are deficient in. We recommend the Carlson brand of cod liver oil.  This brand has an excellent track record of quality and comes in a lemon flavored taste that virtually removes the taste of the oil. 

Testing for vitamin D in the body:

       The common test for measuring blood levels of vitamin D is called 25-hydroxy vitamin D or 25(OH) D.  A blood level of 50ng/ml (nanograns per milliliter of blood) to 70ng/ml of vitamin D is considered optimal.  A reading below 25ng/ml is considered a vitamin D deficiency and a reading of less than 35ng/ml is considered insufficient.  The 25 (OH) D test is available through Milk ‘N Honey.

How much Vitamin D do we need?    

       Current FDA recommendations are between 200 and 400 international units (IU) per day.  Recent and ongoing research is finding that this recommendation is far too low.  Such research has shown that much higher dosages of vitamin D would reduce the risk of not only osteoporosis but such serious health problems as cancer and cardiovascular disease.  In the 2004 October/November issue of “Integrative Medicine,” in an article entitled, “The Clinical Importance of Vitamin D (Cholecalciferol): A Paradigm Shift with Implications for All Healthcare Providers,” the authors provided considerable evidence that there is an epidemic of vitamin D deficiency.  These authors recommended intake of up to 4000 IU of Vitamin D per day for adults and several thousand IU for children.

       At Milk ‘N Honey we recommend getting plenty of sunlight (minus the sunscreen) during the summer months and supplementing with Vitamin D during late fall through early spring.  Cod liver oil and a variety of vitamin D products are available at Milk ‘N Honey.