Vitamin D

This week I am going to discuss Vitamin D. This fat soluble compound exists in many forms however the form utilized primarily by humans is vitamin D3 (cholecalciferol).

Vitamin D is a regulator of calcium and phosphorus status; both of which are vital for normal functioning of the nervous system, as well as for bone growth and density. Vitamin D deficiency has been associated with cancer, cardiovascular disease, diabetes, autism and asthma, among other conditions (see below for more information). Evidence has shown that vitamin D is not stored in our bodies until a level of 50ng/ml is reached, which is why at Kingsway we recommend that patients use a starting dose of 50,000IU daily for three days, and then drop back to a maintenance dose of 4000-5000IU daily.

Animals (including humans) convert cholesterol to 7-dehydrocholesterol, which is a precursor to vitamin D3. Exposure to ultra violet light in sunlight (UVB radiation) converts 7-dehydrocholesterol in the skin to vitamin D3. In fact, adequate exposure to sunlight can eliminate the requirement for vitamin D in the diet, making it only “conditionally essential.” Vitamin D3 is not itself biologically active, but must be modified by the body to have any physiological effects.

As stated above, Vitamin D is a regulator of calcium (and phosphorus) status. Maintenance of blood calcium levels within a narrow range is vital for normal functioning of the nervous system as well as for bone growth and maintenance of bone density (please refer to our last newsletter for more detailed information on calcium). This tight regulation is accomplished through a complex system, sometimes called the “vitamin D endocrine system,” because the active form of vitamin D3 has a mechanism of action similar to some hormones, for example, thyroid hormone.

In infants and children, prolonged vitamin D deficiency results in a condition known as rickets (resulting in failure of bone to mineralize). In adults with prolonged vitamin D deficiency, the collagenous bone matrix is preserved however the bone mineral is progressively lost as a result of normal bone turnover, resulting in bone pain and osteomalacia (soft bones).

Vitamin D has shown to reduce cellular proliferation, induce apoptosis and differentiation, and prevent angiogenesis (a physiological process involving the growth of new blood vessels from pre-existing vessels; a normal and vital process in growth and development, however it is also a fundamental step in the transition of tumors from a dormant state to a malignant one).

Vitamin D deficiency is associated with cancer (especially prostate, colorectal and breast), cardiovascular disease, hypertension, stroke, diabetes, multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease, osteoporosis, periodontal disease, macular degeneration, mental illness, chronic pain and the triple childhood epidemics of autism, asthma and type 1 diabetes (all of which are said to have blossomed after sun-avoidance advice became widespread).

A review article published in the Alternative Medicine Review (2008) on the Use of vitamin D in clinical practice refers to a recent meta-analysis of 18 randomized controlled trials (RCT) which found that supplemental cholecalciferol significantly reduced total mortality; emphasizing the importance of promptly diagnosing, and adequately treating vitamin D deficiency.

Claims that vitamin D may help prevent such a wide array of diseases seems incredible until one realizes that vitamin D is not actually a vitamin; rather, it is the only known substrate for a potent, pleiotropic (producing many effects), repair and maintenance, seco-steroid hormone (compound derived from a steroid in which there has been a ring cleavage) with a single endocrine function, but multiple autocrine functions. It targets more than 200 human genes in a wide variety of tissues, meaning it has as many mechanisms of action as genes it targets.

A journal article published in Medical Hypotheses (2008) looked at Autism and vitamin D. This article spoke of the “apparent increase in the prevalence of autism over the last 20 years corresponds with increasing medical advice to avoid the sun, advice that has probably lowered vitamin D levels and would theoretically greatly lower activated vitamin D (calcitriol) levels in developing brains” (the article also points out that any theory of autism's etiology must take into account its strong genetic basis while explaining its striking epidemiology). The article also refers to:
- Animal data which has repeatedly shown that severe vitamin D deficiency during gestation dysregulates dozens of proteins involved in brain development and leads to rat pups with increased brain size and enlarged ventricles, abnormalities similar to those found in autistic children,
- The different effects which estrogen and testosterone have on calcitriol metabolism; differences that may explain the striking male/female sex ratios in autism, and
- The ability of calcitriol to down-regulate production of inflammatory cytokines in the brain, cytokines that have been associated with autism.

Perhaps because the term “vitamin D” contains the “vitamin,” most people wrongly assume they can obtain adequate amounts by eating a healthy diet. However, the natural diet that most of us consume contains minimal vitamin D, unless those diets are rich in wild-caught fatty fish, sun-dried shiitake mushrooms, or wild reindeer meat. Small amounts of vitamin D are contained in fortified foods, such fortified milk and cereals, but such sources are minor contributors to vitamin D stores.

Although, the traditional human vitamin D system began in the skin and not in the mouth, when taken orally the body can metabolize vitamin D similarly to that generated in the skin. The treatment of choice for vitamin D deficiency is vitamin D as cholecalciferol (also known as vitamin D3).

Dosing Recommendations:
Adequate oral supplementation will require doses that might make a practitioner initially uncomfortable, as physiological doses of vitamin D, in the absence of sun exposure, probably range between 400 IU/day for premature infants to 10,000 IU/day for the morbidly obese. (Pease note – much higher doses than these may also be given to patients if required)

Treatment of vitamin D in otherwise healthy patients with 2,000 to 7,000 IU per day should be sufficient to maintain year round 25(OH)D levels.

At Kingsway we recommend that patients use a starting dose of 50,000IU daily for three days, and then drop back to a maintenance dose of 4000-5000IU daily. Evidence has shown that vitamin D is not stored in our bodies until a level of 50ng/ml is reached.

In general the more a patient weighs, the more vitamin D will be required, and the larger amounts of body fat further increases requirements. Fat malabsorption syndromes may increase oral requirements, along with advancing aging, which impairs the skin’s ability to make vitamin D (therefore an older person will require a higher supplemental dose than a younger person). Those individuals on long term medications, such as anti-psychotics, cardiac drugs and certain antibiotics, should also monitor their vitamin D status, as the cytochrome P-450 enzymes responsible for the initial metabolism and subsequent catabolism of vitamin D are also depended upon by these drugs.

Please feel free to contact us with any questions you have regarding Vitamin D.