Glossary: Vitamin D

vitamin D

Also known as: Calciferol; Cholecalciferol:

What is it?

When parents send their children out in the sun to play, they're not just trying to get them out of the house. They know that sunlight forms this VITAMIN in the skin (actually, it's ultraviolet radiation that does it). Indeed, most people can manufacture enough vitamin D in summer to last them through the winter and there's little danger of ODing on sunlight vitamin D because the body limits the amount formed. Why is vitamin D important? It facilitates the absorption of CALCIUM in the body, regulates calcium and PHOSPHORUS metabolism in the body and thus helps build strong bones and teeth. In the old days, children in cold climates with limited sunshine often suffered from rickets, an acute vitamin D deficiency most often manifested as bowlegs and deformed ribs. Now that milk's FORTIFIED with vitamin D, rickets is almost unheard of. The standard measurement for the vitamin D content of foods, also for determining the RDAs , is micrograms of cholecalciferol.

1997 ADEQUATE INTAKE FOR VITAMIN D
babies: birth to 12 months	5 mcg cholecalciferol per day
children: 1 to 13 years	5 mcg cholecalciferol per day
adults: 14 to 50 years 51 to 70 years More than 70 years	5 mcg cholecalciferol per day 10 mcg cholecalciferol per day 15 mcg cholecalciferol per day
pregnant women	5 mcg cholecalciferol per day
nursing mothers	5 mcg cholecalciferol per day

Deficiency Symptoms

Calcium loss, soft bones and teeth and, in severe cases, rickets. Blacks synthesize vitamin D from sunlight much more slowly than fair-skinned people, which explains why rickets was so prevalent among black children in New York and other northern cities until the 1920s. About that time scientists began administering daily doses of vitamin D-rich cod-liver oil and effecting "magical cures."

Precautions

Being FAT soluble, vitamin D is stored in the body and too much of it is highly toxic, causing stunted growth, weight loss and calcification of soft tissues. Beware of supplements. Also note that most yogurts and cheeses are made from unfortified milk. Finally, be aware that certain medications — barbiturates, CHOLESTEROL-lowering drugs, cortisone, certain anticonvulsants — block the metabolism of vitamin D.

Additional Information

Vitamin D is necessary for thyroid hormone production in the pituitary gland, and possibly in the early stages of T-3 (thyronine) binding to its receptor.

Recent articles indicate that the prevalence of vitamin D deficiency is much higher than previously recognized (more than 90% in patients with chronic pain, according to a recent study published by the Mayo Clinic), and that vitamin D supplementation is much safer than previously recognized. The recent studies by Al Faraj (2003), Vieth, Chan, and MacFarlane (2001), and Heaney et al (2003) all used daily doses of 4,000 IU per day or more with no evidence of adverse effects.

Vitamin D Levels May Affect Blood Pressure

The health benefits of maintaining an adequate serum level of 25'hydroxy vitamin D are numerous. A recent article in the American Journal of Clinical Nutrition hypothesized that systolic blood pressure levels might be influenced by serum levels of 25-hydroxyvitamin D, or 25(OH)D.

In this cross-sectional study, data from the National Health and Nutrition Examination Survey (1988-1992) was evaluated, and the authors found a significant association between age-associated blood pressure increase and serum 25(OH)D in white subjects. Deficient subjects (<50 nmol/L, or 20 ng/ml) had an age-related systolic blood pressure (SBP) increase of 0.50 mm Hg/year, insufficient subjects (50-79 nmol/L or 20-31.6 ng/ml) 0.48 mm Hg/y, and sufficient (>80 nmol/L or 32 ng/ml) subjects had an SBP increase of 0.40 mm Hg/y. "Participants who were vitamin D deficient and insufficient had significantly higher age-associated increases in SBP than did participants who were vitamin D sufficient (p=0.01).

In this population of 7,699 people 19 yrs of age or older, 61% of whites and 92% of blacks were found to have insufficient vitamin D levels as defined as a serum 25(OH)D level less than 80 nmol/L (32 ng/ml). This was of particular concern because 65% of the black participants had vitamin D levels checked in the summer or fall, when levels are typically highest. The researchers were unable to detect a correlation between blood pressure and vitamin D in these subjects because practically all were deficient.
Judd SE, Nanes MS, Ziegler TR, et al. Optimal vitamin D status attenuates the age-associated increase in systolic blood pressure in white Americans: results from the third National Health and Nutrition Examination Survey. Am J Clin Nutr 2008;87:136-141.

Vitamin D Deficiency Increases Risk of Heart Attack, Stroke

Recent vitamin D research has found vitamin D receptors in heart muscle and many other tissues. This may partly explain the results of the Framingham Offspring Study, in which researchers analyzed vitamin D status (serum 25- hydroxyvitamin D [25-(OH)D]) in 1,739 individuals without cardiovascular disease to determine how levels might correspond with the incidence of cardiac events (MI, stroke). Baseline levels were assessed and participants were followed for a mean of 5.4 years. Researchers observed the incidence of cardiovascular disease and found it was correlated positively with serum 25-(OH)D status. Individuals who were seriously deficient (25-(OH)D < 10 ng/mL) had an 80% greater risk of having a cardiovascular incident, while deficient individuals with 25-(OH)D between 10-15 ng/mL had a 53% increased risk, compared to those with 25-(OH)D > 15 ng/mL. A serum 25-(OH)D level less than 30 ng/mL is considered deficient by most vitamin D experts. The authors concluded vitamin D deficiency is positively correlated with incident cardiovascular disease.

Wang TJ, Pencina MJ, Booth Sl, et al. Vitamin D deficiency and risk of cardiovascular disease. Circulation 2008;117:503-511.

Vitamin D Protects Against Colds & Flu

It has long been observed that incidence of colds and influenza rises in the fall and winter months and wanes in the spring and summer. This is the opposite of serum levels of 25-hydroxyvitamin D, which increase in the summer and decrease dramatically as the amount of daylight diminishes. Research has shown adequate blood levels of vitamin D stimulate the genetic expression of antimicrobial peptides in human monocytes. These peptides demonstrate a broad spectrum of antimicrobial activity against viruses, bacteria, and fungi. Vitamin D also has other immune-modulating and anti-inflammatory activity.

An article published in the journal Epidemiology and Infection reports on a three-year study of 208 African-American postmenopausal women (who are at great risk of vitamin D deficiency) who were supplemented with vitamin D or placebo. For the first two years the active group received 800 IU daily, which was increased to 2,000 IU daily in the last year of the study. In the three years of the study 34 patients reported cold and flu symptoms, eight in the supplemented group and 26 in the placebo group (p<0.002). This showed that participants who got a placebo had a 300-percent greater risk of having a cold or flu, and that vitamin D supplementation provided a highly significant protective effect.

Aloia JF. Epidemic influenza and vitamin D. Epidemiol Infect 2007;135:1095-1096.

High-Dose Vitamin D Shows Excellent Safety in MS Patients

Epidemiological studies have shown a significantly increased risk of developing multiple sclerosis (MS) in people who are vitamin D deficient, and have correlated increased symptomatology in MS patients with lower serum levels of 25-hydroxy vitamin D. To test the tolerability and safety of high doses of vitamin D in MS patients, researchers from the University of Toronto and two hospitals in Toronto gave 12 MS patients 1,200 mg elemental calcium along with increasing doses of vitamin D for 28 weeks. The starting dose was 28,000 IU per week, which was increased to 280,000 IU per week. Serum 25-OH vitamin D levels rose dramatically, to a mean of 154 ng/mL at the end of the study. This supraphysiological level was not associated with any negative effects on liver or kidney function, or on serum or urinary calcium levels. MS disease activity was not affected; however, the mean number of gadolinium-enhancing brain lesions was significantly decreased during the study. This is a groundbreaking study, as it demonstrates that a very high vitamin D oral dosage and the resultant very high serum 25-OH vitamin D level are safe in MS patients. This may stimulate researchers to use higher supplemental therapeutic vitamin D doses in the future, which will provide more safety and efficacy data regarding supplementation with this essential nutrient.

Kimball SM, Ursell MR, O'Connor P, Vieth R. Safety of vitamin D3 in adults with multiple sclerosis. Am J Clin Nutr 2007;86:645-651.

Good Sources

Sunshine, cod-liver oil, fortified milk and dairy products, butter, margarine, eggs, liver and such oily fish as salmon.

Note: Because few foods contain vitamin D and because the dairy fortification program has almost eradicated deficiencies, we don't include food-by-food vitamin D contents in this book as we do for other important VITAMINS.

Standard Process™ Supplements

Cataplex D