Vitamin "D"eification Trivia Quiz

Answer: All of these

In the Boston study, 52% of black and Hispanic adolescents were found to have subnormal levels of vitamin D. Some might attribute such a finding to the fact that darker skin pigment interferes with the production of vitamin D in the skin. However, 48% of white girls in Maine were similarly deficient. The 32% of physicians, physicians-in-training and students who had low vitamin D levels were reported to be "drinking a glass of milk and taking a multivitamin daily and eating salmon at least once a week."

Two metabolites of vitamin D have biologic activity. After first being converted to 25-hydroxyvitamin D in the liver, a portion is converted to 1,25-dihydroxyvitamin D in the kidney. 25-Hydroxyvitamin D has more biological activity and is regulated in conjunction with bone calcification. 1,25-Dihydroxyvitamin D is regulated along with parathyroid hormone has different actions than 25-hydroxyvitamin D. 25-Hydroxyvitamin D levels are used as a measure of vitamin D activity.

The "normal" level for 25-hydroxyvitamin D is disputed. The abnormal percentages cited in the question were obtained using a widely accepted normal value for 25-hydroxyvitamin D of 20 ng per milliliter. In fact, the author of the NEJM review article, Michael F. Holick, believes that levels between 21-29 represent "relative insufficiency". Other well regarded textbooks use lower numbers.

Answer: Longitude

In the developed world, in more northern latitudes, increasing use of sunscreens and avoidance of sun exposure are thought to be significant contributors to an increasing incidence of vitamin D deficiency. In more southerly areas of the world, clothing shielding its wearers from sun exposure would seem to be a major factor. Vitamin D deficiency was present in over 30% of children and adults tested in Australia, the United Arab Emirates and India.

Adequate sun exposure would make dietary Vitamin D intake unnecessary. Ultraviolet radiation converts a cholesterol compound found in the skin to previtamin D3 from which vitamin D3 is produced. The process is so efficient that vitamin D intoxication would be the result of prolonged sun exposure were it not for the fact that sunlight degrades excess previtamin D3.

Answer: Both

The clinical condition that childhood vitamin D deficiency produces is termed "rickets". The skeletal consequences of vitamin D deficiency in childhood include bone pain and fractures in addition to small stature and skeletal deformities. However, there are non-skeletal manifestations as well that may include low energy muscle weakness, irritability. If calcium levels are low enough, spasms of the larynx, seizures and even tetany may ensue.

Although it is not a reportable disease in the United States and the true incidence is unknown, it is not a condition confined to economically disadvantaged children. Clinical illnesses may produce rickets in the absence of vitamin D deficiency and such illnesses must be considered and searched for in children who develop rickets.

Answer: Elevated blood calcium

Vitamin D deficiency not only increases fracture risk in the older person by reducing the strength of bones but also increases fracture risk because muscle weakening leads to an increased risk of falling. Osteomalacia refers to a specific disorder of bone occurring as a result of vitamin D lack.

It would not, for instance, be the result of simple calcium deficiency. Osteoporosis is primarily a result of calcium deficiency but vitamin D deficiency can contribute to it.

Answer: All of these

Special tissue receptors are known to mediate many of the actions of activated vitamin D on skeletal tissue. In fact, these receptors have been demonstrated in most body tissues. Although specific mechanisms of action remain largely undiscovered, perhaps actions of vitamin D mediated through these receptors is responsible for what has been demonstrated: vitamin D can reduce the risk of certain cardiovascular, autoimmune and infectious diseases as well as reducing the incidence of some common cancers. Low vitamin D levels are associated with increased rates of breast, colon and prostate cancer. Raised vitamin D levels with increased exposure to ultraviolet light was associated with a six-point reduction in blood pressure. Vitamin D deficiency has been associated with congestive heart failure. Falling vitamin D levels are associated with increases in C-reactive protein, a marker of cardiovascular risk. Even schizophrenia, depression and impaired lung function have been associated with low vitamin D levels.

Answer: A typical portion of canned tuna

The NIH does not feel that there is sufficient data for it to provide a recommended daily allowance for vitamin D and instead provides an "AI", standing for adequate intake. For all intents and purposes, one could say that obtaining meaningful amounts of dietary vitamin D requires one of the "two Fs": fish or fortification (certain mushrooms, particularly the Shitake variety, being an exception). Generally speaking, 1 serving of either a fortified dairy product (or orange juice) or a fortified cereal provides only ½ the daily AI for children and younger adults. Fish and certain mushrooms are the only meaningful unfortified dietary sources of vitamin D, and fish may provide substantially more than the daily requirement in a single serving, as is the case with canned tuna.

Answer: Elderly Adults

The amount the NIH considers adequate doubles for those over 50 and triples for adults adults above 70 years of age. In order to obtain 600 IU of vitamin D, our 71-year-old person would have to drink over a quart of milk or eat over a pound of yogurt! To meet that requirement utilizing fish would require 3 servings of farmed salmon, 2 servings of sardines. Practically speaking, to meet even the minimal amounts represented by the NIH AI, a person above the age of 70 would need to resort either to sunlight or to supplements.

Moreover, Michael Holick in his New England Journal Review article on vitamin D states, "However, most experts agree that without adequate sun exposure, children and adults require approximately 800 to 1000 IU per day." This represents four to five times amount currently recommended for children and young adults.

Answer: Damage to nails

Fair skinned individuals are particularly susceptible to the effects of increased sun exposure, which includes skin cancer. However, sun exposure influences two consequences that many might consider cosmetic and simply age related. The extreme thinning of the skin in older fair-skinned individuals spares the areas not exposed to the sun and is much more noticeable on the lower arms and hands that get the most sun exposure.

The sunlight mediated atrophy (thinning) of the subcutaneous tissue results in there being less tissue supporting small, subcutaneous blood vessels.

These vessels are easily disrupted with very minor "bumps" resulting in bruising.

Answer: 4 tablets

Because of the undesirable effects and inconvenience involved with sun exposure and the difficulty in maintaining nutritional vitamin D intake, some resort to supplements. However, labels for these supplements can be somewhat easily misinterpreted. Particular care must be taken with the "serving size". A popular calcium/Vitamin D supplement label reads as follows:

Supplement Facts
Serving Size: 2 tablets
Servings Per Container: 60

Amount per each tablet % Daily Value
Vitamin D as cholecalciferol 400 IU 100%
Calcium as calcium citrate 630 mg 63%

First, there is no information regarding the "AI" (adequate intake) for calcium and vitamin D or that both vary with age. Secondly, these tablets could not provide an exact AI for both calcium and vitamin D for a 70-year-old person. Lastly, many people of all ages lack the basic math skills necessary to calculate the correct dose from the information provided.

Answer: Vitamin D2 is much less potent than vitamin D3.

I have not encountered an American multivitamin with a different dosage of Vitamin D. Even "Centrum Silver", a preparation marketed to the elderly, has 400 units of vitamin D. Of more concern is the difference between the potency of Vitamin D2 and Vitamin D3. Both are used in over the counter vitamins in the United States (only D2 is found in prescription products). According to the "New England Journal of Medicine" review article previously cited, vitamin D2 is only 30% as potent as vitamin D3.

The usual multivitamin label does not specify whether it contains D2 or D3. Examination of labels for the ten first listed products at Drugstore.com that included such well known products as Centrum, Flintstones, One-A-Day, and Nature Made disclosed only one product which specified whether it contained vitamin D2 or D3: Oncovit specified that it contained 400 units of vitamin D3. Interestingly, a Drugstore.com search for vitamin D3 returned a different Nature Made multivitamin produce that specified vitamin D3.

Finally, the NIH does not specify for normal individuals whether its recommendations are appropriate for vitamin D2, vitamin D3 or both. Yet, for the treatment of vitamin D deficient children the NEJM article states, "Since vitamin D2 is approximately 30% as effective as vitamin D3 in maintaining serum 25-hydroxyvitamin D levels, up to three times as much vitamin D2 may be required to maintain sufficient levels."

Internet advertisements for Australian and British vitamins indicate that Vitamin D3 is exclusively marketed in those countries.