A: D is a fat-soluble vitamin naturally present in some foods, added to others, available as a dietary supplement and is also obtained through ultraviolet rays from the sun. It’s primary function is to maintain normal blood levels of calcium and phosphorous in the body and to help with the absorption of that calcium in attempting to form and maintain strong teeth and bones and to protect older adults from osteoporosis. Adult deficiency can result in osteomalacia — bone softening that results from a defect in the natural process of bone building. When this condition occurs in children, it is known as rickets that can cause bones to bow and fracture.

You do not indicate your age, so I will list a few recommended dietary allowances for this vitamin in otherwise healthy people. Those between the ages of 19 and 70 should consume 600 IU or 15 mcg daily. People over the age of 70 should consume 800 IU or 20 mcg. That translates to 4,200 IU or 105 mcg weekly. I am not sure of the reason for your physician to put you on mega-doses of this vitamin unless you have a deficiency. In this case and without knowing the cause, I can only recommend that you speak with your physician and demand answers. He or she will likely provide information to justify the mega-doses recommended. Be sure to ask the duration of the treatment and if periodic testing will be performed that might allow you to decrease your intake. Knowing the facts about what you are taking and why you are taking it is extremely important. You are responsible for your health and if you don’t ask questions, you can’t make informed decisions.

The best sources of dietary D include salmon, tuna and mackerel. Lesser amounts are found in cheeses, egg yolks and beef liver. Cod liver oil that was once a staple in everyone’s diet contains 1,360 IU per tablespoon, followed by three ounces of swordfish that contains 566 IUs. Nutritional deficiencies are commonly the result of dietary inadequacy, increased excretion, or impaired absorption and use within the body and accordingly, diet should be addressed.

Vitamin D toxicity from excesses can cause anorexia, heart arrhythmias, weight loss, fatigue, muscle weakness, and polyuria. It can also raise calcium blood levels that ultimately leads to vascular and tissue calcification. Excessive sun exposure will not result in D toxicity and because minimal mounts are available in natural foods, toxicity is generally from the over-use of supplements. Long-term intakes above upper intake levels appear to increase the risk of adverse health effects. A toxicity threshold for D is reported at 10,000 to 50,000 IU per day (although for severe malabsorption, 10,000 IU daily may be prescribed and well tolerated), with symptoms of toxicity unlikely at intakes below the 10,000 IU daily. However, keep in mind these guidelines have been set to guide the individual that does not have a major deficiency as you appear to have. With close monitoring 600-800 IU daily, 10,000 IU weekly 50,000 IU monthly are standard dosages for those with deficiency and the 50,000 IU weekly you are currently taking is appropriately prescribed for major deficiency for a period of six to eight weeks. Supplements with vitamin D as an ingredient can also have an adverse effect from the use of some medications, such as prednisone, cholestryramine (Questran), LoCholest, phenobarbital and phenytoin (Dilantin) for seizures and others. You may wish to address this issue with your physician if you are on any of the medications listed.

Other readers who are interested in learning more can order Dr. Gott’s Health Report “Vitamins and Minerals” by sending a self-addressed, stamped number 10 envelope and a $2 US check or money order to Peter H. Gott, MD Health Report, PO Box 433, Lakeville, CT 06039. Be sure to mention the title or print an order form from www.AskDrGottMD.com.

A: Your friend should probably be on a vitamin D supplement. Those over 65 may not get adequate amounts from their diets or enough sunlight exposure. Individuals with darker skin also do not absorb as much sunlight into the skin and the body’s production of vitamin D may be reduced.

If she has osteopenia or osteoporosis (which is likely given her age) she should likely be taking 1000 – 1500 mg of calcium and 800 IU of vitamin D daily and, depending on the severity of the bone loss, an anti-osteoporosis medication. Her swimming is an excellent exercise, but the addition of light weights may be beneficial.

There are many causes, both minor and serious for muscle cramps such as arthritis, certain vitamin or mineral deficiencies (including vitamin D), a medication side effect, restless leg syndrome, and much more. In my opinion, your friend should seek the advice of her physician regarding her cramping particularly since they are interrupting her sleep and have been going on for years.

I suggest your friend also take a good look at what she consumes daily, including foods, beverages, supplements, and medications. Do the cramps occur every day? Are they worse following certain activities or consumption of specific foodstuff or medication? Does anything reduce the severity or eliminate the cramping? If she can find a pattern, it may be helpful to the physician in making a diagnosis.

In the meantime, she can try stretching out her legs and hands thoroughly before retiring or whenever she feels the beginnings of a cramp. She can try drinking a glass of tonic water each night, which contains a very small amount of quinine. She can also try soap-under-the-sheets. She can best achieve the effects by grating the soap directly onto the mattress before placing on the bottom sheet so that her entire body is exposed to the soap rather than placing a bar near the legs. Potassium and magnesium are also known to help alleviate the discomfort.

Readers who are interested in learning more can order Dr. Gott’s Health Reports “Vitamins and Minerals” and “Osteoporosis” by sending a self-addressed, stamped number 10 envelope and a $2 (for each report) US check or money order to Peter H. Gott, MD Health Reports, PO Box 433, Lakeville, CT 06039. Be sure to mention the title or print an order form from www.AskDrGottMD.com.

I am a vegetarian so my sources of D supplements are not animal based. I also had kidney stones years ago so I’m not sure that the vitamin D will not adversely affect my calcium levels. I also have bone spurs and that is a concern with the vitamin D treatment.

Thank you very much for any insight.

DEAR READER: It appears that because you are a vegetarian who hasn’t spent much time in the sun, you have been at risk for a deficiency that has not been recognized until recently. You are obviously well-versed when it comes to your dietary choices and supplements, since most of the natural sources of this vitamin are animal-based. Vitamin D is necessary for the growth and development of teeth and strong bones, as well as for the absorption of calcium and phosphorous from the intestines. D can be used alone or in combination with supplemental calcium to decrease the probability of fractures and increase bone mineral density.

There is an abundance of dietary sources, to include fortified milk, cheese, egg yolks, fish (primarily salmon), butter, and cod liver oil. And, as you have discovered, sunlight makes a significant contribution to the production of D. In fact, it is believed that as little as 10 minutes of sunlight each day can be sufficient to prevent a deficiency but skin color, geographical location, season and sunblock use can alter production.

There are a number of reasons other than being a vegetarian and obtaining minimal exposure to sunlight why an individual such as yourself might be deficient. You don’t mention whether you are dark or light skinned but those with naturally darker skin are at a higher risk for deficiency because the pigment melanin reduces the skin’s ability to produce D when exposed to the sun. Certain digestive diseases to include Crohn’s or celiac disease and cystic fibrosis have been linked with the malabsorption of vitamin D from food in the intestines. You may also be at risk if you have been diagnosed with kidney or liver disease. You don’t indicate your age. As part of the aging process, the kidneys can no longer convert D and the digestive tract can no longer absorb D as easily into its active form as it did when we were younger. Because D is extracted from the blood by fat cells, people who are obese often test low for levels of vitamin D.

Blood testing is the appropriate method of determining whether levels are normal or not. I am not sure what type of testing you had but it appears the most accurate measure is the 25-hydroxy vitamin D test. 25-Hydroxy D changes into an active form of the vitamin. Levels less than 12, the category you now fall in to, indicate deficiency. The answer? Speak with your physician regarding the possibility of the disorders I mention being contributing factors as well as the possibility of a lab error (a repeat test before increasing treatment would be best) as your drop was drastic. Obtain more D through two means – exposure to sunlight (unless you are dark skinned) and supplements. The upper limit considered safe is now 4,000 IUs daily, so your physician is appropriately prescribing what appears to be a jump start to bring you within safer limits.

Readers who would like related information can order my Health Report “Vitamins and Minerals” by sending a self-addressed, stamped number 10 envelope and $2 in the form of a check or US money order to my attention at PO Box 433, Lakeville, CT 06039. Be sure to mention the title when writing or print out an order form from my website www.AskDrGottMD.com.

Can you tell me what could be causing my low vitamin D level? Do you believe that this is the issue, or are the low levels caused by something else?

DEAR READER: Vitamin D is a fat-soluble vitamin that is essential for promoting calcium absorption, maintaining adequate serum calcium and phosphate levels, bone growth and remodeling, reduction of inflammation, and neuromuscular and immune function.

If your levels are low, you are at risk of developing weak, brittle and/or deformed bones. This could also affect your immune system, making you more susceptible to infection, allergens and more. Your low vitamin D level may indeed be the cause of your allergies, which are causing your cold and flu-like symptoms; however, this does not explain why you have a low D level to begin with.

In healthy people, vitamin D deficiency can typically be avoided by adequate sun exposure and a well-balanced diet. Because there are very few foods that naturally contain D, fortified cereals and dairy products are the best way to achieve sufficient dietary amounts.

Older adults, breastfed infants and those with limited sun exposure, dark skin or fat malabsorption are at increased risk of developing deficiency. Obese individuals may have difficulty absorbing vitamin D from sun exposure because the subcutaneous fat essentially blocks part of the D from entering the bloodstream. Those who have undergone gastric bypass may also have difficulty because most forms of this surgery bypass the upper small intestine where D is absorbed.

Symptoms of vitamin D deficiency typically go unnoticed. The most common consequence is weakened bones, also known as rickets in children, osteomalacia in pre-menopausal women and men, and osteoporosis is post-menopausal women. There may be an increased risk of developing cancer, especially that of the digestive tract. There is also research suggesting deficiency may play a role in the prevention and treatment of diabetes types 1 and 2, hypertension, glucose intolerance, multiple sclerosis and more. However, because these studies have not been randomized clinical trials, the implications will continue to be debated until definitive proof is found.

According to the Food and Nutrition Board (FNB) at the Institute of Medicine of the National Academies, adequate intakes (AIs) for healthy people between birth and age 50 should be 200 IU of vitamin D daily. Those aged 51 and over should double that. Recently, the American Academy of Pediatrics issued its own recommended intakes that exceed those of the FNB. This led to an expert committee formation by the FNB, which decided that recommended intakes be re-evaluated. To the best of my knowledge, the decision of this committee should be made public later in 2010. Tolerable upper-intake levels (ULs) for those between birth and 12 months is 1,000 IUs; age 1 and older is 2,000 IUs daily. This, too, was challenged and is currently under review.

I suggest that you speak to your physician to request that the underlying cause be found. It may be as simple as not getting enough sun exposure and may be helped by exposure without sunblock for 15 or 20 minutes each day. Longer unprotected exposure is not recommended because of the increased risk of developing skin cancer.

If the cause cannot be found, follow your physician’s advice regarding supplementation and including more vitamin D-enriched foods into your diet.

You should also be watchful for signs of excess intake. Most commonly, these symptoms are nonspecific and include nausea, weakness, constipation, weight loss, vomiting and poor appetite. If healthy people continually take levels above the UL, it may result in elevated blood levels of calcium, which may cause confusion and other mental-status changes, as well as heart-rhythm abnormalities. There is also an increased risk of developing kidney stones, especially when used in conjunction with calcium; however, because you are deficient and under the care of a physician, these are not likely to result.

To provide related information, I am sending you a copy of my Health Report “Vitamins and Minerals.” Other readers who would like a copy should send a self-addressed stamped No. 10 envelope and a $2 check or money order to Newsletter, P.O. Box 167, Wickliffe, OH 44092. Be sure to mention the title. Order forms are also available for printing on my Web site at www.AskDrGottMD.com.