Q: My doctor has put me on a megadose of vitamin D (50,000) once a week. How safe is that? Are there any side effects or long-term damage to the kidneys, liver or any other organs? Thanks.
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.
