Rachel Zahn, MD is a pediatrician turned health writer who had three kids during medical school and pediatric training—crazy, huh?

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4 responses to “How Much Vitamin D?”

  1. Auburn

    Can you give us examples of the problems you have had to treat that you felt were caused by vitamin D supplementation? I’ve read that back in the ’60’s infants in Finland were regularly given the equivalant of 4,000 IU per day.

  2. Malcolm

    There are very few cases in the litereature of Vitamin D overdose. Where one does find cases, the doses have been in the 100’s of thousands iu per day for many months. Any dose of 10,000iu per day is perfectly safe (R. Vieth-Toronto). Signs of toxcity do not occur until 50,000 iu per day is ingested over an extended period. In any case, the defining measurement is a D blood test. If nature is any guide, then optimum levels are 60-80- ng/ml, the level lifeguards at the end of the summer or sun-exposed people who live in the tropics would have. You state that “more is not always better”, but because vitamin D deficiency is rampant, more is better that less! The following vitamin D researchers do agree that people need more not less vitamin D:
    Reinhold Vieth, Heaney, Michael Hollick etc.

  3. Auburn

    Dr. Zahan, Thank you for responding to my previous comment. I’ve been following the vitamin D research saga (via Internet searches) on a daily basis for more than eight years. You noted “the health risks of excessive intake of vitamin D are elevated levels of calcium in the blood, resulting in abnormal deposition of amounts of phosphate and calcium in soft tissue such as the lungs, heart and kidneys, nausea and vomiting, poor appetite and loss of weight, high blood pressure, heart rhythm irregularities and increased risk of heart disease, kidney stones and renal failure. Overdose of Vitamin D in pregnant women can cause mental or physical retardation in babies.” Such admonitions are quite common and undoubtedly would cause one to be quite cautious. I have observed, for instance, that persons taking Fozamax are quite comfortable with the drug notwithstanding the extremely serious side effects disclosed in the package insert or in advertising, but hesitant to take the amount of D-3 that would be necessary to raise their blood level of 25(OH)D to an effective or optimum level for bone health.

    Other than the several people who inadvertently were taking a dose of probably several hundred thousand IU per day I have not been able to locate actual case studies of overdose adverse consequences. I’ve often wondered if the warnings are based on theoretical results. Apparently people who are borderline deficient in magnesium may experience headaches (and perhaps other conditions associated with magnesium deficiency) after being on a vitamin D supplement for a period. I understand this is usually corrected by taking a magnesium supplement.

    One on the more intriguing studies on the benefits of adequate vitamin D is The Relationship of Vitamin D Deficiency to Health Care Costs in Veterans, Peiris, et al, published in Military Medicine, Vol. 173, December 2008. Deficiency in this study was pegged at <20 ng/mL. Overall medical expenditures were 39% higher in the vitamin-D deficient group over a 24-month period. If controlling health care costs is of national concern this might suggest that an effort to attain an optimum vitamin-D level might be a good way to start. I doubt that such an effort would sit well with health care providers or the pharmaceutical industry. Imagine cutting the need for health care in the magnitude suggested by this study—or even a fraction of that amount.

    I would suggest that there must be a better understanding regarding the association of an adequate intake of vitamin-D with improved health and then striking a proper balance with any highly unlikely or even unproven adverse reactions. In my opinion the unlikely occurrence of an adverse result from taking a daily dose of 5,000-6,000 IU/day or even 10,000 per of D-3 pales in insignificance compared to the potential benefits shown in numerous studies conducted by responsible scientists.

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