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It's time to talk about Vitamin D again

Vitamin D just seems to get more complicated. The office of Dietary Supplements (ODS) at the National Institutes of Health along with other government agencies has engaged in recent discussions to address the need for better assessing and counseling patients regarding Vitamin D. It is more complicated than simply prescribing a Vitamin D supplement.

Laboratories and health care providers are not consistent in how they interpret Vitamin D blood tests or in the recommendations they make regarding Vitamin D levels. This often results in patients receiving contradictory or controversial recommendations. Laboratory reports of serum 25 (OH)D concentrations (the measure for Vitamin D levels) usually include a “normal” value and a “low” and “high” value to compare to the actual results. These comparative values are not standardized or formulated by any authoritative body. Laboratories make their own decisions about these normal values. There is some concern that some labs are establishing relatively high serum levels as normal. There are also some differences in opinions among some organizations as to what should be considered normal. Serum 25(OH)D concentrations are affected by age, obesity, race, inflammation and acute illness, which makes interpreting them more challenging.

Sales of Vitamin D supplements are increasing and supplementation is common but may not always be appropriate. The recommended amount of Vitamin D for 1 to 70 year olds is 600 IU/day and over 70 years is 800 IU/day. The sale of high dose Vitamin D supplements has been increasing with more supplements above 4000 IU being widely available. The 4000 IU/day level is the Institutes of Medicine’s upper limit for 9 years and older and the point at which adverse effects may occur if exceeded. While Vitamin D intoxication is established at over 20,000 IU/day, which can result in kidney damage, there is concern that adverse effects could also occur at much lower intakes. It has been suggested that adverse outcomes could occur in some people when daily intake exceeds 4000 IU/day.

The National Institutes of Health Vitamin D Fact Sheet for Health Professionals states that serum 25-Hydroxyvitamin D (25(OH)D) concentrations greater than or equal to 20 ng/mL (or 50 nmol/l) are generally adequate for bone and overall health in healthy individuals. They also state that, based on emerging evidence, levels above 50 ng/mL (or 125 nmol/L) are linked to potential adverse effects. Note that 25(OH)D levels are reported two different ways – either in ng/ml or nmol/L. Your lab results will tell you which way your results are measured.

Bottom line, don’t take a Vitamin D supplement until you know whether you actually need one. The increasingly common practice of recommending high dose Vitamin D supplementation without knowing the person’s blood level is not a good practice. Vitamin D supplementation needs to be approached with caution, as there are negative consequences of excess supplementation.

posted 7/18/2019