Vitamin D Deficiency

What are symptoms and signs of an excessive vitamin D intake?

In United States, the sales of vitamin D supplements went from $75 million in 2006 to $550 million in 2010; it is likely even higher today. The problem is that this can be a case of too much of a good thing. There is definitely a limit to how much vitamin D supplements you can safely take, but what level is too much remains controversial.

Excessive intakes of vitamin D can lead to high levels of calcium (hypercalcemia). The symptoms of this are weakness, confusion, constipation, loss of appetite, and development of painful calcium deposits. To avoid this, keep your supplement intake below the tolerable upper limits. The 2010 report by the Institute of Medicine set the following tolerable upper limits for vitamin D:

  • 1,000 IU/day for infants 0 to 6 months of age
  • 1,500 IU/day for infants 6 to 12 months of age
  • 2,500 IU/day for 1 to 3 years of age
  • 3,000 IU/day for 4 to 8 years of age
  • 4,000 IU/day for 9 years of age and older
  • 4,000 IU/day for pregnant and lactating women

This limit is set as the most that a person can consume safely. The arguments against these levels stem from the fact that you can get 10,000 to 25,000 IU from exposure to the sun in one day. Studies have shown that supplementation over 10,000 IU/day can cause kidney and tissue damage. A recent study found that high-dose vitamin D supplementation (20,000 to 40,000 IU/week) caused a slight but significant increase in hemoglobin A1C and C-reactive protein and a decrease in serum HDL. Currently, there are not enough credible studies to support the safety of taking a supplement in a dose that exceeds the current tolerable upper limits.

It is clear that many of us are not meeting our vitamin D requirements. The need to protect our skin from cancer has had the most impact on the declining vitamin D levels. Still there is no clear answer on what to do about this. Exposing our skin to the sun for vitamin D while preventing the damage that can happen from this exposure is what is needed. The recommendation for exposure of 10 to 15 minutes a couple of times per week may do just that. When the sun is not an option, it appears that most of us will benefit from vitamin D supplementation while trying to consume foods that are also good sources of it. A blood test is the best way to know what your needs are right now. When you are deficient, it is important to get your levels up to a safe range, so take your supplement and follow up with your doctor.

Reviewed on 7/14/2014
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