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Risks with too much supplemental Vitamin D

I can’t resist writing again about the risks of taking too much Vitamin D. It seems especially important right now with discussions about COVID and Vitamin D ongoing. It is imperative that you maintain healthy vitamin D levels but that does not mean to take large doses when your vitamin D level is normal. I run across so many people who have been told to “take a Vitamin D supplement” in the absence of a deficiency and with no guidance on amounts. Often “more is better” or “it’s a supplement so it can’t hurt” is the thought process, both of which are wrong. While it is hard for me to believe that people would take amounts this high evidently it does happen.

Here’s a synopsis of some recent info from consumerlab.com on Vitamin D overload:

  • A 50 year old English woman took 8000 to 16,000 IU of a Vitamin D supplement daily for 4 months resulting in lethargy, nausea, vomiting, headache and high blood pressure. Her vitamin D blood level was 1800 ng/mL upon hospital admission. She indicated after 2 months on the supplement she started feeling lethargic.
  • High doses of Vitamin D have been found to increase the risk of upper respiratory infections.
  • High dose vitamin D may decrease the body’s production of melatonin, which is important to normal sleep patterns.
  • High dose vitamin D given to individuals who are not deficient in vitamin D can increase cholesterol slightly, possibly because high doses of vitamin D can cause increased calcium absorption in the gut and leave less calcium to bind and remove fats moving through the gut.
  • Several cases of vitamin D overload have resulted from food supplements such as protein powder that contained significantly more vitamin D than the label indicated possibly due to manufacturing errors or because the people affected took more than the suggested amounts.

If your vitamin D level is normal without the use of supplements you don’t need to take a supplement. If your vitamin D is low then you may need to take a supplement. It is generally recommended, that for every 1 ng/ml you need to increase your vitamin D level, you take 100 IU vitamin D per day to correct a deficiency. If you are obese you may need twice that. If you are not getting enough magnesium (many people don’t) then it may be hard to get your vitamin D normalized so you may need to concentrate on good sources of magnesium as well in order to maximize your vitamin D absorption.

Also be aware that vitamin D tests aren’t always accurate. If the test is not done properly your level may show incorrectly as too high. One study found inaccurate low results at least 40% of the time. If your results are inconsistent with your expectation based on your sun exposure, and supplement and food intake then discuss re-testing.

Another interesting point from consumerlab.com is that it is best to take your vitamin D supplement with your largest meal of the day, which will most likely contain the most fat. This can increase absorption by up to 50% as opposed to when taken with fat-free meals or on an empty stomach.

posted on 10/18/2020