Welcome to Vitamin D Dosages~New Information Part II. Yesterday, in Part I, I discussed some background about why Vitamin D is so important for optimal health. There I also reviewed how sunlight and food sources help the body manufacture Vitamin D and what the risks are when your Vitamin D level is low. Today, Part II addresses the big question: what is the best dosage of Vitamin D? Here you’ll find recommended Vitamin D dosages from current sources and how to safely monitor your Vitamin D levels.
Vitamin D levels in your body are most accurately measured by the blood test:
**Please note this is NOT the same lab test as 1,25-dihydroxyvitamin D [1,25(OH)2D]. 1,25-dihydroxyvitamin D [1,25(OH)2D] is considered less accurate for Vitamin D measurement because it is directly impacted by the brain’s regulation of calcium and does not reflect Vitamin D deficiency until it is very severe.
The beauty of this test is that it can cost as little as $32 for the test and lab draw. As a licensed acupuncturist in California, I often order this lab work for my patients. If you are taking Vitamin D supplements but are not quite sure how your body is absorbing them, blood testing every 2-3 months is a perfect way to keep tabs on your Vitamin D level and only take a safe amount. Additionally, blood draws will help you determine your body’s unique response to the amount of Vitamin D dosage supplementation you are taking. I advise guidance of a health care professional with this process.
Lab work reference levels
Your lab work will show your Vitamin D levels measured in nanomoles per liter (nmol/L) or nanograms per milliliter (ng/ml). Later in this article you will see recommended ranges.
What dosage of Vitamin D should I take?
This is not an easy answer because there are multiple recommendations from well-respected sources. As I mentioned in Part I, there is also ongoing debate in the medical community about this topic. For example: the National Institutes of Health (NIH) recommendations are far lower than other sources. I will provide you the recommended doses per the NIH and Harvard Medical School as well as some authors who contest the NIH positions. Also, integrative and functional medicine practitioners advocate higher levels of Vitamin D.
The following Recommended Dietary Allowances (RDAs) are the daily dosage recommendations for Vitamin D taken from Table: 2 in the newly released Vitamin D Fact Sheet for Health Professionalsby the National Institutes of Health Office of Dietary Supplements 1
|0-12 Months||400 IU (10mcg)||400 IU (10mcg)|
|1-13 Years||600 IU (15mcg)||600 IU (15mcg)|
|14-18 Years||600 IU (15mcg)||600 IU (15mcg)||600 IU (15mcg)||600 IU (15mcg)|
|19-50 Years||600 IU (15mcg)||600 IU (15mcg)||600 IU (15mcg)||600 IU (15mcg)|
|51-70 Years||600 IU (15mcg)||600 IU (15mcg)|
|>70 Years||800 IU (20mcg)||800 IU (20mcg)|
The Institute of Medicine (IOM) committee of the National Institutes of Health previously concluded that: Practically all people are sufficient at levels ≥50 nmol/L (≥20 ng/mL); the committee stated that 50 nmol/L is the serum 25(OH)D level that covers the needs of 97.5% of the population.2
It does not take a wide review of research to discover there are strong medical community opinions about optimal blood levels of Vitamin D needing to be higher. There is great debate that Vitamin D blood levels of ≥50 nmol/L (≥20 ng/mL) is too low. The IOM committee also stated that it did not know if there are non-skeletal benefits with respect to Vitamin D levels.
Biology tells us that Vitamin D is necessary for the many tasks in the human body, not just bone health. Additional functions are: improving immune status, maintaining cellular health, reduction of inflammation and controlling overgrowth of cancerous cells. All of these are important mechanisms for health of your body. Thus, it makes sense that the committee could not make any concrete statements as to the blood levels that would support best Vitamin D levels in other body tissues. However, making a statement that 20ng/L is enough does not logically follow. It is more accurate to say that we are not exactly sure what other body tissues need as far as serum blood levels and we cannot rule out that it is necessary.
Respectful and logical dissention of NIH recommendations
Two members who participated on the same Institute of Medicine (IOM) committee noted above wrote a 2011 article of respectful dissention. In that article the authors, Robert P Heaney and Michael F Holick, state:
… during the evolution of human physiology, the intake to which, presumably, that physiology is fine–tuned. So far as can be judged from numerous studies documenting the magnitude of the effect of sun exposure…the primitive intake would have been at least 4000 IU/day and probably two to three times that level, with corresponding serum 25(OH)D levels ranging from 40 to 80ng/mL. The fact that primitive levels would have been higher than current IOM recommendations does not, of course, prove their necessity today. But such intakes should be given the presumption of correctness, and the burden of proof must be placed on those who propose that lower intakes (and lower serum levels) are without risk of preventable dysfunction or disease. The IOM, in its report, has utterly failed to recognize or meet that standard.3
Furthermore, the authors state that an intake of 600 IU of Vitamin D per day will produce only negligible increases in individuals who are overweight or obese.4
There exists a “rule of thumb” in the science world that
for each 100 IU of Vitamin D per day you take in,
your serum 25(OH)D levels will only increase by about 1ng/ml.
Other studies reflect that it might not even be a full 1ng/ml increase. Those studies show only 0.7ng/ml increase for every 100IU of Vitamin D consumed. This means that if you have severely low Vitamin D levels and take just 600IU of Vitamin D per day as a supplement your levels may not raise much.
Interestingly, the 2011 IOM panel acknowledged that intakes of up to 10,000 IU/day are
probably safe for everyone, yet they only officially stated a Total Upper Intake Limit (TUIL) of 4,000 IU/day.4 In contrast the Harvard School of Medicine states that up to 2,000 IU/day of Vitamin D is considered safe.5
Functional medicine ideal ranges of Vitamin D levels
Functional medicine practitioners currently tend to encourage 25(OH)D blood levels in the range of greater than 50 ng/ml and more toward 80 ng/ml.
Safe ways to gauge the best Vitamin D dose you need
Clinically, over the years I have seen many patients who require larger Vitamin D supplementation to maintain their serum Vitamin D levels over 50ng/L. These are patients who started supplementing at lower dosages but did not see increases in their Vitamin D blood levels until they increased their daily dosage. These are patients who also consistently monitored their blood levels through laboratory blood draws at intervals over time and had no complaints about any negative side effects of too much Vitamin D.
Vitamin D can become toxic in excessive doses
Amid the confusion with respect to dosage of Vitamin D, I encourage patients to be careful, consistent, and seek guidance. By monitoring your blood work, you will see what your blood level is and how your body responds to supplementation over time.
Follow up blood work is key. Taking too much can cause side effects such as grogginess or constipation. Massive doses can cause extreme toxicity which leads to elevated calcium levels in the blood. The Harvard Medical School cites that it can even cause death.6 It is best to be under the care of a licensed health care practitioner to be sure you take the right amount of Vitamin D that you need.
I hope this two-part blog series on Vitamin is useful information for you. Thank you for reading! •Please leave any questions you may have here and I am happy to answer them.
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~Karen Reynolds, RN, MS, LAc
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