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Healthy Vitamins

Vitamin D Supplementation

There are some health practitioners that feel you should not supplement over the 200 IU Recommended Daily Intake (RDI) without testing your blood for D levels.  However, there are also some scientists who are trying to get the federal government to boost the vitamin D RDI to at least 1,000 IU and to increase the certified-safe limit beyond the current 2,000 IUs.  There seems to be a lot of mixed information out there, but we do know that those living in the tropics get 4,000 to 10,000 IU per day just from sunshine, and it seems as if along with diet, they easily get an average of over 5,000 IU per day, year round.  Instead of toxic effects, these high vitamin D levels seem to have a protective effect regarding cancer and other diseases.

According to Dr. Mercola, if you are exposed to sub-tropical or summer sun on your skin, you should avoid vitamin D supplementation unless you test your vitamin D blood level. However, if, like is the case for most of the US population, your latitude is above 30 degrees north (or in the southern hemisphere, below 30 degrees south) you can not get enough UV-B to make vitamin D from September to mid April, and hence would be wise to consider supplementation, like with cod liver oil.

Vitamin D Blood Level Testing

If you are not sure if you should supplement, ask your health care practitioner to test your blood.  It seems the best test is called the "calcidiol" test (also called 25-hydroxyvitamin D or 25 (OH) D test.  According to Dr. Mercola,  the optimal vitamin D blood levels should be 45-50 ng/ml.  He says that "Your vitamin D level should NEVER be below 32 ng/ml. Any levels below 20 ng/ml are considered serious deficiency states and will increase your risk of breast and prostate cancer and autoimmune diseases like MS and rheumatoid arthritis."  It is normal that your levels be somewhat higher and be rising in the spring and the summer, and then go down in the fall and winter, but they should not go below 32 ng/ml, even in the winter.

Those who work outside in the sun all day, like lifeguards and farmers, tend to have even higher blood levels of D, between 55 and 65 ng/ml.  A recent study from Omaha, Nebraska showed that in the fall/winter months of October through February, a daily food intake of a rather high amount of 5,000 IUs was necessary in order to maintain 60 ng/ml of D in the blood.

It also seems from the research that adequate levels of vitamin A & vitamin K, and also the minerals calcium and magnesium, found in coral calcium and other sources, seem to protect against vitamin D toxicity.  You can also increase your mineral intake by using dairy products and bone broths on a regular basis.  You can increase your A intake with liver or cod liver oil, and you can increase your vitamin K intake by eating leafy greens and/or cultured vegetables.

WARNINGIf you have any of the following problems, please do not consume vitamin D-rich foods or supplement with vitamin D at any level without consulting your physician:

  • Kidney or liver problems
  • Tuberculosis
  • Hyperparathyroidism
  • Lymphoma
  • Sarcoidosis

Study Comparing D Levels of Urban & Rural Dwellers

In a recent study, blood concentrations of vitamin D were analyzed, comparing urban and rural adults (with the theory that the rural adults would have higher levels of D due to more sun exposure).  Well, their theory was correct, however they actually found that the blood levels of both urban and rural dwellers was low, especially in the winter.  The average concentration of the D in the blood was 14 ng/ml in the urban or city dwellers and 20 ng/ml in the rural group. In the summer, the urban dwellers were actually higher than the rural people:  39 ng/ml compared to 27 ng/ml.  Another interesting observation in this study was that thin people had higher levels of D than the overweight people did.  So this might mean that overweight people need to determine if their D levels are high enough, and if not, find a way to correct that.

Vitamin D Toxicity


  • Vieth, R. Vitamin D Supplementation, 25-hydroxyvitamin D Concentrations, and Safety," Am J Clin. Nutr, 1999:  69:  842-56.
  • Heaney, R.P. Davies, K.M. Chen, T.C. Holick, M.F. Barger-Lux, M.J., Human Serum 25-hydroxycholecalciferol Response to Extended Oral Dosing with Cholecalciferol, Am. J. Clin. Nutr., 2003:  77: 204-10.

FDA Disclaimer:  None of the statements on this website have been evaluated by the Food & Drug Administration (FDA).  They are not intended to diagnose, treat,  cure or prevent any disease or medical condition.  Furthermore, none of  the statements on this website should be construed as making claims  about curing diseases or dispensing medical advice.  Please consult a  physician or another health care provider before trying any nutritional  supplement, making changes in your diet, or doing new exercises,  especially if you are pregnant or have any pre-existing medical  conditions or injuries.


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