North Americans spent more than $936 million on vitamin D pills in 2017, doctors ordered more than 10 million laboratory tests for vitamin D for Medicare patients at a cost of $365 million in 2016, and 25 percent of older adults take vitamin D supplements. A Kaiser Health News investigation recently reported that the man most responsible for the obsession with vitamin D pills, Boston endocrinologist Michael Holick, has been paid hundreds of thousands of dollars by supplement and drug manufacturers, the indoor-tanning industry and commercial laboratories that run blood tests for vitamin D (New York Times, August 18, 2018). Many doctors have been concerned about the recommendations for very high doses of vitamin D for a long time. In 2004, highly-respected Dr. Barbara Gilchrest, then head of Boston University's Department of Dermatology, asked Holick to resign from the department. In 2014, the U.S. Preventive Services Task Force reported that there is not enough evidence to recommend routine vitamin D testing. In 2015, Excellus BlueCross BlueShield reported that they had spent $33 million on 641,000 vitamin D tests.
No Benefits Shown in Recent Studies
• Vitamin D pills were not shown to help prevent heart attacks or cancer: A study led by a Harvard researcher, Dr. Joanne Manson, followed 25,871 men and women for a median of 5.3 years. Participants who took vitamin D3 (cholecalciferol), 2000 IU per day, had no added protection from heart diseases or cancers (NEJM, November 10, 2018).
• Vitamin D and calcium pills do not prevent bone fractures: The largest clinical study ever on the subject, covering more than 500,000 people and 188,000 fractures, showed that vitamin D pills did not prevent bone fractures (BMJ, September 9, 2018). This study agrees with previous studies showing that vitamin D pills do not prevent fractures in older men and women (Cochrane Database Syst Rev, Apr 14, 2014;(4):CD000227), and a review of 33 studies covering more than 50,000 adults showed that neither calcium nor vitamin D pills prevented fractures (JAMA, Dec 26, 2017;318(24):2466-2482). Calcium pills can harm you by increasing risk for heart attacks and kidney stones (BMJ, Sept 29, 2015;351:h4580).
• High vitamin D levels were reported to be associated with increased risk for skin, prostate and blood cancers (American Association for Cancer Research meeting in Chicago, April 16, 2018). Calcitriol, the active metabolite of vitamin D, is an immune suppressant that may increase risk for some types of cancer. This study followed 246,858 people of which 18,000 were diagnosed with cancer and found that every 10 ng/mL increase in blood vitamin D was associated with a nine percent increase in the risk of non-melanoma skin cancer, a 10 percent increase in the risk of melanoma, a five percent increase in the risk of prostate cancer and a three percent increase in the risk of blood cancers. However, a five percent decrease in lung cancer was associated with every 10 ng/mL increase in blood vitamin D.
Confusion About Vitamin D Deficiency Many previous "authorities" have proposed that normal blood levels of hydroxy vitamin D should be as high as 50 to 80 ng/ml, but recent studies suggest 30 ng/ml is more than adequate and most experts feel that any level above 20 ng/ml is normal (Osteoporosis International, February 2017;28(2):505–515). Most of the studies extolling vitamin D pill benefits on 137 diseases show association, not cause and effect, and thus are likely to be due to chance (BMJ, Apr 1, 2014;348:g2035). There is no evidence anywhere that people with hydroxy vitamin D levels above 30 are healthier than those between 20 and 30. If "normal" blood levels of hydroxy vitamin D were set higher than 20 ng/ml, more than 80 percent of North Americans would be misdiagnosed as having low blood vitamin D levels.
My Recommendations Most people can get all the vitamin D that they need by exposing a few inches of skin to sunlight for a few minutes three times a week during the warmer months. During the winter months, you can take up to 1000 IU/day of vitamin D pills if you wish. I believe that sunlight offers benefits that cannot be obtained just by taking vitamin D pills, but take proper precautions to avoid skin cancer.
If you are concerned about your vitamin D level, get a blood test for hydroxy vitamin D (all other vitamin D blood tests are not dependable). If it is above 20 ng/ml, you are presumed to be normal, unless your doctor is concerned that you have a condition that possibly may benefit from higher levels.
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