Thursday, January 24, 2019

To D or not to D, that is the question

Vitamin D is critically important for healthy bones. Infants and children deficient in D develop rickets and adults get weaker bones – either osteoporosis or osteomalacia. The vitamin also plays other important roles in the body, including strengthening our immune systems. Where do we get this key vitamin? The major source is vitamin D produced in our own bodies by the sun acting on our skin – about 20-25 minutes of daily sun exposure gives most of us an adequate supply, though the elderly and dark-skinned people need more. Most foods do not have a lot of D except for fatty fish. The NIH recommends that for children over 1 and adults up to 70, 15 micrograms (equivalent to 600 IU) daily is required. They suggest a higher dose (20 mcg/800 IU) daily in adults over 70. You can get this amount from 3-4 ounces of salmon, swordfish or trout. In the U.S. and Canada, all milk is fortified with vitamin D, and a cup of milk contains about 3 mcg. Many other foods including orange juice and cereals are also fortified – look at the label.
What about supplements? If you look in the pharmacy, you will find enormous shelf space devoted to vitamin D capsules, in sizes varying from 400 IU to 4000 IU or more. Do you need this? According to Boston University endocrinologist Michael Holick, absolutely. His enthusiasm for testing vitamin D levels in the blood and taking supplements, sunbathing and using tanning beds is boundless. More than anyone else, he is responsible for generating billion-dollar sales of testing and supplements. About a quarter of all adults over 60 now take vitamin D supplements. I was disappointed, though not shocked, to read a news report this month from Kaiser Health News reporting that Dr. Holick has been paid $1000/month by Quest Laboratories, who do a lot of vitamin D blood tests, for some forty years. He also received some $163,000 between 2013 and 2017 from pharmaceutical companies who market vitamin D supplements and other bone-related medications. He has also received consulting fees from the tanning industry.
Despite hype as to the value of vitamin D for heart health and cancer prevention, a study just reported in November 2018 at the American Heart Association Scientific Session found that daily use of 2000 IU of vitamin D had no benefit in lowering either invasive cancer or cardiovascular events.
What then should you do? If you are outdoors for half an hour most days, whether walking, gardening or just sitting in your chair and enjoying the view, you are getting all the D you need. Those of us in northern climes might want to think of a supplement for those months when getting outside only happens when you are covered head to toe. If you love fish and have salmon or other fatty fish several times a week, or if you are an avid (quart a day) milk drinker, again you do not need supplements. Those over 70, who are not out a lot and do not drink milk (and no, milk in your coffee or on your cereal is NOT enough) probably should consider a low dose supplement. 1000 IU daily is plenty. Too much D can have harmful effects, and vitamin D is not easily eliminated from the body the way the B vitamins and C are.

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