The ABCs of vitamin D –

Q: I keep hearing about the goodness of vitamin D, but what should I eat more of? Are supplements useful or not? — Katie G., Boston

A: In truth, vitamin D is more hormone than vitamin! A hormone regulates the activity of certain cells or organs and often works on more than one physical process: D maintains blood levels of calcium and phosphorus by enhancing absorption of D in food and supplements through the small intestines. And D regulates over 200 genes, as well as blood pressure in the kidney and blood glucose in the pancreas, while keeping abnormal cells from multiplying in breast and colon tissue. D also appears to help regulate the immune system.

There are two important forms of vitamin D you should know about — ergocalciferol (vitamin D-2), which is made by plants, and cholecalciferol (vitamin D-3), which is made by your skin in response to exposure to sunlight. (D-3 is first converted by the liver and then the kidneys before becoming biologically active calcitriol in your body.) A new study in the American Journal of Clinical Nutrition says D-3 is what you want to make sure you get enough of.

The researchers say: “Those who consume D-3 through fish (we like salmon and ocean trout) or vitamin D-3-containing supplements are twice as likely to raise their vitamin D status than when consuming vitamin D-2 rich foods such as mushrooms, vitamin D-2-fortified bread or vitamin D-2 supplements.”

Your move: Get 10 minutes of exposure to sunlight daily (that’s enough to crank up the D-3 machine to ample levels) without sunscreen; then put it on! Enjoy D-3-packin’ foods like fermented soy and supplemented functional foods like almond and walnut milk. Aim to get the recommended 600 IU of vitamin D-3 a day: Most of you will need a D-3 supplement. Your goal is to reach a blood level of 35-80 ng/mL; ask your doc for a blood test.

Dr. Mehmet Oz is host of “The Dr. Oz Show,” and Dr. Mike Roizen is Chief Wellness Officer and Chair of Wellness Institute at Cleveland Clinic. Email your health and wellness questions to Dr. Oz and Dr. Roizen at


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