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sunglasses, fatty fish and vitamin d supplements

In the past decade, studies have shown that vitamin D — long associated with aiding calcium absorption — helps fend off a wide array of ailments, including diabetes, depression, cancer, multiple sclerosis, heart disease, and chronic fatigue. The key, says Michael Wald, PhD, ND, director of nutritional services at Integrated Medicine of Mount Kisco, N.Y., is that vitamin D “behaves more like a hormone than a vitamin.” In fact, vitamin D is actually a hormone precursor that eventually turns into the hormone calcitriol, which attaches to more than 2,700 sites on the human genome and turns on more than 1,000 genes. Its importance cannot be overstated, says Wald: “It’s necessary for every single cell of every single tissue in the body to work optimally.”

Reasons for Vitamin D Deficiency:

Humans produce vitamin D when they spend time in the sun, a process that Wald says is being increasingly compromised as we spend less and less time outdoors. Even when we are outdoors, we tend to slather on sunscreen, which blocks our absorption of vitamin D. Wald says fatty fish like sardines and mackerel contain high amounts of dietary vitamin D, but few people regularly consume enough of these fish.

And while foods fortified with vitamin D, such as orange juice, milk, and cold cereals, are on the upswing, many experts like  functional-medicine nutritionist Julie L. Starkel, MS, MBA, RDN say that these foods usually don’t help increase your vitamin D intake. The form of vitamin D in fortified foods, Starkel explains, is often vitamin D2, an inactive form that needs sunlight to activate it — a challenge for those living in cloudy locations or with limited time to spend outdoors. It is also fat-soluble, which means you need to eat fat to absorb the vitamin. So, if you’re drinking fat-free orange juice or skim milk, you won’t absorb much of the fortified vitamin D it contains.

[Vitamin D] is also fat-soluble, which means you need to eat fat to absorb the vitamin. So, if you’re drinking fat-free orange juice or skim milk, you won’t absorb much of the fortified vitamin D it contains.

More than three-quarters of all Americans are deficient in vitamin D. The Institute of Medicine, a nonprofit organization that is the health arm of the National Academy of Sciences, recently raised its recommended daily vitamin D intake from 400 international units (IU) to 600 IU for most age groups. Wald and many vitamin D experts think that these revised recommendations still aren’t enough to overcome the epidemic of vitamin D deficiency gripping the country.

How to Get Adequate Vitamin D: 

Wald strongly believes that daily supplementation is the most reliable way to achieve optimal vitamin D levels. “You should get a baseline test of vitamin D3 (dihydroxy) from your doctor, with an ideal level being 75 ng/mL in the blood,” he says. Many multivitamins contain no more than 600 IU, so you’ll likely require a dedicated vitamin D supplement to overcome a deficiency. The supplemental dose Wald often recommends is 5,000 to 10,000 IU daily, or as much as 50,000 IU daily, based on individual needs, such as the degree of deficiency or health status. “The risk for overdose is very low, particularly if you’ve had your levels tested,” says Wald.

Wald strongly believes that daily supplementation is the most reliable way to achieve optimal vitamin D levels.

Not everyone agrees, however, including nutrition expert Alan Gaby, MD, who thinks that excess amounts of fat-soluble vitamin D could accumulate in our bodies and raise the risk for conditions such as kidney stones and atherosclerosis. Gaby suggests a more modest 800 to 1,200 IU daily supplementation as an effective and safe dose for most people, although he does prescribe higher doses for short periods of time if he’s “trying to correct a deficiency rapidly.”

Regardless of the amount of vitamin D you consume, take heed of a 2010 study in the Journal of Bone and Mineral Research, which found that subjects who took their vitamin D supplements with the largest meal of the day increased absorption by about 50 percent. And look for supplements with vitamin D3, the more active form, which is better at boosting blood levels than the D2 form. For more on how much vitamin D to take, see “The Vitamin D Debate.”

This was excerpted from “5 Critical Nutrients and What Happens to Your Body When They’re Missing.”

Photography by: Andrea Bricco; Food Styling by: Alicia Buszczak
Matthew
Matthew Kadey

Matthew Kadey MSc, RD, is a dietitian and food and nutrition writer.

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