Wintertime is upon us, and that means less sun exposure, which results in less vitamin D in our bodies. But waiting for summer isn’t the solution since it’s imperative to get this nutrient all year long. Vitamin D deficiency has been linked to certain cancers; insulin instability; heart disease; osteoporosis; bone, joint and muscle aches;colds and flu; depression; autoimmune
diseases and much more. We’re even seeing a resurgence of rickets in breast-fed children because nursing mothers aren’t being told to supplement with D.

Vitamin D deficiencies were first recognized during the Industrial Revolution, when people found that giving children cod liver oil prevented rickets. In the 1930s rickets was so prevalent that companies started fortifying milk with vitamin D, and today nearly all brands contain 100 international units (IU) per cup. But otherwise, interest in this vitamin has waned and much to our detriment.

The country’s top nutrition experts concur that, collectively, we’re in serious need of this vitamin. The National Health & Nutrition Education Study reveals that 25 million Americans are D-deficient, and consequently it recommends routine monitoring of levels nationwide. The National Institutes of Health (NIH) reports that half of American women fail to get enough in their diets.

This seems like an easily fixed problem: Just increase your intake and get more sun. But the stumbling block is that because there are no obvious symptoms to readily identify this deficiency, people don’t realize they’re deficient and don’t take appropriate action. Here’s what you need to know to keep your levels of D where they should be.

How much is enough?
Your body uses between 3,000 and 4,000 IU of vitamin D daily, which is manufactured mainly from sunshine and stored in your liver and fat until
needed—commonly during winter. The current RDA is 200 IU for those 50 or younger, 400 IU for ages 51 to 64, and 800 IU for 65 and up. Nutrition experts agree that the RDA isn’t enough to combat a host of different ailments, though opinions vary as to exactly what the amounts should be.

The Institute of Medicine of the National Academy of Sciences believes there isn’t sufficient information to establish an RDA for Vitamin D. Instead they base the minimum on what should be an “adequate” intake. Yet most people fail to get even this to readily identify this deficiency, people don’t realize they’re deficient and don’t take appropriate action. Here’s what you need to know to keep your
levels of D where they should be. How much is enough? Your body uses between 3,000 and 4,000 IU of vitamin D daily, which is manufactured mainly from sunshine and stored in your liver and fat until needed—commonly during winter. The current RDA is 200 IU for those 50 or younger, 400 IU for ages 51 to 64, and 800 IU for 65 and up. Nutrition experts agree that the RDA isn’t enough to combat a host of different ailments, though opinions vary as to exactly what the amounts should be. The Institute of Medicine of the National Academy of Sciences believes there isn’t sufficient information to establish an RDA for Vitamin D. Instead they base the minimum on what should be an “adequate” intake. Yet most people fail to get even this level, so over time they develop a deficiency.
New scientific evidence suggests that 1,000 IU daily from food orsupplements will prevent deficiencies in most people, but that still might not be sufficient. The FDA says 2,000 IU daily is completely safe, but since D is stored in the tissues, taking 10,000 IU or more daily in supplements can be toxic, causing nausea, vomiting, appetite loss, weight loss, constipation and weakness. So don’t take more than 2,000 IU unless advised by your doctor.

Where the dilemma lies in terms of dosage comes from a lack of conclusive research determining the optimum level for fighting cancer, heart disease, autoimmune diseases and other ailments. This, no one knows for sure.

Cancer Conqueror
It bears repeating: There’s cogent evidence of real health benefits from taking higher doses than the RDA. One-half of the men and one-third of the women in this country will be afflicted with cancer in their lifetimes. Experts agree that these numbers can be greatly reduced simply by having normal vitamin D levels. The 2007 Harvard Women’s Health study followed 30,000 women over 10 years and found that those who took calcium (1,366 mg) and vitamin D (948 IU) had a one-third lower risk of developing breast cancer than women who received low levels of these nutrients. Another major 2007 study showed that 1,179 women who were given 1,100 IU of vitamin D daily plus calcium for four years had a 60 percent to 70 percent reduction of all types of cancers compared with women who received only calcium or a placebo.

Further supporting this, a research team at the Moores Cancer Center at UC San Diego found that women who had blood levels of 52, nanograms per milliliter [ng/ml] had half the incidence of breast cancer as women with blood levels of 17 or less. Findings show that once you’ve raised your level to 52 it can be maintained either by taking a daily dose of 1,000 IU or by spending 12 minutes in the sun every day. Numerous studies also indicate that vitamin D protects against prostate cancer in men.

Heart Disease Hinderer
At least20 good studies show that the worldwide incidence of heart attack rises in the winter and drops in the summer. David Sane, MD, associate professor of medicine at Wake Forest University
in North Carolina, sees a clear connection between cardiovascular benefits and vitamin D. In the United States, twice as many heart attacks occur in the winter as in the summer, a fact linked to lower D levels. Deficiency is also common in people with strokes, heart failure and atherosclerosis. Current theories about heart disease link it to inflammation, so this vitamin may come to the rescue as it has an anti-inflammatory effect on blood vessels and arteries.

Depression Deterrent
t You may have heard about the depressive ailment Seasonal Affective Disorder (SAD), which causes lethargy, irritability and other symptoms in residents of sunlight-deprived northern climates. Lack of sunlight slows down our body’s production of melatonin and serotonin— two hormones that keep us in a happy, contented state. Many people suffering from SAD respond well to light therapy, which elevates mood.

But a 1999 study showed that a single 100,000 IU dose of vitamin D was found to be superior to light therapy in the treatment of SAD. After one month, all the subjects had higher levels of D and were less depressed. Lower doses—400 IU to 800 IU—proved ineffective. Once your stores of D are depleted, it takes a lot of the vitamin to normalize your levels.

Bone-Health Helper
Whether you get calcium from supplements or food, you require vitamin D to absorb from the mineral and get it into your bones. Research shows that deficiencies may result in increases in osteoporosis, osteopenia, osteomalacia (bone pain) and general joint and muscle ailments. Musculoskeletal aches and pains, such as in fibromyalgia, typically improve when levels are normalized. Since D also seems to affect balance, it will help prevent falls and fractures as we age.

Cold and Flue Fighter
In the coming winter months, vitamin D can help stave off colds and flu. Vitamin D Council founder John Cannell, MD, a psychiatrist at Atascadero State Hospital in California, came to this conclusion by giving his patients D supplements during the winter. He asserts that the rest of the hospital patients reached epidemic levels of colds and flu, but his remained healthy. Children given supplemental D during the winter have fewer bouts of colds and flu. Researchers suspect that the vitamin protects us by stimulating white blood cells to produce catheclicidin, a chemical that kills bacteria, viruses and fungi.

Deficiency Detection
The only way to find out conclusively if you’re lacking this vitamin is to ask your doctor to order you a simple, inexpensive blood test called 25-hydroxyvitamin D, which insurance companies usually cover. As with most tests, there’s a range of what’s considered normal: In this case the range is from 32 to 100. The minimum optimal levels are 45 to 50. From your reading, your doctor can advise whether taking supplements would be beneficial.

There are two types of vitamin D in supplements: D2, or ergocalciferol, found primarily in vitamin D–fortified foods and supplements; and D3, or cholecalciferol, which is manufactured in our bodies and found in fish, cod liver oil and other animal foods. I recommend D3 because the body utilizes it two to five times more efficiently than it does D2, so it takes less to get the same effect. Vegans tend to use D2, since it contains no animal products. Two good veg supplements are made by VegLife and Bluebonnet and are available at many good health stores.

The Sunshine Solution or Not
or not Regardless of whether you supplement, one of the easiest ways to get this important vitamin is to sit in the sun. But come winter, that’s more easily said than done. World-famous vitamin D researcher and Boston University professor of medicine Michael Hollick, MD, PhD., says that people who live north of Atlanta can’t make any vitamin D in the winter, even if they sit outdoors naked at noon. To prove his point, he actually laid out buck-naked on a Boston rooftop. His vitamin D levels were tested before and afterward, and he was proved correct. Even on the sunniest December day, the UVB rays are too slanted which cause the body to produce vitamin D, whereas on a cloudy summer day, you can still get enough of the rays to manufacture it. (UVA rays do not play a role in making this vitamin.)

So if you live at a higher latitude than Atlanta (and many of us do), during the colder months you’ll need to find an alternative to get your daily D. Living in sunnier climes, however, doesn’t guarantee that you’ll get an adequate amount. The NIH estimates that levels drop about 20 percent during the winter.

Expose Yourself
Let’s say you’re on vacation, getting strong sun every day, and you’re about to do as your mother told you and slather on the sunscreen. Wait! Any sunscreen, no matter how low the sun protection factor (SPF), will block D production, so hold off for 15 to 20 minutes.

After you’ve soaked up the rays, don’t shower immediately—you’ll wash off the D that has accumulated in the oil of your sweat. Cool down and wait a few hours before showering, so your skin has ample time to respond and manufacture it. This vitamin stays inactive until our kidneys turn it into a hormone called calcitriol, which is used for virtually every tissue and organ for hormone production; immune, liver, reproductive, digestive and lung functions; making bone, muscle, skin, hair, brain neurons, connective tissue, arteries; and more.

Make Like a Squirrel
Like a squirrel storing up nuts for winter, in 20 to 30 minutes on a summer’s day you can easily produce 10,000 to 20,000 IU of vitamin D, which will then be stored until needed during the year’s colder months. So if you sat out for that same amount of time every day in the summer, you’d have to enough D to carry you through winter. Give yourself a present this holiday: Get your vitamin D levels tested. Prevention is so much easier than the cure. -Liz Lipski