The news about D, the "sunshine" vitamin that loves your bones, nerves, muscles, heart, blood sugar and may even help fight cancer, just got a little better right in time for cold and flu season. In a headline-grabbing report, Japanese researchers found that taking 1,200 IU of D-3 supplements daily can cut your risk of catching influenza A by 50 percent.

And even though there's been recent press about a French meta-study that casts doubt on D's disease-fighting ability, we're still devoted to vitamin D-3: from food, sun and supplements. We think that study didn't look at the results of serious deficiency, and it's estimated that overall around 42 percent of adults have D-3 levels below 20 ng/ml (in general, levels below 30 ng/ml are too low for bone health), while 82 percent of blacks and 70 percent of Hispanics are deficient.

There's plenty of solid research showing the real benefits from vitamin D-3, which won't harm you if taken at recommended doses. A daily dose of at least 600 IU (800 IU if you're 71 or older), but no more than 4,000 IU, helps your body absorb and use more calcium (great for bones), discourages cancers of the colon, breast and prostate, lowers your risk for autoimmune disorders such as Type 1 diabetes and can assist with blood pressure control, too.

There's also growing evidence that having sufficient D-3 helps your cells absorb blood sugar properly.

One reason we're excited by the Japanese study of D-3's impact on the flu is that it highlights how vitamin D-3 boosts immune cells' ability to spot and pick off invaders, such as viruses. But D-3's no substitute for a flu vaccine. Go get one (it's not too late!), then do this:

Get your doc to check your D level. Levels below 20 ng/ml, that's where almost half of all North Americans come in, are dangerously low, raising the risk for thinning bones and surgical complications. We recommend aiming for 50-80 ng/ml. If your levels are low, your doctor may prescribe a high-dose D-3 supplement for a few months, then test your blood again.

Aim for 1,000 IU daily. Make sure your supplement is D-3, also known as cholecalciferol. It's more stable and does a better job of raising D blood levels, and that's what counts. It's also smart to reach for D-3-rich foods: fortified dairy products (fat-free milk, low-fat cheese, low-fat, no-sugar-added yogurt) have D- 3; so do fortified breakfast cereals and orange juice. Salmon's a rich natural source with a whopping 447 IUs in a 3- ounce serving. But, it would be tough getting enough every day just from food.

Mix brands. After a recent analysis found big variations in the actual amount of D-3 in many supplements, Dr. Mike started taking D-3 from more than one brand. Switching back and forth on different days could help average out low or high levels in supplements.

Take it with lunch or dinner. A study at the Cleveland Clinic, home of Dr. Mike's Wellness Institute, says you can increase vitamin D-3 absorption 50 percent by taking it with your biggest meal of the day, since D-3 is fat-soluble. Don't rely on the sun. Older people, those with darker skin and anyone living in Canada and the northern half of the U.S. (where the sun's rays are weaker) just can't make enough D-3 from the sun during the winter. If you live further south or just about anywhere during spring, summer and fall, expose your face, hands and arms for 15 minutes to get a natural dose. (Skip this step if you're at high risk for skin cancer.) Then apply a sunscreen with an SPF of 30 that protects against UVA and B. A lightskinned person in the Northeast can stimulate the release of around 20,000 IU of D-3 into the bloodstream with 15 minutes of sun exposure on face, arms and legs, without sunscreen. Dark-skinned people generate half or less of that amount.
