The days are getting short and dark now that it’s mid-November, and at the end of many a busy day I realize I haven’t managed to get out in the sun once all day. That’s not a good thing, because more and more evidence is pouring in that getting enough vitamin D — sometimes called the “sunshine vitamin” because our bodies synthesize it from the sun — is absolutely crucial to staying healthy. In fact, the latest studies are so convincing that I’ve talked to doctors who wonder aloud whether low vitamin D levels could turn out to be the “missing link” that’s at the root of many of the chronic health ailments plaguing our generation.

Here’s a roundup of the latest reasons to make sure you’re getting enough vitamin D:

  1. It protects against breast cancer, and helps prevent breast cancer from spreading. There have been many studies supporting this claim; one recent Canadian study found that women diagnosed with breast cancer who were vitamin D deficient had almost double the risk of their cancer progressing.

  2.  It protects against colon cancer. One study found colon cancer patients deficient in vitamin D were almost twice as likely to die as patients with healthy levels.
  3. 
It protects against 16 other types of cancer. These include deadly pancreatic and lung cancer.

  4. It protects you from stroke and heart attack. Recent research at Harvard found that those with low vitamin D had a 60 percent higher risk of stroke, heart attack, or heart failure over five years.

  5. It boosts your immune system. Some researchers think low vitamin D levels are going to turn out to be the “X-factor” that makes some people more susceptible to serious illness with H1N1. 
  6. 
It protects against fracture. One study found that people taking vitamin D supplements lowered hip fracture risk by almost 20 percent.

  7. It helps you live longer. Experts don’t yet know exactly why, but a study published just last month followed 3,000 people over the age of 73 and found those who fell into the lowest quarter of vitamin D levels had an 83 percent higher risk of death from any cause.

Convinced yet? I sure hope so. Polls of doctors show that vitamin D is one of only a few supplements doctors say they’re careful to take themselves. And studies show that about 41 percent of men and 53 percent of women in the U.S. have vitamin D levels that are too low.

There also seems to be confusion about how much vitamin D to take, and no wonder. That’s because the U.S. daily guidelines are wrong. There, I said it; they’re just plain wrong. The majority of medical experts agree, but bureaucracy is slow, especially in the case of public health recommendations, and they’ve not yet been changed.

Do what vitamin D researchers recommend and ignore the guidelines (in this particular case). The consensus of medical opinion is to take 2000 IUs of vitamin D3 daily. (This form of vitamin D is better absorbed and stays in your blood longer, and you can’t get it from food.) In the summer, it’s also a good idea to go outside in the sunlight for 15 minutes a day without sunscreen, but it’s winter right now and unless you live in the south or southwest, the sun won’t be strong enough to have a vitamin D-building effect.

An even more reliable option is to ask your doctor to have your vitamin D blood level measured the next time you test your cholesterol and lipids. The result you want? Optimum is between 35 and 55 nanograms per milliliter, also measured as between 80 and 120 nanomoles per liter. If your vitamin D levels are low, you can take drugstore vitamin D or ask for a prescription vitamin D supplement; these are even stronger than what you can get over the counter. Have your doctor check your vitamin D level again in six months and see if it’s now in the optimum range.

And if you’re supplementing with vitamin D on your own and worried you might take too much, move on to other worries — it’s really not a serious risk. The reason it’s so puzzling to many experts why people aren’t taking vitamin D is that there’s very little downside; vitamin D causes no side effects and you’d have to take an enormous amount before your blood levels would rise too high.

For those of us who love to travel and adventure in the great outdoors, catching some vitamin D-building UV rays is just another incentive. All it takes is 15 minutes a day (between 10 a.m. and 2 p.m.) of bright sunlight, so take that into account when planning your next trip or outing.

–Go for a hill walk and look at the view.
–Take a kayak out on a lake or river.
–Go for a bike ride — just make sure you’re not too covered up. (You need some skin exposed.)
–Go for a swim if you’re lucky enough to live in a warm-winter climate.
–Have a picnic.

But remember, between November and March the sun is only high enough to fuel vitamin D synthesis south of latitude 37 degrees (draw a line across the country from Richmond, Virginia through San Francisco).

So plan your winter trips accordingly: Arizona, New Mexico, Texas, Florida, Costa Rica, Mexico ……here we come!!