Last week’s deluge of snow, ice and cold weather has got me thinking again about the “sunshine” vitamin (otherwise known as vitamin D)…and how most of us aren’t getting enough of it this winter.

As frequently noted in the Guide to Good Health, the best source of vitamin D is the sun. You can get up to 10,000 IUs a day just by spending 30 minutes in the sun. But during the winter, many of us just scurry back and forth from the house to the car. Spending time in the sun just doesn’t happen.

That’s not good, especially when you start looking at all the diseases that vitamin D has been shown to help prevent.

It’s not just about osteoporosis

Most of us know vitamin D is good for the bones. But it’s actually much more versatile than that. In fact, some nutritionists and scientists now believe vitamin D can protect you against:

  • cognitive decline
  • depression
  • heart failure
  • back pain
  • cancer
  • insulin resistance
  • pre-eclampsia during pregnancy
  • impaired immunity
  • macular degeneration
  • weight gain

It’s food for your brain

In addition to building strong bones, vitamin D seems to help prevent dementia and support brain function for older adults.

In a study published in December 2008, researchers assessed the cognitive levels of almost 2,000 adults aged 65 and older. Scientists found that patients with the highest levels of serum vitamin D3 (an overall indicator of vitamin D levels in the body) also had the best cognitive functioning. By contrast, those with the lowest levels of D3 were four times as likely to have cognitive impairment.

But that’s not all the vitamin D can do.

It’s also one of nature’s best antidepressants

Vitamin D helps to regulate melatonin and other neurotransmitters in the brain that give you a sense of well-being. Without enough of it, you’re at risk of feeling low.

For instance, in a study published two years ago in the American Journal of Geriatric Psychiatry, vitamin D3 was identified as a factor in regulating mood in older adults. Researchers found that patients with a D3 deficiency experienced depression.

Some scientists also believe vitamin D is helpful in alleviating “seasonal affective disorder.” Not surprisingly, this condition is common up north where folks spend much of the year under snowy skies. They simply don’t get enough sunlight, their bodies lack vitamin D, and they become susceptible to the winter blues.

But that’s not all. Recent studies suggest vitamin D also plays a role in heart health.

Sunshine for your heart

A few months back, one research team from the University of Michigan showed that vitamin D can protect against heart failure in rats. For 13 weeks, rats in a Michigan lab were divided into four groups:

1. Rats given high-salt diet (designed to simulate a “fast food” diet)
2. Rats on a high-salt diet given vitamin D
3. Rats on a healthy diet
4. Rats on a healthy diet given vitamin D

At the end of the study, researchers found that rats on the fast food diet + vitamin D regimen faired much better than their counter parts receiving just the fast food diet.

After just 13 weeks, the vitamin D treated rats had a lower heart weight. (This was really big news because an enlarged heart—known as “hypertrophy”—is all too common in heart failure patients. When hypertrophy happens in men and women, it makes the heart work harder to pump blood through the body. Your blood pressure rises. Even a simple walk to the mailbox becomes too much.) The treated rats’ hearts also worked less for each beat. They also maintained normal blood pressure.

According to the study’s lead researcher, University of Michigan pharmacologist Robert U. Simpson, Ph.D., "Heart failure will progress despite the best medications. We think vitamin D retards that progression and protects the heart."

Simpson has studied vitamin D’s effects on the heart for more than 20 years. At first, his ideas were thought of as far-fetched and improbable. Now—his research is starting to bear fruit. I’m sure there’s more to come on the heart + vitamin D link…

Even for Oprah and Vogue readers?

There’s much more to learn about vitamin D, from its role in preventing cancer to stabilizing blood sugar to improving autoimmune disorders. It seems like even some mainstream news junkies are starting to catch on. A colleague told me that Vogue magazine ran a bit on it this month. And evidently, even Oprah’s spoken publically about being vitamin D deficient.

You too may be deficient in this important vitamin. Many of us don’t spend much time outside (even in good weather). And many of us dutifully follow the marching orders to lather up the sun block before setting foot outdoors. Sun screen blocks the rays that help your body make vitamin D.

Or perhaps you’re of Latino or African-American descent and your skin contains lots of melanin (Just like sun screen, melanin blocks the rays that help your body make vitamin D.) Some scientists believe that anyone living above New York City’s line of latitude NEVER absorbs enough vitamin D through their skin, even in the summertime.

Whatever the reason why, I’m convinced most of us need more vitamin D.

You can get a simple blood test if you think you might have a deficiency. Optimal levels are between 50-70 ng/mL.

For anyone not getting regular sun exposure, I usually recommend taking 2000 IUs of vitamin D daily. In winter months, I’d go for 4000 IUs daily. (Remember, exposure of your full body to the sun for 30 minutes will give you 10,000 IUs or more of vitamin D. So there’s little risk of reaching an upper limit with this supplement.)

You can also get vitamin D into your diet by eating more eggs (naturally found in yolks), liver, and fatty fish (such as salmon, tuna, and sardines).

Keep up the good work and get some sunshine if you can.