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By Julie Upton
From Health magazine

You may already know that vitamin D can help build strong teeth and bones, but wait until you hear what else it can do for the rest of your body. D can keep you trim, boost your mood, ward off sniffles, drastically cut your risk of cancer, and more.

“We could prevent 150,000 cases of cancer annually if we could just increase vitamin D to optimal levels,” says Cedric Garland, a doctor of public health, a leading vitamin D researcher, and a professor of family and preventive medicine at the University of California, San Diego.

That’s great news, right? Yes, except for one huge problem: A startling report found that more than a third of all women fail to get enough D for healthy bones—and more than 75% of us lack the higher amounts needed for the vitamin to do its disease-fighting best.

Downing a daily glass of milk is a smart way to get more D. But the most significant source is sunlight, and that’s where the trouble lies. Our bodies produce D with exposure to ultraviolet radiation, but as we’ve gotten smarter about dodging skin cancer—staying out of the sun and slathering ourselves with mega-SPF sunblock—our vitamin D levels have plummeted. Fortunately, there are smart and safe ways to boost your intake while you enjoy all the benefits that vitamin D can deliver.

Lower your risk of cancer
Vitamin D may substantially cut the risk of breast, colon, prostate, and ovarian cancers, according to a growing body of research. In fact, Dr. Garland found that women with D blood levels that were more than double the current national average of 25 nanograms per milliliter (ng/ml) had a 50% lower risk of breast cancer than those with the lowest blood levels. Scientists believe that D helps regulate genes in a way that protects healthy cells and stops the growth of cancerous ones.

There are receptors for vitamin D in virtually all of the body’s cells, and to “feed” them you need an adequate blood level of the vitamin. That depends not only on how much time you spend outside and what you eat but also on where you live. People living at higher latitudes, for example, soak up fewer UVB rays from November through March, which means they’re more likely to have low blood levels of vitamin D and a higher risk of cancer. In fact, studies have shown twice as many colon cancer deaths and 50% more breast cancer deaths in the far North compared with the sunnier South, Dr. Garland says. So how much sun is enough to lower the risk of cancer without upping your risk of skin damage?

Fight off winter weight gain
Cold weather may seem a long way off right now, but more indoor time and fewer hours of sunlight can lead to a decrease in D production for many women. Researchers think that may explain why some women bulk
up a bit
when the temps fall: Low levels of D can cause a dip in leptin, a hormone that regulates appetite. When this happens, your brain may not send the signal that you’re full and should stop eating. Overweight women are especially at risk because excess fat can absorb vitamin D, making it unavailable to the body.

Safeguard your healthy heart
Vitamin D is thought to help lower blood pressure and regulate hormones that affect blood vessels and the muscles of the heart. Studies suggest that people with the highest D levels may have up to a 50% lower risk of heart disease. And researchers from Harvard Medical School reported a 62% increased risk of heart attacks or strokes among adults with the lowest blood levels of vitamin D, compared with those who have the highest levels of D. “We’ve also noticed that deaths from cardiovascular events are highest in the winter months, when vitamin D is generally at its lowest,” Dr. Garland says.

Say good-bye to seasonal blues
Low vitamin D levels may be linked to yet another winter bummer: seasonal affective disorder, a type of depression that is more common in northern states. Researchers believe that vitamin D helps keep the brain flush with the “happy hormone,” serotonin, which plays a critical role in regulating mood.

The nutrient also seems to offer a lifetime of brain-health benefits, from aiding development in infants to keeping adults sharp in their later years. “Vitamin D receptors in the brain seem to turn on several genes that are important for normal neurological function,” says Bruce Hollis, PhD, a vitamin D researcher and professor of molecular biology at the Medical University of South Carolina.

Boost your defenses against colds and flu
Research shows that colds and the flu are worst when vitamin D levels decline, and they tend to hit hardest in countries at higher latitudes, where D levels tend to be lowest. So should we pitch out the C and hail the “sunshine vitamin” as the cure for the common cold? Experts aren’t making that claim just yet, but there’s compelling evidence that keeping your D level high may slash your chances of picking up the bug that’s going around the office. In one study, women who took 800 IU of vitamin D daily were three times less likely to develop colds or the flu—and those who popped 2,000 IU reported even fewer symptoms. Small wonder some scientists have started calling D the “antibiotic vitamin.”

Prevent autoimmune disorders
Vitamin D seems to interact in a protective way with genes that raise the risk for diseases like multiple sclerosis (MS), a debilitating nerve illness that strikes mostly young women. In one Harvard University study, researchers found a 40% lower risk of MS in women who took a daily supplement of at least 400 IU of vitamin D. In fact, some studies suggest that vitamin D may help prevent many other autoimmune disorders—including rheumatoid arthritis, type 1 diabetes, and Crohn’s disease. Even in healthy women, low levels of vitamin D may lead to increased inflammation, a negative response of the immune system.

Build stronger bones
The work that D does with calcium to keep bones healthy may be old news, but it’s no less important, especially for women. Osteoporosis and fractures due to bone weakness strike up to half of all females, according to the National Osteoporosis Foundation, and loading up on calcium-rich foods may not help much if you’re D-deficient. The nutrient helps your body absorb calcium and phosphorus, minerals that enhance bone strength. A supplement can help: A recent study found that, regardless of their calcium intake, women who added 482 to 770 IU of vitamn D slashed their risk of fractures by up to 20%.