Do you need more vitamin D?

Are you at risk for vitamin D deficiency? Find out how to get more vitamin D and why your body really needs it.

The "sunshine vitamin" is essential for bone health and is also believed to strengthen the immune system and possibly prevent some cancers. Technically a hormone, vitamin D is produced in the body when the skin is exposed to the ultraviolet B (UVB) rays in sunlight. Theoretically, spending some time in the sun each day supplies all the vitamin D your body needs, but many people don't get enough sun to generate adequate vitamin D, especially in the winter (and people living in northern climates may not get enough UVB rays even during other seasons). What's more, the body's ability to manufacture vitamin D declines with age, so vitamin D deficiencies are common in older people.

• Certain forms of cancer
• Osteoarthritis
• Osteoporosis
• Tooth decay

The basic function of vitamin D is to regulate blood levels of calcium and phosphorus, helping to build strong bones and healthy teeth. Studies have shown that vitamin D is important in the prevention of osteoporosis, a disease that causes porous bones and thus an increased risk of fractures. Without sufficient vitamin D, the body cannot absorb calcium from food or supplements — no matter how much calcium you consume.

Plus, some studies suggest that vitamin D is important for a healthy immune system. Others indicate that it may help prevent prostate, colon, or breast cancer. One study found that adequate vitamin D slowed the progression of osteoarthritis in the knees, although it did not prevent the disease from developing in the first place.

In Northern climates, the sun's rays aren't strong enough to stimulate vitamin D production in the winter. If you get sufficient sun the rest of the year, your body can store enough vitamin D to carry you through to spring. If you don't, consider taking a daily vitamin D supplement in the winter, especially if you are over 50.

• As little as 10 to 15 minutes of midday sunlight on your face, hands, and arms two or three times a week can supply all the vitamin D you need, unless you live in a northern climate. But if you are over age 50, have dark skin, don't drink milk, don't get outdoors much between the hours of 8 a.m. and 3 p.m., or always wear sunscreen, you might want to consider taking vitamin D supplements.
• A 20-year study of more than 80,000 nurses found that those who took 1,200 milligrams of calcium and 800 IU of vitamin D per day had a 33 per cent lower risk of diabetes than those who got much lower amounts.

• Salmon
• Tuna, canned in oil
• Milk, fortified
• Cereal, fortified
• Egg yolk