When you think of vitamin D, you probably also think immediately about bone health since vitamin D makes it possible for our bodies to absorb calcium. But research now has suggested that women who get lots of vitamin D are also less likely to develop breast cancer.

Researchers at the University of Toronto found that women who were deficient in vitamin D and who also had breast cancer were almost twice as likely to see their cancer spread and were eventually more likely to die from the cancer.

So how much vitamin D do you need? Here are the recommended amounts:

• For people from birth to age 50, the adequate dose of vitamin D for both males and females has been set at 200 International Units (IU).
• For men and women ages 51-70, the adequate vitamin D intake is 400 IU.
• For those ages 71 and older, the adequate intake level is 600 IU.

The reason we need more vitamin D as we get older is that, as the body ages, the skin is less able to make vitamin D from the sun, and also the kidneys become less able to convert vitamin D to a form the body can use.

You can get your vitamin D from sunlight, food, and supplements. Many people can produce sufficient amounts of vitamin D by getting out in the sun twice each week, without sunscreen, for 5 to 30 minutes each time, between 10 a.m. and 3 p.m.

Only a few foods naturally contain vitamin D, including salmon, tuna, sardines, mackerel, cod liver oil, egg yolk, and liver. Salmon or mackerel (3.5 ounces) contains about 350 IU, whereas an egg yolk furnishes only 20 IU. Most of our dietary intake of vitamin D comes from fortified foods such as milk, yogurt, margarines, and cereals. For example, one cup of fortified milk contains 100 IU of vitamin D, and one tablespoon of fortified margarine contains 60 IU.

Now that you know how much vitamin D you need, the next question is, do you need a supplement?