Up your intake of this cancer-fighting vitamin during gloomy winter months.

Cloudy winter days may leave you deficient in vitamin D, an important cancer-fighting nutrient that your body can manufacture using sunlight. Research shows that vitamin D may help reduce the risk of colon, breast, prostate, and ovarian cancers. Seek out fortified cereal and dairy products or a supplement to help ensure you get the optimal amount.

Vitamin D enhances immunity, helps the body utilize calcium, and may help reduce the risk of many cancers. Your skin manufactures vitamin D with help from the sun so you may be deficient in this vitamin during months when sunshine hours are fairly short and the weather brings more clouds. You're more likely to be deficient in vitamin D if you live in extreme northern locales or have darker skin. Make up for the lack of sunshine by including ample amounts of vitamin D in your diet. Food sources of vitamin D include Atlantic mackerel, eggs, and fortified cereal and dairy products. It's difficult for most people to get the daily RealAge Optimum dose (RAO) of vitamin D -- 400 IU for people under the age of 70 and 600 IU for people who are 70 or older -- through diet alone. So seek out a supplement, especially during overcast months.

RealAge Benefit: Getting 400 IU of vitamin D and 1,200 milligrams of calcium per day can make your RealAge as much as 1.3 years younger.

RealAge Smart Search: View more research on the health benefits of vitamin D with our expert-driven search engine.

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