In books and movies, double agents can cause chaos and intrigue - just think about Gerald in John Le Carre's "Tinker Tailor Soldier Spy." But in your circulatory system, HDL cholesterol is a double agent that's working on two fronts for your good health, and that's great news all around.

We've known for some time that HDL (high density lipoprotein) is a heavy lifter that shuttles artery-clogging LDL (low density lipoprotein) to the liver for removal from the body. Aim for an HDL level of 50 (and an LDL level of 100 or less) to protect your heart, brain, sexual function and the rest of your organs!

But what's more, a new study discovered that HDL also fights cancer - stopping the spread of cancer cells and even reducing tumor size. It appears that for every 10 mg/dl increase in HDL, there may be a 30 percent reduction in the risk for cancer.

So if you're one of the more than 120 million adults in North America with low HDL (or high LDL) cholesterol, try these four steps to increase your HDL level:

• Ask your doc about taking an HDL-raising statin: Rosuvastatin and atorvastatin boost HDL to some degree.
• Exercise daily; aim for 10,000 steps a day, plus two to three days a week of strength-building workouts.
• Eat heart-friendly oils such as olive and canola, salmon and ocean trout or supplements of DHA omega-3 (900 mg a day) and purified omega-7 (210 mg a day).
• Eat an ounce of nuts (we love walnuts) daily, raw and unsalted.