The healthier your diet, the better your sex life - but Viagra does help.

The same foods that help maintain cardiovascular health can improve sexual function (just like Viagra), even preserve it into middle age and beyond, according to authors of a new book, "Great Food, Great Sex."

The plumbing is all connected," says co-author and New York-based health psychologist Lynn Edlen-Nezin. "Everything you do that insults your heart insults your sexual organs, and everything that's good for your heart is good for your sexual function."

Put simply, clear, healthy, properly-fueled blood vessels may mean adequate blood flow to where it counts. That doesn't bode well for the sex lives of millions of Americans who already have heart disease. That "cardiosexual" crisis led Edlen-Nezin and Robert Fried to develop an eating plan that protects the heart, by extension, and promotes sexual vitality.

The plan, featured in their book, emphasizes two cardiovascular principles: 1) Arteries must be healthy and clear of the plaque that hampers blood flow throughout the body, including the sex organs, and 2) Blood vessels need specific nutrients — nitrogen and an amino acid called L-arginine — to create the gas that improves blood flow.

The first principle is well established. The second is a new area of research. The National Heart, Lung, and Blood Institute is currently funding a study to determine whether diet can produce nitric oxide in the body.

In any case, both principles rely on dietary rules that ought to be familiar by now. Fruits and vegetables: good. Lean meats: good. Whole grains: good. Antioxidants: good. Cholesterol and saturated fat: bad.

"The Great Food, Great Sex" plan identifies three important food factors: Greens and beans: Nitrogen-rich vegetables and legumes help your blood vessels produce nitric oxide, the gas that triggers vessel dilation critical to sexual performance and pleasure. The Staminators: Meats and nuts high in the amino acid L-arginine also help your body produce nitric oxide. The Brights: Brightly colored foods and drinks with plenty of antioxidants to combat the free radicals that can clog and damage arteries.

Sure, the food-and-sex transaction is chemically complex. Think of it this way: If nitrogen and L-arginine are the bank deposits, nitric oxide is the debit card that delivers the goods.

Nitric oxide triggers a biochemical process that ultimately leads to relaxed arteries in the sex organs when they're stimulated. When those arteries are relaxed, they can dilate and flush with the blood that causes sexual arousal, key to sexual performance and satisfaction.

But, alas. Nitric oxide only lasts so long, especially in people with high blood pressure. That's where the first two food factors, and yes, Viagra comes in.

The right foods provide the ingredients that the body needs to produce nitric oxide. Viagra essentially prolongs the effect of nitric oxide.

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