When you hear the words 'heart' and 'sex life' in the same sentence, odds are the speaker is probably talking about love. But your heart - or, more accurately, your cardiovascular system - actually has a lot to do with your ability to perform in the bedroom.This concept was brought home to me recently when I caught up with my colleague, Dr. Madeleine Castellanos, author of a recent book dealing with male sexual issues. She reminded me that there’s no way we can talk about sexual issues like erectile dysfunction (ED) or other arousal disorders without talking about cardiovascular health."When you break it all down, everything in the body, including sex, is dependent on good blood flow," says Castellanos. "Our body's way of nourishing itself and keeping itself vibrant and alive is by carrying oxygen, hormones, and nutrients via the bloodstream to all tissues and cells. The more activity that a certain part of our body engages in, the more blood flow is directed to that area."Although you might typically associate blood flow with your heart, brain or muscles, it's also a crucial factor in the way your genitals function. In men, blood flow to erectile tissue produces an erection and stimulates the prostate gland to start releasing pre-ejaculatory fluid. Blood flow also benefits women by increasing the clitoris’s size and sensation and by enhancing vaginal lubrication.Good blood flow also affects our biggest sex organ - the brain - by ensuring proper flow of hormone signals back and forth from the brain to the genitals.Often, a sexual issue like ED is the first sign that blood flow is impaired throughout the body, and a trip to the doctor’s office for a Viagra prescription could end with a diagnosis of atherosclerosis or another serious cardiovascular problem. A recent analysis of 12 previous studies, published in the Journal of the American College of Cardiology, found that men with ED are significantly more likely to have cardiovascular disease.So how can you keep blood flowing optimally? Dr. Castellanos recommends addressing these three areas:Arteries. When arteries become clogged, or 'hardened,' due to atherosclerosis, they can’t respond as well to the hormonal signals that occur during sexual arousal. As a result, “there may not be enough increase in blood flow to engorge the erectile tissues in either men or women,” says Castellanos.Eat a balanced diet low in sugars (including fructose and high-fructose corn syrup), trans fats, high-glycemic carbohydrates, and salt to keep arteries in good shape. For more on eating for a healthy sex life, see my previous column on the topic.Nerves. If your nerves aren’t working properly, you lose sensation and your body - including your genitals - doesn’t respond as well as it should. Diabetes and elevated blood sugar are the biggest threats to nerve damage, so keep blood sugar under control, eating smaller, more frequent meals, and limiting alcohol intake.Tissues. Just as the advice 'move it or lose it' applies to our muscles, it also applies to sex."If you want to have good blood flow to your genitals," explains Castellanos, "you need to keep using them." In fact, people who have sex at least once a week are more likely to retain good sexual function as they get older.If you’re following the steps above but want to do more to encourage proper blood flow, consider this: Your body depends on the molecule nitric oxide to keep blood vessels healthy and relaxed so that blood can flow through them."If you want more nitric oxide, you need more of the amino acid L-arginine," says Dr. Elizabeth Owings, a Missouri-based physician who is passionate about the benefits of L-arginine. Viagra and other members of a class of drugs called phosphodiesterase (PDE) inhibitors also influence nitric oxide - but they only enhance its effects. On the other hand, L-arginine helps your body produce more nitric acid, improving blood flow all over.L-arginine is naturally found in protein-rich foods such as peanuts and walnuts, meats, seafood and legumes such as soybean and chickpeas, but you may need a supplement to give your sex life that extra boost.Although more research is needed, some evidence suggests that supplemental L-arginine may have sexual benefits for both men and women. A 1999 study of men with ED found that those who took L-arginine for six weeks had greater improvement in symptoms than those who didn’t take this supplement. And a 2002 study published in the Archives of Sexual Behavior showed that women who took a combination of L-arginine and the herb yohimbine experienced more signs of sexual arousal while watching an erotic film than those who took a placebo.Dr. Owings recommends that healthy people try taking 5 grams of L-arginine a day and points out that this supplement appears to lack the side effects associated with PDE inhibitors, including visual disturbances and hearing problems. That said, some research does suggest that L-arginine isn’t a good idea for people with liver or kidney failure or cancer.As always, it's best to talk to your doctor before taking any type of supplement. It may seem difficult, but sharing your concerns with a professional can help open an honest conversation about sex, and about health in general - and that's always a good thing.