Don't worry about the calories in those Valentine's Day chocolates – a proper celebration in the bedroom can help keep you in shape. In fact, sex can benefit your health in many ways. Here are seven reasons to give and get a little love – not just this special day, but any time. Good for the heart Sex is good for your heart. Like any physical exertion, sex is a form of cardio-exercise, which gets your heart pumping faster and helps it stay in shape. What's more, studies have shown that men who have sex two or more times per week cut their risk of a fatal heart attack by half. Helps you lose weight Like any form of exercise, sex helps you lose weight. Having sex for 30 minutes can burn off 85 calories. To put that in perspective: 15 minutes on the treadmill could burn up to 200 calories; 42 of these half-hour sessions, then, could shave a pound off your weight. Boosts your immune system While it's possible to contract a wide range of diseases, both from sex and from simple contact with others, safe sex between healthy partners can make you better equipped to fight illness. Those who have sex once or twice a week have been shown to have higher levels of immunoglobulin A or IgA, an antibody which helps protect you from respiratory diseases like the cold and flu. Don't go overboard, though – in studies, those who had sex three or more times a week had the lowest levels of antibodies. Reduces the risk of prostate cancer For younger men, sex reduces the risk of prostate cancer. Researchers have found that men in their 20s who had five or more ejaculations per week were one third less likely to develop the cancer in later life. Although they found no such correlation for older men, you could try to prove them wrong. Relieves stress There's a medical explanation for the mood boost sex gives you. The brain releases endorphins during and after sex, and these neurotransmitters create a feeling of euphoria while masking the negative effects of stress. Researchers have also found that sex lowers your blood pressure, which is good for your health and allows you to better keep your cool in stressful situations. It relieves pain Endorphins and lower blood pressure also mean that sex relieves pain. Endorphins are released during sex because of the heightened levels of the hormone oxytocin in your body. This has been known to alleviate arthritic and menstrual pain, among other things. Lower blood pressure can also help relieve migraines. It helps you sleep In addition to relieving stress and pain, the oxytocin generated during sex helps you sleep better. Sex relaxes you, promoting deeper, more restful sleep. What more do you need?