The medical reality is that some foods can improve the systems of the body that are involved in sexual functions. For example, foods that improve circulation inevitably improve sexual endurance.
What do grapes, oysters, and chocolates have in common? Well, aside from being food, they're all supposedly aphrodisiacs. For the unaware, an aphrodisiac is basically a food or drug that has effects on sexual health, typically by either making it easier to become sexually aroused or by boosting sexual performance.
Now, while all of the above foods have been known to release varying levels of endorphins into the body in the same way sex does, they are not necessarily all that beneficial to one's sexual health. Of course, that doesn't mean that food and meals don't play a part in a person's sex life, because there's quite a bit of scientific data saying that it does.
Working from the top and going down, the brain is the core of all activity that concerns the body, including sexual functions. Replacing full meals with snacks or junk food can seriously decrease the usual flow of nutrients to the brain, making it less capable of processing all the stimuli and emotions involved in sexual activity. In short, the lack of nutrients can dampen someone's ability to enjoy sexual intercourse.
Moving a little lower, it makes sense that sexual health is connected to the overall state of the circulatory system. Blood circulation is necessary not only for the proper functioning of internal organs but also for ensuring the functions of the male and female reproductive organs. So, if the heart or the blood vessels are in poor condition, it also has a detrimental effect on the body's ability to perform properly during sexual intercourse. Increased or improved blood flow helps increase the sensitivity to stimuli of the appropriate organs and heightens the level of physical endurance during intercourse.
For more specific help regarding food and sexual health, some might want to look into Nitric Oxide, which is not to be confused with Nitrous Oxide. Nitric Oxide (NO) is the substance found on the lining of the internal workings of male and female genitalia. Without it, men can't obtain or sustain an erection (even with proper blood flow), while women are unable to become lubricated, regardless of what stimulation is put in there. Some doctors suggest that the ingestion of arginine, another substance which encourages the body to produce NO. Arginine helps improve circulation and sexual health. Arginine is typically found in walnuts, almonds, and salmon.
Antioxidants, particularly the ones that are chemically abundant in dark chocolate, also have positive effects on sexual performance and health. Antioxidants are linked to improved blood circulation, something that has already been mentioned as being beneficial to sex. Other good sources include tomatoes, spinach, garlic, red peppers, and red grapes. However, some point out that chocolate somehow also increases desire along with improving performance, likely because certain components in chocolate can improve circulation.