Our senses--what we see, hear, feel, touch, smell and taste--have a strong effect on how we feel and what we want, so it makes sense that foods can influence sexual desire. While some foods heighten sex drive by lifting the mood, others actually affect the production of libido-boosting sex hormones like testosterone and progesterone.
According to historical accounts, 18th-century lover Casanova used to eat 50 oysters every morning for breakfast. Science suggests he had the right idea: a 2009 study published in the "Journal of Human Reproductive Sciences" reported that zinc, a major component of oysters, boosts sexual activity in male rats. And in 2005, Australian biologist George Fisher chemically analyzed raw oysters and found that they contained two amino acids, D-aspartic acid and N-methyl-D-aspartate, which are rarely found in nature. When other scientists injected these amino acids into rats, they boosted the production of the sex hormone testosterone in males and progesterone in females, both of which boost libido.
The reason chili peppers are spicy is because they contain a compound called capsaicin, which stimulates nerve endings and causes heart rate to spike. This then leads the body to release endorphins, which give a natural high that might be conducive to sexual desire, according to the website Discovery Health.
Valentine's Day is not the only reason that people associate chocolate with romance. Chocolate also contains phenylethylamine, a chemical that engenders a sense of well-being and excitement, which might boost libido. However, the effects of chocolate may be moderate: a February 2010 article published in The New York Times notes that a 130-pound woman would have to eat 25 pounds of chocolate to notice an effect on her sex drive.