Erotic foods need to be special. There has to be an edge of decadence, of luxury. A feeling that this is something unusual, to be treasured and enjoyed. Everyone knows that some foods are sexier than others – but why are they? What makes one substance erotic and another not?

Well, there's lots of reasons. The cost has a part to play: it helps to feel that this is something that you wouldn't – and indeed couldn't – have every day. That's part of the reason why truffles are treasured as erotic; why drinking champagne is more sensual than a pint of lager. It marks the moment out as An Occasion rather than just another meal.

Eating foods which you know you 'shouldn't' is also sexy. Erotic eating takes no consideration of diets; a meal loses something of its romance when you're worrying about how many calories you're consuming, or virtuously avoiding foods high in fat or sugar. It's why thick double cream is sexy and crème fraiche, no matter that it has the same texture, isn't. Forgetting your usual diet and just going for it also has the bonus of creating a tingling feeling that you're doing something a little bit naughty – and naughtiness and sex go together perfectly.

Chocolate, of course, has to have its place in discussions about erotic food, with some people (usually women) claiming that chocolate is better than sex. So if you could get both chocolate and sex, that's surely the best answer! But again cost and type is important. The deepest, darkest chocolate is best (which, of course, costs more than milky chocolate) – the higher the cocoa solids level the better.

With all erotic foods, though, less is more. With its deep chocolate-y taste, plain dark chocolate is far less likely to encourage bingeing on it than the every day types. One glass of champagne encourages eroticism; more might increase desire but would lower performance levels. A heavy meal is not the best foundation for passionate love-making.

Of course, it's not solely about the food itself. The surroundings matter – a salad and chicken at a high-class restaurant will always be a more sensual experience than the same at McDonald's, no matter the difference (or not) in the quality of food. Candle-light, soft music, a feeling of being waited upon rather than helping yourself, the chance to linger over the food, clasp hands with your lover, have low-toned romantic conversation – these are all things which a fast food outlet won't give you but which add to the erotic potential of a meal.

Treat yourself – and your partner. Go out to a restaurant a little more up market than you'd usually choose. Eat whatever you fancy – in moderation – and sip at ice cold champagne. And then see if you can tell me that you'd be just as much in the mood for sex if you'd eaten fish and chips at the local takeaway…