Joan Smith: I have measured out my life in chocolate. And now I'm going to have some more

It may be a forbidden pleasure, it may be all about sex. But Joan Smith will be tucking in, whatever

When I was a child, I couldn't wait for Easter. Like Christmas, Easter meant chocolate, and I always woke up early on Good Friday, eager to peel the foil off the first egg before breakfast. I liked them best if there was more chocolate inside – chocolate shapes or ones with toffee centres – and they never made me sick, no matter how much I ate. By the end of the day it was all gone, and I was astonished when a boyfriend told me years later that you're supposed to wait until Easter Sunday before tearing the packaging part. He didn't understand that what the annual Christian festivals represented for me was the chance to gorge on Cadbury's Creme eggs and (each Christmas morning) a Terry's Chocolate Orange.

Today, people in Britain will consume around 100 million chocolate eggs, rabbits, chicks and lambs. I doubt whether they regard chocolate as the food of the gods – the literal meaning of theobroma cacao, the Central American tree it comes from – but there's much more choice than I remember as a child. I grew up on the brands familiar to every British household in the 1960s and 70s: Aero, Bounty, Cadbury's Flake, and chocolate has become a lifelong passion.

Maybe it goes back to living near the Mars factory in Slough when I was five or six, when one of my parents' friends would bring round mis-shapen seconds. I can remember the type of chocolate I was eating at different periods in my life: the Kit Kats and Penguins I ate in school breaks, the Marathon bars that kept me going when I was writing my first book, the Belgian truffles I discovered with astonishment (my first upmarket chocolate experience) some time in the 1980s.

Like most women, I gobble chocolate when I'm miserable; I once ate two whole 100g bars of Swiss milk chocolate on the way home from Sainsbury's after breaking up with someone. It's the best comfort food I know, much more tempting than alcohol and without having to endure the hangover. But I also eat it when I'm happy, and anecdotal experience does seem to suggest that women crave chocolate more than men. All sorts of explanations have been advanced for this, from women having a sweeter tooth generally – which is certainly true in my experience – to the proposition that chocolate has a different effect on women's brains. Some researchers say that chocolate triggers mood-enhancing chemicals and neurotransmitters; it contains phenylethylamine, which apparently releases dopamine – a substance which peaks during orgasm – in the female brain.

It's even been suggested that when women eat chocolate it affects activity in the amygdala, a part of the brain which regulates sexual behaviour and desire. Other researchers scoff at such suggestions, arguing that the quantities in your average bar of chocolate are too small to have the dramatic effects claimed for it. What is clear is that chocolate has been democratised since its arrival in Europe, evolving from a drink reserved for Aztec emperors to a cheap, instant hit of energy and sweetness. An Aztec ruler wouldn't recognise a Yorkie bar but just over five centuries since the Spanish conquistador Cortes watched Moctezuma II drink whipped chocolate in the Aztec capital, Tenochtitlan, you can have something similar whipped up in one of the American or Italian coffee chains which dominate British high streets.

It was the Spanish who brought chocolate to Europe, where the industry eventually flourished in unexpected locations such as Belgium and Switzerland (plenty of cows, I suppose, to provide milk for milk chocolate). Bitter drinking chocolate arrived at the Spanish court in the 16th century but the solid chocolate we know today wasn't created until the second half of the 19th century. The Marquis de Sade once used bitter chocolate to disguise the taste of cantharides, a dangerous aphrodisiac, and found himself sentenced to death in absentia for poisoning and sodomy.

These days, the top and bottom ends of the market have next to nothing in common. Cheap British chocolate contains so few cocoa solids that the EU had to be coaxed into recognising it as chocolate at all, though I don't think the objection was motivated by snobbery or Anglophobia; I still enjoy the occasional Mars bar but it's an entirely other experience from a mouthful of the darkest, densest Valrhona. It's like the difference between a mug of milky Nescafé and a freshly-made espresso doppio.

The top end of the industry has come up with a brilliant marketing strategy, turning expensive chocolate into one of the most desirable luxury products. Like good wine, it has its own vocabulary, describing cocoa beans as lovingly as grapes, and it's sold in the most upmarket shops in Europe; even a small box of Godiva costs a small fortune in Brussels. I love shopping at Fauchon near La Madeleine in Paris, where the ambience and packaging are as seductive as the items it sells: I once gave my boyfriend a box from Fauchon in the shape of a huge pair of red lips, the sexiest container for chocolates I've ever encountered. In this country I get chocolate from Theobroma Cacao, a wonderful boutique in West London where you can smell the chocolate being made.

The most interesting explanations for the enduring popularity of chocolate aren't scientific. Psychological explanations favour the notion that chocolate is attractive to women because it's taboo for anyone on a diet, giving it the status of a forbidden pleasure. I'm not entirely convinced – entire supermarket aisles are given up to chocolate in its various forms, from the cheapest to Green & Black's, for the discerning consumer – but it could be that some women regard eating it as "naughty".

If there is a taboo associated with chocolate, it may be related to the broader notion of self-denial imposed on the population at large by religion. This is the subject of Joanne Harris's hugely successful novel Chocolat, which identifies chocolate with pleasure and seduction, pitting her mysterious female chocolatier against the Catholic church in a fictional French village. The novel is set in the austere years after the Second World War and opens in Lent, the period of self-denial which precedes Easter, when the newly arrived Vianne Rocher sets about tempting her neighbours – and infuriating the priest – with irresistible varieties of chocolate.

The book suggests that the pleasure of eating chocolate is physical, liberating and almost pagan. And the best chocolate is certainly a sensual experience, a seduction involving most of the senses: sight, smell and taste. It's an oral pleasure, linking back to early childhood experiences and pre-dating the dietary prohibitions imposed by priests, doctors and the fashion industry. That may be why the link between women, chocolate and sex is made so often; in the Judaeo-Christian tradition, women are supposed to think of other people, and it's pretty hard to see having orgasms or eating chocolate as altruistic.

One researcher, Dr Andrea Salonia, even claims that women who eat chocolate regularly have better sex. He interviewed 163 women at San Raffaele hospital in Milan to reach this conclusion, and I'm certainly not going to argue with him. Whether chocolate can actually improve your sex life is a different matter, but I've come a long way since my idea of chocolate heaven was an Easter egg stuffed with Cadbury's Milk Tray. These days, it has to be a high-heeled chocolate shoe from Theobroma Cacao – now there is an artefact which really deserves to be worshipped.