THAT'S THE WHY:IT'S THE morning after the night before. A few hours ago the drink was flowing, and now you are paying the price with a sore head, a queasy stomach and a lack of energy.

“Never again,” you think.

Why do we feel so physically bad if we overdo it on alcohol? Veisalgia, otherwise known as a hangover, is considered to be down to a cocktail of factors.

One is dehydration. When alcohol gets into your body it affects your pituitary gland and inhibits the hormone vasopressin, an anti-diuretic hormone, so your kidneys excrete more water and salts, adding up to a headache the next morning.

Alcohol also affects levels of biochemicals in the body like neurotransmitters and cytokines, which have been linked to headaches and nausea.

And for good measure, alcohol dilates blood vessels serving the brain, again contributing to a sore head.

Meanwhile, a heavy drinking session prompts you to use up ready stores of energy called glycogen, which contributes to fatigue the next day.

Nor does a high intake of alcohol invite a restful night’s sleep as your body biochemically rebounds from its depressive effects.

Alcoholic drinks like red wine and brandy can also contain “congeners” or toxic byproducts of fermentation like methanol, which explains why they may give rise to more severe hangovers.

There are few scientific studies of hangover cures, but you can probably give yourself an easier post-party recovery by drinking moderately and slowly, preferably with food, and ensuring that you drink plenty of water between alcoholic beverages and before hitting the hay.