Spanish residents do not drink enough water, even in summer, says Europe-wide study

According to a research paper presented at Spain's Royal National Academy of Medicine, only 13% of men drink the recommended two-and-a-half litres of water a day, and only 22% of women drink their advised two litres.

The average man in Spain only drinks 1.7 litres of water, and a typical woman in the country consumes 1.6 litres.

This deficit may appear minor, but at just 20% - 400 millitres below the recommended amount for women, or half a litre for men – can cause tiredness and early-onset dehydration; in fact, it is said that even 'feeling thirsty' means the body is starting to dehydrate.

The human body is 65% water, meaning it needs constant rehydration to function.

Medics from the International Cathedra of Advanced Hydration Studies (CIEAH) recommend 70% to 80% of daily liquid consumption should be water, and in the 'drink pyramid', the next layer up would be fluids with no calories, such as green tea or fruit or herbal infusions, or water with a squeeze of lemon.

The third level should be drinks that provide some nutritional value, such as hot beverages with milk, and finally drinks with added sugar, although these are not necessary and occupy the same slot on the 'liquid pyramid' as refined sugar, sweets and desserts do on the 'nutritional pyramid'.

Compared with France, Spaniards do not get enough water despite longer periods of the year with a higher temperature – in Spain's northern neighbour, men drink 2.3 litres of water on average per day and women, 2.1.

Even then, men consume a below-average amount, but given that northern French climates are similar to those of southern England in winter, their need is not as great as those in Spain.

Acording to the European Food Safety Authority, however, drinking enough water is necessary year-round, even in the depths of winter – albeit more fluid is needed when it is hot, especially in children, pregnant or breast-feeding women, and the elderly.

The report, Beverage consumption habits among the European population: Association with total water and energy intake also compared Italians with Spain, and found the amount of water drunk per day is very similar in both countries.

Previous studies have claimed humans can count infusions, tea – even with milk – and non-sugary water-based drinks towards anything between a quarter and a half of their daily two litres, depending upon where the figures come from.

Extra water is needed to offset alcohol, which dehydrates, and although coffee has been found in recent years to bring health benefits – with claims it can even stave off dementia, as well as being high in fibre – this also reduces body fluid and cannot count towards the 'allowance'.

Few studies are available on the maximum recommended water intake per day, despite the fact that too much can be dangerous.

Excessive water consumption can cause light-headedness, dizziness, headaches and malnutrition due to vitamins and minerals being lost.

Dieticians normally advise judging by urine colour, which should be a very pale shade of straw, but not completely clear.