Water and Health

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Water and Health

• The effects of dehydration
• Hilary Forrester
• Research for Water UK

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• The fact that water is good for our health seems
  fairly obvious.
• Benefits were recognised by ancient physicians,
  eg Hippocrates.
• But the exact reasons why water keeps us healthy
  have not always been clear
• Pisanelli, physician 1586 had a curious
  explanation for the health benefits of chilled
  drinking water
• He noticed that a glass of cold water becomes
  clouded as if it were coated by expelled noxious
  humours and concluded that drinking cold water
  would have the same ability to remove toxic
  substances from the body.
• ------------------
• Water forms about 60 of body weight.
• One third of body water is outside the cells, eg
  blood, lymph etc.
• Two thirds is inside cells (intracellular)
• Water can move freely between these compartments
  because cell membranes are permeable to water.

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• Water gains and losses
• The main sources of water are
• fluid drunk and
• any water contained in food.
• Third source is metabolic water which is
  created by the body as a result of the breakdown
  (oxidation) of food components, eg fats, proteins
  and carbohydrates.
• Water losses occur via urine, faeces and
  evaporation from the skin and lungs.
• The amount lost from skin is about 920 ml per
  day,
• and from the lungs about 300 ml,
• depending on exertion rates, temperature and
  humidity.
• In order to remain healthy, water gains and
  losses must be balanced.

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• Daily water requirements
• Normal daily turnover of water is about 4 of
  total body weight in adults.
• For a 70kg adult this is about 2.5 to 3 litres
  per day under average conditions
• The recommendation from the Food Standards Agency
  is that average sized adults should drink about
  2.5 litres per day, (about 8 glasses) more in
  warm weather or if you exercise.
• Pregnant women need about an extra 30ml of water
  per day due to the needs of the fetus and
  amniotic fluid.
• Breastfeeding women need about an additional
  litre of water per day to replace that lost in
  milk.
• In children the daily turnover of water is about
  15 of total body weight. Compared to adults
  they have a larger surface area to body weight
  ratio and so are more likely to lose water by
  evaporation. In addition their kidneys are less
  efficient at concentrating urine so they cant
  save as much water as adults can.

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• Estimated actual water intakes of populations
• There arent many studies into peoples actual
  water intakes.
• But those that exist, clearly show that we dont
  drink enough.
• One study found that on average, people drink
  less than one-third of the recommended daily
  amount, ie 800ml instead of 2,500 ml !
• Another study showed average water consumptions
  to be as low as 1.5-1.7 litres per day.

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• Dehydration
• Defined as a 1 or greater loss of body weight as
  a result of fluid loss.
• This is mild dehydration, but even at this level,
  some physical functions are impaired.
• Dehydration in excess of 3-5 of body weight
  decreases endurance, strength and mental
  abilities and can cause heat exhaustion.
• Loss of more than 10 of body weight is life
  threatening.

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• Signs of dehydration
• Some early signs of dehydration are
• Sunken features particularly the eyes
• Headache
• Tiredness
• Loss of appetite
• Flushed skin
• Heat intolerance
• Light-headedness
• Dry mouth and eyes
• Loss of skin elasticity
• Reduced urine output
• Dark urine healthy urine should be very pale
  yellow, or straw coloured

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• Thirst
• The kidneys play a key role in regulating the
  amount of water in the body. They help maintain
  water balance by adjusting the concentration of
  urine.
• However, there is a limit to how much they can
  concentrate the urine because they require a
  minimum amount of water to excrete the bodys
  waste products.
• Thirst is triggered when the kidneys cannot save
  enough water to prevent an increase in plasma
  sodium levels and osmolality.
• But, the trigger of thirst only occurs at a
  point when a person is already dehydrated to a
  level of about 2 loss of body weight.
• So in other words Dont wait until you are
  thirsty before you drink because by that time
  you will already be suffering the effects of
  dehydration.
• Incidentally, tea, coffee and other caffeine
  drinks dont count towards your total daily water
  intake because caffeine is a diruetic which
  means that it causes the body to lose water. In
  fact it quenches your thirst without actually
  increasing your bodys water content. In one
  study the consumption of 750mg of coffee (over
  the course of a day) resulted in an overall
  decrease in total body water of 2.7

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• Adverse health effects of dehydration
• We have seen that we should be drinking about 2.5
  litres of water per day,
• and that it is very easy to become dehydrated.
• Also that the majority of people do not drink
  enough.
• But you may be thinking slight dehydration, I
  can cope with that, it only causes a headache or
  feeling a bit tired.
• This is where my research uncovered some quite
  startling findings about the potential damage
  that we could be doing to our health even by
  being only mildly dehydrated

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• Adverse effects of dehydration
• The research findings are detailed, so Im going
  to run through them quite quickly without quoting
  the authors, just to give you a flavour.
• Breast cancer
• Women who drink an adequate amount of water can
  cut their risk of breast cancer by 79
• Colon cancer
• The risk of developing colon cancer was reduced
  by 45 in women and 32 in men who were
  adequately hydrated.
• Prevention of this type of cancer is particularly
  important since research has shown that sufferers
  of colon cancer are more likely to go on to
  develop other forms of cancer.
• Bladder, kidney, prostate and testicular cancer
• are all associated with dehydration and research
  shows that adequate intake of water can protect
  against such cancers.
• The main theory about why increased water
  consumption has a protective effect against
  cancer is that because water balance is closely
  linked to cell metabolism, dehydration may
  adversely affect the cells ability to get rid of
  carcinogens.

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• Cardiovascular disease
• Controlling high blood pressure is important for
  the prevention of cardiovascular disease.
  Essential hypertension is usually viewed as being
  due to inappropriate excretion of sodium from the
  body (hence low salt diets). However, the body
  uses water to get rid of excess sodium and this
  function is impaired by dehydration. Adequate
  water intake is therefore also important in
  controlling hypertension.
• In addition, there is some evidence to suggest
  that the mechanical function of the heart may be
  affected by dehydration. Cells shrink when
  dehydrated and this may alter the distances
  between cardiac muscle cells and consequently
  affect the transmission of electrical impulses
  that stimulate contraction of the heart. In
  addition, cell shrinkage may disturb
  intracellular calcium levels which are also
  important for muscle contraction.
• Gallstones
• Inadequate daily water intake is associated with
  the formation of gallstones since they are more
  likely to if the bile is too concentrated.
• Oral health
• Saliva is important for good oral health, however
  saliva production is impaired by dehydration.

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• Pressure sores
• Particular important in older people.
  Dehydration leads to a loss of padding especially
  over bony points and hence increases the risk of
  ulcers forming.
• Falls in the older people
• Falls in older people can result in factures and
  even death. Dehydration is one of the causes of
  falls as it can lead to dizziness and fainting.
  Older people are particularly susceptible to
  dehydration because they have a diminished thirst
  response.
• Urinary tract
• Dehydration leads to the formation of
  concentrated urine and this is associated with
  the formation of urinary tract stones (kidney
  stones). Urinary tract stones can also increase
  the chances of getting urinary tract infections.
• Urinary tract infection can themselves cause
  serious damage to the kidneys, particularly in
  children. Drinking adequate amounts of water and
  emptying the bladder regularly can help protect
  against UTIs.

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• Pregnancy
• Inadequate intake of water during pregnancy can
  lead to a serious condition called
  oligohydramnios, where there is too little
  amniotic fluid surrounding the baby. This may
  result in too few nutrients and oxygen reaching
  the baby and prevent the baby turning to the
  cephalic position (head first) before birth. In
  very severe cases it can impair fetal lung
  development. Drinking adequate amounts of water
  has been shown to increase amniotic fluid volume
  in such cases.
• Skin
• The skin acts as a water reservoir and
  participates in the fluid regulation of the whole
  body. Skin thickness depends, among other
  things, upon its fluid content. In mild
  dehydration the skin may appear flushed (because
  it is thinner and blood vessels are more
  obvious). It may also be dry and loose due to
  loss of elasticity. Since loss of skin
  elasticity is also a sign of ageing dehydration
  may make your skin appear older than it actually
  is.
• The cosmetics industry would do just as well
  promoting drinking water as anti-ageing creams!

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• Sport and exercise
• There is a lot of money in sports research and
  hence a lot of data on the effects of dehydration
  on athletic performance.
• Briefly, mild dehydration of as little as a 2
  decrease in body weight can reduce aerobic
  endurance and cause increased body temperatures,
  heart rate, and perceived exertion
• At a dehydration level of only 2, physical
  performance is reduced by 20.
• Performance become substantial impaired when
  fluid losses exceed 5 of body weight.
• Swimmers are particularly susceptible to
  dehydration because water immersion depresses the
  thirst response.

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• Mental performance
• And finally dehydration can also affect mental
  performance to quite a surprising degree.
• Studies have shown that mental performance is
  adversely affected even at very low levels of
  dehydration (1 loss of body weight), but the
  effects become highly significant at a mere 2
  loss of body weight.
• Functions that were affected included, short-term
  memory, hand-eye motor coordination, symbol
  recognition and classification, arithmetic
  efficiency, attention and concentration.
• At greater levels of dehydration the decline in
  mental performance becomes progressively worse.

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• So we have seen that whilst it might seem obvious
  that water is good for our health, medical
  science is only just beginning to uncover the
  extent of its protective role.
• Dehydration has now been implicated in a
  surprisingly large number of conditions, some of
  which can be very serious, eg cancer.
• We are all aware of the dangers of driving when
  tired, but driving when dehydrated could be just
  as dangerous in view of the detrimental effects
  on mental performance.
• Future research will no doubt strengthen our
  knowledge of waters vital health protection
  role.
• So, now that you know the risks make sure you
  drink enough water aim for 2.5 litres per day,
  and dont wait until you are thirsty before you
  drink because by then it will be too late!