HYDRATION:
CONSUMER INFORMATION AND
MISINFORMATION
Catherine Collins RD FBDA
Principal Dietitian
St Georges Hospital London
Water ….
Is both a food and a nutrient
Acts as a solvent in which inorganic salts, organic
compounds and dissolved gases interact
Participates in metabolic reactions
Stabilises cell membranes
Maintains structure of macromolecules
Transports nutrients
Key agent in thermoregulation
Where is it?
70kg man
42 litres total body water
28 litres intracellular water
14 litres extracellular water
3.2 litres plasma
5-10% of water turnover daily
Total body water is tightly regulated within ±0.2%
of body weight each day
10.8 litres interstitial fluid
Sawka M et al; Nutr Rev 2005
Bossingham M et al; AJCN 2005
Water composition of tissues and organs
(% by weight)
% water by weight:
blood
heart
muscle
skin
liver
bone
adipose tissue
83%
79%
76%
72%
68%
22%
10%
Body has no provision for water storage
Water must be replenished by regular intake
A wide range of fluid intake will cause neither dehydration or overhydration in an individual
Dehydration: how soon a risk?
“humans cannot survive for more than a few days
without ingesting water in excess of solutes”
Adolph EF: Physiology of Man in the Desert. New York, Interscience
Publishing Co., 1947
“Humans can only survive for a few days without water”
discovery.com/survival/medical-conditions/dehydration.html
Terri Schiavo
Bulimic. Gastrostomy fed for 15 years for PVS
Feeding tube removed under Florida court order after
widespread media campaign of husband v parents
Survived a further 13 days without fluids
Died March 2005
Quill, T. NEJM 352:1630 1995
IN
FLUID BALANCE
‘Preformed’ water:
OUT
Obligate losses:
Urine output
Fluid as pure water
Faecal losses
Fluid in beverages
Insensible losses
Fluid from food
Influenced by:
Metabolic water:
Oxidation of macronutrients
Plasma osmolarity
defines fluid status
Environment temp
Humidity
Pyrexia
Breakdown of body tissue
Blood volume
Intensive care
gastric aspirates
enteral feed
iv infusions x 10
hourly fluid balance charts
central venous pressure
clinical biochemistry
clinical observation
drain/ wound losses
haemofilter
insensible losses
3rd space oedema
Proxy markers of hydration:
Urine volume:
There are limits to concentrating and diluting effect of the kidney:
Maximum urine osmolarity 900-1400 mOsm/l
Minimum urine omolarity 50mOsm/l
Concentrating ability of the kidney by 3.4mOsm/ l per year after the age of 20
(Manz and Wentz, 2003)
affected by insensible losses
Urine colour:
The darker the urine, the more concentrated it is
can be affected by non-hydrating factors:
vitamin B supplements can turn urine bright yellow
anthocyanins in blackberries, beetroot can turn urine brown/purple
Body weight
Thirst:
nature’s early warning, not sign of dehydration doom
stimulated by:
an increase in plasma osmolality
a decrease in plasma volume
a decrease in blood pressure
vasopressin is responsible for controlling water balance on a
daily basis
net fluid loss of as little as 1% of body weight will increase
plasma osmolality
thirst begins when the concentration of blood has risen by < 2%
a moderate fluid deficit of 7-10% is intolerable in cognisant
individuals
water deficit of 20% is life-threatening
Bossingham M et al; AJCN 2005
Heitz and Horne, 2001
Survey of 1000 office workers:
how can you tell if you’re dehydrated?
Feel thirsty
Headache
Dry mouth
Dark coloured urine
Fatigue or weakness
Dry Skin
Irritable
Hungry
Hangover
83%
75%
60%
60%
44%
39%
21%
21%
15%
Keep It ‘ Light’
campaign
51% of office workers drink between 1-4 cups of
tea a day
52% drank between 1-4 cups of coffee a day
79% drank no carbonated drinks at all
95% drank no enriched waters
Double the amount of “Younger” people are
drinking vitamin/juicy water compared to “older”
people
8% of the 16–24 and 25-34 age ranges drank these
only 4.1% of the 45+ age range drank these
NDNS 2008-9:
intake of drinks, grams per day
All: 11-18y
mean intake
All: 19-64y
mean intake
11-18y 19-64y
Fruit juice
160
134
48
42
Soft drinks
not low calorie
368
259
83
55
Soft drinks
low calorie
287
287
60
35
Tea, coffee,
water
523
1134
90
97
Milk, all types
283
372
% consumers
How many cups of tea to build
St Pancras International station?
15,000,000 man hours to build:
1,875,000 days
1,875,000 x 4 cups of tea = 7.5m
20% of builders state they don’t
drink tea at work
Total: 6 million cups of tea
68% found tea to have relaxing and stress relieving properties.
81% polled revealed the daily tea ritual helped them bond with fellow workers
70% believe tea breaks provide the opportunity to make important decisions
about work and keeps them focused on the job in hand.
online poll with the Federation of Master Builders, 2007
?
“We find that the main reason consumers are drinking so much
water is that it seems to alleviate stresses and tensions caused
by a lack of ritual in the workplace and in home life…..”
“In essence the ubiquitous bottles of water kept at hand by
countless millions have begun to resemble the security blankets
of childhood”
The rise and fall of bottled water, 2007 report
The ‘8 glasses of water’ myth
US National Academy of Sciences Food and Nutrition Board
RDA 1945 edition:
“A suitable allowance of water for adults is 2.5 liters daily in
most instances. An ordinary standard for diverse people is 1
milliliter for each calorie of food. Most of this quantity is
contained in prepared foods”
8 x 150ml = 1200ml
8 x 568ml = 4544ml
How much water a day?
70.4% quoted 6-8 glasses a day (1.5 – 2 litres)
78% of females and 58% of males chose this
response
14.8% stated 4-5 glasses a day
1.8% thought 2-3 glasses
0.6% thought 1 glass of water a day
7.1% had no idea
% Water by weight in foods
90
88
67
Canteloupe melon
Carrot
Chicken
% water by weight:
80% of fluid comes
from fluids
20% from foods
36
Cheese
7
Crackers
Mouthfeel mistakes
Many drinks are discounted by consumers as nonhydrating, even when evidence proves they are
This can be due to mouthfeel factors:
Tea and wine astringency: the drying sensation in the
mouth caused by unoxidised catechin polyphenols
Adhesion of substances to oral mucosa, stimulating feeling
of secretions: eg fat globules feel like mucus. Research
proves that milk does not increase nasal congestion or
nasal secretion volume.
Pinnock et al; Am Rev Resp Dis 1990
Misconception: all fluids are hydrating
Plain water v diet drinks: no difference in hydrating status
Grandjean AC et al. J Am Coll Nutr. 2003
18 healthy males
crossover study
Combination of four different beverages (caffeinated/
caffeine free; energy drinks/ plain drinks) did not differ in
effects on hydration
Grandjean AC et al. J Am Coll Nutr. 2000
CONCLUSION:
No significant difference between the regimens on indicators
of hydration status
The source of water doesn’t matter when the outcome is
hydration
the popular notion that caffeinated beverages cause
dehydration is a myth
Functional fluids:
Water
Flavoured or enriched water
Soup
Juice
Milk
Plant infusions – tea, coffee, herbal teas
Alcohol
Probiotic ‘shot’ drinks
Cholesterol lowering drinks
Health-promoting juices
Functional drinks:
don’t live up to the hype
claims included:
being able to reduce atherosclerosis; reduce
blood flow/pressure; slow the onset of
prostate cancer; improve erectile function;
improve circulation; reduce cholesterol
Advertising support information:
results of four tests of antioxidant potency (TEAC, ORAC,
DPPH, and FRAP)
Seeram et al; J Agric Food Chem 2008
Plasma antioxidant
concentration over time
Pomegranate juice:
ellagitannins and anthocyanins
Seeram et al; AJCN 1996
Tea:
theaflavones, catechins,
and phenolic acids
Warden et al; J Nutr 2001
Functional fruit drinks:
style over substance?
£1.39
beta-carotene
vitamin E
vitamin C
vitamin B6
vitamin B12
niacin
folic acid
pantothenic acid
calcium
potassium
85p+9p = 94p
these 10 +
vitamin D
vitamin K
biotin
iron
magnesium
zinc
iodine
copper
chromium
manganese
selenium
Worth overhydrating?
it is “difficult to believe
that evolution left us
with a chronic water
deficit that needs to be
compensated by
forcing a high fluid
intake."
Valtin, H. Am J Physiol 2002
Risk of water loading: fitness
25yo male admitted with GCS 5
via A+E
Found collapsed at home
Na 120 mmol/l (NR 135-145) on
admission
Urinalysis negative for drugs
Had joined a gym to tone up/
lose weight two months earlier
Fitness instructor had advised
him to drink 4-6 litres of water a
day and avoid ‘processed foods’
Adopted low energy diet with
moderate-to-low sodium content
Took 3 days to restore plasma
sodium safely
Naturally woke on day 2
Discharged home @ day 6
Risk of water loading: weight loss
Dawn Page, 54 year old mother of two
in 2008 awarded £800,000 in damages at the High Court after
nutritional therapist recommended radical detox diet that left her brain
damaged and epileptic
Warning signs of water intoxication were present and ignored by
therapist
Therapist still practices, promoting ‘healthy hydration diets’
Scientific Consensus Statement on Hydration and
Health
Water is essential for life.
Foods and beverages contribute varying amounts of water in the
diet.
Consuming a variety of non-caffeinated and caffeinated beverages,
including water, milk, tea, coffee, juice, soft drinks and sports drinks
can contribute to meeting the body’s water requirement.
Foods, including certain fruits, vegetables, soups and dairy products,
can also contribute to meet the body’s water requirement.
Appropriate beverage and food choices for an individual may vary on
the basis of energy, nutrient and water needs, as well as consumer
preference
J Am Coll Nutr 2007
“ I am not a heavy drinker.
I can sometimes go for hours
without touching a drop”
Noel Coward
1899-1973