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Effect of fluid intake on skin physiology: distinct
differences between drinking mineral water and tap
water
S. Williams, N. Krueger, M. Davids, D. Kraus and M. Kerscher
Division of Cosmetic Sciences (FB 13), University of Hamburg, Martin-Luther-King Platz 6, D-20146 Hamburg,
Germany
Received 3 July 2006, Accepted 20 December 2006
Keywords: bioengineering, drinking, fluid, skin, water
1
Part of this study was presented as a poster on the 64th Annual Meeting of the American Academy of
Dermatology, 3–7 March 2006 in San Francisco, CA, USA.
Synopsis
It is generally stated that drinking plenty of water
has a positive influence on skin condition. How-
ever, there is no published scientific study that has
investigated this matter. The aim of our explorat-
ory ‘before-after’ study was to evaluate the in vivo
influence of drinking more than 2 L of mineral
water or ordinary tap water per day on skin physi-
ology. Ninety-three healthy subjects were included
in our prospective study. After an initial run-in
phase of 2 weeks to monitor individual drinking
habits, subjects had to drink 2.25 L day
)1
of either
mineral water (n¼53) or tap water (n¼40) for
4 weeks. Bioengineering in vivo measurements on
the volar forearm included sonographic evaluation
of skin thickness and density, determination of
skin surface pH, assessment of skin surface mor-
phology, and measurement of finger circumfer-
ence. Eighty-six subjects completed the study. In
the mineral water group measurements revealed a
statistically significant decrease in skin density.
Skin thickness increased slightly, albeit not at a
statistically significant level. However, when sepa-
rately analysing those individuals from the mineral
water group, who had routinely drunken compar-
ably little before the start of the study, their skin
thickness increased at a statistically significant
level. Skin surface pH remained almost unchanged
in the physiologically optimal range. In the tap
water group, skin density increased significantly,
while skin thickness decreased significantly. Skin
surface pH decreased at a statistically significant
level. While in the mineral water group finger cir-
cumference decreased significantly, measurements
in the tap water group revealed a statistically sig-
nificant increase. Objective skin surface morphol-
ogy did not change in any group. In summary,
drinking more than 2 L of water per day can have
a significant impact on skin physiology. The exact
effects within the skin seem to differ depending on
the nature of the water ingested. Randomized,
controlled, double-blind follow-up trials are war-
ranted to confirm the findings of our exploratory
pilot study.
Re
´sume
´
Il est ge
´ne
´ralement e
´tabli que boire abondamment
de l’eau influence l’e
´tat de la peau. Cependant,
aucune e
´tude scientifique publie
´e ne traite de ce
sujet. Le but de notre e
´tude exploratoire ‘avant/
apre
`s« a e
´te
´d’e
´valuer in vivo l’influence de
l’absorption de plus de 2 litres par jour d’eau
mine
´rale ou du robinet sur la physiologie de le
peau. 93 sujets en bonne sante
´ont participe
´a
`
Correspondence: Professor Martina Kerscher, MD,
Division of Cosmetic Sciences (FB 13), University of
Hamburg, Martin-Luther-King Platz 6, D-20146
Hamburg, Germany. Tel.: +49 40 42838 7235;
Fax: +49 40 42838 2592;
e-mail: martina.kerscher@uni-hamburg.de
International Journal of Cosmetic Science, 2007, 29,131–138
ª2007 Society of Cosmetic Scientists and the Socie
´te
´Franc¸aise de Cosme
´tologie 131
cette e
´tude prospective. Apre
`s une phase initiale
de 2 semaines pour contro
ˆler les habitudes indivi-
duelles des sujets pour se de
´salte
´rer, on leur a
demande
´de boire 2,25 litres par jour d’eau
mine
´rale (n¼53) ou d’eau du robinet (n¼40)
pendant 4 semaines. Les mesures biophysiques
in vivo sur la face interne de l’avant bras incluai-
ent l’e
´valuation sono graphique de l’e
´paisseur de
la peau et de sa densite
´,lade
´termination de son
pH de surface, l’e
´valuation de sa morphologie de
surface et la mesure de la circonfe
´rence du
doigt. 86 sujets ont termine
´cette e
´tude. Dans
le groupe traite
´par l’eau mine
´rale, les mesures
re
´ve
`lent des diminutions significatives de la densite
´
de la peau. Son e
´paisseur augmente le
´ge
`rement
mais a
`un niveau non-significatif. Cependant,
quand on analyse se
´pare
´ment les individus de ce
groupe, on constate que ceux qui habituellement
buvaient peu d’eau avant le de
´but de cette e
´tude
ont l’e
´paisseur de leur peau qui augmente de fac¸on
significative. Le pH de surface de la peau reste a
`
peu pre
`s inchange
´dans la fourchette physiologi-
que optimale. Dans le groupe traite
´a
`l’eau du
robinet, la densite
´de la peau augmente de fac¸on
significative, alors que son e
´paisseur diminue
significativement. Le pH de surface de la peau
diminue de fac¸ on significative. Alors que la cir-
confe
´rence du doigt du groupe qui a bu de l’eau
mine
´rale diminue de fac¸ on significative, celle du
groupe traite
´a
`l’eau du robinet augmente de fac¸on
significative. La morphologie de la surface de la
peau ne change pas, quel que soit le groupe. En
re
´sume
´, l’absorption de plus de 2 litres d’eau par
jour peut avoir un impact significatif sur la physio-
logie de la peau. Les effets au niveau de la peau
semble de
´pendant de la nature de l’eau inge
´-
re
´e. Des tests ale
´atoires contro
ˆle
´s en double aveu-
gle seront ne
´cessaires pour augmenter les re
´sultats
de cette e
´tude exploratoire.
Mots cle
´s: biophysique, boisson, fluide, peau, eau
Introduction
Depending on age, gender and body mass index,
approximately 45–70% of our body weight con-
sists of water with one-third of the total body
water being extracellular and two-thirds within
the intracellular compartment [1]. The movement
of water across cell membranes, which are freely
permeable to water, maintains the osmotic equilib-
rium between the two compartments. Our overall
body fluid balance is dependent on the input of
water on the one hand (e.g. from drinking, food
and metabolism) and the loss of water on the
other hand (e.g. through urine, faeces, skin and
lungs). The daily intake of appropriate amounts of
fluid is of uttermost importance for optimal func-
tion of the human body, as water is one of the
most vital macronutrients for the maintenance of
life [2,3]. Water plays an important physiological
role in temperature regulation, cardiovascular
function, transportation of oxygen and nutrients
to cells, removing waste, tissue structure mainten-
ance and many others [3]. It has been proposed
that fluid consumption in general and water
intake in particular can have an effect not only on
the risk of nephrolithiasis, but also on hyperten-
sion, hyperglycaemia in diabetic ketoacidosis and
constipation [4–13]. Regarding the potential effect
of water on cancer, the findings of epidemiological
studies investigating the relationship between fluid
intake and bladder or colon cancer are inconsis-
tent [14]. Two new reports confirm this general
statement [15–17].
The recommended daily water intake is usually
stated as 1 mL kcal
)1
of energy expended for
adults [18,19]. However, this recommendation is
often increased to 1.5 mL kcal
)1
to cover varia-
tions in conditions of energy expenditure and envi-
ronmental exposure. The Food and Nutrition
Board of IOM bases water needs on adequate
intake which is based on experimentally derived
intake levels that are expected to meet nutritional
adequacy for essentially all members of a healthy
population. The DRIs for water are 3 L day
)1
for
an adult man and 2.2 L day
)1
for an adult
woman [20], although there are other voices chal-
lenging the frequently encountered advice of
drinking about 2 L of fluid per day [21]. American
Food Consumption Surveys indicated that a signifi-
cant portion of the population may be chronically
mildly dehydrated and it has been stated that
humans, unlike other mammals, have a delay in
rehydration after fluid loss [2,22]. If a fluid deficit
is not replaced adequately, the human body will
eventually extract water not only from the blood,
but also from tissues including skin and mucous
membranes [23]. To restore the body’s fluid
losses, water is especially suited, as added ingredi-
ents such as carbohydrates, proteins and/or fat
themselves affect the body’s water balance. Con-
sumption of alcohol and caffeine-containing bever-
ª2007 International Journal of Cosmetic Science,29,131–138132
Effect of fluid intake on skin physiology S. Williams et al.
ages is not ideal as they promote an increased rate
of diuresis [24,25].
All three components of the skin – epidermis,
dermis, and subcutaneous fat tissue – participate
in water regulation, but the main water reservoir
within the skin is the dermis. However, it is the
stratum corneum water content which plays a
crucial role in maintaining many of the skin’s bio-
physical properties [26–29]. A healthy stratum cor-
neum consists of about 20–30% water and a
water content of less than 10–20% results in clin-
ical xerosis with reduced elasticity and increased
skin surface roughness [30]. Already more than
50 years ago, Irvin H. Blank’s pioneer work pub-
lished in the Journal of Investigative Dermatology
highlighted the critical role of the cutaneous water
content and its effect on the plasticity of the skin
[31]. Blank concluded that ‘…its (the skin’s) phys-
ical characteristics are a function more of its water
content than its lipid content’.
Despite increasing medical and public interest in
water intake, very little scientific data are available
on the effect of water consumption and systemic
hydration state on skin physiology. Although it is
generally said that drinking about 2 L water per
day is supposed to have a positive influence on
skin condition and skin quality, there is no con-
vincing study available supporting this statement.
The aim of our study was to evaluate the in vivo
influence of drinking 2.25 L mineral water or
ordinary tap water per day on skin physiology.
Subjects and methods
The study took place from January 2005 to July
2005 in the skin physiology laboratory of the Divi-
sion of Cosmetic Sciences, University of Hamburg.
A convenience sample of healthy volunteer men
and women aged 18–60 years with no systemic
illness or skin diseases was recruited. Exclusion cri-
teria included chronic and acute systemic diseases
(e.g. diabetes, viral infections, etc.), chronic and
acute skin diseases (e.g. eczema, psoriasis, urtic-
aria, etc.), pregnancy, breast feeding, and adminis-
tration of a systemic medication or application of
topical preparations within the test area. Ninety-
three subjects (67 women, 26 men) were included.
All volunteers continued living in their usual envi-
ronment. After an initial non-intervention run-in
phase of 2 weeks to monitor individual drinking
habits, subjects had to drink 2.25 L day
)1
of either
mineral water (n¼53; 38 female, 15 male) or
tap water (n¼40; 29 female, 11 male) for
4 weeks. The water was at room temperature. The
mineral water used was Staatlich Fachingen med-
ium
(Fachingen, Germany), a mineral-rich water
of pH 5.8 (measured inside the bottle) and a total
mineral content of 2711 mg L
)1
(see Table I for
details). The tap water used for this study (pH 7.0)
was supplied by Water works (Nordheide, Ger-
many; see Table I for details). Subjects in the
mineral water group were provided with 84 bot-
tles of Staatlich Fachingen medium
(each bottle
containing 0.75 L), of which they had to drink
three bottles per day. Subjects in the tap water
group measured the required amount of tap water
themselves after thorough instruction by one of
the investigators. As the taste of Staatlich Fachin-
gen
mineral water and tap water is very different
and thus a double-blind design would not have
been possible, we decided to conduct this pilot
study on an exploratory basis. Subjects were asked
to drink the water evenly distributed over the
whole day, to avoid excessive sun exposure and
intense physical activity and not to change their
dietary and daily life habits during the study per-
iod. To monitor their diet and fluid intake and
screen for potentially confounding influences, all
subjects led a food and drink diary over the entire
run-in phase and study period.
Bioengineering measurements were performed
on the volar forearm at the beginning (baseline)
and after 4 weeks drinking phase at randomized
Table I Mean values (mg L
)1
) of consumed mineral and
tap water
Mineral water (Staatlich Fachingen medium)
Sodium (in particular as NaHCO
3
) 560
Calcium 92.5
Magnesium 56.6
Hydrogen carbonate 1812
CO
2
4500
Tap water (Water works, Nordheide, Germany)*
Sodium 8
Calcium 42
Magnesium 2
Hydrogen carbonate 130
Potassium 1
Ion 0.03
Chloride 10
Sulphate 12
Nitrate 0.6
Fluoride 0.09
*Mean values, may vary slightly from year to year.
ª2007 International Journal of Cosmetic Science,29, 131–138 133
Effect of fluid intake on skin physiology S. Williams et al.
times during the day. All subjects were measured
in an air-conditioned room under standardized
conditions after an acclimatization period of at
least 20 min. Noninvasive in vivo measurements
included evaluation of (i) skin thickness and skin
density, (ii) skin surface morphology, (iii) skin sur-
face pH and (iv) finger circumference.
‘Skin’ thickness (thickness of dermis and epider-
mis) and skin density in the dermal compartment
were quantified with high-frequency ultrasonogra-
phy. The 20 MHz ultrasound scanner ‘DUB 20’
(Taberna pro medicum, Lu
¨neburg, Germany) was
used to obtain cross-sectional images of the skin
(B-mode), which were analysed digitally. Objective
evaluation of skin surface morphology was per-
formed using the ‘Visioscan VC 98’ (Courage &
Khazaka, Cologne, Germany). This instrument
allows a direct optical analysis of skin surface
topography through means of a high resolution
UVA-light video camera together with special soft-
ware. The following Visioscan parameters for skin
roughness und wrinkleness were evaluated: SEr,
SEsm, volume and C_R2. Skin surface pH was
measured using the ‘pH Meter PH 900’ (Courage
& Khazaka), which consists of a flat glass probe
combining measurement and reference electrode
in a single probe. The pH metre was calibrated
using standard buffers. Each time three pH mea-
surements were taken on the skin surface with the
mean of these three measurements being used for
subsequent calculations and statistical analysis.
Exact finger circumference was measured manu-
ally at the base of the right ring finger.
Statistical analysis was performed on an
exploratory basis using SPSS. All values are
expressed as mean ± standard error (SEM). Intra-
individual statistical comparison of values before
and after the 4-week drinking period was per-
formed descriptively through means of two-tailed
statistical tests (nonparametric Wilcoxon test
for paired samples). P£0.05 was considered
statistically significant (marked with * asterisk in
diagrams), P£0.001 was considered statisti-
cally highly significant (marked with *** in dia-
grams).
Results
Eighty-six subjects completed the study; 50 sub-
jects in the mineral water group (36 female, 14
male; mean ± SD: 31.8 ± 8.9 years) and 36 sub-
jects in the tap water group (26 female, 10 male;
mean ± SD: 31.8 ±8.7 years). Seven of the recrui-
ted 93 volunteers did not complete the study for
personal reasons or protocol violations. An over-
view of our results with exact P-values can be
viewed in Table II.
Skin density
In the tap water group, skin density increased
highly significantly from 47 ± 2.4 at baseline to
54 ± 1.9 after the 4-week drinking phase (Fig. 1).
In contrast, measurements in the mineral water
group revealed a significant decrease from
45 ± 2.15 before to 39 ± 2.49 at the end of our
study (Fig. 1).
Skin thickness
Skin thickness decreased in the tap water group at
a highly significant level (1122 ± 26.66 at base-
line vs. 1062 ± 22.8 after the drinking period, see
Fig. 2). In the mineral water group overall, skin
Table II Summary of results with
P-values (paired Wilcoxon test,
before vs. after the 4-week drinking
phase)
Parameter Mineral water group Tap water group
Skin density fl(P¼0.003) ›(P¼0.001)
Skin thickness ƒ(entire group: P¼0.187)
›(subgroup of subjects, who had
previously drunken little: P¼0.031)
fl(P¼0.001)
Skin surface pH fi(P> 0.05) fl(P< 0.001)
Finger circumference fl(P¼0.005) ›(P¼0.038)
Skin surface morphology
(SEr, SEsm, R2, and volume)
fi(P> 0.05) fi(P> 0.05)
›: statistically significant increase; ƒ: slight increase; fl: statistically significant decrease;
fi: no change.
ª2007 International Journal of Cosmetic Science,29,131–138134
Effect of fluid intake on skin physiology S. Williams et al.
thickness did not change at a statistically signifi-
cant level (slight increase from 969 ± 22.19 at
baseline to 977 ± 24.19 after the drinking period,
Fig. 2). However, when separately analysing those
individuals from the mineral water group, who
had routinely drunken comparably little before
the start of the study (<2 L day
)1
), their skin
thickness increased statistically significant
(P¼0.031).
Skin surface morphology
The mean values of all evaluated Visioscan skin
surface morphology parameters (SEr, SEsm, R2
and volume) did not reveal any statistically signifi-
cant alteration after drinking 2.25 L of mineral or
tap water daily for 28 days. However, in individ-
ual subjects in both groups, a considerable
smoothening of the skin surface texture was
observed (Fig. 3).
Skin surface pH
While the skin surface pH remained unchanged in
the physiologically optimal range in the mineral
water group (P> 0.05; see Fig. 4 for details), pH
significantly decreased in the tap water group
(5.19 ± 0.10 before vs. 4.79 ± 0.08 after the
drinking phase; Fig. 4).
Finger circumference
In the mineral water group the finger circumfer-
ence measured on the base of the ring finger
decreased significantly from 6.34 ± 0.09 to
6.16 ± 0.10 cm, while measurements in the tap
water group revealed a significant increase from
6.74 ± 0.10 to 6.81 ± 0.08 cm (Fig. 5).
Discussion
Adequate fluid intake, in particular from non-alco-
holic, non-caffeinated and non-caloric beverages
such as water has been shown to be beneficial
for various aspects of general health and to be
protective against diverse medical conditions
[2–7,9–13]. Despite the acknowledged physiologi-
cal significance of water to life and the general
claim that the consumption of ample amounts of
water is somehow beneficial for skin, very little is
known about the objective in vivo influence of
47
45
54
39
30
35
40
45
50
55
60
Mineral water Tap water
Skin density (arbitrary units)
Day 0
Day 28
**
***
Figure 1 Sonographic skin density before (baseline) and
after 28 days of drinking 2.25 L of mineral water
(n¼50) or tap water (n¼36) per day (**P£0.01,
***P£0.001).
0.8 %
–5.3 % ***
–6%
–4%
–2%
0%
2%
4%
6%
Change of skin thickness (%)
Mineral water
Tap water
Figure 2 Change in sonographic skin thickness after
28 days of drinking 2.25 L of mineral water (n¼50) or
tap water (n¼36) per day (***P£0.001, compared to
baseline).
Figure 3 Visioscan example (female
subject, 30 years of age) of skin sur-
face morphology on the volar fore-
arm before (a) and after (b) 4 weeks
of drinking mineral water.
ª2007 International Journal of Cosmetic Science,29, 131–138 135
Effect of fluid intake on skin physiology S. Williams et al.
water intake on different aspects of skin physiol-
ogy. With our study, we were able to demonstrate
that the consumption of more than 2 L of water
per day can indeed have a measurable influence
on skin physiology in healthy volunteers. Further-
more, the concrete effects seem to depend on the
exact nature of the ingested water. In detail, our
measurements revealed that mineral water causes
a significantly reduced finger circumference, a sta-
tistically significant decrease in sonographic skin
density and in those individuals, who had previ-
ously drunken comparably little a significantly
increased skin thickness. The observed changes
were higher in probands, who had previously
drunken comparably little. Pure tap water on the
other hand led to a significantly increased finger
circumference, significantly increased skin density
and significantly decreased skin thickness.
Not all of the objectively measured changes can
be explained straightforwardly, as the exact under-
lying mechanisms necessitate further research in
this area. However, the decrease in skin density
with increase in skin thickness in the mineral
water group might be due to an increased dermal
fluid content, for example though means of a sti-
mulation of cutaneous metabolism with improve-
ment of dermal water binding capacity. It is well
known that skin thickness does not only depend
on the amount of cells and extracellular fibres
such as collagen, but also on the interstitial fluid
content. High-frequency ultrasound studies have
confirmed that an increasing fluid content leads to
increased skin thickness with inverse changes in
cutaneous echodensity [32,33]. The fact that the
finger circumference did not rise, but actually
decreased at a statistically significant level, sug-
gests that our probands did not develop any clin-
ical oedema by tissue fluid retention. The
decreased finger circumference could also be a sign
of a general loss of body weight, which was not
measured in our study. Mineral water originates
from rain water, which over decades and centuries
trickled through various layers of rock in the
ground and thus acquired a mixture of minerals
from these stone layers. The mineral water we
used for our experiment was obtained from a
depth of 400 m. It has been shown that minerals
from mineral water are highly bioavailable and
well absorbed [34–36]. In contrast to mineral
water, ordinary tap water contains a much lower
content of minerals such as hydrogen carbonate
and magnesium (Table I). It has previously been
shown that consumption of mineral-rich water
can exert distinctively different effects on the skin
compared to water with low mineral content. In
patients with atopic eczema for example deep sea
water intake was able to improve clinical skin
symptoms and decrease serum IgE, IL-4, IL-13 and
IL-18, while distilled water intake had no effect
[37].
Objective assessment of skin surface profile did
not reveal statistically significant changes in any
group. This is interesting, as it is generally claimed
that drinking lots of water might reduce visible
signs of cutaneous ageing such as wrinkles and
lines. We could not confirm any objective improve-
ment of wrinkles or skin surface roughness after
increasing the daily water uptake to more than
2 L over 4 weeks. Whether there might be meas-
urable changes after a longer drinking phase
remains to be investigated in future research. In
this context, it would also be interesting to objecti-
fy the in vivo elasticity of the skin through means
of bioengineering measurements, e.g. cutometry.
6.34
6.74 6.81
6.16
4.5
5.0
5.5
6.0
6.5
7.0
7.5
Mineral water Tap water
Finger circumference (cm)
**
*
Day 0
Day 28
Figure 5 Ring finger circumference before (baseline) and
after 28 days of drinking 2.25 L of mineral water
(n¼50) or tap water (n¼36) per day (*P£0.05,
**P£0.01).
5.19
5.38
4.79
5.49
4.0
4.5
5.0
5.5
6.0
Mineral water Tap water
Skin surface pH
***
Day 0
Day 28
Figure 4 Skin surface pH before (baseline) and after
28 days of drinking 2.25 L of mineral water (n¼50) or
tap water (n¼36) per day (***P£0.001).
ª2007 International Journal of Cosmetic Science,29,131–138136
Effect of fluid intake on skin physiology S. Williams et al.
The skin surface pH is another important
parameter of skin physiology and influences var-
ious other factors such as composition of stratum
corneum lipids, hydration, epidermal barrier func-
tion and growths of physiological and pathological
micro-organisms. Even small alterations in stratum
corneum pH may cause significant modifications
at the molecular level. While after drinking min-
eral water, the skin surface pH remained in the
physiologically optimal range of approximately
5.5, the pH actually decreased at a statistically sig-
nificant level in the tap water group, although the
ingested tap water itself had a neutral pH of 7,
while the mineral water was with 5.8 within the
acidic range. The exact reason of the lower skin
surface pH after drinking ample amounts of tap
water remains unclear. However, these data are in
accordance with a study from Boelsma et al., who
described an inverse relationship between fluid
intake and skin surface pH in men [38]. It remains
to be elucidated why there was no decrease
observed when drinking mineral water, especially
after Boelsma et al. also described a significant
association between increased dietary calcium
intake and decreased skin surface pH in men [38].
However, there might have been confounding
influences of other minerals such as magnesium
with impact on, for example, regulation of prolifer-
ation, differentiation and desquamation of kera-
tinocytes [39], which potentially could have
prevented the pH from decreasing.
In conclusion, drinking more than 2 L of water
per day can have a significant impact on skin
physiology, the exact pathogenetic factors of
which remain to be revealed in future research.
Interestingly the effects within the skin seem to
differ depending on the nature of the water inges-
ted. Randomized, controlled, double-blind follow-
up trials are warranted to confirm the findings of
our exploratory pilot study. However, this is an
important new area of research into applied skin
physiology which will in future hopefully bring
out many more insights into the influences of
macro- and micronutrient intake on skin physiol-
ogy, especially as in recent years, commercial
offers of ‘functional foods’ claiming skin benefits
have increased enormously.
Acknowledgements
We are indebted to all participating subjects for
their cooperation and compliance throughout this
study. We would also like to thank Heike Bunt-
rock, Volker Braun, Sandra Schro¨ der, Alexandra
Bu
¨tehorn, Annette Schu
¨ler and Tatjana Schwill
for their dedication and diligence, which made the
successful execution and completion of this study
possible.
Part of this study was sponsored by Staatlich
Fachingen, Fachingen, Germany.
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