J. Nutr.-1963-Consolazio-407-15

8/11/2019 J. Nutr.-1963-Consolazio-407-15

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Excretion of Sodium , Potassium , M agnesium and Iron

in Human Sweat and the Relation of Each to

Balance and Requirements

C. FRANK CONSOLAZIO, LEROY O. M ATOUSH, RICHARD A. N ELSON,

RICHARD S. HARDING AND JOHN E. CA NHAM

U . S. Arm y M edical R esearch and N utrition Laboratory,

F itz sim on s G en era l H osp ita l, D en ve r, C olo ra do

In two recent studies on calcium (Con-

solazio et al., '62a) and nitrogen (Conso-

lazio et al., '62b) excretions in sw eat, it w as

observed that sweat losses were fairly

high, accounting for 18 to 30% of the total

calcium excretion and 13 to 18% of the

total nitrogen excreted, of men exposed

to 100 Fenvironm ental tem peratures. A s

a result of these fairly high excretions of

calcium and nitrogen in sweat, other m in

eral contents were also investigated in

relation to intake, balance and require

ments. These minerals included sodium ,

potassium , magnesium , phosphorus and

iron. In addition, the daily osm olarity w as

also computed from the freezing point of

the sw eat.

A considerable amount of data is avail

able in the literature on the concentration

of minerals in sweat, but very few, if

any, of these studies have been related to

balance and requirements. Many values

for the sodium , potassium , magnesium ,

iron and phosphorous concentrations in

sweat have been thoroughly reviewed by

Schwartz ('60) and Altman and D ittmer

('61). Sodium values ranged from 13 to

104 mEq/liter of sweat (30 to 240 mg/

100 m l), potassium from 2.3 to 16.0 m Eq/

liter (9 to 62 mg/100 ml), magnesium

from 0.04 to 4.5 mg/100 ml, iron from

0.10 to 5.3 m g/hour, and phosphorus from

9 to 43 ug/100 ml of sweat.

The fairly high nitrogen and calcium

excretions in sweat reported previously

(Cons ola zio e t a l., '6 2a ,b ), e sp ec ia lly d urin g

profu se sw eatin g conditions, indicate that

m in eral losses in sw eat m ay be sufficiently

important to warrant further investiga

tion. It is the opinion of investigators

(M itchell and Hamilton, '49; M itchell

and Edman, '62) that sweat losses should

be included as part of the total daily out

p ut in b ala nc e stu die s, o th erw ise e rro ne ou s

conclusions can be draw n.

An attempt was made to design a study

to answ er som e of the follow ing questions :

(a) what are the mineral losses in rela

tion to high sweat rates; (b) what are the

mineral losses in relation to the daily in

take and their effect on balance studies;

(c) what are the m ineral losses in rela

tion to mineral allowances and require

ments; and (d) do these sweat losses de

c re as e a fte r a cc lima tiz atio n?

EX PER IME NTA LDE SIGN

A study was conducted for a total of 32

days on three healthy young men. It con

sisted on an 8-day prelim inary period (1)

at 24 C(75 F) and 50% relative hum id

ity (RH), four 4-day periods at 37.8C

(100F) and 70% RH (1, 3, 4 and 5),

and an 8-day recovery or adjustment

period at 24 C(75 F) and 70% RH (6),

and sweat rates were computed daily for

each man. Sweat samples were collected

during morning and afternoon periods.

Since the quantities of sweat collected

during the control and adjustm ent periods

at 75F were lim ited, no values will be

reported in this paper. The daily physical

activity was constant and consisted of

only 30 minutes of moderate activity on

the bicycle (ergom eter), the rem ainder of

the day being spent in sedentary type ac

tivities. When the men left the test area

(evening) no m oderate to heavy activities

were perm itted, the test subjects being

closely supervised by the M etabolic W ard

personnel, durin g these hours.

R eceived for publication O ctober 3 1962

J . NDTK IT ION . 9: '6 3

7


2/9

8

CON SOL A Z IO , M AT OUSH , N E L SO N , H A R DING A ND CA NHA M

A ll of the test phases w ere perfo rmed in

an environmental chamber from 8:00 AM

to 11:30 AM and from 12:30 PM to

4:30 PM daily with the exception of each

fourth evening when the men slept over

night in the hot room at 100F. At this

time sweat samples were collected for 2-

to 5-hour intervals to determine w hether

the sw eat concentrations of the minerals

were decreased with longer exposure to

the heat.

The menus consisted of 4 diets that

were rotated during each period. The

diets supplied 8.7 gm of sodium, 2.49 gm

of potassium, 343 mg of magnesium, 23.4

mg of iron and 1.41 gm of phosphorus per

day. All food w as offered and consumed

at regular mealtimes and no other food

was permitted during the day. Salt was

the only mineral available ad libitum and

was measured for each man during each

period.

Chemical analyses of the food com

posites, urine, feces and sweat were per

fo rmed fo r s odium , po tas sium (Baird, '5 3) ,

magnesium, iron, and phosphorus (Con-

solazio and Johnson, '60). In addition

freezing points (Fiske, '54) were per

formed on the daily sw eats.

Sweat rates were measured for each

period using the method of Adolph et al.

('4 7). These sweat rates w ere determ ined

by measuring w eight changes during the

morning and afternoon periods and then

adjusting fo r w ater intake, and for w ater

loss in urine and feces. (Gaseous ex

chang es o f re spiratio n co ntributes a small

quantity, which usually consitutes less

than 1 o f the observed decrease in body

weight.) Sweat samples were collected

daily during both the morning and after

noon periods for a total of 7.5 hours.

These sample s w ere co llected in po ly ethy l

ene bags which covered one whole arm,

and were representative for the entire

period each subject w as in the chamber.

The arm and the bag w ere rinsed w ith dis

tilled w ater and dried before each collec

ti on pe riod be gan.

Complete urine and fecal collections

w ere made for 4-day periods coinciding

w ith the repetition of the 4 diets utilized.

Mineral balances w ere computed on each

man for each period, based on the inclu

sion and exclusion of the minerals in

sweat as a source of mineral loss.

RESULTS

The chemical analyses of the various

minerals performed on the cell free sw eat

are presented in quantities/100 ml of

sweat (table 1). This table also includes

the means and standard dev iatio ns duringthe 7 .5 hours' ex po sure to 1 00 tempera

tures. A fter the firs t 4 day s o f acclim atiza

tion to heat, the potassium excretion in

sweat ranged from 25 to 28 mg/100 ml,

magnesium excretion ranged from 0.61 to

0.64 mg/100 ml, iron from 25 to 39 ug/

100 ml, and phosphorus from 0.11 to 0.26

mg/100 ml of sweat. The mean excretion

rate in milligrams per hour for the same

exposure periods ranged from 78-106 mg

fo r po tassium, 2 .0 -2 .4 mg fo r magne sium,

0.11-0.16 mg iron, and 0.45-0.81 mg/

hour for phosphorus. The sodium excre

tion in sw eat w as quite variable due to the

fact that salt intake was not controlled(table 1). The daily 7.5-hour mineral ex

cretion and total osmolarity in sweat for

16 consecutive days at 100F are com

pared in table 2.

On three separate occasions when the

men spent 2 4 hours co ntinuously at 1 00F,

it w as observed that the sw eat rate and the

so dium, potassium and iron excretio ns in

TABLE 1

Concentration of minerals in sweat;1 mean for three men for 16 days of exposure at 100F 1961 study

Days exposure

S odium, mg/100 ml

Potassium , mg /1 00 ml

M agnesium, mg/100 ml

Iro n, f ig /1 00 m l

Pho spho rus , mg/ 10 0 m l1 -4 33 7

183.02

84 72.1

0.70 0.29

36.4 21.2

0 .1 55 0 .1 19 5-8 11 3

67.5

25 12.6

0.61 0.21

33.2 16.0

0 .2 60 0 .1 5 29 -1 21 18

99.4

25 6.3

0.61 0.16

38.6 21.1

0 .1 09 0 .0 87 13 -1 64 20

296.3

28 9.7

0.64 0.28

25.0 20.9

1C on cen trat ion /100 m l of sw eat as collected an d cen tr ifu gea. C hem ical an aly sis on su p ern atan t f lu id

ean SD.


3/9

MI NERALS I N SWEAT AND MI NERAL BALANCE

9

TABLE 2

Sweat excr etion of miner al s and total osmolar ity; mean dai ly excr etion of thr ee men dur ing

daily 7.5-hour exposures at 100F temperatures

Day s o f

exposure

100F12345678910111213141516Sodiummg111766210353525002379469626233050164440507090765033806310Potassi

1 -1.86Cfor each 1000 mil lio smole s.

TABLE 3

D iurnal variations of minerals in sw eat, excretion per hour; mean for three men (1961 study)

Days at

100Fhours10-3.54.5-8.59.5-1515-23

(sleeping)0-3.5

(next day)Sodium7-8mg375844123544162611-12mg234289159058294514-15mg94418371331262841Potassium7-8mg5

14-15' //74651015285mg1081048259115Magnesium7-8

1-124-15mg3.22.02.21.8mg2.32.11.82.2mg2.82.21.52.27-

1Zero time was 8 AMdai ly .

TABLE 4

Sodium bal ance, wi th and without sweat losses; mean for thr ee men for

16 consecutive days 1961 study

Day s at

100-F1-45-89-1213-16Intakemg/day10229872987292Urinemg/day2600217023602440OutputFecesmg/day105819594BalanceSweat1mg/

excludedmg/day+

7524+

6478+

6274Sweat

includedmg/day+

1740+

3290+

3434Sweat

as of

total

output68.158.553.7

1 Inc lude s o nly so dium ex cre ted in sw eat w hile in env iro nm ental chamber fo r 7 .5 -ho ur period.

D uring three o ve rnig ht ex pos ure s to 10 0 Fthe so dium ex creted in sw eat ave rag ed 9 02 mg /hour

or 14 .88 gm/the 16 .5 -hour period.

2Ex tra sal t f rom shaker not re co rded .

sw eat w ere decreased by approximately

50 during the sleeping hours. On aris

ing and being active again, the morning

sweat mineral losses were again at a

higher level (table 3).

Mineral balances, during the 7.5-hour

collection period, w ere computed for so

dium, potassium, magnesium, iron and

phosphorus. These balances w ere calcu

lated with and without the inclusion of


4/9

41 0

CONSOLAZIO, MATOUSH, NELSON, HARDING AND CANHAM

TABLE 5

P ota ssiu m b ala nce, w ith a nd w ith out sw ea t lo sses; m ea n fo r three m en fo r

1 6 con secu tive d ays 19 61 stud y)

Day s a t100-F1-45-89-1213-16Intakem

n. ill l2493249324932493Urinemg/day2150240018601820Fecesmg/day898310372BalanceSweat1mg/day1776588596796Sweat

excludedmg/day+

254+

10+

530+

601Sweat

includedmg/day-1522-578-66-195Sweatas

% of

total

output44.319.123.433.5

1 Includes only potassium excreted in sw eat for 7.5 hours in environmental chamber. D uring the

three overnight exposures to 100 ',he potassium excreted in sweat averaged 84 mg/hour for a

total of 1.39 gm for the 16.5-hour period.

TABLE 6

M ag nesiu m b ala nce, w ith a nd w ith ou t sw ea t lo sses; m ea n fo r th ree m en fo r

1 6 co nsecu tiv e da ys 1 96 1 stu dy)

Days at

100F1-45-89-1213-16Intakemg/day343343343343Urinemg/day25.723.623.121.9OutputFecesmg/day10711210276BalanceSweat1mg/day17.215.217.717.8

excludedmg/day+

210.3+

207.4+

217.9+

245.1Sweat

includedmg/day+

193.1+

192.2+

200.2227.3Sweat

as % of

total

output11.510.112.515.4

1 Includes only magnesium excreted in sweat for 7.5 hours in environmental chamber. During

the three overnight exposures at 100F, the magnesium excreted in sweat averaged 1.82 mg/hour

for a total of 29.7 mg during the 16.5-hour period.

TABLE 7

Iron balance, w ith and without sweat losses; m ean for three m en for

1 6 co nsec utive d ay s 19 61 stu dy)

D ays at

100'F1-45-89-1213-16Intakemg/day23.423.423.423.4OutputUrine1

Fecesmg/day

mg/day20.519.421.121.5BalanceSweat2mg/day1.010.961.070.86Sweat

excludedmg/day+

2.9+

4.0+

2.3+

1.9Sweat

includedmg/day+

1.9+

3.0+

1.2+

1.0Sweat

as % of

total

output4.74.74.83.9

1Neg li gi bl e o ut pu t.

* Includes only iron excreted in sweat for 7.5 hours in environmental chamber. During the three

overnight exposures at 100F, the iron excreted in sweat averaged 0.102 mg/hour, a total of 1.68 m g

for the 16.5-hour exposure.

TABLE 8

P ho sp ho ru s ba la nce, w ith a nd w ith ou t sw ea t lo sses; m ea n fo r th ree m en fo r

16 co nsecu tive d ays 1 96 1 stud y)

Days at

100F1-45-89-1213-16IntakeFoodmg/day1405140514051405Urinemg/day770891896868OutputFecesmg/day9.87.88.78.1Sweatmg/day9.96.13.4Bala

625+

500+

497+

529Sweat

as % of

totaloutput1.20.70.4


5/9

MINERALS IN SWEAT AND MINERAL BALANCE

41 1

T A B L E 9

To ta l da ily excretio n o f minera ls; mea n fo r three men 19 61 study

T o t a l e x cr e ti on

7.5 h ou rs 16.5 h ou rs1

7.5 h ou r s 16.5 h ou r s

Sw e at e x cr e ti on

as ofto ta l e x cre t ion

7.5 h ou rs 16.5 h ou rs

SodiumPotassiumMagnesiumIrongm4.510.94> /17.00.98gm14.91.39mg29.71.68mg/hour6011252.30.131mg/hour902841.80.10262.830.

i M inerals ex creted in sw eat d u r ing th e regu lar 7.5-h ou r d aily ex p osu re an d for th ree ev en in gs

w h en th e m en sp en t th e rem ain in g d aily t im e (16.5 h ou r s) at 100 F.

the sweat m ineral losses. The sodium bal

ance varied due to the variation in daily

intake (table 4). The potassium balance

was positive when the sweat losses were

excluded but were negative when the

sweat losses were included, averaging

- 1522, - 578, - 66 and - 195 mg/day

fo rh e 4 con se cu tiv e 1 00Fp erio ds (t ab le

5). M agnesium balances did not vary

greatly w hen com paring the inclusion and

exclusion of the sweat losses, due to the

extremely high retention of magnesium

(table 6). Iron balances, even though

they were reduced by approxim ately one-

half, were still on the low positive side

(table 7). The quantities of phosphorus

in sweat were so small in comparison to

the total daily intake that they did not

change the highly positive balances sig

nificantly (table 8).

The sweat losses during the 7.5-hour

exposure periods are presented as per

centage of the total excretion in tables 4

8. Sodium in sweat accounted for 54 to

68% , potassium for 19 to 44% , magne

sium for 10 to 15% , iron for 4 to 5% and

phosphorus for 0.4 to 1.2% of the total

excretion of each respective element. If

one included an average value for m in

eral losses in sweat during the rem aining

16.5 hours of the day when the men were

exposed to 100F temperature (days 7,

11 and 15) the total daily mineral excre

tion in sweat was approximately doubled

(table 9).

DI SCUSS ION

It has been mentioned previously that

sweat collections were made daily using

the polyethylene bag, that covered one

whole arm . The arm sweat which was

representative for the entire period, was

assumed to be comparable to the total

body sweat. But a question arises w hether

this is a valid comparison. It has been

shown by some investigators (Dill et al.,

'38; Johnston et al., '50; and Ladell, '48)

that the various constituents of arm sw eat

are reasonably representative of the total

body sweat. Van Heyninger and Weiner

('52) on the other hand are in disagree

ment, observing that the arm sweat is

more concentrated than the rest of the

body. Another factor to be considered is

w hether the arm bag w ill cause depression

of the sweat rate. Collins and Weiner

('62) have observed a rapid depression

of sweat gland activity in the forearm

when the arm was covered w ith a sweat

collection bag . D ata are presented show ing

that the sweat rate is considerably less in

humid environments than in dry condi

tions. These authors believe that the

sweat depression in the arm bag may have

been due to obstruction of the sweat

gland ducts, by the excessive skin hydra-

tion.

Sodium is essential for the norm al func

tioning of the body since it contributes to

the acid-base balance of the body and

since it is responsible in large measure,

for the total osm otic pressure of the extra

c ellu la r flu id s (N atio na l R ese arc h C ou nc il,

'58). M inimal allowances have not been

established by the NRC due to lack of suf

ficient information, but it has been ob

served that a normal American intake

will range from 3 to 7 gm of sodium/day.

It has been reported (NRC, '58) that un

der normal conditions 90 to 95% of the


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41 2

CON SOL A Z IO , M AT OUSH , NE L SON , H A R DING A ND CA NHA M

sodium intake is excreted in the urine and

usually sweat sodium losses are not con

sidered in sodium balance studies, under

these conditions. Sodium can be excreted

in sweat in fairly large quantities to dis

turb hom eostasis and as a result seriously

impair the economy of the organism

(Schwartz, '60). Sodium excretion in

sw eat is variable, being dependent on phys

ical activity, acclim atization, adrenal cor

tic al a ctiv ity , e nv iro nm en ta l temp era tu re ,

humidity and body temperature. Under

conditions of this study, where the daily

sodium intake ranged from 8 to 10 gm /

day, the losses of sodium in sweat ac

counted for more than 50% of the total

daily excretion. Since the salt intake was

ad libitum it was not possible to study the

full effects of acclim atization on sodium

excretion, but it was observed that the

sweat sodium decreased appreciably dur

ing the first 12 days exposure to heat,

which is in agreement with data reported

in the literature. The sodium balance was

highly positive by more than 3 gm even

w ith the inclusion of the losses in sweat.

Potassium has been shown to be a re

quired nutrient and is one of the principle

basic elem ents in intrac ellular fluid, being

found in greatest quantities within the

cell. It is also a very im portant extracellu

lar fluid constituent since it can influence

muscular activity, notably the cardiac

m uscle, and can affect the excitability of

the nerve tissue . M uscle protein repletions

may demand an additional potassium in

take of 2.7 mEq for each gram of nitro

gen. The NRC ('58) has not established

minimal allowances for potassium but a

norm al U nited S tates diet u sually c ontains

from 2.4 to 4.5 gm . An intake between

0.8 to 1.3 gm of potassium/day would be

very close to the daily recom mended allow

ances (N RC , '58 ). P otassium deficienc ies,

manifested by muscular weakness, in

creased nervous irritability, mental dis-

orientation and cardiac irregularities, can

be produced by gastrointestinal losses, by

renal losses or by low potassium intake,

and are frequently accompanied by meta

bolic alkalosis. The data in the literature

are too lim ited to draw any specific con

clusions on the relationship of potassium

excretion in sweat and the total daily po

tassium excretion, as they m ay be related

to such variables as body temperature,

acclimatization to extreme heat, sweat

rate and physical exercise. In some in

stances appreciable quantities of potas

sium in sweat have been reported

(Schw artz, '60; A ltm an and D ittm er, '61)

in m an, living and exercising in extrem ely

hot environm ents, but D avidson et al. ('59)

and the British M inistry of Agriculture

('59) believe that sweat potassium losses

are usually negligible, in relation to the

daily intake. The potassium excreted in

sweat accounted for approximately 30%

of the total daily excretion. If the potas

sium losses in sweat for the remainder of

the day were included, these losses could

account for up to 50% of the total daily

excretion. The potassium balances, w ith

the addition of the sw eat potassium losses,

were all on the negative side.

Even though magnesium is a very im

portant cellular constituent, there is very

lim ited information in the literature in

relation to magnesium metabolism in the

body. It is known that for normal func

tion, cardiac and skeletal muscles and

nervous tissue depend greatly on a proper

balance betw een calcium and m agnesium

ions. Magnesium will replace the cal

cium in bone salts when there is a cal

cium deficiency, but m agnesium in excess

w ill inhibit calcification. Even though the

NRC has set up no minimal allowance, it

has been calculated that the daily magne

sium intake of adults in the United States

is between 250 to 350 mg/day (NRC, '58).

Unlike sodium and potassium , the m ag

nesium excretion in sw eat did not decrease

appreciably during acclim atization. The

sw eat accounted for approxim ately 12.5%

of the total daily excretion of m agnesium

but when the overnight sweat losses are

included, this excretion could account for

25% of the total. This sweat loss did not

greatly affect the magnesium balance,

s in ce th e d aily re te ntio n w as a pp ro xim ate ly

200 mg/day. This retention may be in

part compensation for the negative cal

cium balance reported in the same study

(Consolazio et al., '62a), or it may be that

the estimate of the minimal daily allow

ances of 250 to 300 m g of m agnesium /day

may be too high. Under the conditions of

this study, the magnesium loss in sweat

is relatively unim portant, but in studies on


7/9

MI NERALS I N SWEAT AND MI NERAL BALANCE

4

low m agnesiu m intak es, these losses should

be conside red.

Even though a few studies have been

perform ed on the relationship of sw eat

losses of iron to the daily requirem ents,

the quantitativ e im portance of the cutane

ous iron losses is still a disputed issue. It

is the feeling of one group (Foy and K ondi,

'57) that the inclusion of the integ um ental

iron losses m ay possibly increase the

iron requirem ents by as m uch as 50

under non-stress co nditions, and that these

ex ces siv e sw e at lo sses in h ot e nv iro nm e nts

m ay be a contributing factor in the dev el

opm ent of iron def icient anem ias. On the

other hand H ussain and Patw ardhan ('59)

feel that the body tends to conserv e iron

in the anem ia state by reducing the losses

through the sk in. Dubach et al. ('55) us

ing radio iron as a tracer observ ed that

during m ax im um sw eating in norm al hu

m ans, f rom 0.33 to 0.52 m g of iron m ay

be lost in sw eat in a 24-hour period.

Com parisons have been m ade on the

cell-rich an d cell-f ree sw e at iro n (H ussain

and Patw ardhan, '59) show ing that the

cell rich portion is f rom 3 to 10 tim es m ore

concentrated than the cell f ree sw eat. It

w as concluded that the m ajor portion w as

present in the products of cellular desqua

m ation; and since activ e therm al sw eating

is alw ay s accom panied by cell desquam a

tion, the loss of iron in sw eat could be of

far greater im portance than is generallysupposed.

Iron loss v ia the sw eat am ounted to ap

prox im ately 1 m g during the exposure

period, w hich w as 4.5 o f the total daily

ex cretion. If the iron losses in sw eat dur

ing the rem ainder of the day are included,

they could account for as m uch as 11

of the total d aily ex cretion.

W ith a fairly high iron intak e of 23.4

m g/day , the iron balance w as positiv e by

approx im ately 1 m g/day w hen the sw eat

iron losses w ere included. T hese sw eat

iron ex cretions are f airly hig h, especially

if one includes the ev ening losses.

Prior to the beginning of the study the

test subjects w ere on leav e at hom e for a

three-w eek interv al. H ence, it is assum ed

that they w ere eating a norm al diet w hich

m ay have been com parable to the experi

m ental diet. W ith the ex ception of potas

sium all of the m ineral balances w ere posi

tiv e. U nder these conditions, the subjects

could hav e been increasing body m ass, but

this m ay not be probable since the sub

jects lost a total of 1.05 kg during the ex

perim ental periods at 100 F (table 10).

TA BLE 10

Body weight changes; mean change for three men

for each 4-day period 1961 study

D ay s M ean change in w eight

Controleriod100F

periodRecovery

period1-45-81-45-89-1213-161-45-8kg/period+

0.14+

0.49+

0.17-0.21-0.64-0.37+

0.77-0.15kg

/day+

0.08-0.066+

0.08

It has been observ ed that sodium and

potassium excretion in sw eat decreased

appreciably af ter acclim atiz ation w hich is

in agreem ent w ith data reported in the

literature (B ass et al., '55; D ill et al., '38).

On the other hand neither iron nor m ag

nesium excretion in sw eat decreased ap

p re ciab ly d urin g ac cl imatiz atio n.

T he data suggest that the ex cretion of

sodium , potassium and iron in sw eat are

quite appreciab le, especially under condi

tions that produce prof use sw eating. T hesem ineral losses m ust be considered in bal

ance studies otherw ise balance and daily

m inim al allow ance data w ould be greatly

m isinterpreted. S tudies in the literature

w here equilibrium w as attained , under

conditions of profuse sw eating, should be

reevaluated.

T he concentration of phosphorus in

sw eat w as found to be the low est of any

of the m inerals analy z ed in this study ;

av eraging less than 0.5 of the to tal daily

e xcretio n. T h ese v alu es, w h ich ag ree f airly

w ell w ith data from other inv estigators,

are relativ ely unim portant in com puting

balan ce s tu die s.

T he total osm olarity of sw eat (f reez ing

poi nt) was d ec re as ed af te r ac climatiz atio n

ranging f rom 116 to 141 m illiosm oles af ter

the acclim atiz ation period. T hese v alues

are com parable to other v alues f or hum an

sw eat reported in the literature, and re-


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41 4

CONSOLAZIO, M ATOUSH, NELSON, H ARDING AND CANHAM

viewed by Adams et al. ('58). These

authors concluded that the osmotic con

centration of sw eat is hypotonie to serum

and as the sweat increases, the osmotic

c on ce ntra tio n u su ally d ec re ase s.

SUMMARY

The results of this study show that a

considerable quantity of sodium , potas

sium , magnesium and iron are lost in

sweat of men during 16 consecutive days'

ex posure to environm ental tem perature s o f

100F. During a 7.5-hour collection

period, the sweat excretions averaged

0.601 gm/hour for sodium , 0.125 gm/

hour for potassium , 2.3 mg/hour for mag

nesium and 0.13 mg/hour for iron. Very

small quantities of phosphorus are ex

creted in sweat, averaging between 0.45

to 0 .8 1 mg/h ou r.

In the past, w ith the exception of so

dium , very few investigators have recog

nized the fact that the mineral losses in

sweat could be appreciable and as a result

these losses have, all too frequently, been

neglected in com puting m ineral balance.

This could result in m isinterpretation of

the data, especially under conditions of

profuse sweating. The total m ineral loss

should include the mineral loss in sweat.

This in turn would help in estim ating m ore

realistically the m in im al d aily allow ances

o f m ine ra ls .

ACKNOWLEDGMENTS

W e w ish to express our sincere appreci

ation and thanks to the following mem

bers of the Bioenergetics D ivision SSG J.

B . Torres, SP5 O . Tarnowieckyi, SP5 G. L.

B eai, SP4 E. E. Preston, SP4 S. D . W ilkins,

SP5 L. J. Maland, SP4 W . E. Hendricks

and SP4 L. E. Jones.

W e are particularly indebted to the Uni

versity of Colorado and Dr. Norman F.

W itt, and are especially thankful for the

full cooperation of the test subjects, w ith

out whom this study could never have been

performed. They include Levi M . Yoder,

W arren E. Kennel and Fred J. B icker.

Our sincere thanks to Gerhard J. Isaac

of the Statistics Branch, for setting up the

experimental designs and schedules in

t he se expe rimen ts .

L ITERATURE CITED

Adams, R., R . E . Johnson and F. Sargent, II.

1958 T he osm otic pressure (freezing point)

of human sweat in relation to its chemical

co mpo sitio n. Q uart. J. E xp . P hy sio l., 4 3: 2 41 .

A dolph, E . F ., and A ssociates 1947 P hysiology

o f M an in th e D esert. In terscien ce P ub lishe rs,

In c., N ew Y ork .

Altman, P. M ., and D. S. D ittmer 1961 Bio

logic al Handbooks . B lood and o th er body f lu id s.

F ederatio n o f A merican S ocieties fo r E xp eri

m en tal B io lo gy , W ash in gton , 2 5, D . C .

B aird A ssociates 1953 Flam e P hotom eter M an

ual, e d. 3 ., C amb ri dg e, Ma ss ac hu se tts .

Bass, D. E ., C . R. Kleeman, M . Quinn, A. Hen-

schel and A. H. Hegnauer 1955 M echanism

of acclim atization to heat in m an. M ed., 34:

323.

Collins, K. J., and J. S. W einer 1962 Observa

tions on arm bag suppression of sw eating and

its re la tio ns hip to th erm al sw ea tin g fa tig ue .

J. P hysiol., 161: 538.

Consolazio, C. F., and R. E . Johnson 1960 Bio

chem ical and dietary procedures. U . S. A rm y

M edical Research and N utrition L aboratory

R ep . n o. 2 42 . D env er, C olo rad o.

Consolazio, C. F., L . O . M atoush, R . A . N elson,

L . R. Hackler and E. E . Preston 1962a Cal- '

cium in sweat and its possible relation to cal

cium requirem ents. J. N utrition, 78: 78.

Consolazio, C . F., R . A . N elson, L . O . M atoush,

R. S. Harding and J. E . Canham 1962b The

nitrogen excretion in sw eat and its relation to

n itro ge n b ala nc e a nd re qu ireme nts . U . S . A rmy

M edical Research and N utrition L aboratory

R ep . n o. 2 70 , D en ve r, C olo ra do .

D av id so n, S ., A . P . M eikeljo hn an d R . P assm ore

1959 Human nutrition and dietetics. The

W illiam s and W ilkins C om pany, Baltim ore,

Maryland.

D ill, D. B., F. G. Hall and H. T . Edwards 1938

Changes in composition of sweat during ac

clim atization to heat. Am . J. Physiol., 123:

412.

D ubach, R., C. V. M oore and S. Callender 1955

S tu die s in iro n tra ns po rta tio n a nd m eta bo lism.

IX. The excretion of iron as measured by the

iso to pe tech niqu e. J. L ab. C lin . M ed ., 4 5: 59 9.

Fiske Associates 1954 The Fiske Osmometer

I ns tr uc ti on Manual, Bos ton, Ma ss .

Foy, H., and A . Kondi 1957 Anemias of the

tropics in relation to iron intake, absorption

a nd lo sse s d urin g g rowth , p re gn an cy a nd la cta

tion. J. Trop. M ed. Hyg., 60: 105.

Hussain, R., and V . N. Patwardhan 1959 Iron

content of therm al sweat in iron-deficiency

anaem ia. L ancet, 276: 1073.

Johnston, F. A ., T . J. M cM illan and E. R. Evans

1950 P erspiration as a factor influencing the

requirem ents for calcium and iron. J. N utri

tion, 42: 285.

Ladell, W . S. S. 1948 The measurement of

chloride losses in the sw eat. J. P hysiol., 107:

465.

M in istry o f A gric ultu re , F ish erie s a nd F oo d 1 95 9

Manual of Nutrition, ed. 5. Her Majesty's

S ta ti one ry Of fi ce , London, Eng land.


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MI NERALS I N SWEAT AND MI NERAL BALANCE 4 5

M itchell, H . H., and M . Edm an 1962 N utr - anees, pub. 589, N ational A cadem y of S ci-

tional signif icance of derm al losses of nutri- enees N ational R esearch Council, W ashing-

ents in m an, particularly of nitrogen and m in- ton, D. C.

erais. A m . J. C lin. N utrition, 10: 162. S chw artz , I. L . 1960 Ex trarenai regulation w ith

M itchell, H . H., and T . S . Ham ilton 1949 T he special reference to the sw eat glands. In M in-

derm al ex cretion under controlled env iron- eral M etabolism , an A dvanced T reatise, eds.,

m ental conditions of nitrogen and m inerals C . L . Com ar, and F. B ronner. A cadem ic Press,

in hum an subjects w ith particular reference to N ew Y ork .

calcium and iron. J. B iol. Chem ., 178: 345. v an Heyninger, R ., and J. S . W einer 1952 A

N ational R esearch Council, Food and N utrition com parison of arm -bag sw eat and body sw eat.

B oard 1958 R ecom mended Dietary A llow - J. Phy siol., 136: 395.

J. Nutr.-1963-Consolazio-407-15

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