Krüger, M

Loots, J.M.

van der Merwe, A le R.

English

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153298S.A. MEDICAL JOUR AL(SlIpplemelll-Sourh African Journal of IItrition)20 December 1969the thiamin from the column is complete or not. This iea y to determine where only one or two ample areconcerned, but with a large number of sample it is notpossible. ln one sample we found that even purificationon the Decalso column wa inadequate and in the oxida-tion step with potassium ferricyanide solution a browncolour developed which pa ed into the iso-butanol phase.We also found that some batches of Decalso, whenactivated according to the well-known procedure ofboiling in 3°~ acetic acid, gave low thiamin recoveries. Wethen had to use another method of activating the Decalso.Occa ionally a ample which give a clear extract, andwhich it therefore seem unnece ary to purify on theDecalso column, gives a higher blank reading than eventhe ample plus the added tandard (we use 20% hydro-chloric acid to de troy the thiochrome). Under these cir-cumstances purification on the colunm is again theanswer.The microbiological method for thiamin determinationappears to be difficult, and, as a consequence, few labora-tories employ this method.The chemical method for riboflavin assay cannot beused for highly coloured extracts, either because it isimpossible to obtain a result, or because the readings ob-tained are erroneous. Sometimes, even colourless extractsdevelop a brown colour during the permanganate oxida-tion step. Purification of the extract on a ftoridin-earthcolumn is one answer to the problem, but it is not a verysatisfactory solution for routine determinations. For suchsamples the microbiological method is the answer. Thegrowth of Lactobacillus casei is, however, stimulated byfat which must, therefore, be removed by ether extraction.We use this method as a routine for all coloured extractsor for colourle extracts giving questionable results withthe chemical method.Due to the fact that carotene and ascorbic acid are 0readily destroyed in the preparation of samples for analy-si , we doubt whether it is po ible to obtain absolutevalue for these two nutrients unle s extreme precautionsare taken in handling the am pIes before and during theweighing of an aliquot for analysis. Perhap one must,for nutritional purpo cs, accept the inevitable lower re-suIts which are obtained by analysis. The fact that somany different methods are available for the determina-tion of vitamin C stre e the difficulties which lie aheadfor the analy t who has to determine this vitamin. How-ever, some consolation lies in the fact that losses ofnutrients also occur when the people who eat thesefruits or plants peel or otherwi e proces them.CO ClUSIONThere are thus indeed many pitfalls in the path of theanalytical food chemist and accurate results can be ob-tained only if a number of methods for assaying a parti-cular nutrient in a foodstuff can be tried out and the bestone used. However, this is seldom, if ever, possible,especially in the case of edible wild fruits and plantswhere the amount of sample available is often barelysufficient for carrying out one determination for eachnutrient.SUMMARYFreeze-dried samples are used for analysis and the methods ofpreparation of samples for freeze-drying are discussed. Freeze-drying has obvious advantages but has also a few minor dis-advantages.Difficulties encountered in the determination of some of thenutrients are discussed.CHANGES IN THE BODY-WEIGHTS AND SUBSCAPULAR SKINFOLD THICKNESSES OFMEMBERS OF AN ANTARCTIC EXPEDITION*J. M. LooTS A D A. LE R. VAN DER MERWE, National Nutrition Research Institute, CSIR, Pretoria, AND M. KRUGER,Medical Officer, South African National Antarctic Expedition 1967 - 1968Changes in the body-weights of members of polar ex-peditions who wintered in the polar regions have beenreported by several workers.'--Wilson' found a seasonal variation in the body-weightsof members of the Norwegian-British-Swedish Expedition(1949 - 1952) to Queen Maud Land. The weights rose to amaximum during the winter months and decreased duringspring. The progressive decrease in body-weights duringspring coincided with an increase in outdoor activity, andwas apparent even before dog-sledging started. Wilsonattributed the weight increase during the polar night to thesedentary indoor life and did not regard it as a functionof cold-acclimatization.A imilar seasonal variation in body-weight was notedamong the members of the British North Greenland Ex-pedition, by Lewis et al.' These authors also maintainedthat the variations were inversely associated with the de-gree of activity, and were directly associated with anexaggerated positive calorie balance during periods ofreduced activity in winter.'Paper presented at the Congress of the South African utrition Society.Cape Town, April 1969.The average individual increase in body-weight of agroup of 13 men who were mainly engaged in sedentaryoccupations at the polar station Little America V, was3·8 kg. compared with a body-weight increase of 0·86 kg.in 13 normally active men out of doors.' The esti-mated food intake of the latter group was twice as greatas that of the indoor group. It appeared that, outdoors,the metabolic rate was increased not only by activity, butalso by the exposure to extremely low temperatures.Studies on calorie balances were carried out by Milanand Rodahl' on 9 scientists and 4 avy personnel duringthe International Geophysical Year in 1957 at LittleAmerica V in the Antarctic. The scientists were studied inMarch, June and September, and the avy personnelwere studied in September only. It was found that thecalorie intakes were on the whole in excess of actualcalorie requirements under Antarctic conditions. On thisregimen all the subjects gained weight during their Ant-arctic stay. These two workers thought that the increasedappetites may have been caused by psychological factor.Further, Lewis et al.' found that the increase in weightof men living in polar regions was associated with a20 De ember 1969 S.A. TYDSKRIF \HR GE EE KU'DE(Byvoegsel-Suid-A/rikaanse Tydskri/ vir Voeding)1533V 99SO3·373·232-432·972·422-432'182·743·092·232·52o LEFT(WITH A OARDYTAAEBEi IOct Nov Doethicknesses of theSubscapular skin/oldlIIeaSllrelllellTS (111111.)R lIIonThly L lIIonThly//lean SO //lean11·6 2·64 11·11·1 2·74 11·410·9 2-4 11·011·1 1·95 11·612·0 2·39 11·911·5 1·71 11·911·7 2·23 12·212·1 2·29 12·811·6 1·92 12·5120 2·26 12·412-4 1·75 13·1SO7·137-617·297·216· 97·317·697·679·219·198-46Body-weighT(kg.)74·475·076·576·677·777-877-777·676·77-777·4MonThlylIIeanfirst 6 months at the Antarctic ba e. The maximummean weight was attained in July when the mean increasein body-weight was 3·4 kg. For the remainder of the yearbody-weights remained approximately at the July level,except in October when they decreased by 1·0 kg. DuringTABLE I. MEB AP LAR KI FOLD THI KDE IAno ) OF 1E OURIMonThFeb.Mar.Apr.MayJun.Jul.Aug.Sep\.Qc\.ov.D~c.on theof the(1967 -0-------0 L.ft .id.)t------j( Right .id.,\"" ,I''''It., ..,/,'"-._---jt-..---74-075·078·i iF.b Mat I>fX May Aln All Aug SeptFig. 2. The mean monthly left and right sub capular skinfoldmen during their stay at the Antarctic base.:ECl..~76-..,oID~ ~ ~ ~ ~ M ~ ~ ~ ~ ~Fig. J. The mean monthly body-weights of the men during their stay at the Antarcticbase.increa e in the thicknes of the ubcutaneou fat. Theyfound a clo e positi e correlation between body-weight(adju ted to tandud heights) and kinfold thickne e.mea ured at each of 6 body ite. The increa es in the eparameter were du~ not only to exce calorie intake butal 0 to diminished activity.Indication of a positi e relation hip between sub-capular kinfold thicknesses and body-weights have al 0been found by one of us (v.d.M.).The above findings were reinve tigated by tudiebody-weights and skinfold thickne e of member8th South African ational Antarctic Expedition1968) to Queen Maud Land.MATERtALS AND METHODSThe 1967 - 1968 South African ational Antarctic Ex-pedition arrived at the SANAE base towards the end ofJanuary 1967, and departed in mid-February 1968. Body-weights and skinfold thicknesses of 12 members of theexpedition were measured regularly at monthly intervals.Control measurements could not be obtained beforethe departure of the team for the Antarctic, nor after itsreturn, owing to the fact that themembers of the team worked indifferent parts of the country,often widely separated.The men were weighed nakedonce every month at 0800 hours,after they had urinated. The samebalance (Sensitive, type 184, madeby C. W. Brecknell Ltd, England)wa used throughout the year, andbody-weights were determined towithin 0·05 kg.The ubscapular skinfolds weremeasured on or within 3 days ofweighing, dependent on the activi-ties of the member. A pair ofHarpenden skinfold calipers with ajaw pressure of 10 G/sq.mm. wasused.Skinfold thickness was measuredimmediately below the tip of theinferior angle of the scapula in adiagonal plane at an angle of 45°while the subject stood with hishands on his hips, and with hishoulders relaxed.Several readings were taken onboth the left and right sides oneach occasion. The average ofthree readings which correspondedto within ± 0·1 mm. was noted forconsideration.RESULTSThe result of the measurementsare hown in Table I and the meanvalues of the body-weights and thekinfold thicknesses are plotted inFigs. 1 and 2.A general increase in body-weight was apparent during the1534/00.A. MEDICAL JOUR ALtSupplel11elll-Solllh African Journal of utririon)20 Decem ber 1969the full year tay 10 ntarctica the a erage net gain inweight wa 3·0 kg.During the fir t 3 month at the ba e the ubscapularkinfold decreased in thickne s (Fig. I). During the re-mainder of the year, with the exception of October, theyincrea ed at a substantially con tant rate to values higherthan the initial thicknesses recorded in February 1967. Theskinfold measurement taken on the left side of the bodywere generally higher than tho e taken on the right ideoo significance could be attached to the decrea e in themean body-weights and kinfold thicknes e observed inOctober. as during thi month 4 of the men were undulyexposed to cold when their tent were destroyed in atorm.DISC SSIOThe steady gain in body-weight during the first half ofthe year confirmed the observations of other workers.'·'In the observations under di cu sion body-weight alsoattained a maximum level in the winter. A reduction inbody-weight in spring, which was observed with otherexpeditions,'" did not occur, the average weight of theSA AE members remaining approximately at the Julylevel. Except for .Iedging, the pattern of phy ical activi-tie remained essentially unchanged throughout the year.The SA AE ba e had been established for 5 years, waswell below the snow urface. and required much indoormaintenance work. During the polar night, outdoor worksuch a digging, restacking supplies, and feeding of thedogs was done at midday. In addition, a few membersparticipated in strenuous weight-lifting and physical-fitness courses during the winter months.It appeared that the food intake at regular meals wasless in the second half of the year than in the first, parti-cularly at breakfast and the midday meal. The decreaseof food intake during the main meals could be partiaUyattributed to the fact that as time elapsed the men atemore snacks between meals and at bedtime.In spite of a decrease in subscapular skinfold thickness,a general increase in body-weight was observed duringthe first 3 months at the base. It can be assumed that thisinitial increase in body-weight was due to an increase inmusculature.Before departure, the men were unaccustomed to hardphysical work. The environment was entirely new to them,and unnecessary energy was expended when they per-formed outdoor tasks before they had become accustomedto the irregularity of the snow surface.During this initial period it appeared that the amountof food taken at regular meals was very high. In spite ofthis, a loss of uperficial body fat occurred, which indi-cated that the high food intake was not excessive.During the following two months body-weights andskinfold thicknesses increased, indicating a more pro-nounced positive calorie balance.The subscapular skinfold thicknesses continued to in-crease during the second half of the year, although thebody-weights remained stationary. This phenomenon indi-cated a relative loss of muscle mass and a proportionateincrea e of body fat. The relative decline in muscle masscould be explained by assuming that the men becamemore efficient in performing their various task as theyear progressed. Thi~ would re ult in the expenditure ofle energy in the econd half of the year, a uming thatthe ame ta ks were undertaken.The high po itive correlation between changes in body-weight and kinfold thicknesses which was ob erved byLewis er al.' and indicated by one of u (v.d.M.-un-published data) was not confirmed by this study (r = 0·29,p > 5%).In spite of the reduced calorie intake during the secondhalf of the year, the body-weights remained stationarywhile the kinfold thicknesses increa ed. This can beascribed to the fact that the calorie intake wa till ex-ce ive in relation to alorie expenditure. Fatty depositswere thereby increased, as i indicated by the increasedkinfold thicknesses. However, the increase in the deposi-tion of subcutaneous fat could also have been augmentedas the result of an adaptive mechanism providing protec-tion against cold. That the latter was possible has beendemonstrated on members of the same team.'The qu-::stion of the discrepancy between the presentresults and those of Lewis et al.' remains unsettled, due toa Jack of detail on living and eating patterns. It is postu-lated that the variation in the calorie balances was greaterin the te t subjects of previous surveys than those of thepresent study. It could also be deduced that reducedcaloric intaf.e accompanied by increased fat deposition atthe expense of the muscle mass may be a necessary ex-pedient to provide additional insulation of the bodyagainst cold.SUMMARYThe body-weights and subscapular skinfold thicknesses of 12members of the 8th South African ational Antarctic Expedi-tion were recorded regularly once every month for 11 monthsduring 1967.A sharp increase in body-weight was observed during thefirst 5 months at the base. The subscapular skinfold thicknesses,however, decreased during the first 3 months in the Antarctic,which indicated that, although the apparent food intake washigh, it was not excessive. The increase in body-weight duringthese 3 months was ascribed to an increase in musculature.During the following 2 months the skinfold thicknessesstarted to increase, indicating a more pronounced positivecalorie balance.During the second half of the year the skinfold thicknessesincreased while the body-weights remained approximately atthe level attained in July. This phenomenon indicated arelative loss of muscle mass and a proportionate increase inbody fat. This can be ascribed to the fact that the calorieintake was excessive in relation to calorie expenditure. How-ever, the increase in the deposition of subcutaneous fat couldalso have been augmented as a result of an adaptive mechanismproviding protection against cold.This work was done under the auspices of the South AfricanScientific Committee of Antarctic Research and the Depart·ment of Transport, by whom it was financed. We wish tothank the Antarctic Medical Advisory Subcommittee ofSASCAR, for guidance; the members of the 8th South Africa.national Antarctic Expedition, whose co-operation made thiSstudy possible; and, Mrs L. M. Venter, of the Nationa~ ~e­search Institute for Mathematical Sciences, for the statistIcalanalysis.REFERENCESt. Wilson, O. (1960): Brit. J. Nutr., 14, 391.2. Lewis. H. E., Masterton, J. P. and Rosenhaum, S. (1960): Clin. Sci.,19. 551.3. Milan, F. A. and Rodahl, K. (1961): J. Nutr., 75, 152.4. Perlitsh. M. J, ielsen, A. G. and Stanmeyer, w. J. (l96t): J. Denl.Res., 40, 789.5. Wyndham, C. H. and I.oots, H. (1969): J. Appl. Phy,.,,1. (in the press)

Changes in the body-weights and subscapular skinfold thicknesses of members of an Antarctic expedition

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Changes in the body-weights and subscapular skinfold thicknesses of members of an Antarctic expedition

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