An investigation was carried out on 77 steelworkers, divided into two groups, at their work places. Group I (30 subjects) drank ad lib. a special
tea containing (17.1 mmol/l NaCl, 1.34 mmol/l KCl, 0.14 mmol/l Na2HPO4, and 0.57 mmol/l
vitamin C). Group II (47 subjects) drank ad lib. ordinary drinks (
water, mineral water, and
soda-water). Determination of water balance was performed seven times in all within 3 weeks. In groups I and II sweat losses were 5.1 +/- 1.2 kg and 5.0 +/- 1.3 kg, and intakes were 4.1 +/- 1.1 kg and 3.4 +/- 1.1 kg, respectively. When the intake period of the drinks with
salts was extended it was found that voluntary
dehydration decreased and amounted to 10% of sweat rate on the last day of the study. The voluntary
dehydration in group I was lower by 40%, the difference being highly significant in comparison with group II (P < 0.001). Data obtained from anamnesis and a questionnaire results showed smaller
fatigue, higher work capability and better subjective feelings in group I. Five subjects who previously had complained of recurrent
pain and
muscle spasm experienced disappearance of these symptoms. The importance of intake of water containing
salts in hot working conditions and their role in maintaining the water-electrolyte balance for normal physiological functions and subjective feelings were discussed.