The effects of dietary sodium intake on heat acclimation and thermoregulation during heat exposure
The effects of dietary sodium intake on heat acclimation and thermoregulation during heat exposure
The effects of dietary sodium intake upon the physiological heat acclimation responses were investigated over 8 days. In a 'temperate' study (25oC), two dietary sodium groups: MNa - 170 mmol/d (n=4); and MLNa - 170 mmol/d reduced to 70 mmol/d from day 4 (n=5), were examined. In two 'hot' investigations subjects were exposed to 25oC for 3 days, followed by 40oC (between 0800h and 1800h) for 5 days whilst dietary sodium intake was controlled as follows: HNa - 340 mmol/d (n=7); MNa - as above (n=9); LNa - 70 mmol/d (n=9); and MLNa - as above, n=8.
In the 'temperate' environment, sodium balance was restored by a reduction (P<0.05) in renal and sweat excretion. The MLNa group experienced a greater (P<0.05) loss of body weight and plasma volume than the MNa group. In the 'hot' environment sodium balance was maintained for the HNa and MNa groups, but LNa and MLNa experienced a deficit upon heat exposure, which tended to be smaller and restored more rapidly (P<0.1) in the LNa group. Plasma aldosterone increased upon heat exposure and this was potentiated (P<0.05) by a reduced sodium intake (LNa). The increase of aural temperature during exercise diminished as heat acclimation progressed, the magnitude of this change being smaller (P<0.05) for MLNa compared to all the other subjects (HNa, MNa and LNa).
These results support the hypothesis that aldosterone secretion in the heat is potentiated by prior reduction of sodium intake. Furthermore, thermoregulation is attenuated by a negative sodium balance. Thus dietary sodium manipulation has implications for heat acclimatisation and the avoidance of heat illness.
University of Southampton
Allsopp, Adrian John
d4120e46-4565-4365-b5a3-bf013e70c317
1997
Allsopp, Adrian John
d4120e46-4565-4365-b5a3-bf013e70c317
Allsopp, Adrian John
(1997)
The effects of dietary sodium intake on heat acclimation and thermoregulation during heat exposure.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The effects of dietary sodium intake upon the physiological heat acclimation responses were investigated over 8 days. In a 'temperate' study (25oC), two dietary sodium groups: MNa - 170 mmol/d (n=4); and MLNa - 170 mmol/d reduced to 70 mmol/d from day 4 (n=5), were examined. In two 'hot' investigations subjects were exposed to 25oC for 3 days, followed by 40oC (between 0800h and 1800h) for 5 days whilst dietary sodium intake was controlled as follows: HNa - 340 mmol/d (n=7); MNa - as above (n=9); LNa - 70 mmol/d (n=9); and MLNa - as above, n=8.
In the 'temperate' environment, sodium balance was restored by a reduction (P<0.05) in renal and sweat excretion. The MLNa group experienced a greater (P<0.05) loss of body weight and plasma volume than the MNa group. In the 'hot' environment sodium balance was maintained for the HNa and MNa groups, but LNa and MLNa experienced a deficit upon heat exposure, which tended to be smaller and restored more rapidly (P<0.1) in the LNa group. Plasma aldosterone increased upon heat exposure and this was potentiated (P<0.05) by a reduced sodium intake (LNa). The increase of aural temperature during exercise diminished as heat acclimation progressed, the magnitude of this change being smaller (P<0.05) for MLNa compared to all the other subjects (HNa, MNa and LNa).
These results support the hypothesis that aldosterone secretion in the heat is potentiated by prior reduction of sodium intake. Furthermore, thermoregulation is attenuated by a negative sodium balance. Thus dietary sodium manipulation has implications for heat acclimatisation and the avoidance of heat illness.
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Published date: 1997
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Local EPrints ID: 462993
URI: http://eprints.soton.ac.uk/id/eprint/462993
PURE UUID: 22f32674-722d-4a54-829b-a08c34ef6f4b
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Date deposited: 04 Jul 2022 20:35
Last modified: 16 Mar 2024 19:00
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Author:
Adrian John Allsopp
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