A PILOT INVESTIGATON INTO THE EFFECT OrF A SHOT-TERM RESTRICTION IN SODIUM INTAKE ON BLOOD PRESSURE, SODIUM CHLORIDE TASTE THRESHOLD AND THE PROBLEMS ASSOCIATED WITH SUCH A DIETARY RESTRICTION Brian McLaughlin and John Kevany Human Nutrition Unit, Department of Community Health, Trinity Callege, Dublin. Summary A GROUP of 5 non-smoking males aged 20-30 years reduced their sodium intake over a period of two weeks. The subjects' salt taste thresholds, systolic and diastolic blood pressure were meas- ured over the trial period and compared with a control group of 5 similar males who also had the same variables meas- ured over a two week period. Diastolic pressure fell significantly in one of the control group over the two week period while three of the experimental group had significant decreases and a fourth had a decrease which almost reached significance. There was a significant decrease in systolic pressure in one of the control group subjects. Taste thresholds showed some fluctuations over the trial period in both groups and no clear trend could be found. Probiems with the low sodium diet were encountered in regards to food selection. Introduction The role of restricted sodium intake has long been recognised, Ambard et al (1904), Allen et al (1922). It is only in recent years that attention has been focused on the potential of a low sodium intake in the prevention of hypertension and in its correction. Several studies have presented evidence to support the theory that reduced sodium intake will lower blood pressure in mild hypertension. McGregor et al (1982), Beard et al (1982), Dobson (1981). However, it is not as yet clear whether low sodium inputs will produce any blood pressure reductions in normotensive subjects. Holly et al (1981) found in normotensives that there was no blood pressure reduction when sodium intake was reduced. Skrabal et al (1981) reduced sodium input in 20 normotensive males (age 21- 25), 10 of which had a family history of hypertension and the remaining 10 had no such history. A 5-11 mm Hg reduction in diastolic pressue was found in 12 of the subjects, 8 of which had a family hypertension history. A Lancet editorial (1980) recognised the need for such types of treatment but questions whether people reared on high sodium diet can become accustomed to a low sodium intake. Verdonk (1980) considers a reduction in daily sodium intake to be only a matter of training and within a fortnight such people will only have few difficul- ties. The question of salt taste threshold is clearly of importance in determining tol- erance of low salt diets and may also be important in determining habitual intake. Conteras (1978) reviewed the literature concerning the role of salt taste sensitivity in controlling hyperi(ension and gave thought to the idea that.;a ~hange in salt taste sensitivity may chan~e salt intake. However, he concluded that the studies of taste thresholds in hypertensives gave discrepent results. This study set out to examine, on a pilot basis, whether a reduction in sod- 399

A pilot investigaton into the effect of a shot-term restriction in sodium intake on blood pressure, sodium chloride taste threshold and the problems associated with such a dietary

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A PILOT INVESTIGATON INTO THE EFFECT OrF A SHOT-TERM RESTRICTION IN SODIUM INTAKE ON BLOOD PRESSURE, SODIUM CHLORIDE TASTE THRESHOLD AND THE PROBLEMS ASSOCIATED WITH SUCH A DIETARY

RESTRICTION

Brian McLaughlin and John Kevany

Human Nutrition Unit, Department of Community Health, Trinity Callege, Dublin.

Summary A GROUP of 5 non-smoking males aged

20-30 years reduced their sodium intake over a period of two weeks. The subjects' salt taste thresholds, systolic and diastolic blood pressure were meas- ured over the trial period and compared with a control group of 5 similar males who also had the same variables meas- ured over a two week period. Diastolic pressure fell significantly in one of the control group over the two week period while three of the experimental group had significant decreases and a fourth had a decrease which almost reached significance. There was a significant decrease in systolic pressure in one of the control group subjects. Taste thresholds showed some fluctuations over the trial period in both groups and no clear trend could be found. Probiems with the low sodium diet were encountered in regards to food selection.

Introduction The role of restricted sodium intake

has long been recognised, Ambard et al (1904), Allen et al (1922). It is only in recent years that attention has been focused on the potential of a low sodium intake in the prevention of hypertension and in its correction. Several studies have presented evidence to support the theory that reduced sodium intake will lower blood pressure in mild hypertension. McGregor et al (1982), Beard et al (1982), Dobson (1981). However, it is

not as yet clear whether low sodium inputs will produce any blood pressure reductions in normotensive subjects. Holly et al (1981) found in normotensives that there was no blood pressure reduction when sodium intake was reduced. Skrabal et al (1981) reduced sodium input in 20 normotensive males (age 21- 25), 10 of which had a family history of hypertension and the remaining 10 had no such history. A 5-11 mm Hg reduction in diastolic pressue was found in 12 of the subjects, 8 of which had a family hypertension history. A Lancet editorial (1980) recognised the need for such types of treatment but questions whether people reared on high sodium diet can become accustomed to a low sodium intake. Verdonk (1980) considers a reduction in daily sodium intake to be only a matter of training and within a fortnight such people will only have few difficul- ties.

The question of salt taste threshold is clearly of importance in determining tol- erance of low salt diets and may also be important in determining habitual intake. Conteras (1978) reviewed the literature concerning the role of salt taste sensitivity in controlling hyperi(ension and gave thought to the idea that.;a ~hange in salt taste sensitivity may chan~e salt intake. However, he concluded that the studies of taste thresholds in hypertensives gave discrepent results.

This study set out to examine, on a pilot basis, whether a reduction in sod-

399