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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 26, No 2, March/April 2015
60
AFRICA
Table 3 shows means (SD) and medians (25th and 75th
percentiles) of urine volume, urinary sodium, urinary potassium
and salt intake, according to gender. Compared to women,
men had significantly higher mean values for urine volume and
sodium-to-potassium ratio. There was no statistically significant
difference between men and women for urinary sodium and
potassium concentration and daily salt intake. The proportion of
participants exceeding the limit of 5 g/day of salt in the overall
population was 96.7%, without a gender difference.
Discussion
The purpose of this study was to determine salt intake so as to
assess the knowledge, attitude and behaviour regarding dietary
salt in a representative sample of medical students. The main
findings were a high average daily salt intake and inadequate
behaviour regarding dietary salt consumption in the majority of
participants.
The level of salt intake seen in this study was more than
two-fold the maximum internationally recommended limit,
7
indicating a salt-rich diet consumed by our participants. This
finding corroborates with that reported for the general population
worldwide.
7,17,19
Despite the known relationship between salt
intake and blood pressure levels, data on salt consumption based
on properly collected 24-hour urine samples are lacking for
young medical students.
Participants for this study were randomly selected from a
population of medical students and we used the ‘gold-standard’
24-hour urine method to assess salt intake. Their knowledge,
behaviour and attitudes on dietary salt intake were also assessed
using a standardised WHO questionnaire.
24
Salt intake was estimated using sodium concentration in
24-hour urine samples, and checks for completeness of 24-hour
urine collection were based on a combination of self-reported
urine loss, 24-hour urine volume measured at the laboratory, and
the recorded timing of urine collection. These criteria enabled us
to exclude 15% of the urine samples assumed to be incomplete
collections for the 24-hour period, with the majority of them
excluded due to incomplete timing of the urine collection.
The validated urine samples were therefore 80.4% of the total
collected.
Identifying the main source of dietary salt is important to
control high salt intake in the population. Therefore, behavioural
change in the use of salt is one of the strategies recommended
to reduce high salt intake in contexts where most sodium intake
comes from salt added during cooking or at the table at home.
7
From the survey, we found that almost all our participants
were aware of the health consequences of a high-salt diet, and
reported more frequently eating food with salt added during
cooking in their homes, and less frequently eating food with salt
added at the table. However, less than half the total participants
reported being aware of their high sodium intake, and the
Table 2. Knowledge, attitude and behaviour on dietary salt
Question
Total
n
(%)
Is salt added in cooking the food that you eat at the home?
Never
0 (0.0)
Rarely
1 (0.8)
Sometimes
0 (0.0)
Often
19 (15.4)
Always
103 (83.7)
How much salt do you think you consume?
Far too much
4 (3.3)
Too much
4 (3.3)
Just the right amount
69 (56.1)
Too little
31 (25.2)
Far too little
2 (1.6)
Don’t know
13 (10.6)
Do you add salt to food at the table?
Never
30 (24.4)
Rarely
46 (37.4)
Sometimes
40 (32.5)
Often
2 (1.6)
Always
5 (4.1)
Do you think that a high-salt diet could cause a health problem?
Yes
122 (99.2)
No
0 (0.0)
Don’t know
1 (0.8)
How important to you is lowering the salt/sodium in your diet?
Not at all important
2 (1.6)
Somewhat important
9 (7.3)
Very important
112 (91.1)
Do you do anything to control your salt or sodium intake?
Yes
56 (45.5)
No
63 (51.2)
Don’t know
4 (3.3)
If answered ‘yes’, what do you do to control your salt intake?
Avoid/minimise consumption of processed foods
4 (7.1)
Look at the salt or sodium labels on food
0 (0.0)
Do not add salt at the table
47 (83.9)
Buy low-salt alternatives
2 (3.6)
Buy low-sodium alternatives
1 (1.8)
Do not add salt when cooking
1 (1.8)
Use spices other than salt when cooking
0 (0.0)
Avoid eating out
1 (1.8)
Table 3. Mean and median values of urinary data according to gender
Variables
All
(
n
=
123)
Men
(
n
=
54)
Women
(
n
=
69)
p
-value
Urine volume (ml/d)
Mean
±
SD
1429.7
±
649.0 1579.0
±
738.5 1312.8
±
546.7 0.023
Median
(25th, 75th pc) 1320 (900, 1800) 1443.5 (915, 2152.5) 1250 (870, 1645)
U Na (mmol/l)
Mean
±
SD
94.8
±
34.4
99.2
±
37.4
91.3
±
31.7 0.221
Median
(25th, 75th pc) 95.2 (65.1, 116.0) 102.8 (63.7, 122.3) 92.6 (66.7, 113.8)
U K (mmol/l)
Mean
±
SD
33.9
±
13.6
33.0
±
15.9
34.7
±
11.6 0.496
Median
(25th, 75th pc) 33.3 (24.9, 42.9) 29.0 (22.0, 39.4) 34.7 (25.4, 43.5)
Na:K ratio
Mean
±
SD
3.0
±
1.2
3.3
±
1.3
2.8
±
1.0
0.029
Median
(25th, 75th pc) 2.7 (2.2, 3.5)
2.8 (2.3, 4.0)
2.7 (2.1, 3.3)
Salt intake (g/d)
Mean
±
SD
14.2
±
5.1
14.8
±
5.6
13.7
±
4.7
0.221
Median
(25th, 75th pc) 14.2 (9.7, 17.3)
15.4 (9.5, 18.3)
13.8 (10.0, 17.0)
High salt intake
(> 5 g/d),
n
(%)
119 (96.7)
53 (98.1)
66 (95.7)
0.439
SD, standard deviation; U Na, urinary sodium; U K, urinary potassium; Na:K,
sodium-to-potassium ratio; 25th, 75th pc, 25th and 75th percentiles.