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The present study set out to determine whether morning spot urine samples can be used to monitor Na (and K) intake levels in South Africa, instead of the ‘gold standard’ 24 h urine sample.
Participants collected one 24 h and one spot urine sample for Na and K analysis, after which estimations using three different formulas (Kawasaki, Tanaka and INTERSALT) were calculated.
Between 2013 and 2015, urine samples were collected from different population groups in South Africa.
A total of 681 spot and 24 h urine samples were collected from white (n 259), black (n 315) and Indian (n 107) subgroups, mostly women.
The Kawasaki and the Tanaka formulas showed significantly higher (P≤0·001) estimated Na values than the measured 24 h excretion in the whole population (5677·79 and 4235·05 v. 3279·19 mg/d). The INTERSALT formula did not differ from the measured 24 h excretion for the whole population. The Kawasaki formula seemed to overestimate Na excretion in all subgroups tested and also showed the highest degree of bias (−2242 mg/d, 95 % CI−10 659, 6175) compared with the INTERSALT formula, which had the lowest bias (161 mg/d, 95 % CI−4038, 4360).
Estimations of Na excretion by the three formulas should be used with caution when reporting on Na intake levels. More research is needed to validate and develop a specific formula for the South African context with its different population groups. The WHO’s recommendation of using 24 h urine collection until more studies are carried out is still supported.
To assess the impact of a food-based intervention on blood pressure (BP) in free-living South African men and women aged 50–75 years, with drug-treated mild-to-moderate hypertension.
A double-blind controlled trial was undertaken in eighty drug-treated mild-to-moderate hypertensive subjects randomised to an intervention (n 40) or control (n 40) arm. The intervention was 8-week provision of six food items with a modified cation content (salt replacement (SOLO™), bread, margarine, stock cubes, soup mix and a flavour enhancer) and 500 ml of maas (fermented milk)/d. The control diet provided the same quantities of the targeted foods but of standard commercial composition and 500 ml/d of artificially sweetened cooldrink.
The intervention effect estimated as the contrast of the within-diet group changes in BP from baseline to post-intervention was a significant reduction of 6·2 mmHg (95 % CI 0·9, 11·4) for systolic BP. The largest intervention effect in 24 h BP was for wake systolic BP with a reduction of 5·1 mmHg (95 % CI 0·4, 9·9). For wake diastolic BP the reduction was 2·7 mmHg (95 % CI −0·2, 5·6).
Modification of the cation content of a limited number of commonly consumed foods lowers BP by a clinically significant magnitude in treated South African hypertensive patients of low socio-economic status. The magnitude of BP reduction provides motivation for a public health strategy that could be adopted through lobbying of the food industry by consumer and health agencies.
To develop and validate a short food-frequency questionnaire to assess
habitual dietary salt intake in South Africans and to allow classification
of individuals according to intakes above or below the maximum recommended
intake of 6 g salt day−1.
Cross-sectional validation study in 324 conveniently sampled men and
Repeated 24-hour urinary Na values and 24-hour dietary recalls were obtained
on three occasions. Food items consumed by >5% of the sample and
which contributed ≥50 mg Na serving−1 were
included in the questionnaire in 42 categories. A scoring system was
devised, based on Na content of one index food per category and frequency of
Positive correlations were found between Na content of 35 of the 42 food
categories in the questionnaire and total Na intake, calculated from 24-hour
recall data. Total Na content of the questionnaire was associated with Na
estimations from 24-hour recall data (r =
0.750; P < 0.0001; n = 328) and urinary Na (r = 0.152; P
= 0.0105; n = 284). Urinary Na was higher
for subjects in tertile 3 than tertile 1 of questionnaire Na content
(P < 0.05). Questionnaire
Na content of <2400 and ≥2400 mg
day−1 equated to a reference cut-off score of 48 and
corresponded to mean (standard deviation) urinary Na values of 145 (68) and
176 (99) mmol day−1, respectively (P < 0.05). Sensitivity and
specificity against urinary Na ≥100 and <100 mmol
day−1 was 12.4% and 93.9%, respectively.
A 42-item food-frequency questionnaire has been shown to have content-,
construct- and criterion-related validity, as well as internal consistency,
with regard to categorising individuals according to their habitual salt
intake; however, the devised scoring system needs to show improved
To determine the dietary intake, practices, knowledge and barriers to dietary compliance of black South African type 2 diabetic patients attending primary health-care services in urban and rural areas.
A cross-sectional survey. Dietary intake was assessed by three 24-hour recalls, and knowledge and practices by means of a structured questionnaire (n=133 men, 155 women). In-depth interviews were then conducted with 25 of the patients to explore their underlying beliefs and feelings with respect to their disease. Trained interviewers measured weight, height and blood pressure. A fasting venous blood sample was collected from each participant in order to evaluate glycaemic control.
An urban area (Sheshego) and rural areas near Pietersburg in the Northern Province of South Africa.
The sample comprised 59 men and 75 women from urban areas and 74 men and 80 women from rural areas. All were over 40 years of age, diagnosed with type 2 diabetes for at least one year, and attended primary health-care services in the study area over a 3-month period in 1998.
Reported dietary results indicate that mean energy intakes were low (<70% of Recommended Dietary Allowance), 8086–8450 kJ day−1 and 6967–7382 kJ day−1 in men and women, respectively. Urban subjects had higher (P<0.05) intakes of animal protein and lower ratios of polyunsaturated fat to saturated fat than rural subjects. The energy distribution of macronutrients was in line with the recommendations for a prudent diet, with fat intake less than 30%, saturated fat less than 10% and carbohydrate intake greater than 55% of total energy intake. In most respects, nutrient intakes resembled a traditional African diet, although fibre intake was low in terms of the recommended 3–6 g/1000 kJ. More than 90% of patients ate three meals a day, yet only 32–47% had a morning snack and 19–27% had a late evening snack. The majority of patients indicated that they followed a special diet, which had been given to them by a doctor or a nurse. Only 3.4–6.1% were treated by diet alone. Poor glycaemic control was found in both urban and rural participants, with more than half of subjects having fasting plasma glucose above 8 mmol l−1 and more than 35% having plasma glycosylated haemoglobin level above 8.6%. High triglyceride levels were found in 24 to 25% of men and in 17 to 18% of women. Obesity (body mass index ≥30 kgm−2) was prevalent in 15 to 16% of men compared with 35 to 47% of women; elevated blood pressure (≥160/95 mmHg) was least prevalent in rural women (25.9%) and most prevalent in urban men (42.4%).
The majority of black, type 2 diabetic patients studied showed poor glycaemic control. Additionally, many had dyslipidaemia, were obese and/or had an elevated blood pressure. Quantitative and qualitative findings indicated that these patients frequently received incorrect and inappropriate dietary advice from health educators.
To review data on selected risk factors related to the emergence of non communicable diseases (NCDs) in the black population of South Africa.
Data from existing literature on South African blacks were reviewed with an emphasis placed on changes in diet and the emergence of obesity and related NCDs.
Review and analysis of secondary data over time relating to diet, physical activity and obesity and relevant to nutrition-related NCDs.
Urban, peri-urban and rural areas of South Africa. National prevalence data are also included.
Black adults over the age of 15 years were examined.
Shifts in dietary intake, to a less prudent pattern, are occurring with apparent increasing momentum, particularly among blacks, who constitute three-quarters of the population. Data have shown that among urban blacks, fat intakes have increased from 16.4% to 26.2% of total energy (a relative increase of 59.7%), while carbohydrate intakes have decreased from 69.3% to 61.7% of total energy (a relative decrease of 10.9%) in the past 50 years. Shifts towards the Western diet are apparent among rural African dwellers as well. The South African Demographic and Health Survey conducted in 1998 revealed that 31.8% of African women (over the age of 15 years) were obese (body mass index (BMI) ≥ 30 kgm−2) and that a further 26.7% were overweight (BMI ≥ 25 to <30 kgm−2). The obesity prevalence among men of the same age was 6.0%, with 19.4% being overweight. The national prevalence of hypertension in blacks was 24.4%, using the cut-off point of 140/90 mmHg. There are limited data on the population's physical activity patterns. However, the effects of the HIV/AIDS epidemic will become increasingly important.
The increasing emergence of NCDs in black South Africans, compounded by the HIV/AIDS pandemic, presents a complex picture for health workers and policy makers. Increasing emphasis needs to be placed on healthy lifestyles.
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