Provitamin A carotenoids in biofortified maize and their retention during processing and preparation of South African maize foods.

Provitamin A-biofortified maize may contribute to alleviating vitamin A deficiency (VAD), in developing countries. However, processing the maize into food products may reduce its provitamin A content. The aims of this study were to determine the composition of provitamin A carotenoids in biofortified maize varieties as well as to assess their retention during processing of popular maize foods consumed in KwaZulu-Natal, South Africa. The non-provitamin A carotenoid, zeaxanthin and the provitamin A carotenoids, ß-cryptoxanthin, and trans and cis isomers of ß-carotene, and other unidentified trans and cis isomers of ß-carotene were detected in varying concentrations in the maize. Milling provitamin A-biofortified maize into mealie meal resulted in a higher retention of carotenoids compared to milling into samp. The highest retention of provitamin A carotenoids was observed in cooked phutu and cooked samp, whilst cooking into thin porridge resulted in the lowest retention of provitamin A carotenoids. In phutu, 96.6 ± 20.3% ß-cryptoxanthin and 95.5 ± 13.6% of the ß-carotene were retained after cooking. In samp, 91.9 ± 12.0% ß-cryptoxanthin and 100.1 ± 8.8% ß-carotene; and in thin porridge, 65.8 ± 4.6% ß-cryptoxanthin and 74.7 ± 3.0% ß-carotene were retained after cooking. This study demonstrates that provitamin A retention in maize is affected by the cooking method (and hence cooked food form) and therefore cooking methods that result in a good retention of provitamin A need to be identified and recommended.

Effect of Nutrition Education on Knowledge, Complementary Feeding, and Hygiene Practices of Mothers With Moderate Acutely Malnourished Children in Uganda.

BACKGROUND: Inappropriate infant and young child complementary feeding practices related to a lack of maternal knowledge contributes to an increased risk of malnutrition, morbidity, and mortality. There is a lack of data regarding the effect of nutrition education on maternal knowledge, feeding, and hygiene practices as part of a supplementary feeding intervention targeting infants and young children with moderate acute malnutrition in low-income countries like Uganda. OBJECTIVE: To determine whether nutrition education improves knowledge, feeding, and hygiene practices of mothers with infants and young children diagnosed with moderate acute malnutrition. METHODS: A cross-sequential study using a pretest-posttest design included 204 mother-infant pairs conveniently sampled across 24 randomly selected clusters. Weekly nutrition education sessions were embedded in a supplementary porridge intervention for 3 months. Mean scores and proportions for knowledge, feeding, and hygiene practices were determined at baseline and end line. The difference between mean scores at the 2 time points were calculated with the paired t test analysis, while the proportions between baseline and end line were calculated using a z test analysis. RESULTS: Mean scores for knowledge, dietary diversity, and meal frequency were higher at end line compared to baseline (P < .001). Handwashing did not improve significantly (P = .183), while boiling water to enhance water quality improved (P < .001). CONCLUSION: Nutrition education in conjunction with a supplementary feeding intervention targeting infants and young children with moderate acute malnutrition improved meal frequency, dietary diversity and water quality.

Diet and blood pressure in South Africa: Intake of foods containing sodium, potassium, calcium, and magnesium in three ethnic groups.

OBJECTIVES: We investigated whether habitual intakes of sodium (Na), potassium, magnesium, and calcium differ across South African ethnic groups, assessed the proportion of Na intake, which is discretionary, and identified which food sources were the major contributors to Na intake. METHODS: This was a cross-sectional study of 325 black, white, and mixed ancestry hypertensive and normotensive subjects. Three repeated 24-h urine samples were collected for assessment of urinary Na, and three corresponding 24-h dietary recalls were administered by trained fieldworkers. Blood pressure and weight were measured at each visit. Secondary analyses were performed on existing dietary databases obtained from four regional surveys undertaken in South African adults. RESULTS: Mean urinary Na excretion values equated to daily salt (NaCl) intakes of 7.8, 8.5, and 9.5 g in black, mixed ancestry, and white subjects, respectively (P < 0.05). Between 33% and 46% of total Na intake was discretionary, and, of the non-discretionary sources, bread was the single greatest contributor to Na intake in all groups. Ethnic differences in calcium intake were evident, with black subjects having particularly low intakes. Urban versus rural differences existed with respect to sources of dietary Na, with greater than 70% of total non-discretionary Na being provided by bread and cereals in rural black South Africans compared with 49% to 54% in urban dwellers. CONCLUSION: White South Africans have higher habitual intakes of Na, but also higher calcium intakes, than their black and mixed ancestry counterparts. All ethnic groups had Na intakes in excess of 6 g/d of salt, whereas potassium intakes in all groups were below the recommended level of 90 mM/d. Dietary differences may contribute to ethnically related differences in blood pressure.

Evolution of epidemiologic methods and concepts in selected textbooks of the 20th century.

Textbooks are an expression of the state of development of a discipline at a given moment in time. By reviewing eight epidemiology textbooks published over the course of a century, we have attempted to trace the evolution of five epidemiologic concepts and methods: study design (cohort studies and case-control studies), confounding, bias, interaction and causal inference. Overall, these eight textbooks can be grouped into three generations. Greenwood (1935) and Hill (first edition 1937; version reviewed 1961)'s textbooks belong to the first generation, "early epidemiology", which comprise early definitions of bias and confounding. The second generation, "classic epidemiology", represented by the textbooks of Morris (first edition 1957; version reviewed 1964), MacMahon & Pugh (first edition 1960; version reviewed 1970), Susser (1973), and Lilienfeld & Lilienfeld (first edition 1976; version reviewed 1980), clarifies the properties of cohort and case-control study designs and the theory of disease causation. Miettinen (1985) and Rothman (1986)'s textbooks belong to a third generation, "modern epidemiology", presenting an integrated perspective on study designs and their measures of outcome, as well as distinguishing and formalizing the concepts of confounding and interaction. Our review demonstrates that epidemiology, as a scientific discipline, is in constant evolution and transformation. It is likely that new methodological tools, able to assess the complexity of the causes of human health, will be proposed in future generations of textbooks.

Ethnic differences in intake and excretion of sodium, potassium, calcium and magnesium in South Africans.

OBJECTIVES: To determine any differences in the urinary excretion and dietary intake of sodium, potassium, magnesium and calcium intake in three South African ethnic groups, and to assess whether the blood pressure-cation association varies according to ethnic status. DESIGN: A cross-sectional study of 325 black, white and mixed-ancestry men and women, conveniently sampled in Cape Town. Twenty-four-hour urine samples were collected on three separate occasions for assessment of urinary electrolytes, and three 24-h dietary recalls for the corresponding urine collection times were administered by two trained fieldworkers. Para-amino benzoic acid was used as a marker of the completeness of urine collection. RESULTS: Mean urinary sodium values equate to a daily salt (sodium chloride) intake of 7.8, 8.5 and 9.5 g in black, mixed-ancestry and white individuals, respectively. In normotensive individuals, black and mixed-ancestry subjects had significantly lower median urinary sodium concentrations than white subjects, but these differences were not evident between black and white hypertensive subjects. No ethnic differences were found for urinary potassium, except for mixed-ancestry normotensive individuals having a lower excretion than white normotensive individuals. Urinary magnesium excretion did not differ across ethnic groups. In both normotensive and hypertensive individuals, urinary calcium concentrations differed between all three groups, with black subjects having the lowest values, approximately less than half those of white subjects. CONCLUSION: White normotensive subjects in Cape Town have higher habitual intakes of sodium, but also higher calcium intakes than their black and mixed-ancestry counterparts. Dietary differences may contribute to ethnic-related differences in blood pressure.

The nutritional status of asymptomatic HIV-infected Africans: directions for dietary intervention?

OBJECTIVE: To compare the relationships between food (nutrient) intakes and biochemical markers of nutritional status of asymptomatic HIV-infected with HIV-uninfected subjects, to gain more information on the appropriate diet for HIV-infected persons at an early stage of infection. DESIGN: Cross-sectional population-based survey. SETTING: North West Province, South Africa. SUBJECTS: Two hundred and sixteen asymptomatic HIV-infected and 1550 HIV-uninfected men and women volunteers aged 15 years and older, recruited as 'apparently healthy' subjects from 37 randomly selected sites. OUTCOME MEASURES: Food and nutrient intakes, measured with a validated food-frequency questionnaire, and nutritional status indicated by anthropometric and biochemical variables, measured by a standardised methodology. RESULTS: The prevalence of HIV infection in the study population was 11.9%. The anthropometric indices and nutrient intakes of HIV-infected and uninfected subjects did not differ significantly, indicating that these 216 HIV-infected subjects were at an early stage of infection. Of the biochemical nutritional status variables, high-density lipoprotein cholesterol and total cholesterol, haemoglobin, albumin and triglycerides were significantly lower in infected subjects. They also had higher globulin and liver enzyme levels than uninfected subjects. In infected subjects, serum albumin correlated significantly with serum lipids, serum vitamin A, serum vitamin E, serum iron, total iron-binding capacity and haemoglobin. The significant positive correlations of the liver enzymes with serum lipids, albumin, vitamin A and iron, observed in HIV-uninfected subjects, disappeared in the infected subjects. Polyunsaturated fat intake showed significant positive correlations with the increased liver enzymes in infected subjects. A principal components analysis indicated that, in infected subjects, increased liver enzymes correlated with higher consumption of maize meal and lower consumption of meat and vegetables. CONCLUSIONS AND RECOMMENDATIONS: This survey indicated that asymptomatic HIV-infected subjects who followed a diet rich in animal foods had smaller decreases in serum albumin, haemoglobin and lipid variables, and smaller increases in liver enzymes, than those who consumed a diet based on staple foods. This suggests that animal foods are associated with improved nutritional status in HIV-infected persons. These results should be confirmed with intervention studies before dietary recommendations for asymptomatic HIV-infected individuals can be made.