Relationships of alcohol intake with biological health outcomes in an African population in transition: the THUSA study

Abstract

Objective: Because present recommendations on alcohol intake are based mainly on evidence of beneficial effects in populations of developed countries, this study examines biological effects of alcohol consumption in an African population in transition to assess whether these recommendations are also valid for Africans. Design: A cross-sectional, comparative, population-based study. Setting: Thirty-seven randomly selected sites in the North West province of South Africa, representing both rural and urban areas. Subjects: A total of 1 854 apparently healthy men and women older than 15 years volunteered to participate. Complete data of 1 757 participants were available for analysis. Pregnant and lactating women as well as subjects taking any form of chronic medication, those with oral temperatures above 37 °C and those who were inebriated were excluded. Outcome measures: A validated, quantitative food frequency questionnaire was used to measure dietary intake, including alcoholic beverages, expressed as absolute alcohol in grams per day. Anthropometric measurements and blood pressure were taken in triplicate using standardised equipment and procedures. Fasting blood samples were used to determine biochemical variables related to nutritional status and health. Serum gamma glutamyl transferase was used to examine the reliability of reported alcohol intake. The SPSS package was used to relate alcohol intake to blood pressure and biochemical variables, controlling for age, body mass index and blood glucose. Data from men and women, as well as drinkers and non-drinkers, were analysed separately and compared. Results: In total, 61.5% of the men and 25.2% of the women reported that they consumed alcoholic beverages. The mean alcohol intake of men (30.2 ± 47.8 g/day) exceeded the recommend value of 21 g/day. The women had a mean intake of 11.4 ± 18.8 g/day, falling within the 12 to 15 g/day recommendation. Older drinkers (> 40 years) and those infected with HIV drank more. The level of urbanisation had little effect on amounts consumed. Drinkers had significantly higher HDL cholesterol (HDL-C), serum triglycerides, blood pressure and iron status variables than non-drinkers. These effects represent some beneficial but mostly detrimental consequences of alcohol consumption. When serum ferritin was used to classify subjects into those in negative iron balance (< 12 μg/L), ‘normal’ iron balance (12–150 μg/L) and positive iron balance (> 150 μg/L), it became evident that alcohol intake almost doubled the proportion of subjects in positive iron balance (in men from 25 to 46%; in women from 11 to 23%). Conclusion: Although the beneficial effect of alcohol consumption on HDL-C was seen in this population, the effects on iron status and balance are of concern and should be researched in more detail.