To the Editor: I agree with Berry that the case reports reviewed in the article by Tsimihodimos et al. (1) represent excessive cola consumption. But I do not fully accept his assertion that ‘the consumption range of the normal consumer is comfortably within 2 l a day.’ The available data on soft drink consumption suggest that a significant minority, among both adolescents and adults, may exceed 2 l/day. An analysis of 1999–2002 data from the National Health and Nutrition Examination Survey (NHANES) on consumption of non-diet carbonated soft drinks and fruit drinks showed that 10% of 13- to 18-year-old boys in the US drank at least 1.95 l/day, and 5% drank at least 2.45 l/day. In all, 5% of US 13- to 18-year-old boys and girls were estimated to drink at least 2.19 l/day (2). In adults, 1999–2004 data from NHANES reveal that the average daily consumption of men who had one or more sugar-sweetened drinks on the survey day was 32 ounces (0.95 l), and the average serving size was 17 ounces (0.50 l) (3). Further analysis of the NHANES 1999–2004 1-day recall data, after adjusting for race-ethnicity, gender, age, marital status, income and employment status, showed that 9.2% of adults (age 20+) had consumed at least 68 ounces (2.01 l) of sugar-sweetened drinks in the prior 24 h (4) (It should be noted that this estimate is based on only 1 day of dietary recall, rather than two, which may underestimate the day-to-day variability in high-end consumers.). These are substantive minorities, not outliers. A total of 5–10% of adolescents and adults in the US alone would amount to about 10–20 million people. Data on high-end consumption worldwide are not available, but I suspect that soft drink overconsumption is not restricted to the US. In discussing my case report (5), Berry states that normal potassium homeostasis was re-established when my patient reduced his cola consumption from 4 l to 2 l/day. Follow-up on this patient, however, has shown improvement but not complete normalisation of his serum potassium levels. When he drank 4 l/day, the average of 18 serum potassium values over 2 years was 3.09 meq/l (range 2.2–3.8 meq/l). In the 14 months, since he reduced his consumption to 2 l/day, the average of 12 serum potassium levels is 3.47 meq/l (range 2.7–4.0 meq/l). This is still below the recognised lower limit of normal value of 3.7 meq/l and suggests that there might be a dose–response relationship between cola consumption and hypokalaemia. It follows that moderately heavy (but not grossly excessive) consumers of cola drinks might be at risk for mild hypokalaemia, which has been shown to increase the risk for myocardial infarction, cardiovascular death and stroke in patients with pre-existing cardiovascular disease (6). Regarding the question of osmotic diarrhoea and hypokalaemia from high-fructose corn syrup (HFCS), two studies using both breath hydrogen testing and symptom scores have shown that about two-thirds of normal subjects develop fructose malabsorption with a 50 g oral load (7,8). Fructose can be absorbed in the small intestine in two ways, either by low-capacity facilitated diffusion via the GLUT-5 receptor, or in the presence of glucose, by rapid diffusion via the GLUT-2 receptor (9). HFCS is formulated with various fructose-to-glucose ratios, ranging from 42 : 58 to 90 : 10. A person drinking 4 l of Pepsi–Cola per day with a 55 : 45 fructose-to-glucose ratio would be consuming 43 g of excess fructose per day. Individual variability in the capacity to absorb fructose might account for the lack of diarrhoea in some cases; however, mild chronic malabsorption (even with minimal symptoms) might over time lead to significant potassium deficiency. Breath hydrogen testing and symptom scoring on a series of patients at progressively increasing levels of cola intake would be one way to settle the question of the role of HFCS in cola-induced hypokalaemia. Perhaps, as Berry states, cola-induced hypokalaemia is just a problem of the ‘extreme consumer.’ But I contend that there are millions of these extreme consumers out there, including many of our friends, family members and co-workers, who may face significant health risks if they continue to consume excessive amounts of soft drink. The author has not received funding or honoraria from any source.
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Apr 1, 2013
Debra R Keast + 2
Open Access
