Recommendations for moderate alcohol consumption, or in fact any level of alcohol consumption, remain controversial, especially in the management of type 2 diabetes (T2D). There has been a lack of long-term randomised controlled trials (RCTs) in this area. Thus in this study, the authors did a 2-year RCT [the two-year CArdiovaSCulAr Diabetes & Ethanol (CASCADE) trial] among 224 controlled diabetes patents, who had been abstaining from alcohol, following their previous 3-month alcohol pilot trial (Shai I, et al. Diabetes Care 2007).
The patients were randomised into three equal groups to have mineral water, white wine, or red wine (150ml serving) with dinner each night for 2 years. Wine and mineral water was provided free of charge for the study. The wine and mineral water provided was the same for the whole study.*
All groups followed a non-calorie restricted Mediterranean diet. Group sessions were held for all participants with clinical dietitians at one-month intervals for the first three months and at three-month intervals thereafter. Wine issues were not discussed at these meetings. Adherence was followed using several validated dietary assessment tools. Compliance for alcohol intake was also tightly monitored, with patients returning their empty wine bottles and receiving their new supplies. The trial was performed in Israel, at Ben-Gurion University, by Professor Shai’s research group which is focused on performing long-term dietary randomised controlled trials.
Most patients (87%) completed the two-year study. The results showed that red wine was found to be superior in improving metabolic profiles, by modestly increasing good (HDL) cholesterol and apolipoprotein A1 (one of the major constituents of HDL cholesterol), while decreasing the ratio between total cholesterol and HDL cholesterol.
Around one in five of the participants were found to be fast alcohol metabolisers, identified through genetic tests showing they had a particular variation related to alcohol metabolism. Slow alcohol metabolisers who drank wine were found to have better blood sugar control than fast alcohol metabolisers who drank wine.
Wine of either type did not affect medication usage, blood pressure, or liver function tests. Although both wine groups modestly improved glucose metabolism, overall, improvements in the metabolic profiles were mainly attributed to red-wine.
The authors say: “This first long-term large scale alcohol trial suggests that ini¬tiating moderate wine intake, especially red-wine, among well-controlled T2D, and as part of healthy diet, is apparently safe and decreases car¬diometabolic risk. While the genetic interaction supports specific causal roles for ethanol, the red-wine's superiority suggests that non-alcoholic constituents of red wine could be having a positive impact.”
They add: “The differences found between red and white wine were opposed to our original hypothesis that the beneficial effects of wine on lipids are mediated predominantly by the alcohol. Yet, the differential effects in patients with the genetic variation for alcohol metabolism on their blood sugar control support a causal role of alcohol on blood sugar control. Thus, genetic profiling may assist in identifying patients with type 2 diabetes in whom moderate wine consumption may induce greater clinical benefit.”