Can we believe our own eyes? Lower risk of diabetes for moderate wine drinkers?

Wine with food: lower diabetes risk

It is already known that the risk of type 2 diabetes is lower for moderate wine drinkers as several meta-analyses of prospective cohort studies have confirmed. Controlled interventional studies – the gold standard in medical research – also suggest that moderate wine consumption is beneficial for managing type 2 diabetes. However, skeptics have repeatedly cautioned that this evidence may not be believable.

A new analysis of the UK Biobank study confirms that wine consumption in particular with a meal can be recommended for diabetes prevention. The British Biobank study has the advantage that a very large number of participants from England, Wales and Scotland are included. Consequently, a very large data set is available to investigate many different research questions. For example, one of them is the influence of different types of alcoholic beverages when consumed with or without a meal on the risk of developing type 2 diabetes. Here, American researchers (Tulane University, New Orleans and Harvard TH Chan School of Public Health, Boston) examined how the risk in different sub groups varied.

Data from more than 300.000 persons analysed

For the current study, more than 300,000 current drinkers in the UK Biobank were followed for approximately 11 years to investigate the occurrence of type 2 diabetes. At the start of the study, they were free from diabetes, cancer and cardiovascular disease. In a validated questionnaire, they were asked about their eating pattern, their smoking status, exercise habits and about the following drinking pattern:

• Type of drink: wine, beer and/or spirits
• Frequency and number of drinks, which were translated into amount of alcohol (1 drink is the equivalent of 8g of alcohol, 125 ml wine is approx. 13 g of alcohol in most European countries but can vary in other countries)
• Whether the drinks were usually consumed with the meal
• Whether their consumption had ever been reduced due to health problems

The last point was intended to exclude “ex-drinkers” (former drinkers) from the analysis since it is known that they could distort the results. Also, non-drinkers were excluded preventing concerns about abstainers. Key confounders such as body weight, smoking status, exercise habits, eating pattern, socioeconomic status, as well as type of alcoholic beverage and drinking pattern, were adjusted for.

Ideal for diabetes prevention: moderate wine consumption with the meal

A U-shaped relationship between the consumption of alcoholic beverages and the risk of type 2 diabetes was observed, with the lowest risk among consumers of between 100 and 200 g of alcohol (i.e., ∼8–16 drinks) per week. In addition, the authors found a statistically significant 14% lower risk of type 2 diabetes for those consuming an alcoholic beverage with a meal than for those drinking outside meals. A closer look at the consumption habits revealed that the most beneficial effect was drinking mainly wine with a meal: at 250 g of alcohol/ week or less -which is the equivalent of up to 300 ml of wine per day- the risk of diabetes decreased even further.

Is wine only a marker or the decisive component?

These results can be explained biologically (are biologically plausible) because light to moderate wine consumption has been shown in randomized controlled studies to lower insulin resistance, the blood HbA1c concentration (a measurement related to the mean plasma glucose level in the last 3 months as well as the inflammation marker C-reactive protein (CRP). Notably CRP was reduced only with increasing wine consumption, whereas in beer and spirit consumers, it increased with an increasing amount drunk.

In addition, consuming alcoholic beverages with a meal was also associated with a higher concentration of HDL-cholesterol, the “good” and protective fraction of cholesterol.

The UK Biobank study is observational and thus cannot ultimately prove whether wine with its many biologically active compounds is causally related to the prevention of type 2 diabetes or whether it is the behavioural pattern of wine drinkers. They generally have a healthier lifestyle, healthier eating habits and a more responsible drinking pattern than individuals who prefer other alcoholic beverages. However, since the risk markers for type 2 diabetes decrease with increasing wine consumption, which indicates a dose-related effect, wine per se could at least in part be causally responsible for the preventive effects.

Take away message: This important study has unambiguously shown that moderate, regular consumption of wine was associated with a lower risk of type 2 diabetes, but specifically when consumed in a pattern that minimizes higher blood alcohol concentrations (such as drinking with a meal and a low-quantity consumption per drinking occasion).