Researchers in Denmark have shown that drinking alcohol on 3 to 4 days every week can drastically reduce a person's chance of developing diabetes.
The researchers, from the University of Southern Denmark in Copenhagen, report their findings in the journal Diabetologia.
There are two types of diabetes: type 1 and type 2. Type 1 develops when the pancreas is unable to produce enough insulin. Type 2, which accounts for the majority of diabetes cases, results from the body's inability to use insulin effectively.
If diabetes is not controlled, it results in a state of raised blood sugar, or hyperglycemia. Over time, this causes serious damage to the body, especially to the heart, eyes, kidneys, blood vessels, and nerves.
Worldwide, the proportion of adults living with diabetes has risen from 4.7 percent in 1980 to 8.5 percent in 2014.
In 2015, diabetes was directly responsible for 1.6 million deaths, while another 2.2 million were attributed to high blood sugar in 2012.
Pattern as opposed to volume
Previous studies that have examined how alcohol consumption might be related to the risk of developing diabetes have consistently found that light to moderate consumption, compared with abstaining, is linked to lower risk. However, these studies have only looked at volume of consumption, and they have not examined how that volume is spread out over time.
The Danish team also notes that while other studies have examined patterns of drinking - for example, number of drinking days per week - their findings have been inconclusive, as have those of studies examining the effects of different types of alcoholic drinks.
Thus, they decided to investigate the association between patterns of alcohol consumption and risk of developing diabetes among men and women in the general Danish population.
From the Danish Health Examination Survey 2007-2008, the team analyzed responses from 70,551 participants (28,704 men and 41,847 women) without diabetes, all of whom had answered questions about lifestyle and health and given detailed information about their drinking habits.
The participants were followed for a median of 4.9 years until 2012, during which time the team found out from a Danish national diabetes register that 859 men and 887 women had developed diabetes.
Types of drink also assessed
From the data, the team was able to determine patterns of alcohol drinking, binge drinking, average weekly intake, and consumption of different beverages.
The questions asked participants not only about their frequency of alcohol consumption, but also about their patterns of consumption of specific types of alcoholic drink.
Thus, the team was able to categorize the participants into: lifetime and current abstainers; those who drank alcohol on less than 1 day per week; on 1 to 2 days per week; on 3 to 4 days each week; and on 5 to 7 days every week.
In Denmark, a standard drink contains 12.0 grams of ethanol. This is less than the standard used in the United States, which is 14.0 grams (0.6 ounces) of pure alcohol.
The researchers were also able to assess binge drinking, which was defined as consuming five or more alcoholic drinks at one session, into three categories: never, on less than 1 day per week, and on more than 1 day each week.
The researchers also categorized patterns of drinking for three types of drink: wine, beer, and spirits. These were assessed as: fewer than one drink per week; between one and six drinks per week; and seven or more drinks each week. For men, this last category was further split into seven to 13 drinks, and 14 or more drinks per week.
Lowest diabetes risk with 3 to 4 days
In analyzing the data for links with diabetes risk, the researchers adjusted them to take into account the effect of other factors that might influence it. These factors included age, sex, education level, smoking, body mass index (BMI), type of diet (such as levels of fibre, fruit, vegetables, and fish), blood pressure (current or previous), family history of diabetes, and leisure activities.
In line with previous studies, the analysis showed that, in terms of average weekly consumption, the lowest risk for developing diabetes was among participants who drank moderate amounts of alcohol.
Men who drank 14 alcoholic beverages per week had a 43 percent lower risk, and women who had nine drinks every week had a 58 percent lower risk of diabetes, compared with abstainers.
When they analyzed the patterns of drinking, the team found that the lowest risk of developing diabetes was among participants who consumed alcohol on 3 to 4 days per week. For men, the risk was 27 percent lower, and for women, it was 32 percent lower, compared with men and women who only drank alcohol on less than 1 day each week.
Analysis of the binge drinking data showed no clear link to diabetes risk. However, the Danish team says that this could be because of the low numbers of survey participants who reported binge drinking, which makes it difficult to produce a meaningful statistical result.
Lowest diabetes risk associated with wine
In terms of alcoholic drink type, the researchers found that, as previous studies have discovered, moderate to high consumption of wine was linked to a lower risk of developing diabetes.
This has been attributed to the presence of polyphenols in red wine, which are thought to help with blood sugar control.
Consuming seven or more drinks of wine every week was linked to a 25 to 30 percent lower risk of developing diabetes, compared with drinking fewer than one per week.
In terms of beer consumption, the analysis showed that consuming between one and six each week was tied to a 21 percent lower risk in men, compared with drinking fewer than one every week. For women, the results showed no link to diabetes risk.
In analyzing the data on spirits consumption, the Danish team found that for men, there was no statistically significant link between the amount of spirits they drank and diabetes risk. However, women who had seven or more drinks of spirits per week had an 83 percent higher risk of developing diabetes compared with women who had fewer than one per week.
"Our findings suggest that alcohol drinking frequency is associated with the risk of diabetes and that consumption of alcohol over 3-4 weekdays is associated with the lowest risks of diabetes, even after taking average weekly alcohol consumption into account."